CN101860925B - High speed media access control with legacy system interoperability - Google Patents
High speed media access control with legacy system interoperability Download PDFInfo
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Abstract
Techniques for MAC processing for efficient use of high throughput systems that is backward compatible with various types of legacy systems are disclosed. In one aspect a first signal is transmitted according to a legacy transmission format to reserve a portion of a shared medium, and communication according to a second transmission format transpires during the reserved portion. In another aspect, a communication device may contend for access on a legacy system, and then communicate according to a new class communication protocol with one or more remote communication devices during the access period. In another aspect, a device may request access to a shared medium according to a legacy protocol, and, upon grant of access, the device may communicate with or facilitate communication between one or more remote stations according to a new protocol.
Description
Require priority according to 35U.S.C § 119
Present patent application requires to enjoy the priority of following U.S. Provisional Patent Application:
On October 15th, 2003 submitted to, exercise question is the provisional application No.60/511 of " Method and Apparatus forProviding Interoperability and Backward Compatibility in WirelessCommunication Systems ", 750;
On October 15th, 2003 submitted to, exercise question is the provisional application No.60/511 of " Method, Apparatus, and Systemfor Medium Access Control in a High Performance Wireless LANEnvironment ", 904;
On October 21st, 2003 submitted to, exercise question is the provisional application No.60/513 of " Peer-to-Peer Connections inMIMO WLAN System ", 239;
On December 1st, 2003 submitted to, exercise question is the provisional application No.60/526 of " Method, Apparatus, and Systemfor Sub-Network Protocol Stack for Very High Speed Wireless LAN ", 347;
On December 1st, 2003 submitted to, exercise question is the provisional application No.60/526 of " Method; Apparatus; and Systemfor Multiplexing Protocol data Units in a High Performance WirelessLAN Environment ", 356;
On December 23rd, 2003 submitted to, exercise question is the provisional application No.60/532 of " Wireless CommunicationsMedium Access Control (MAC) Enhancements ", 791;
On February 18th, 2004 submitted to, exercise question is the provisional application No.60/545 of " Adaptive CoordinationFunction (ACF) ", 963;
On June 2nd, 2004 submitted to, exercise question is the provisional application No.60/576 of " Method andApparatus for RobustWireless Network ", 545;
On July 8th, 2004 submitted to, exercise question is the provisional application No.60/586 of " Method and Apparatus forDistribution Communication Resources Among Multiple Users ", 841; And
On August 11st, 2004 submitted to, exercise question is the provisional application No.60/600 of " Method, Apparatus, and Systemfor Wireless Communications ", 960;
Above-mentioned provisional application all transfers the application's assignee, so incorporate into herein with way of reference clearly.
Technical field
The present invention relates generally to communication, relate in particular to the media access control.
Background technology
For the various communications such as voice-and-data are provided, widespread deployment wireless communication system.Typical radio data system or network provide access to one or more shared resources for a plurality of users.A kind of system can use multiple access technology, such as frequency division multiplexing (FDM), time division multiplexing (TDM), code division multiplexing (CDM) etc.
The wireless network of example comprises the data system based on honeycomb.Some such examples are as follows: (1) " TIA/EIA-95-B Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System " (IS-95 standard); (2) standard (W-CDMA standard) that (3GPP) is provided by " 3rd Generation Partnership Project " by name, it is included among one group of document 3G TS 25.211,3G TS25.212,3G TS 25.213 and 3G TS 25.214; (3) standard (IS-2000 standard) that (3GPP2) is provided by " 3rd GenerationPartnership Project 2 " by name, it is included in " TR-45.5 Physical Layer Standard for cdma2000 Spread SpectrumSystems "; (4) follow high data rate (HDR) system of TIA/EIA/IS-856 standard (IS-856 standard).
Other examples of wireless system comprise WLAN (wireless local area network) (WLAN), such as IEEE 802.11 standards (i.e. 802.11 (a), (b) or (g)).Employing comprises multiple-input and multiple-output (MIMO) WLAN of OFDM (OFDM) modulation technique, can realize the improvement to these networks.In order to improve some shortcomings of standard before 802.11, introduced IEEE 802.11 (e).
Along with the development of wireless system design, can provide higher data rate.Higher data rate has been created possibility for advanced the application, such as voice, video, high speed data transfer and various other application.But different application has different requirements for its transfer of data separately.Numerous types of data has time-delay and throughput requirement, perhaps needs certain service quality (QoS) to guarantee.Do not having to reduce the capacity of system in the situation of resource management, and system possibly can't work efficiently.
Media access control (MAC) agreement is often used in distributing between a plurality of users the communication resource of sharing.The MAC agreement is joined together high-rise physical layer with being used for transceiving data usually.For benefit from data rate increases, the MAC agreement must be designed to utilize efficiently shared resource.Usually also wish to keep interoperability with communication standard that replace or tradition (legacy).Therefore, need to utilize efficiently the MAC of high throughput systems to process in this area.Also this need to keep the MAC of backward compatibility to process with various types of legacy systems in this area.
Summary of the invention
Embodiment disclosed herein has solved utilizing efficiently high throughput systems and can keeping with various legacy systems the demand of the MAC processing of backward compatibility.In one aspect, send first signal with the part of reservation shared medium according to the conventional transmission form, and during the part of reserving, communicate according to the second transformat.
According to an aspect of the present invention, a kind of method of carrying out interoperability on the transmission channel between one or more equipment that communicate according to the first transformat and one or more equipment that communicates according to the second transformat is provided, described method comprises: according to described the first transformat transmitted signal on described transmission channel, in order to described transmission channel is reserved one period duration; The duration of wherein said reservation is corresponding to the interval according to described the first transformat, and comprises at least one interval according to described the second transformat; And at the duration of described reservation, communicate according to described the second transformat.
According to another aspect of the present invention, provide the communication means on a kind of transmission channel, comprising: distributed for the first duration for communicating at transmission channel according to the first communication format in the multiple communication format; And distributed for the second duration according to the second communication format in the multiple communication format for communicating at described transmission channel, wherein said the first duration comprises described the second duration.
According to another aspect of the present invention, provide a kind of method for communicating at transmission channel, comprising: send beacon according to the first communication protocol; According to the described transmission channel of described the first communication protocol contention access; Between the access periods that described competition is arrived, communicate at described transmission channel according to the second communication protocol, wherein said competition to access comprise and contain at least one according to the competing cycle at the interval of described second communication agreement.
According to a further aspect of the invention, equipment a kind of and the access point operation is provided, described access point is established uncontended periods and competing cycle according to the first communication protocol, described equipment comprises: the contention access module is used for during described competing cycle according to described the first communication protocol contention access transmission channel; Wherein said competition to access comprise and contain at least one according to the competing cycle at the interval of second communication agreement; Transmitter, be used for described competition to access periods between send at described transmission channel according to described the second communication protocol; And receiver, be used for described competition to access periods between receive at described transmission channel according to described the second communication protocol.
In one aspect, communication equipment can be on legacy system contention access, and subsequently during access period, communicate according to new a class communication protocol and one or more telecommunication equipment.In one aspect of the method, equipment can be according to legacy protocol request access shared medium, and when granting access, this equipment can communicate (perhaps being convenient to communicating by letter between two or more distant stations) according to New Deal with one or more distant stations.
In another aspect, novel (new class) access point has distributed uncontended periods and competing cycle, wherein according to novel agreement the part of uncontended periods is distributed to communication, and according to conventional communication protocols the second portion of uncontended periods is distributed to communication.Competing cycle can use the combination of one of two kinds of agreements or two kinds of agreements.Give various other sides.
Description of drawings
Fig. 1 is a kind of exemplary embodiment of system, and it comprises high speed WLAN;
Fig. 2 has provided an exemplary embodiment of Wireless Telecom Equipment, and it can be configured to access point or user terminal;
Fig. 3 has provided 802.11 interFrameGap parameters;
Fig. 4 has provided an exemplary physical layer (PHY) span line (segment), is used for illustrating that using DIFS to add back off time (backoff) according to DCF accesses;
Fig. 5 has provided an exemplary physical layer (PHY) span line, is used for explanation and used SIFS before ACK, and it has than the higher priority of DIFS access;
Fig. 6 shows large packet fragmentation is become little burst (fragment), and the latter has the SIFS that is associated;
Fig. 7 has provided an exemplary physical layer (PHY) span line, is used for illustrating that every frame has the TXOP of affirmation;
Fig. 8 shows has the TXOP that piece is confirmed;
Fig. 9 has provided an exemplary physical layer (PHY) span line, is used for the poll TXOP that HCCA is used in explanation;
Figure 10 is the exemplary embodiment of TXOP, and it comprises a plurality of continuous transmission without any the gap;
Figure 11 is the exemplary embodiment of TXOP, is used for explanation and reduces required preamble transmissions amount;
An exemplary embodiment of the method that Figure 12 shows various aspects integrated, it comprise merge lead code, deletion such as SIFS the gap and insert as required GIF;
Figure 13 has provided an exemplary physical layer (PHY) span line, and the wheel that is used for the explanation merging is inquired about corresponding TXOP;
Figure 14 has provided an illustrative methods that is used for merging poll;
Figure 15 has provided an exemplary mac frame;
Figure 16 has provided an exemplary MAC PDU;
Figure 17 has provided an exemplary point to point link;
Figure 18 shows the physical layer bursts (burst) of a prior art;
Figure 19 has provided an exemplary physical layer bursts, and it can be used for point to point link;
Figure 20 has provided an exemplary embodiment of mac frame, and it comprises optional self-organizing (ad hoc) section;
Figure 21 has provided an exemplary physical layer bursts;
Figure 22 shows an exemplary point-to-point data transmission method;
Figure 23 has provided an exemplary point to point link method;
Figure 24 has provided and has been used for connecting the illustrative methods that Rate Feedback is provided at point-to-point;
The managed point-to-point that Figure 25 shows between two stations and the access point connects;
The point-to-point that Figure 26 shows based on competition (or self-organizing) connects;
Figure 27 has provided an exemplary mac frame, is used for the managed point to point link between the explanation station;
Figure 28 shows to divide to mix in identical frequency and supports tradition and novel station;
Figure 29 shows tradition and new media access control is combined;
Figure 30 has provided a kind of illustrative methods of getting transmission opportunity;
Figure 31 has provided a kind of illustrative methods of sharing single FA with a plurality of BSS;
Figure 32 shows the overlapping BSS that uses single FA;
Figure 33 provided with traditional B SS interoperability in carry out a kind of illustrative methods of high speed point to point link;
Figure 34 shows the point to point link that uses the MIMO technology, and it is contention access on traditional B SS;
Figure 35 shows one or more mac frames (or burst) is encapsulated in the aggregate frame;
Figure 36 shows a traditional mac frame;
Figure 37 shows an exemplary decompressed frame;
Figure 38 has provided an exemplary condensed frame;
Figure 39 has provided another exemplary condensed frame;
Figure 40 has provided an exemplary polymerization header;
Figure 41 has provided an exemplary embodiment of the scheduling access period frame (SCAP) that uses in ACF;
How Figure 42 shows SCAP and HCCA and EDCA is combined use;
Figure 43 shows beacon (Beacon) interval, comprises a plurality of SCAP, has interted therebetween based on the access period of competing;
Figure 44 shows the low delay operation of adopting a large amount of MIMO STA;
Figure 45 has provided an exemplary SCHED message;
Figure 46 has provided an exemplary power management field;
Figure 47 has provided an exemplary MAP field;
Figure 48 has provided and has been used for the exemplary SCHED control frame that TXOP distributes;
Figure 49 shows a traditional 802.11PPDU;
Figure 50 has provided an exemplary MIMO PPDU who is used for transfer of data;
Figure 51 has provided an exemplary SCHED PPDU;
Figure 52 has provided an exemplary FRACH PPDU; And
Figure 53 show can with another embodiment of the method for legacy system interoperability.
Embodiment
The physical layer of the very high bit rate of combining wireless LAN (perhaps, using the similar application of emerging transmission technology) discloses the exemplary embodiment of supporting efficient operation here.This exemplary WLAN supports to surpass the bit rate of 100Mbps (MBPS) in the 20MHz bandwidth.
Various exemplary embodiments have kept simplicity and the robustness of the distributed collaboration operation of traditional wlan system, and for example, they are 802.11 (a-e).Can realize the advantage of various embodiment, keep simultaneously the backward compatibility with these legacy systems.(should be noted in the discussion above that in the following description, 802.11 systems are described as exemplary legacy system.Those skilled in the art will find that these improve same system and operating such with replacing.)
A kind of exemplary WLAN can comprise the Subnetwork protocol stack.The Subnetwork protocol stack can be supported the physical layer transmission mechanism of high data rate, high bandwidth usually, including, but not limited to: based on the mechanism of OFDM modulation; The single-carrier modulated technology; Use system's (multiple-input and multiple-output (MIMO) system comprises the single output of many inputs (MISO) system) of a plurality of emissions and a plurality of reception antennas, be used for the very operation of high bandwidth efficiency; With a plurality of transmit and receive antenna and space multiplexing technique combine use with within the identical time interval to a plurality of user terminal to transmit data or from the system of a plurality of user terminal receive datas; And employing code division multiple access (CDMA) technology realizes the system that a plurality of users are transmitted simultaneously.The example of replacing comprises single many outputs of input (SIMO) and the single output of single input (SISO) system.
One or more exemplary embodiment given here is launched to introduce for the wireless data communication system environment.Although preferably in this environment, use, also different embodiments of the invention can be applied to different environment or configuration.Generally, processor, integrated circuit or the discrete logic of various systems described herein available software control are realized.The data that run through the application and quote, instruction, order, information, signal, symbol and chip preferably make up to represent with voltage, electric current, electromagnetic wave, magnetic field or particle, light field or particle or its.In addition, the square frame shown in every width of cloth block diagram can represent the step of hardware or method.In the situation that does not depart from protection range of the present invention, method step can exchange." exemplary " used herein word means " as example, example or explanation ".Here being described to any embodiment of " exemplary " or design should not be interpreted as more preferred than other embodiment or design or have advantage.
Fig. 1 is an exemplary embodiment of system 100, and it comprises an access point (AP) 104, and this access point 104 is connected to one or more user terminals (UT) 106A-N.According to 802.11 terms, in this article, AP and UT are also referred to as station or STA.AP and UT communicate via WLAN (wireless local area network) (WLAN) 120.In this exemplary embodiment, WLAN 120 is high speed MIMO ofdm systems.But WLAN 120 also can be any WLAN.Access point 104 communicates via network 102 and any amount of external equipment or processing procedure.Network 102 can be the Internet, Intranet or any other wired, wireless or optical-fiber network.Connect 110 physical layer signal is sent to access point 104 from network.Equipment or processing procedure can be connected to network 102, perhaps, and as the UT on the WLAN 120 (or via with its be connected).The example of the equipment that can be connected with network 102 or WLAN 120 comprises: phone; Personal digital assistant (PDA); Various types of computers (terminal of laptop computer, personal computer, work station, any type); Video equipment is such as camera, video camera, web camera; And the data equipment of any other type in fact.Process can comprise voice, video, data communication etc.Various data flow may have different transmission requirements, and these can be met by using different service quality (QoS) technology.
In one embodiment, AP 104 provides Ethernet self adaptation (adaptation).In this case, except AP, can also dispose an ip router, with the connection (not showing its details here) that is provided to network 102.Ethernet frame can transmit (below will describe in detail) by the WLAN subnet between router and UT 106.Ethernet self adaptation and connectivity are the known technologies in this area.
In an alternative embodiment, AP 104 provides the IP self adaptation.In this case, for the set that connects UT, AP serves as a gateway router (not showing its details).In this case, AP 104 can be routed to IP datagram UT 106, and, the IP datagram from UT 106 is carried out route.IP self adaptation and connectivity are the known technologies in this area.
Fig. 2 has provided an exemplary embodiment of Wireless Telecom Equipment, and this Wireless Telecom Equipment can be configured to access point 104 or user terminal 106.Fig. 2 shows access point 104 configurations.Transceiver 210 receives and sends in connection 110 according to the physical layer requirement of network 102.From or be sent to the equipment that is connected with network 102 or the data of application are passed to mac processor 220.These data are called as stream 260 here.Stream may have different characteristics, and the type based on the application that is associated with this stream may need different processing.For example, the feature of video or voice is low delay stream (video usually has higher throughput than voice and requires).A lot of market demands are not too responsive to time-delay, require (that is, some packet loss can be tolerated in voice, but file transfer can't stand packet loss usually) but may have higher data integrity.
In one exemplary embodiment, adaptation layer (ADAP) and data link control layer (DLC) are carried out in mac processor 220.Physical layer (PHY) is carried out at WLAN transceiver 240.One skilled in the art will appreciate that and under arbitrary configuration, to carry out cutting apart of various functions.Mac processor 220 can be carried out part or all of physical layer process.The WLAN transceiver can comprise a processor, is used for carrying out MAC and processes or its part.Can adopt any amount of processor, specialized hardware or its combination.
Except storing the instruction and data that is used for carrying out function described here, memory 255 also can be used to store the data that are associated with individual queue.
WLAN transceiver 240 can be the transceiver of any type.In an exemplary embodiment, WLAN transceiver 240 is OFDM transceivers, and it can utilize MIMO or MISO interfaces.To those skilled in the art, OFDM, MIMO and MISO are known.On August 27th, 2003 submitted to, title is the U.S. Patent application No.10/650 common co-pending of " FREQUENCY-INDEPENDENT SPATIAL-PROCESSING FORWIDEBAND MISO AND MIMO SYSTEMS ", in 295, described OFDM, MIMO and the MISO transceiver of various exemplary, this part application has transferred assignee of the present invention.The embodiment that replaces can comprise SIMO or SISO system.
Shown WLAN transceiver 240 is connected with antenna 250A-N.In different embodiment, can support any amount of antenna.Antenna 250 can be used to carry out sending and receiving at WLAN 120.
WLAN transceiver 240 can comprise the spatial processor that is connected with one or more antennas 250.This spatial processor can be processed the data that each antenna will send independently, perhaps, the signal that receives on all antennas is carried out Combined Treatment.The example of independent process can be based on channel estimating, the feedback from UT, channel counter-rotating (channel inversion) or multiple other technologies as known in the art.This processing is with one of any execution in the multiple spatial processing technique.A plurality of such transceivers can use wave beam formation, beam steering (beamsteering), feature guiding (eigen-steering) or other space technologies, improve the throughput that is sent to a given user terminal and from the throughput of a given user terminal.In an exemplary embodiment that wherein sends the OFDM symbol, this spatial processor can comprise a plurality of subspaces processor, is used for processing each OFDM subchannel or frequency range (bin).
In an example system, this AP can have N antenna, and an exemplary UT can have M antenna.Therefore, the MxN paths is arranged between the antenna of this AP and this UT.In the art, the various space technologies that improve throughput with described mulitpath all are known.In a kind of space-time emission diversity (STTD) system (, being also referred to as " diversity " here), the transmission of data formats and encodes, and then, sends by all antennas as individual traffic.Use M transmitting antenna and N reception antenna, can form the individual independent channel of MIN (M, N).Spatial reuse utilizes these independent pathways, and can send different data at every independent pathway, thereby improves transmission rate.
The various technology that are used for learning and adapt to the characteristic of channel between AP and the UT are known.Can send unique pilot tone from each transmitting antenna.Receive and measure these pilot tones at each reception antenna place.Then, information feedback can be returned to transmitter, for use in transmission.Can carry out the feature decomposition of measuring channel matrix, to determine the channel characteristics pattern.Another kind avoids carrying out the feature decomposition of channel matrix in receiver technology is to use the feature guiding of pilot tone and data, comes the spatial manipulation in the simplified receiver.
Therefore, according to current channel status, the transmission for each user terminal in system can provide different data rates.Particularly, the particular link between AP and each UT has superior performance than multicast link or broadcasting link, and multicast link or broadcasting link can be shared from AP to above UT.The below further is elaborated to the example of this respect.Use which kind of spatial manipulation based on the physical link between AP and the UT, WLAN transceiver 240 can be determined supported speed.This information can feedback by connecting 280, processes to be used for MAC.
The quantity of antenna can be disposed according to the demand data of UT and size and form factor.For example, because its higher bandwidth requirement, the high definition video display can comprise, for example, and four antennas; And PDA can have two antennas.An exemplary access point can have four antennas.
Can by the mode similar to access point shown in Figure 2 104, dispose user terminal 106.Not to allow stream 260 be connected to the LAN transceiver (although UT can comprise such transceiver, wired or wireless), stream 260 is normally from one or more application of being attached thereto the equipment that connects or UT work or process and receive, or is delivered to and is attached thereto equipment or upper one or more application or the processing of working of UT that connects.The high level that is connected with AP 104 or UT 106 can be any type.Layer described herein only is illustrative.
Traditional 802.11MAC
As mentioned above, in order to keep compatible with legacy system, can adopt various embodiment described herein.IEEE 802.11 (e) function set (keeping backward compatibility with 802.11 standards early) comprises the various functions that will sum up in this section, and in the function of introducing in the standard morning.For the detailed description of these functions, please refer to corresponding IEEE 802.11 standards.
Basic 802.11MAC comprises based on the Carrier Sense Multiple Access of distributed coordination function (DCF) and point coordination function (PCF)/conflict and avoids (CSMA/CA).DCF can not have to access media in the situation of center-control.In AP, use PCF that center-control is provided.For fear of conflict, DCF and PCF utilize the continuously various gaps between the transmission.Transmission is called as frame, and the gap between the frame then is called as interFrameGap (IFS).Frame can be user data frame, control frame or management frames.
The type of interFrameGap duration according to the insertion gap changes.Fig. 3 shows 802.11 interFrameGap parameters: short interFrameGap (SIFS), some interframe interval (PIFS) and DCF interFrameGap (DIFS).Note that SIFS＜PIFS＜DIFS.Therefore, compare with before attempting to access channel, waiting for the transmission of long period, be positioned at the transmission afterwards of shorter duration and will have higher priority.
According to carrier sense (CSMA) function of CSMA/CA, channel is when idle in the duration at least one DIFS detecting, and stand (STA) can obtain the access right of channel.(employed term " STA " can refer to an access any station of WLAN here, and can comprise access point and user terminal).For fear of conflict, except DIFS, each STA also waits for a back off time () of selecting at random, then could access channel.STA with longer back off time will be noted that when high priority STA begins to send at channel, has therefore avoided conflicting mutually with this STA.(STA of each wait can reduce its corresponding back off time it and listen to the time quantum of waiting for before other transmission on this channel, thereby keeps its relative priority).Therefore, avoid (CA) function according to the conflict of this agreement, STA keeps out of the way a random time section between [0, CW], and wherein selecting at first CW is CWmin, increases the factor 2 when conflicting, until maximum CWmax at every turn.
Fig. 4 has provided an exemplary physical layer (PHY) span line 400, is used for illustrating that how to add back off time according to DCF with DIFS accesses.Existing transmission 410 busy channels.In this embodiment, when transmission 410 stops, the access of higher priority does not appear, so, after DIFS and the back off time section that is associated, begin new transmission 420.In the following discussion, think that transmitting 420 STA has obtained this transmission opportunity by competition in this case.
Only expecting that a specific STA makes current transmission in the frame sequence of response, using SIFS.For example, when sending an acknowledgement frame (ACK) in response to the Frame of receiving, can receive that data send this ACK after adding SIFS immediately.Other transfer sequence also can use SIFS between frame.After a request sends (RTS) frame, can follow SIFS and one and permit sending (CTS) frame, then, and transmission data during SIFS that can be CTS after, after this, the SIFS after data can follow an ACK.As mentioned above, these frame sequences all are interspersed with SIFS.The SIFS duration can be used for: (a) detect the energy on the channel, and judge whether energy exhausts (that is, channel clear); (b) if having time previous message is decoded and judge the ACK frame whether show the transmission be correctly received; (c) the STA transceiver switches to emission and switches to reception from emission from reception if having time.
Fig. 5 has provided an exemplary physical layer (PHY) span line 500, is used for illustrating how to use SIFS before ACK, and it has higher priority than the DIFS access.An existing transmission 510 takies this channel.In this embodiment, when transmission 510 stops, when finishing a rear SIFS, transmission 510 followed ACK 520.Note that ACK 520 DIFS at the expiration before beginning, so any other STA that attempts to win transmission can be not successful.In this embodiment, ACK 520 access of higher priority do not occur after finishing, so, after DIFS and the back off time that is associated (if any), begin new transmission 530.
RTS/CTS frame sequence (except flow control function is provided) can be used to improve the protection to data frame transfer.RTS and CTS comprise the Duration Information of subsequent data frame and ACK and any middle SIFS.Listen to the STA of RTS or CTS and mark the shared duration at their network allocation vector (NAV), and within this duration, media are considered as busy.Typically, utilize RTS/CTS, the frame longer than designated length can be protected, and short frame is sent out away in the unprotect situation.
PCF can be used to make AP that the centralized control of channel is provided.Detecting media when PIFS is the free time in the duration, AP can obtain the control to these media.PIFS is shorter than DIFS, so have higher priority than DIFS.Compare with DCF, in case AP has obtained the access right to channel, it just can provide uncompetitive access chance to other STA, thereby improves MAC efficient.PCF note that SIFS has higher priority than PIFS, so must wait for, until all SIFS EOSs before control channel.
In case AP uses the PIFS acquisition to the access right of media, it just can establish a uncontended periods (CFP), and within this cycle, AP can provide the polling type access to the STA that is associated.Uncompetitive poll (CF-Poll), or be simply referred to as poll is sent and it is followed later is transmission from the STA that is subjected to poll to AP by AP.Equally, STA must wait for the SIFS duration after CF-Poll, although be subjected to the STA of poll needn't wait for DIFS or any back off time.802.11 (e) introduced various enhancings, comprise the enhancing to poll, below in conjunction with Fig. 9 such example is described in further detail.
The beacon that AP sends is established the duration of CFP.This is similar to RTS or CTS and prevents contention access.But some terminal can't be heard this beacon, but its transmission may cause interference to the transmission of being dispatched by AP, so hidden terminal problem still can occur.Each terminal that begins to transmit in CFP can realize further protection by using CTS-to-self.
ACK and CF-Poll can be contained in the frame, and can contain together with data frame packet, thereby improve MAC efficient.Note that it is that channel access provides a kind of certainty priority mechanism that SIFS＜PIFS＜DIFS closes.In DCF, the contention access between the STA is probabilistic based on avoidance mechanism.
802.11 early stage standards have also been stipulated large packet fragmentation is become less burst.An advantage of this segmentation is: the mistake in section needs less re-transmission than the mistake in the larger grouping.Segmentation shortcoming is in these standards: for the transmission of affirmation type, need to send an ACK for each section, wherein, additional SIFS is corresponding to additional ACK transmission and burst transmission.Fig. 6 shows this point.This exemplary physical layer (PHY) span line 600 has provided N section and the corresponding transmission of confirming thereof.Existing transmission 610 is sent out away.When transmission 610 finished, a STA waited for DIFS 620 and back off time 630, to obtain the access right to channel.The one STA sends N section 640A-640N to the 2nd STA, and the delay of the individual corresponding SIFS 650A-650N of N must arranged respectively thereafter.The 2nd STA sends N acknowledgement frame 660A-660N.Between each burst, a STA must wait for SIFS, so, there be N-1 SIFS 670A-670N-1.Therefore, compare with a SIFS with a grouping of transmission, an ACK, the grouping through segmentation needs the identical transmitted in packets time, but N ACK and 2N-1 SIFS are arranged.
802.11 (e) standard has been added the enhancing function so that improve 802.11 (a), (b) and (g) in former MAC.802.11 all be ofdm system (g) and (a), they are very similar, but work in different frequency bands.The various functions of the low speed MAC agreement such as 802.11 (b) pass on to forward has the more system of high bit rate, thereby has introduced poor efficiency, and the back will be elaborated to this.
In 802.11 (e), DCF has obtained enhancing, strengthens distributed channel access (EDCA) so be called as.It is to have introduced arbitration interFrameGap (AIFS) that the main services quality (QoS) of EDCA strengthens.AIFS[i] be associated with the type of service (TC) that identifies with numbering i.AP can use can employed AIFS[i from other STA] AIFS[i that value is different] value.Only have AP can use the AIFS[i that equates with PIFS] value.In other cases, AIFS[i] more than or equal to DIFS.In the default situation, for " voice " and " video " type of service, select to equal the AIFS of DIFS.If AIFS is larger, then is indicated as type of service " best effort (besteffort) " and " background " and has selected lower priority.
The size of competition window also is the function of TC.The limit priority type allows to arrange CW=1,, does not have back off time that is.For other TC, different contention window size provides probabilistic relative priority, but can not be used for reaching delay guaranteed.
802.11 (e) introduced transmission opportunity (TXOP).In order to improve MAC efficient, when STA got access to media by EDCA or by the access of the polling type among the HCCA, STA can send more than one frame.The one or more frame is called as TXOP.In the media, the maximum length of TXOP depends on type of service and is determined by AP.In addition, for the TXOP that is subjected to poll, AP indicates the allowance duration of TXOP.During TXOP, STA can send a series of frame, is interspersed with SIFS therebetween and from the ACK of destination party.Except waiting for that DIFS adds the back off time to each frame, the STA that has won a TXOP can know that it can keep this channel to be used for subsequent transmission.
During TXOP, can be (just as the same in 802.11MAC early) of every frame from the ACK of destination party, perhaps, can use piece ACK at once or delay, as described below.In addition, for specific Business Stream, such as broadcast or multicast, allow the strategy without ACK.
Fig. 7 has provided an exemplary physical layer (PHY) span line 700, is used for explanation and has the TXOP that confirms frame by frame.An existing transmission 710 is sent out away.After transmission 710 and after wait DIFS 720 and the back off time 730 (if any), STA wins TXOP 790.TXOP 790 comprises N frame 740A-740N, and N corresponding SIFS 750A-750N followed in each frame back.The STA that receives makes response with N corresponding ACK760A-760N.ACK follows 760 back N-1 SIFS 770A-770N-1.Should be noted in the discussion above that each frame 740 comprises lead code 770, and header and grouping 780.The exemplary embodiment that the below describes in detail can be reduced to the transmission time amount that lead code is reserved greatly.
Fig. 8 shows has the TXOP 810 that piece is confirmed.TXOP 810 can win by competition or poll.TXOP 810 comprises N frame 820A-820N, and N corresponding SIFS 830A-830N followed in each frame back.After the transmission of frame 820 and SIFS 830, send a piece ACK request 840.The STA that receives will ask to make response in a certain moment in future to this piece ACK.This piece ACK can perhaps can postpone immediately following after the piece end of transmission of frame, processes with the software that allows receiver.
The exemplary embodiment that the below describes in detail can greatly reduce the transmission time amount (being in this embodiment SIFS) between the frame.In some embodiments, there is no need continuously delay between the transmission (being frame).
Should be noted in the discussion above that in 802.11 (a) and other standards for specific transformat, defined a kind of signal extension (Signal Extension), its end at every frame increases additional delay.Although be not included in technically in the definition of SIFS, each embodiment that describes in detail below also can remove signal extension.
Piece ACK function can be raised the efficiency.In an example, STA can send and 1024 maximum 64 MAC service data units (SDU) (each can also be divided into 16 bursts) that frame is corresponding, and destination party STA can provide single response in the end of the piece of frame, to show each the ACK state in this 1024 frame.Typically, when speed was high, MAC SDU can not be carried out burst, and for low delay, before need to the piece ACK from destination party, can send and was less than 64 MAC SDU.In this case, in order to send M frame, total time reduces to M frame+M SIFS+ piece ACK from M frame+M SIFS+M ACK+M-1 SIFS.The embodiment that the below describes in detail further improves the efficient of piece ACK.
802.11 can directly being transmitted to frame STA, the direct link agreement (DLP) of (e) introducing is in interior another destination party STA of a set of basic (BSS) (by identical AP control).AP can provide for this direct frame transmission between the STA TXOP of poll.Before introducing this function, in the polling type access procedure, from the destination party of the frame that is subjected to poll STA AP always, and AP is transmitted to destination party STA with these frames.Transmit by the frame of eliminating double bounce, media efficient is improved.The embodiment that the below further describes is that the DLP transmission increases obvious efficient.
802.11 (e) also introduced in-dash computer F, be called as Hybrid Coordination Function (HCF).In the channel access (HCCA) of HCF control, AP can access channel at any time, thereby sets up controlled access phase (CAP), and this is similar to CFP, the any time that is used within the competitive stage provides transmission opportunity, rather than only immediately following behind beacon.Then AP accesses media not having to wait for PIFS in the situation of back off time.
Fig. 9 has provided an exemplary physical layer (PHY) span line 900, is used for the TXOP that is subjected to poll that HCCA is used in explanation.In this embodiment, AP competes this poll.An existing transmission 910 is sent out away.After transmission 910, AP waits for PIFS, and then the side of sending and receiving is the poll 920 of a STA.Other STA that should be noted in the discussion above that this channel of competition must wait at least DIFS, because the poll 920 that sends causes this can not occur, as shown in the figure.Be subjected to the STA of poll after poll 920 and SIFS 930, to send the TXOP 940 that is subjected to poll.AP can continue poll, waits for PIFS between the TXOP 940 that respectively is subjected to poll and poll 920.In another kind of situation, AP can wait for PIFS from transmitting 910, thereby establishes CAP.AP can send one or more polls during CAP.
MAC improves
As mentioned above, the various poor efficiency functions of former MAC also pass in later on the version.For example, the very long lead code that designs for the 11Mbps relative with 64Mbps can cause poor efficiency.Along with the increase of speed, Medium Access Control (MAC) Protocol Data Unit (MPDU) constantly dwindles, so, make various interFrameGaps and/or lead code keep the constant corresponding reduction that just means channel utilization.For example, high data rate MIMO MPDU transmission may only have several microseconds on length, and by contrast, 802.11 (g) have the lead code of 72 μ s.Eliminate or the reduction delay, such as SIFS, signal extension and/or lead code, will improve throughput and the utilance of channel.
Figure 10 is the exemplary embodiment of TXOP 1010, and it comprises a plurality of continuous transmission frames, and without any the gap.TXOP 1010 comprises N frame 1020A-1020N, and they are (SIFS required among this and the TXOP 810 shown in Figure 8 are compared) of transmission in an orderly manner in without any the situation in gap.The quantity of the frame among this TXOP only is subject to buffer and the decoding capability of receiver.When STA sends successive frame together with piece ACK in TXOP 1010, needn't intert (intersperse) SIFS duration, this is because there are not other STA need to obtain access right to media between successive frame.Behind N frame, add an optional piece ACK request 1030.The business of some type may not need to confirm.Be right after after TXOP, can make response to a piece ACK request, perhaps can send after a while.The expansion of frame 1020 undesired signals.Any embodiment that TXOP 1010 can be used for describing in detail here is as long as wherein need TXOP.
As shown in figure 10, when sending all frames by same STA, between the successive frame of TXOP, needn't send SIFS.In 802.11 (e), these gaps have been reserved, so that the complexity requirement at restriction receiver place.In 802.11 (e) standard, the SIFS period of 10 μ s and the ofdm signal of 6 μ s expand to receiver altogether 16 μ s are provided, for the treatment of the frame of receiving (comprising the demodulation code).But if PHY speed is very large, this 16 μ s can lower efficiency significantly.In some embodiments, process by introducing MIMO, even if 16 μ s also are not enough to finish processing.And in this exemplary embodiment, from a STA to AP or to the continuous transmission of another STA, do not need SIFS and ofdm signal expansion (using the direct link agreement).Therefore, if receiver needs the additional period section to be used for that the MIMO receiver is processed after the end of transmission and channel-decoding (for example, turbo/ convolution/LDPC decoding), then this receiver can be carried out these functions, simultaneously media is used to additional transmitted.After a while, can send an affirmation, (for example, use piece ACK) as mentioned above.
Because the different propagation delays between the STA; different STA between transmission can separate with protective time slot; the continuous transmission from different STA bumps at the receiver place (Figure 10 does not show, but will make further detailed description in the back) on these media to avoid.In one exemplary embodiment, all working environment of the protective time slot of an OFDM symbol (4 μ s) for 802.11 all is enough.Transmission from same STA to different destination party STA does not need to separate (as shown in figure 10) with protective time slot.The below also will further describe, and these protective time slots can be called as guard band interFrameGap (GIFS).
Do not use SIFS and/or signal extension, by the ARQ scheme (rollback N or selectively repetition) of using window based, the required receiver processing time (for example, being used for MIMO processing and decoding) can be provided, and these technology are known for those skilled in the art.Stop-and-wait (stop-and-wait) the MAC layer ACK of tradition 802.11 has been enhanced to the mechanism of window type in 802.11 (e), reach at most in this embodiment 1024 frames and piece ACK.The ARQ scheme of the window based of preferred introducing standard, but not the self-organizing piece ACK scheme of design among 802.11 (e).
The maximized window that allows depends on receiver processing complexity and buffering.Transmitter can according to transmitter-receiver between accessible peak value PHY speed, send enough data and fill up receiver window.For example, because processing, receiver possibly can't get caught up in PHY speed, so receiver may need to store the output of soft (soft) decoder, until they can be decoded.Therefore, the buffer requirement of physical layer process can be used to determine the maximum window that allows during peak value PHY speed.
In one exemplary embodiment, receiver can be announced it and can the maximum with a specific PHY rate processing allow PHY piece size in the situation that its physical layer buffer is overflowed.Perhaps, receiver also can be announced it and can the maximum with maximum PHY rate processing allow PHY piece size in the situation that its physical layer buffer is overflowed.When PHY speed is low, can in the situation that does not have buffer to overflow, process long piece size.The maximum of announcing during according to maximum PHY speed allows PHY piece size, and the maximum that transmitter can calculate with known formula for specific PHY speed allows PHY piece size.
If the maximum PHY piece size of announcement is a static parameter, then in that can to process physical layer buffer and the receiver time quantum before being ready to receive next PHY burst be known at the transmitter place for another and also be known receiver parameters at the scheduler place.Perhaps, according to the situation that takies of physical layer buffer, the maximum PHY piece size of announcing can dynamically change.
The receiver processing delay can be used to determine that ARQ come and go (round-trip) postpones, and the latter can be used to the delay that definite application program is observed.Therefore, in order to support the low delay service, can limit the PHY piece size of permission.
Figure 11 has provided the exemplary embodiment of TXOP 1110, is used for explanation and reduces required preamble transmissions amount.TXOP 1110 comprises lead code 1120, and that follow later is N continuously transmission 1130A-1130N.Can add an optional piece ACK request 1140.In this embodiment, transmission 1130 comprises a header and a grouping.TXOP 1110 is compared with the TXOP 790 of Fig. 7, and each frame 740 also comprises a lead code among the latter except header and grouping.For the transmission data of same amount, by sending single lead code, required preamble transmissions only is a lead code, rather than N lead code.
Therefore, lead code 1120 can be excluded from continuous transmission.Receiver can obtain with the fine frequency that initial preamble 1120 is obtained signal and is used for OFDM.For the MIMO transmission, to compare with current OFDM lead code, initial preamble 1120 can be expanded, so that receiver can the estimation space channel.But the subsequent frame in the same TXOP can not need the lead code of adding.Pilot tone in the OFDM symbol is enough to carry out signal trace usually.In an alternative embodiment, additional (being similar to lead code) symbol can be periodically staggered in TXOP 1110.But, can obviously reduce total lead code expense.Can only just send where necessary lead code, and can differently send lead code based on the time quantum of since the last lead code that sends, having passed.
Should be noted in the discussion above that TXOP 1110 also can combine with the function of legacy system.For example, piece ACK is optional.Also can support more frequently ACK.Even so, less gap such as GIFS, can be replaced long SIFS and (add signal extension, if you are using).Continuous transmission 1130 can also comprise a plurality of sections of larger grouping, as mentioned above.The header that should also be noted that the continuous transmission 1130 of mailing to same recipient STA can be carried out compression.The below also will describe an example of header compression in detail.
Figure 12 has provided an exemplary embodiment of method 1200, and it is combined with above-mentioned each side, comprises merging lead code, remove the gap such as SIFS and inserting as required GIFS.This flow process starts from frame 1210, wherein, uses any technology of describing in detail here, and a STA has won a TXOP.In frame 1220, as required, send a lead code.Equally, traditional lead code can is longer than or be shorter than to this lead code, and can change according to various parameters (for example, the time that has passed since last transmission lead code), so that recipient STA can estimate the MIMO space channel.In frame 1230, STA sends one or more groupings (perhaps, more generally, the continuous transmission of any type) to destination party.Should be noted in the discussion above that does not need to send additional lead code.In an alternative embodiment also can send one or more additional lead codes alternatively, perhaps, as required, can intert the symbol of similar lead code.In frame 1240, STA can be alternatively to an additional recipient STA transmitted signal.In this case, insert as required GIFS, and, one or more continuous transmission can be sent to additional recipient STA.Then, this flow process can finish.In various embodiments, STA can continue to plural STA transmitted signal, inserts required GIFS and/or the lead code of estimated performance grade.
Therefore, as mentioned above, by the transmission from a STA to a plurality of destination party STA is merged into continuous transmission, can further improve MAC efficient, thereby save a lot of or whole protective time slots and reduce the lead code expense.For a plurality of continuous transmission from same STA to different destination party STA, can use single lead code (perhaps, pilot transmission).
Merge by poll, can obtain extra efficient.In one exemplary embodiment, several polls can be merged in the control channel, the below will describe its example in detail.In an example, AP can be to a plurality of destination party STA transmitted signals, comprising the polling message that is used for distribution T XOP.By contrast, in 802.11 (e), have before each TXOP from the CF-Poll of AP and the SIFS that follows.When several such CF-Poll message being merged into single control channel message (in the exemplary embodiment that is discussed in more detail below, being referred to as SCHED message) when being used for distributing several TXOP, can raise the efficiency.In a common embodiment, any time section can be distributed to poll and the corresponding TXOP thereof after the merging.Describe an exemplary embodiment below in conjunction with Figure 15, and this paper also comprises other examples.
In order further to raise the efficiency, can encode to control channel (being SCHED) message with the speed structure of layering.Correspondingly, the polling message that mails to any STA can be encoded according to the channel quality between AP and the STA.The order of transmission of polling message needs not to be the order of the distribution T XOP of institute, but can be ranked according to the coding robustness.
Figure 13 has provided an exemplary physical layer (PHY) span line 1300, is used for poll and corresponding TXOP thereof that explanation merges.The poll 1310 that merges is sent out away.Can use the control channel structure of describing its example here in detail, perhaps can use to it will be apparent to those skilled in the art that various other technologies, send these polls.In this embodiment, in order need between poll and any forward link TXOP, not use interFrameGap, the poll 1310 rear direct transmission forward link TXOP 1320 that merging.After forward link TXOP1320, send various reverse link TXOP 1330A-1330N, wherein can insert GIFS 1340 as required.Should be noted in the discussion above that when transmitting in order from a STA, needn't comprise GIFS (be similar to for the forward link transmissions that sends to different STA from AP, do not need GIFS).In this embodiment, reverse link TXOP comprises that STA is to the TXOP (for example, using DLP) of STA (that is, point-to-point).Order of transmission shown in should be noted in the discussion above that is illustrative.Forward direction and reverse link TXOP (comprising the point-to-point transmission) can exchange, and perhaps, intert mutually.The number of gaps that some configuration is eliminated may be different from the number of gaps that other configurations are eliminated.By the enlightenment here, those skilled in the art can revise out multiple interchangeable embodiment at an easy rate.
Figure 14 shows an exemplary embodiment for the method 1400 that merges poll.Flow process starts from frame 1410, wherein, with channel resource allocation in one or more TXOP.Can use any scheduling feature, make this TXOP and distribute definite.In frame 1420, coming the poll of distribution T XOP to merge according to this assignment information.In frame 1430, by one or more control channels, the poll of this merging is sent to one or more STA (that is, in the exemplary embodiment that is discussed in more detail below, the CTRLJ section of SCHED message).In an alternative embodiment can send with any message delivery techniques the poll of merging.In frame 1440, STA distributes to send TXOP according to the poll in the poll of this merging.Then, this flow process can finish.The method can be used in conjunction with the polling interval of the merging of any length, and the poll of the merging of described any length can comprise all or part of of system's beacon interval.As mentioned above, the poll of merging can be used for based on the access of competition or traditional poll off and on.In one exemplary embodiment, can periodically or according to other parameters repeat method 1400, described other parameters such as system load or transfer of data requirement.
Below in conjunction with Figure 15 and 16, describe an exemplary embodiment of MAC agreement in detail, with the explanation various aspects.Be 20050135416 " Wireless Lan Protocol Stack " (file number is 030428) in the U.S. Patent Application Publication No. common co-pending of submitting to simultaneously with the application, publication number is 20050135403 " Method; Apparatus; and system for MediumAccess Control " (file number is 030433), publication number is this MAC agreement to be described in further detail, these three pieces of assignees that application has transferred the application in 20050135291 " Method; Apparatus; and system for Multiplexing Protocol Data Units " (file number is 030436).
An exemplary TDD mac frame interval 1500 has been shown among Figure 15.Term " TDD mac frame interval " used in this occasion refers to a period of time, wherein, has defined the various span lines of describing in detail below.TDD mac frame interval 1500 is different from the term " frame " of normal operation, so that describe the transmission in 802.11 systems.In 802.11 terms, TDD mac frame interval 1500 is similar to the sub-fraction of beacon interval or beacon interval.Parameters in conjunction with Figure 15 and 16 detailed descriptions only are illustrative.Some or all of the use parts of describing and various parameter value, those of ordinary skills can make this example be adapted to multiple other embodiment at an easy rate.MAC function 1500 is distributed between following transmission channel section: broadcasting, control, forward direction and reverse traffic (being called as respectively downlink phase and uplink phase) and at random access.
In this exemplary embodiment, TDD mac frame interval 1500 is time division duplex (TDD) within 2 milliseconds the time interval, is divided into five transmission channel section 1510-1550, as shown in the figure.In the embodiment that replaces, can use other order and different frame sizes.Duration distribution on the TDDMAC frame period 1500 can be quantized into a certain mini-bus time interval.
These five exemplary transmission channels in the TDD mac frame interval 1500 comprise: (a) broadcast channel (BCH) 1510, and it transmits Broadcast Control Channel (BCCH); (b) control channel (CCH) 1520, it transmits on the forward link frame control channel (FCCH) and accesses at random feedback channel (RFCH); (c) Traffic Channel (TCH), it transmits user data and control information, and further is subdivided into forward traffic channel (F-TCH) 1530 and (ii) reverse traffic channel (R-TCH) 1540 on the reverse link on (i) forward link; (d) Random Access Channel (RCH) 1550, it transmits access request channel (ARCH) (being used for the UT access request).Pilot beacon also is to send in section 1510.
The downlink phase section of the comprising 1510-1530 of frame 1500.The uplink phase section of comprising 1540-1550.The beginning at section 1560 next TDD mac frame interval of expression.The below further describes the embodiment of a replacement that comprises the point-to-point transmission.
Broadcast channel (BCH) and beacon 1510 are sent by AP.The first of BCH 1510 comprises the common physical layer expense, such as pilot signal, comprises sequential and frequency acquisition pilot tone.In an exemplary embodiment, beacon comprises 2 short OFDM symbols that are used for frequency and timing acquisition by UT, and the back is 8 short OFDM symbols that are used for the public MIMO pilot tone of estimation channel by UT.
The second portion of BCH 1510 is data division.The BCH data division has defined the distribution condition with respect to transmission channel section CCH 1520, F-TCH 1530, R-TCH 1540 and RCH 1550, TDDMAC frame period, also defines the combination with respect to subchannel, CCH.In this embodiment, BCH 1510 has defined the coverage of WLAN 120, so sent under the most healthy and the strongest available data-transmission mode.The length of whole BCH is fixed.In an exemplary embodiment, BCH has defined the coverage of MIMO-WLAN, and uses the binary phase shift keying (BPSK) of 1/4 rate coding to send under space-time emission diversity (STTD) pattern.In this embodiment, the length of BCH is fixed as 10 short OFDM symbols.In the embodiment that replaces, can use various other signaling technologys.
The control channel (CCH) 1520 that is sent by AP has defined the combination of the remainder at TDD mac frame interval, and shows the poll that how to use merging.CCH 1520 sends in a plurality of subchannels with very healthy and strong transmission mode, and each subchannel has different data rates.The first subchannel is the most healthy and the strongest, and expection can be decoded by all UT.In an exemplary embodiment, the BPSK of 1/4 rate coding is used for a CCH subchannel.Also provide other robustnesss to reduce the subchannel of (efficient rising).In one exemplary embodiment, use maximum three additional subchannels.Each UT attempts all subchannels are decoded in order, until decode unsuccessfully.CCH transmission channel section in each frame has variable length, and this length depends on the quantity of CCH message in every sub-channels.For reverse link at random the affirmation information of access burst be that the most healthy and the strongest (first) subchannel at CCH transmits.
CCH is included in physical layer bursts assignment information on forward direction and the reverse link (being similar to the poll for the merging of TXOP).Distribute and be used in forward direction or reverse link transmitting data.Usually, the physical layer bursts distribution comprises: (a) MAC ID; (b) value of an interior time started (in F-TCH or R-TCH) of distributing of this frame of expression; The length of (c) distributing; (d) length of special-purpose physical layer overhead; (e) transmission mode; (f) be used for coding and the modulation scheme of physical layer bursts.
The assignment information of upper other exemplary types of CCH comprises: the assignment information on the reverse link is used for transmission from the dedicated pilot of UT; Assignment information on the reverse link is used for transmission from buffer and the link-state information of UT.CCH can also define the reservation unused portion of frame.These unused portions of this frame can be used for carrying out noise floor (and interference) by UT to be estimated, and measures the adjacent system beacon.
Random Access Channel (RCH) the 1550th, reverse chain channel, UT can send at random access burst by it.For each frame, in BCH, specify the variable-length of RCH.
Forward traffic channel (F-TCH) 1530 comprises one or more physical layer bursts that send from AP 104.The specific MAC ID that each burst is pointed at CCH assignment information indicating.Each burst comprises special-purpose physical layer overhead, for example, and the pilot signal (if any) and the MAC PDU that send according to the transmission mode of CCH assignment information indicating and coding and modulation scheme.F-TCH has variable length.In an exemplary embodiment, special-purpose physical layer overhead can comprise the MIMO pilot tone of a special use.Figure 16 has provided an exemplary MAC PDU in detail.
Reverse traffic channel (R-TCH) 1540 comprises the physical layer bursts transmission from one or more UT 106.Each burst is that the specific UT of by CCH assignment information indicating sends.Each burst can comprise a dedicated pilot lead code (if any) and MAC PDU who sends according to the transmission mode of CCH assignment information indicating and coding and modulation scheme.R-TCH has variable length.
In this exemplary embodiment, F-TCH 1530, R-TCH 1540 or the two, can usage space transmit when multiplexing or CDMA (Code Division Multiple Access) realizes with different UT are associated MAC PDU, comprise the MAC ID that is associated with MAC PDU (namely, transmit leg on the up link, or the expection recipient on the down link) a field can be included in the MACPDU header.All addressing uncertain problems that this can may occur when solving the multiplexing or CDMA of usage space.In the embodiment that replaces, when multiplexing during strictly based on time division technique, do not need MAC ID in the MAC PDU header, because addressing information is included in the CCH message, CCH message has been given a concrete MAC ID with the special time period allocated in the TDD mac frame interval.Can adopt the combination of spatial reuse, code division multiplexing, time division multiplexing and any other technology known in the art.
Figure 16 shows the exemplary MAC PDU 1660 from a grouping 1610, and in this embodiment, grouping 1610 can be IP datagram or ethernet segment.Exemplary field type and size have been described in diagram.One skilled in the art will recognize that in protection scope of the present invention various other sizes, type and configuration also can be imagined and obtain.
As shown in the figure, segmentation is carried out in packet 1610 in adaptation layer.One of in each these section 1620 of self adaptation sublayer PDU 1630 carryings.In this embodiment, packet 1610 is divided into N section 1620A-N.Self adaptation sublayer PDU 1630 comprises payload 1634, and payload 1634 comprises corresponding section 1620.Type field 1632 (being a byte in this embodiment) is affixed among the self adaptation sublayer PDU 1630.
Logical links (LL) header 1642 (being 4 bytes in this embodiment) is added in the payload 1644, and payload 1644 comprises adaptation layer PDU 1630.The exemplary information of LL header 1642 comprises flow identifier, control information and sequence number.Calculate CRC 1646 for header 1642 and payload 1644, and this CRC1646 of affix is to form logical links sublayer PDU (LL PDU) 1640.Logic link control (LLC) and Radio Link control (RLC) PDU can form by similar fashion.LL PDU 1640 and LLC PDU and RLC PDU are placed on (for example, high QoS formation, best effort formation or control message formation) in the formation, with the service that is used for being provided by the MUX function.
MUX header 1652 is affixed on each LL PDU 1640.An exemplary MUX header 1652 can comprise length and type (in this embodiment, header 1652 is two bytes).For each control PDU (that is, LLC and RLC PDU), can form similar header.LL PDU 1640 (or LLC or RLC PDU) consists of payload 1654.Header 1652 and payload 1654 consist of MUX sublayer PDU (MPDU) 1650 (MUX sublayer PDU is also referred to as MUX PDU here).
In this embodiment, the communication resource on the shared medium is distributed in a series of TDDMAC frame periods by the MAC agreement.To describe in detail below in the alternative embodiment of its example, the TDD mac frame interval of these types can be by interspersed various other MAC functions, comprise based on competition or poll, and comprise that the access protocol and the legacy system that use other types carry out alternately.As mentioned above, scheduler can determine to distribute to the size (being similar to the TXOP of the poll of merging) of the physical layer bursts of one or more MAC ID in each TDD mac frame interval.Should be noted in the discussion above that not to be that each MAC ID that has data to send can both be assigned to space in any specific T DD mac frame interval.In protection scope of the present invention, can use any access control or scheduling scheme.When dividing timing for MAC ID, the corresponding MUX function of this MAC ID will consist of MAC PDU 1660, and it comprises one or more MUX PDU 1650, so that be included in this TDD mac frame interval.To be included in the TDD mac frame interval (that is, TDD mac frame interval 1500, the above is described in detail in conjunction with Figure 15) for one or more MUX PDU 1660 of one or more MAC ID that distributed.
In one exemplary embodiment, an aspect makes it possible to send a part MPDU1650, thereby realizes efficient package in MAC PDU 1660.In this embodiment, all part MPDU 1650 remaining byte that do not send in front once transmission can be included, and by part MPDU 1664 signs.In present frame, these bytes 1664 will send before at all new PDU 1666 (that is, LL PDU or control PDU).Header 1662 (being 2 bytes in this embodiment) comprises the MUX pointer, and it points to the beginning of first new MPDU (being in this embodiment MPDU 1666A) that will send in the present frame.Header 1662 also comprises MAC Address.
Therefore, this exemplary MAC PDU 1660 shows a transmission (perhaps, being frame by 802.11 terms), and it can send to another STA from a STA, comprises the data division from the one or more streams that point to this destination party STA.By using alternatively part MUX PDU, can realize efficient package.The time of the poll indicating of the merging that comprises in CCH, each MAC PDU can send in a TXOP (using 802.11 terms).
The exemplary embodiment of describing in detail among Figure 15 and 16 has been listed various aspects, comprise by from each STA (comprising AP) thus sending in an orderly manner physical layer bursts merges poll, reduces preamble transmissions and eliminates the gap.These aspects also are applicable to any MAC agreement, comprise 802.11 systems.The below further provides the embodiment of replacement, and other various technology are described, these technology can realize the high efficiency of MAC, and supports the point-to-point transmission, and can existing legacy protocol or system combine and/or cooperate.
As mentioned above, the various embodiment that describe in detail here can adopt channel estimating and strict speed control.By the unnecessary transmission on the media is minimized, the MAC efficient that can obtain to improve, still, in some cases, inadequate speed control feedback will reduce overall throughput.Therefore, for channel estimating and feedback, can provide enough chances, so that the maximization of the transmission rate under all MIMO patterns, thereby prevent that inadequate channel estimating can be offset any MAC efficient to be increased because the throughput that insufficient channel estimating causes reduces.Therefore, MAC embodiment that can design example so that enough preamble transmissions chances to be provided, and allows receiver have an opportunity to provide speed control feedback to transmitter, and the above introduces this, and the below also will further describe.
In an example, AP periodically interts MIMO pilot tone (every at least TP millisecond, wherein, TP can be fixing or variable parameter) in its transmission.Each STA can begin the TXOP that it is subjected to poll with a MIMO pilot tone, and this MIMO pilot tone can be used for estimating channel by other STA and AP.For the transmission of using direct link agreement (below will further describe) to AP or another STA, the MIMO pilot tone can be guiding reference signal (steeredreference), so that the receiver that helps to simplify among the destination party STA is processed.
AP also can offer an opportunity to destination party STA, in order to allow it that ACK feedback is provided.Destination party STA also can use these feedback chances, and the speed control feedback of available MIMO pattern is provided to transmit leg STA.Such speed control feedback is not defined in tradition 802.11 systems that comprise 802.11 (e).Introduce the total amount (for every kind of MIMO pattern) that MIMO can improve rate control information.In some cases, for will be at improved maximum effect aspect the MAC efficient, these can replenish by strict speed control feedback.
Here by the agency of and what below will further describe is deposit (backlog) information and the scheduling of STA on the other hand.Each STA can begin its TXOP with a lead code, and the request duration of next TXOP is followed in this lead code back.This information purpose guiding AP.AP collects next request TXOP for information about from a plurality of different STA, and determines for next TDD mac frame interval TXOP duration distribution condition in the media.AP can use different priority or QoS rule, determines how to share these media, and perhaps it can come according to share these media from the request of STA proportionally with very simple rule.Can also adopt any other dispatching technique.TXOP distribution for next TDD mac frame interval is what to be assigned in the rear control channel message from AP.
The access point of appointment
Among the embodiment that here describes in detail, network can be supported real access point or not have operation in the situation of real access point.When having real AP, for example, it can be connected to wired extra heavy pipe road and connect (that is, cable, optical fiber, DSL or T1/T3, Ethernet) or home entertainment server.In this case, this real AP can be information source and the stay of two nights of most of data that equipment room flows in the network.
When not having real AP, a plurality of stations still can be used as enhanced distributed channel access of aforesaid distributed coordination function (DCF) or 802.11b/g/a or 802.11e etc. and mutually be communicated.What the below also will further describe is that when the needs additional resource, employing centralized scheduling scheme can use media more efficiently.For example, this network architecture may occur in the family, and wherein a lot of distinct devices (that is, DVD-TV, CD-Amp-Speaker etc.) need to communicate mutually.In this case, these network stations specify a station to serve as AP automatically.Should be noted in the discussion above that as described belowly, self adaptation coordination function (ACF) can be used by the access point by appointment, and can be at centralized scheduling, adopt in the situation of access, self-organizing communication or its combination in any at random.
Some non-AP equipment but not every non-AP equipment has the MAC ability of enhancing is so be suitable for as the AP of appointment and work.Should be noted in the discussion above that not all equipment all needs to be designed to have the AP MAC ability of appointment.When QoS (for example, secure time-delay), high-throughput and/when efficient was very important, an equipment in the network must be able to be supported the operation of the AP of appointment.
This means that the ability of the AP of appointment is associated with the equipment that possesses high ability usually, for example, has one or more attributes, such as line power (line power), a large amount of antenna and/or transmit/receive chains or high-throughput requirement.(additive factor for the AP that selects appointment below will be described in further detail).Therefore, low side devices such as low side camera or phone, do not need to possess the ability of the AP of appointment, and high-end equipment such as high-end video source or high definition video display, can possess the ability of the AP of appointment.
In not having the network of AP, the AP of appointment is bringing into play the effect of real AP, and can or can not have still less functional.In various embodiments, the AP of appointment can carry out following function: (a) establish network set of basic (BSS) ID; (b) by sending beacon and broadcast channel (BCH) network configuration information (BCH can define the media combination before next BCH), the network sequential is set; (c) use forward control channel (FCCH), by the transmission at the station in the network is dispatched, connect thereby manage; (d) management related (association); (e) for providing, QoS stream admits control; And/or (f) various other functions.The AP of appointment can realize complicated scheduler, the perhaps dispatching algorithm of any type.Can adopt simple scheduler, the below describes in further detail its example.
Below in conjunction with point to point link, describe improved physical layer convergence protocol (PLCP) header in detail, this also is applicable to the AP of appointment.In one embodiment, the PLCP header of all transmission sends with the master data speed that can be stood by all (AP that comprises appointment) decodes.The data reserve that comprises the place, station that is associated with certain priority or stream from the PLCP header of the transmission at a plurality of stations.Perhaps, it comprises a duration request for a rear transmission opportunity of certain priority or stream.
By " spying upon (snooping) " in the PLCP header of all station transmission, the AP of appointment can determine by the deposit of these station requests or transmission opportunity duration.Based on load, conflict or other congested indexs, the AP of appointment can determine portion of time is distributed to (distributed access) based on EDCA, and portion of time is distributed to uncompetitive poll (centralized) access.The AP of appointment can move a basic scheduler, and it distributes and the proportional bandwidth of request, and in uncontended periods it is dispatched.The scheduler that strengthens also is fine, but is not necessary.The transmission of process scheduling is by specifying AP at the enterprising announcement that works of CCH (control channel).
The AP of appointment does not need another station (that is, serving as springboard) is arrived in the transmission loopback (echo) at a station, but this function is also permitted.Real AP can possess loop-back capabilities.
When selecting the access point of appointment, can create a kind of hierarchical system, determine which equipment should serve as access point.Admissible example factors comprises following when selecting the access point of appointment: (a) user's configuration (over-ride); (b) higher preference grade; (c) safe class; (d) ability: line power; (e) ability: antenna amount; (f) ability: maximum transmission power; (g) based on the additional consideration (break a tie) of other factors: media access control (MAC) address; (h) equipment of first start; (i) any other factor.
In fact, the AP of appointment preferably is positioned at the center, and has best total Rx signal to noise ratio cumulative distribution function (SNR CDF) (that is, can receive all stations in the situation of good SNR).Usually, the antenna that station has is more, and receiving sensitivity is just better.In addition, the AP of appointment can have higher transmitting power, thereby so that the AP of this appointment can be listened to by a large amount of stations.When adding the station and/or station when mobile, can assess these attributes, and utilize them, so that network can dynamically reconfigure.
If network configuration has the AP of a real AP or an appointment, then can support point-to-point to connect.Next joint will be described point-to-point in detail and connect.In one embodiment, can support two types point-to-point to connect: (a) managed point-to-point connects, and wherein, AP dispatches the transmission that each station participates in; (b) connection of self-organizing, wherein, AP do not participate in standing management or the scheduling of transmission.
The AP of appointment can set the mac frame interval, and sends a beacon when frame begins.Broadcasting and control channel can be specified the duration of having distributed in the frame that allows the station send.Asked the station (for AP, these requests are known) that transmission distributes concerning point-to-point for those, AP can provide through the dispensing section of scheduling.AP can announce these dispensing sections in control channel, for example, and in each mac frame.
Alternatively, AP can also be included in A-TCH (self-organizing) section in this mac frame (below will be elaborated to this).Whether exist A-TCH to indicate at BCH and FCCH kind in the mac frame.In A-TCH, stand and to carry out point to point link with the CSMA/CA process.Can revise the CSMA/CA process of IEEE WLAN standard 802.11, to get rid of the at once requirement of ACK.Rob when accounting for channel when a station, this station can send a MAC-PDU (protocol Data Unit), and it comprises a plurality of LLC-PDU.One stands in the maximum duration that can take among the A-TCH and provides in BCH.For the LLC through confirming, can according to required application delay, window size and maximum affirmation be postponed to hold consultation.Describe improved mac frame in detail below in conjunction with Figure 20, it has the A-TCH section, can be used for real AP and the AP of appointment.
In one embodiment, non-guiding (unsteered) MIMO pilot tone can make all stations understand they self and dispatching station between channel.In some cases, this is useful.In addition, the AP of appointment can use non-guiding MIMO pilot tone, to carry out channel estimating and to be convenient to carry out the demodulation of PCCH, then can therefrom derive distribution.In case the AP of appointment receives all requested distribution in the frame of a special MAC, then it can be dispatched them for follow-up mac frame.Should be noted in the discussion above that rate control information needn't be included among the FCCH.
In one embodiment, scheduler can be carried out following operation: at first, for next mac frame, scheduler is collected all requested dispensing sections, and calculates total requested dispensing section (Total Requested).The second, scheduler calculates the total available resources (Total Available) that can distribute to F-TCH and R-TCH.The 3rd, if Total Requested, then uses the ratio of being determined by Total Available/Total Requested greater than TotalAvailable, all requested dispensing sections are carried out convergent-divergent.The 4th, for less than dispensing section behind any convergent-divergent of 12 OFDM symbols, these dispensing sections are increased to 12 OFDM symbols (like this in this exemplary embodiment, but the embodiment that replaces can use different parameters).The 5th, in order to hold the dispensing section of gained in F-TCH+R-TCH, by reducing in a looping fashion all dispensing sections greater than 12 OFDM symbols, from maximum, next symbol can hold any extra OFDM symbol and/or guard time.
An example can illustrate above-described embodiment.Consider following distribution request: 20,40,12,48.So, Total Requested=120.Suppose Total Available=90.Suppose that more required guard time is 0.2 OFDM symbol.Therefore, as described in the 3rd top operation, the dispensing section behind the convergent-divergent is: 15,30,9,36.As described in the 4th top operation, dispensing section 9 is increased to 12.According to the 5th operation, with amended dispensing section and guard time addition, the total allocation section is 93.8.This means that dispensing section will reduce by 4 symbols.From maximum, once remove a symbol, thereby determine that final dispensing section is 14,29,12,34.(that is, altogether 89 symbols and for the protection of 0.8 symbol of time)
In one exemplary embodiment, when having appointment AP, it can be set up the beacon of BSS and the network sequential is set.A plurality of equipment are associated with the AP of this appointment.When needing a QoS to be connected with two equipment of specifying AP to be associated, for example, have the HDTV link of low delay and high-throughput requirement, so, they provide operational indicator to this appointment AP, in order to admit control.This appointment AP can admit or refuse this connection request.
If the media utilance is enough low, then can use CSMA/CA, reserve the whole duration of media between beacon, be used for the EDCA operation.If EDCA operation operation is smooth and easy, for example, do not have excessive conflict, keep out of the way and postpone, then this appointment AP needn't provide coordination function.
The AP of appointment can continue to monitor the media utilance by the PLCP header of monitoring station transmission.According to the observation to media, and storage level or the request of transmission opportunity duration, specify AP can determine when the satisfied required QoS that permits stream of EDCA operation.For example, it can observation station the storage level of report and the trend of duration of asking, and based on the stream of permitting, itself and desired value are compared.
When the AP of appointment determined not satisfy required QoS in distributed access situation, it can convert the operation on the media to the operation with poll and scheduling.The latter provides and has more deterministic time-delay and higher throughput efficiency.The below will describe the example of this operation in detail.
Therefore,, can convert adaptively scheduling (centralized) to from EDCA (distributed access mechanism) and operate from the transmission opportunity request of dispatching station with will ask and permit QoS stream and carry out comparison by observation media utilance, conflict, congested and observation.
As previously mentioned, described therein among any embodiment that the application of access point describes in detail, it will be appreciated by those skilled in the art that this embodiment can adapt to and real access point arranged or specifying in the situation of access point and work.Just as describe in detail here like that, can adopt and/or select one to specify access point, this appointment access point can be according to any agreement work, comprises the agreement do not mentioned among the application or any combination of various protocols.
Point-to-point transmission and direct link agreement (DLP)
As mentioned above, point-to-point (or referred to as " point-point ") transmission makes a STA directly send data to another STA, and needn't send the data to first AP.Here the various aspects of describing in detail can be used to the point-to-point transmission.In one embodiment, can revise direct link agreement (DLP), as described below.Figure 17 shows an exemplary point to point link in the system 100.System 100 in this example is similar to system shown in Figure 1 100, and it is through revising, and can realize the direct transmission (in this embodiment, show between UT 106A and the UT 106B transmission 1710) from a UT to another UT.UT 106 can pass through WLAN 120, directly communicates with AP 104, will be described in greater detail here.
In various exemplary embodiments, can support two types a point-connection: (a) managed point-connection, wherein, AP dispatches the transmission that each STA participates in; (b) point of a self-organizing-connection, wherein, AP does not participate in management or the scheduling of STA transmission.An embodiment can comprise the one or both of these two kinds of connections.In one exemplary embodiment, the signal that sends can comprise: a part, and it comprises the public information that can be received by one or more stations (also may comprise access point); And, carried out specially format so that by information that point-receiving station receives.Public information can be used for scheduling and (for example, as shown in figure 25), perhaps is used for competition by various neighbor stations and keeps out of the way (for example, as shown in figure 26).
The various exemplary embodiments that the below describes in detail introduce a little-the closed loop rate control of a connection.Can adopt this speed control, take full advantage of available high data rate.
For ease of explanation, do not describe various functions (that is, confirming) in the exemplary embodiment in detail.It will be recognized by those skilled in the art that function disclosed herein can combine, thereby in different embodiment, form set or the subclass of any amount.
Figure 18 shows the physical layer bursts 1800 of prior art.Can send first lead code 1810, the back is a physical layer convergence protocol (PLCP) header 1820 and then.802.11 traditional system definitions a kind of PLCP header, comprise speed type and modulation format, be used for as data symbol 1830 and the data of transmission.
Figure 19 has provided an exemplary physical layer bursts 1900, and it can be used for a little-transmission.As Figure 18, lead code 1810 and PLCP header 1820 are includable, and what follow later is the point that is marked as P2P a 1940-transmission.P2P 1940 can comprise the MIMO pilot tone 1910 of being used by recipient UT.MIMO Rate Feedback 1920 is also includable, so that used in the transmission in future that sends back to transmit leg UT by recipient UT.Rate Feedback can generate in response to last transmission from the receiving station to the dispatching station.Then, data symbol 1930 can send according to selected rates and the modulation format of a point-connection.Should be noted in the discussion above that physical layer bursts, such as PHY burst 1900, can be used for the point of an AP management-connection, and the point of a self-organizing-transmission.The Rate Feedback embodiment of following detailed description exemplary.The below also comprises the embodiment of the replacement of the physical layer transmission burst that comprises these aspects.
In an exemplary embodiment, AP sets TDD mac frame interval.Can indicate the duration of having distributed in the TDD mac frame interval with broadcasting and control channel.For having asked a point-STA that transmission distributes (be known for AP), AP can provide the distribution through scheduling, and announces them in each TDD mac frame interval in control channel.Top Figure 15 has provided an exemplary system.
Figure 20 shows an exemplary embodiment at TDD mac frame interval 2000, and it comprises an optional self-organizing section, is identified as A-TCH 2010.Can comprise the part identical with top numbering described in conjunction with Figure 15 in the TDD mac frame interval 2000.Can indicate among BCH1510 and/or the CCH 1520 in the TDD mac frame interval 2000 and whether have A-TCH 2010.During A-TCH 2010, STA can carry out point to point link with any competition process.For example, can use 802.11 technology, such as the SIFS, the DIFS that describe in detail above, back off time etc.Also can use the QoS technology, such as those (that is, AIFS) technology of introducing among 802.11 (e).Can also use various other schemes based on competition.
In one exemplary embodiment, be used for the CSMA/CA process of competition, for example, the process that is defined in 802.11 can be carried out following modification.Do not need ACK at once.When robbing when accounting for channel, a STA can send and comprise that a plurality of PDU are (that is, LLC-PDU) at interior Medium Access Control (MAC) Protocol Data Unit (MAC-PDU).Can indicate STA shared maximum duration in A-TCH among the BCH.When hope during through the transmission confirmed, can be according to required application delay, consult window size and maximumly confirm to postpone.
In this embodiment, F-TCH 1530 is the parts at TDD mac frame interval, is used for the transmission from AP to STA.In A-TCH 2010, can carry out the point to point link of the use competition technology between the STA.In R-TCH 1540, can carry out the point to point link of the scheduling between the STA.In these three sections any one can be made as sky.
Figure 21 has provided an exemplary physical layer bursts 2100, is also referred to as " PHY burst ".PHY 2100 point that the can be used for dispatching-connection that happen suddenly, for example during R-TCH 1540, or during the self-organizing such as A-TCH 2010 connected, the above described in detail this in conjunction with Figure 20.PHY burst 2100 comprises non-guiding MIMO pilot tone 2110, reciprocity Common Control Channel (PCCH) 2120 and one or more data symbol 2130.Non-guiding MIMO pilot tone 2110 can receive at place, one or more stations, and, can be by receiving station with the respective channel of estimating between dispatching station and the receiving station for referencial use.This exemplary PCCH comprises following field: (a) destination party MAC-ID; (b) for the distribution request of transmitting continuous time of expection at next TDD mac frame interval; (c) transmission rate designator is used to indicate the transformat that current data is divided into groups; (d) (that is, CCH) subchannel is used for receiving any distribution from AP to control channel; And (e) CRC.PCCH 2120 and non-guiding MIMO pilot tone 2110 are common segment, so can be received by various monitoring stations (comprising access point).Can in PCCH, insert and distribute request, so that in the TDD in future mac frame interval, realize a managed point-connection.Such PHY burst can be included in the self-organizing connection, and, still can ask the point-to-point of the scheduling in following TDD mac frame interval to connect.In this exemplary embodiment, non-guiding MIMO pilot tone is 8 OFDM symbols (among the embodiment that replaces in the following detailed description of, less symbol just is enough to realize channel estimating), and PCCH is two OFDM symbols.In common segment (comprising non-guiding MIMO pilot tone 2110 and PCCH2120) afterwards, use spatial reuse and/or the higher modulation form determined by each STA in the point-connection, send one or more data symbols 2130.The rate control information that embeds in the data division of this part of transmission according to transmission is encoded.Therefore, the part of PHY burst 2100 can be received by a plurality of peripheries station, and actual data have been passed through special finishing, so that high efficiency of transmission is to station or the AP of an one or more specific points-connection.Data 2130 can as access point distribute send or, connect according to self-organizing and to send the process of CSMA/CA competition (that is, based on).
An exemplary embodiment of PHY burst comprises a lead code, and this lead code is made of 8 OFDM symbols of non-guiding MIMO reference.Equity Common Control Channel (PCCH) MAC-PDU header is included in 2 follow-up OFDM symbols, has used the STTD pattern, encodes with R=1/2BPSK.MAC-ID is 12 bits.Also comprise the distribution request of 8 bits, so that by receiving (therefore, largest request is 256 short OFDM symbols) in the expected duration of AP in next TDD mac frame interval.TX speed is 16 bits, is used to indicate the speed of using in the current group.FCCH subchannel preference is two bits, and corresponding to the preference between maximum four sub-channels, based on this, AP makes any applicable distribution.CRC is 10 bits.Any amount of other fields and/or field size can be included among the PHY burst embodiment of replacement.
In this embodiment, the spatial reuse determined by each STA in the point-connection and the modulation of Geng Gao are used in remaining MAC-PDU transmission.This part of this transmission is to encode according to the rate control information that embeds in the data division that transmits.
Figure 22 has provided the defeated illustrative methods 2200 of point-point data.In frame 2210, flow process begins, and wherein, a station sends non-guiding MIMO pilot tone.In frame 2220, this station sends the information that can jointly decode.For example, non-guiding MIMO pilot tone 2110 be connected an example of the mechanism that request distributes in managed connection with PCCH2120, and AP or other control stations needs can be decoded to the signal section that comprises this request.Those skilled in the art can recognize to also have the request mechanism of countless replacements, be used on shared channel a point-connection being dispatched.In frame 2230, according to the transformat that consults, data are sent to another station from a station.In this embodiment, guiding data is to use the determined speed of measurement result and parameter according to non-guiding MIMO pilot tone 2110 to send.Those skilled in the art can recognize to also have the means of multiple replacement to can be used to be sent as a concrete point-channel and the data of special finishing.
Figure 23 shows a kind of illustrative methods 2300 of point to point link.This illustrative methods 2300 has provided many aspects, and the part of these aspects can be used in any specific embodiment.In decision box 2310, flow process begins.In decision box 2310, if there are data will carry out the STA-STA transmission, then enter decision box 2320.If no, then enter frame 2370, carry out the communication of any other type, comprise other access styles (if any).Enter frame 2360, flow process can be returned decision box 2310 and carry out repetition, and perhaps, flow process can finish.
In decision box 2320, if there are the STA-STA data to transmit, then judge this a point-connection be scheduling or self-organizing.If this transmission is dispatched, then enter frame 2330, and ask to divide to be equipped with to win a TXOP.Should be noted in the discussion above that to send in the at random access part of TDDMAC frame period as mentioned above and distribute request, perhaps, it can be included in the self-organizing transmission.In case make distribution, just can in frame 2350, send a STA-STA physical burst.In one exemplary embodiment, method 2200 can be used for class STA-STAPHY burst.
In decision box 2320, if do not wish the point a dispatched-connection, then enter in the frame 2340, so that contention access power.For example, can use 2010 sections of the A-TCH at TDD mac frame interval 2000.When by compete successfully win access right after, enter frame 2350, and send STA-STA PHY burst, as mentioned above.
Enter decision box 2360 from frame 2350, wherein, flow process can repeat, and as mentioned above, perhaps, can stop.
Figure 24 shows a kind of illustrative methods 2400 that Rate Feedback is provided, and is used for a point-connection.Other steps that the figure shows various transmission and can be carried out by two station STA 1 and STA 2.STA 1 sends a non-guiding pilot tone 2410 to STA 2.STA 2 measures channel 2420 when receiving non-guiding pilot tone 2410.In one exemplary embodiment, but STA 2 determines the supporting rate of the transmission on the measured channels.This speed is determined that the result sends to STA 1 as Rate Feedback 2430.In the embodiment of various replacements, can transmit other parameters, judge so that in STA 1, make Rate Feedback.In 2440, STA 1 receives the distribution through scheduling, and perhaps contention transmission opportunities is for example in A-TCH.In case won transmission opportunity, in 2450, STA 1 just with according to Rate Feedback 2430 determined speed and modulation formats, sends data to STA 2.
Method shown in Figure 24 can be promoted the use of among the various embodiment, this is apparent to those skilled in the art.The below will describe in further detail, and a bit integrated-point velocity feeds back and more otherwise examples.
Method 2500 among Figure 25 shows managed point between two stations STA 1 and STA 2 and access points (AP)-connection.In 2505, STA 1 sends non-guiding pilot tone, and distributes request.Also can send data according to early distribution and previous Rate Feedback, the below will be explained.In addition, the Rate Feedback according to communicating by letter from the self-organizing of a previous managed point-connection or next free STA 1 or STA 2 initiations can send any such data.STA 2 and access point all can be received non-guiding pilot tone and transmission request (can be received by various other stations in this zone).
Access point is received transmission request, and a kind of according in the multiple dispatching algorithm, determines when and whether make distribution for point to point link.STA 2 measures channels, and in 2505, non-guiding pilot tone is sent out away simultaneously, but and STA 2 can determine to carry out with STA 1 supporting rate of point to point link.Alternatively, STA 2 also can according to front once transmission, receive feedback and/or data from STA 1.
In this embodiment, access point has been determined and will have been distributed for the transmission of asking.In 2515, a distribution is transferred to STA 1 from access point.In this embodiment, the distribution of R-TCH 1540 is transmitted in control channel (CCH 520 described above).Equally, in 2520, for STA 2, make the distribution on the R-TCH.In 2525, STA 1 receives the distribution from access point.In 2530, STA 2 receives the distribution from access point.
In 2535, according to distributing 2520, STA, 2 transmission rates feedback.Alternatively, can comprise the request of aforesaid transmission for dispatching, and any data that will send according to last request.As mentioned above, the Rate Feedback of transmission is selected according to channel measurement 2510.2535 PHY burst also can comprise non-guiding pilot tone.In 2540, the channel that STA 1 measures from STA 2 receives feedback, and can receive optional data.
In 2545, according to distributing 2515, STA 1 to send data according to the Rate Feedback information of receiving.In addition, for the distribution in future, can make request, and according to the channel measurement result in 2540, provide Rate Feedback.Data are that the concrete channel measurement result according to point to point communication sends.In 2550, STA 2 receive datas, and, any speed control that sends alternatively.STA 2 also can measure channel, so that provide Rate Feedback for transmitting future.
Should be noted in the discussion above that transmission 2535 and 2545 all can be access in a little and receives, is that non-targeting part can be received, as mentioned above at least.Therefore, for any request that comprises, access point can provide the additional allocation for the transmission in future, respectively by the distribution 2555 of mailing to STA 1 and STA 2 and 2560 expressions.In 2565 and 2570, the distribution that STA 1 and STA 2 receive separately.Then, this flow process ad infinitum repeats, wherein, the access on the access point management shared medium, STA 1 and STA 2 directly send point to point communication mutually according to supported selected speed and modulation format on the point-channel.Note that in the embodiment that replaces, also can carry out the self-organizing point to point communication, also carry out simultaneously managed point to point communication as shown in figure 25.
Figure 26 shows (or, the self-organizing) point-connection based on competition.STA 1 and STA2 communicate mutually.Other STA also can be in the range of receiving, and can access shared channel.In 2610, the STA 1 that has data will send to STA 2 monitors shared channel, and contention access power.In case won transmission opportunity, just a point-PHY burst 2615 is sent to STA 2, PHY burst 2615 also may be received by other STA.In 2620, other STA of supervision shared channel may receive the transmission from STA 1, and the old friend avoids in the road accessing this channel.For example, above-described PCCH can be included in the transmission 2615.In 2630, STA 2 measures channel according to PHY 2615 pilot tones that happen suddenly, and the return access on the competition shared channel.STA 2 also can send data as required.Notice that the competition time can change.For example, in traditional 802.11 systems, after SIFS, can return an ACK.Because SIFS priority is the highest, so STA 2 can make response in the situation of not losing channel.Different embodiment can allow lower delay, and can provide high priority for return data.
In 2635, STA 2 is to STA 1 transmission rate feedback and optional data.In 2640, STA 1 receiving velocity feedback is competed the access right to shared channel again, and in 2645, according to the Rate Feedback of receiving, to STA 2 transmitted signals.In 2640, STA 1 can also measure channel, so that be provided for the Rate Feedback of following transmission to STA 2, and can receive any optional data that is sent out by STA 2.In 2650, speed and modulation format that STA 2 determines according to measured channel conditions, receive data transmission 2645.STA 2 also can feed back by receiving velocity, to be used for returning a transmission to STA 1.STA 2 also can measure channel, so that following Rate Feedback to be provided.Therefore, get back in 2635, allow STA 2 return Rate Feedback and data, this flow process can repeat.
Therefore, self-organizing communication can be carried out by contention access power in two stations two-wayly.Transmission by using Rate Feedback and special finishing to mail to receiving station, make a little-connection itself is very efficient.But when using the public receiving unit (such as PCCH) of PHY burst, so, shown in 2620, other STA can access this information, and cause interference at channel in the known holding time of avoiding showing in PCCH.As shown in figure 25, before step shown in Figure 26, point to point communication managed or self-organizing can be initiated transfer of data, and, can be used for proceeding subsequently point to point communication.Therefore, can use any combination scheduling and point to point communication self-organizing.
Figure 27 has provided an exemplary TDD mac frame interval 2700, is used for the managed point to point communication between the explanation station.In this embodiment, F-TCH and A-TCH duration all are set as 0.Beacon/BCH 1510 and CCH 1520 transmissions the same as before.Beacon/BCH1560 represents the beginning of next frame.CCH 1520 indicates the distribution for point to point communication.Distribute according to these, during the burst 2710 that has distributed, STA 1 is to STA 2 transmitted signals.Note that in identical TDD mac frame interval STA 2 distributes the section of obtaining 2730, be used for STA 1 is made response.Can comprise above-mentioned various compositions in the arbitrary specific point-PHY layer burst, such as Rate Feedback, request, guiding and/or non-guiding pilot tone, guiding and/or non-guiding data.Distributing in 2720, STA 3 is to STA 4 transmitted signals.Distributing in 2740, STA 4 in a similar manner, to STA 3 transmitted signals.Can comprise various other rl transmission among the R-TCH, comprise a non-point-connection.The below further provides the additional exemplary embodiment of these and other aspects of explanation in detail.
Note that in Figure 27, as required, can dispatch the protection interval between the section.A major issue about point to point communication is, generally, be unknown path delay between two STA.To this, a kind of processing method is, allows each STA keep its transmitting time to fix, thereby makes the clock of they and AP synchronizedly arrive AP.In this case, AP can provide guard time at the two ends that each point-to-point distributes, to compensate the unknown path delay between two STA in the communication.Under many circumstances, Cyclic Prefix will be enough, and needn't adjust at STA receiver place.Then, STA must determine their time migrations separately, so that know the transmission that when receives other STA.The STA receiver may need to keep two receive clocks: one is used for AP frame sequential, and another is used for a point-connection.
As top various embodiment were described, receiver can obtain confirming and channel feedback within it distributes, and feed back to transmitter.Even if total Business Stream is unidirectional, receiver also can send reference and request distributes with acquisition.The AP scheduler is guaranteed to provide enough resources for feedback.
With traditional station and the interoperability of access point
Just as describing in detail here, described various embodiment provide the improvement with respect to legacy system.But because legacy system extensively existed already, a system preferably can keep backward compatibility with existing legacy system and/or legacy user terminals.Term used herein " novel " is used for distinguishing with traditional system.The system of newtype can be integrated with one or more aspects or the feature of describing in detail here.An exemplary novel system is to describe the MIMO ofdm system below in conjunction with Figure 35-52.In addition, the below describes in detail is used for making the aspect of novel system and legacy system interoperability also be applicable to other still systems leaved for development, and no matter whether comprise any particular refinement of detailed description here in this system.
In an exemplary embodiment, distribute (FA) by using different frequencies, can keep backward compatibility with other system, thereby a novel system is worked at the FA different from the legacy user.Therefore, novel system can be searched for the available FA that works thereon.Dynamic frequency selection (DFS) algorithm can be implemented in this New WLAN to realize this function.Preferably adopt the AP of multicarrier.
The traditional STA that attempts to access WLAN can adopt two kinds of scan methods: active scan and drive sweep.In the situation of drive sweep, by the scanning work frequency band, STA obtains near the tabulation of the feasible set of basic (BSS) it.In the situation of active scan, STA sends an inquiry, with the response of request from other STA among the BSS.
Traditional standard does not relate to the STA how to confirm and adds which BSS, still, in case make a decision, just can attempt carrying out association.If unsuccessful, STA will move by its BSS tabulation, until success.When a traditional STA can't understand the beacon message that sends, this STA can not attempt to be associated with a New WLAN.But, keeping the method for single WLAN type as a kind of at single FA, a novel AP (and UT) can ignore the request from traditional STA.
A kind of technology of replacement is, allows new A P or New type of S TA use effectively tradition (that is, 802.11) message delivery techniques, refuses the request of any traditional STA.If a legacy system is supported this message delivery techniques, then can provide redirect message for this tradition STA.
To support the frequency spectrum that two types STA need to add from the obvious drawback that is associated of working at different FA.A benefit is, is convenient to manage different WLAN, kept such as functions such as QoS.But, just as describing in detail among the application, for as the high data rate supported of the novel system of the mimo system embodiment that describes in detail here, traditional CSMA MAC agreement (such as, those agreements of describing in detail in traditional 802.11 standards) is usually efficient not.Therefore, preferably adopt the mode of operation of backward compatibility, so that novel MAC coexists at identical FA with traditional MAC.Several exemplary embodiments are described below, and wherein, tradition can be shared identical FA with novel system.
Figure 28 shows method 2800, be used for identical frequency divide mix support tradition and novel station the two.In this embodiment, for ease of explanation, suppose BSS work (that is, between a plurality of overlapping BSS less than coordination) isolatedly.Flow process starts from the frame 2810, establishes a uncontended periods with traditional signaling.
The below is the several illustrated examples for traditional 802.11 systems, and wherein, New WLAN AP can reserve time by the special use of novel station with built-in hook in traditional 802.11 standards.In addition, for various types of legacy systems, can establish a uncontended periods with any amount of other signaling technologys.
A kind of technology is to establish uncontended periods (CFP) under the PCF/HCF pattern.AP can establish a beacon interval, and announces a uncontended periods in this beacon interval, and wherein, it can provide service for novel and traditional STA under poll pattern.This is so that the duration of the CFP that all traditional STA are arranged to its network allocation vector (NAV) to announce, and network allocation vector is the counter of following the tracks of CFP.So, in CFP, receive that traditional STA of this beacon must not use channel, unless by the AP poll.
Another kind of technology is by RTS/CTS and duration/id field, establishes CFP and NAV is set.In this case, this new A P can send a specific RTS with reservation address (RA), and this RTS shows that to all New type of S TA this AP is reserving this channel.Traditional STA resolves to this RA field and points to a specific STA, and does not make response.Novel STA makes response with a specific CTS, thereby, remove BSS in the time period that in the duration/id field of CTS/RTS message pair, provides.At this point, channel can freely be used in novel station within the reservation duration, and not conflict.
In frame 2820, received the STA wait for the traditional type of the signal of establishing uncontended periods, until polled or uncontended periods end.Like this, access point has become distribution of work shared medium uses for novel MAC agreement.In frame 2830, new STA can access according to this agreement.Any set or the subset of the aspect that describes in detail here may be used in a kind of so novel MAC agreement.For example, can adopt forward direction and the rl transmission of scheduling, and, managed point-some the transmission, self-organizing or based on the competition communication (comprising a little-point), perhaps, the combination in any of above-mentioned transmission.In frame 2840, use any in the multi-signal type, finish novel access period, signal type can change according to the legacy system that adopts.In this exemplary embodiment, send a uncontended periods end signal.In an alternative embodiment, in uncontended periods, also can poll tradition STA.Such access can after novel access, perhaps, can intert therein.
In frame 2850, if stipulated a competing cycle for legacy system, then all STA can contention access power.The legacy system that in uncontended periods, can not communicate like this, the request of just can sending and/or attempt transmitted signal.In decision box 2860, this flow process can be continued by turning back to frame 2810, perhaps, also can stop.
Figure 29 shows the combination of tradition and new media access control.Provided traditional MAC agreement 2910 in novel agreement 2930, when these two combines, just formed a MAC agreement, such as the MAC agreement 2950 after the combination.In this embodiment, for purpose of explanation, 802.11 traditional signaling message have been used.It will be recognized by those skilled in the art that technology disclosed herein also is applicable to any and any novel MAC agreement in the multiple legacy system, comprises the combination of function disclosed herein.
Note that in CFP 2904 traditional STA should not disturb any New WLAN transmission.AP can be in CFP any traditional STA of poll, thereby in this section, allow to carry out mixed mode operations.In addition, AP can reserve whole CFP 2904 for novel use, and all traditional businesses is pushed to competing cycle (CP) 2906 when beacon interval finishes.
These exemplary 802.11 traditional standards need CP 2906 to look is enough to support two exchanges between the conventional terminal.So, can adopt beacon, but this can cause the time jitter (time jitter) in the system.If necessary, in order to reduce shake, can shorten the CFP interval, thereby keep fixing beacon interval.Can be provided for establishing the timer of CFP and CP, so that CFP (that is, about 1.024 seconds) is longer than CP (that is, less than 10 milliseconds).But if AP poll conventional terminal during CFP, then the duration of their transmission may be unknown, and may cause extra time jitter.Therefore, in the time of on traditional STA being contained in identical FA, must be noted that to keep the QoS of New type of S TA.802.11 traditional standards are synchronized to 1.024 milliseconds time quantum (TU).In this embodiment, adopt the mac frame duration of 2TU or 2.048 milliseconds, novel MAC can be designed to legacy system synchronous.
In some embodiments, preferably guarantee to make novel mac frame synchronous.That is to say that the mac frame clock of system can be continuous, and when sending, this mac frame border starts from the integral multiple of 2.048 milliseconds of frame periods.Like this, be easy to keep the sleep pattern of STA.
Novel transmission does not need with conventional transmission compatible.Header, lead code etc. can be distinctive for novel system, and their example runs through among the application to be described in detail.Tradition STA can attempt its demodulation, but can't correctly decode.Traditional STA under the sleep pattern can not be affected usually.
Figure 30 shows the method 3000 that obtains transmission opportunity.Method 3000 can be as the frame 2830 in the exemplary embodiment of aforesaid method 2800.This flow process starts from decision box 3010, and wherein, access can be dispatched, or non-scheduled type.It will be recognized by those skilled in the art, although this example shows two types access, in any specific embodiment, can support in these two kinds of access styles one or both of.In decision box 3010, if expect the access of non-scheduled type, then enter frame 3040, thus contention access power.Can use any amount of access technology based on competition.In case obtained transmission opportunity (TXOP), then in frame 3050, sent according to this transmission opportunity.Then, flow process can finish.
In frame 3010, if the access of expectation scheduling then enters frame 3020, with the request access.This access request can be made in Random Access Channel during Self-organizing Competition, perhaps, uses any other technology disclosed herein.In frame 3030, after granting this access request, will receive a distribution.Enter in the frame 3050, according to the distribution of receiving, send TXOP.
In some cases, preferably use overlapping traditional B SS, in identical frequency is distributed, between new A P and the BSS that is associated thereof, realize interoperability.Traditional B SS can be operated under DCF or the PCF/HCF pattern, so between novel B SS and the traditional B SS may not be to reach synchronously.
If traditional B SS is operated under PCF or the HCF pattern, then new A P can attempt to be synchronized to TBTT.If this is possible, then new A P can use various mechanism to occupy channel in competing cycle, so that be operated in the overlapping BSS zone, the above has made description to the example of described mechanism.If traditional B SS is operated under the DCF, then new A P also can attempt to occupy channel, and announces a CFP, to remove channel.
Under some occasion, some or all STA among the traditional B SS may can not receive new A P transmission.In this case, these traditional STA may disturb the operation of New WLAN.For fear of this interference, novel station can be given tacit consent to based on CSMA operation, and relies on a point-transmission (following also in connection with Figure 33-34 it is described in further detail).
Figure 31 shows a kind of exemplary method 3100, so that a plurality of BSS shares single FA.In frame 3110, traditional access point sends a beacon.The novel access point of sharing identical frequency assignments can be synchronized to the TBTT (optionally) that is associated with this beacon.In frame 3120, if traditional uncontended periods stipulate according to this beacon, then carry out it.In case uncontended periods (if any) finishes, then all STA just can weigh by contention access in the competing cycle of regulation.In frame 3130, novel access point is contention access power in competing cycle.In frame 3140, New type of S TA can access shared medium in novel access point has been competed time of access right.Access style during this novel access can comprise to be described in detail aspect any one here.Can use the multiple technologies as describing in detail above, indicate the time quantum of this access point channel reservation to traditional STA.In frame 3150, in case this end cycle, then traditional STA just can compete.In decision box 3160, this flow process can continue by turning back in the frame 3110, perhaps, can finish.
Figure 32 shows the overlapping BSS that uses single FA.Legacy system 3210 sends beacon 3205 (there is shown 3205A and 3205B, be used for TBTT and total beacon interval of explanation legacy system).Beacon 3205A identifies uncontended periods 3210 and competing cycle 3215.In uncontended periods 3210, can carry out traditional contention free-poll 3220A-N, what follow later is the end indicator 3225 of uncontended periods.
Station monitoring channel in the New WLAN 3240 receives beacon 3205, and gains control of oneself and do not access media, until the chance of contention access power is arrived.In this embodiment, the earliest chance is in uncontended periods.After PIFS 3230, novel access point sends a classical signal 3245, to indicate the time quantum with busy channel to the tradition station.Multiple symbol can be used to carry out this function, and their example is described in detail in the above.Can adopt various other signals, this depends on expectation and which legacy system realization interoperability.Traditional STA in the range of receiving of classical signal 3245 can avoid accessing channel, until novel access period 3250 finishes.Cycle 3250 comprises one or more TDD mac frames interval 3260 (in this embodiment, being 3260A-N).TDD mac frame interval 3260 can be any type, and its example comprises one or more aspects of describing in detail here.
In an exemplary embodiment, new A P occupies channel (that is, in per 40 milliseconds, 20 milliseconds of new A P busy channels) in the interval of fixed length.New A P can keep a timer, guaranteeing its only busy channel in expected duration, thereby guarantees the fairness of Channel Sharing.In seizing the process of channel, new A P can use any signaling technology.For example, can send CTS/RTS or conventional beacon, announce new CFP.
In novel interval 3250, exemplary TDD mac frame interval can be as giving a definition: at first, send a beacon and add F-CCH, this F-CCH indicate will be in current mac frame UT in the tabulation of poll.Behind F-CCH, broadcast one section MIMO pilot tone, so that STA obtains the accurate tolerance result of mimo channel and formation mimo channel.In one exemplary embodiment, each antenna can be realized fabulous performance with 2 short OFDM symbols.This means that the F-TCH in the initial mac frame comprises 8 MIMO frequency pilot signs substantially.The R-TCH part of the first mac frame can be constructed such that the STA on the polling list sends non-guiding MIMO pilot tone and rate indicator (being used for down link) to AP, and confirms.In this embodiment, at this point, all terminals on the polling list are prepared to be operated under the normal consistency type mode in next TDD mac frame interval.After this, under the coordination of AP, use any technology disclosed herein, the TDD mac frame interval after the TDD mac frame interval can be used for swap data.
As mentioned above, under specific circumstances (for example, when some or all STA among the traditional B SS can not receive new A P transmission), novel station acquiescence is based on the operation of CSMA, and a dependence point-transmission.At this moment, the circulation of above-described ON/OFF may not have advantage, perhaps or even impossible.In these cases, novel station can be given tacit consent to a little-point operation.
Figure 33 has provided a kind of illustrative methods 3300, and it uses various technology disclosed herein, carries out the high speed point to point communication, simultaneously with traditional B SS interoperability.Flow process starts from frame 3310, wherein, has data will issue the STA contention access power of the 2nd STA.In frame 3320, successfully compete access right after, classical signal is used at this station, those signals as described above are cleared up media.In frame 3330, a STA sends a request (with pilot tone) to the 2nd STA.The 2nd STA can according to the pilot tone that sends, measure channel.The 2nd STA sends to a STA with channel feedback.Therefore, in frame 3340, first stop is received the have channel feedback response of (for example, Rate Feedback).In frame 3350, according to this feedback, a STA sends pilot tone and guiding data to second station.In frame 3360, the 2nd STA can send to a STA and confirm, and can send follow-up Rate Feedback, to be used for other transmission.Be used for clearing up media classical signal so that: use any high speed technology and with respect to the improvement of legacy system, those technology are carried out frame 3330 to 3360 as disclosed herein.In protection scope of the present invention, in case STA has cleared up media, just can use an any point-MAC agreement.Shown in decision box 3370, by returning frame 3310, flow process can be continued, and perhaps flow process can finish.
In one exemplary embodiment, adopt point-dot pattern, seize channel and work according to the traditional rule of CSMA.In this embodiment, do not adopt PCF and HCF, and a centralized network architecture needn't be arranged.When a New type of S TA wishes that with another New type of S TA (or AP) this STA seizes channel when communicating.The first transmission comprises enough MIMO pilot tones, adds the message that a certain request connects.Can adopt CTS and RTS to come cut-back region and set aside some time.Requesting party STA message must comprise STA BSS ID, STA MAC ID and target STA MAC ID (if knowing).Response should comprise the BSSID of responder STA.Like this, these STA just can judge whether they need to carry out the receiver correction (if having used guiding) of emission guiding vector.Note that in this embodiment and to use emission guiding and nonessential, although if STA has used the appointment AP that coordinates BSS and calibrated, do like this and have superiority.
As shown in figure 33, response can comprise MIMO pilot tone (if adopt, lead) and adds speed and indicate.In case should exchange occur, just can be each link lead ().But if these STA belong to different BSS, the first guiding transmission of then initiating between the STA of this connection can comprise guiding MIMO pilot signal, so that the receiver of responder STA can be proofreaied and correct the phase difference value between the different B SS.
In this exemplary embodiment, in case initial exchange has occured, just can lead.These exchanges should be followed the SIFS interval between down link and the ul transmissions.Owing to calculate the potential processing delay for the characteristic vector that leads, this may need STA to use least mean-square error (MMSE) to process, rather than characteristic vector is processed.In case calculate guiding vector, STA just can begin at launch party's use characteristic vector, and the recipient can continue to adopt MMSE to process, and changes towards optimal spatial matched filter solution.Periodic feedback between two STA helps to follow the tracks of with speed to be controlled.Can follow the SIFS interval, so that allow STA keep control to channel.
Figure 34 shows point to point communication, and it uses MIMO technology, contention access on traditional B SS (that is, managed).In this embodiment, initiator 106A contention access power on channel.Successfully rob when accounting for channel when it, send MIMO pilot tone 3405, the back and then asks 3410 again.This message can comprise the MAC ID of BSS ID, initiator STA and the MAC ID (if known) of target STA.Other signalings such as CTS and RTS, can be used to further clear up channel.Responder STA 106B sends guiding pilot tone 3420, and the back is and then confirmed and Rate Feedback 3425.Guiding pilot tone 3420 sends when the SIFS 3415 that asks after 3410.In this exemplary embodiment, traditional access point is 802.11 access points, and SIFS has limit priority, and therefore, response station 106B keeps the control to channel.The various transmission that Figure 34 describes in detail can phase mutual edge distance SIFS and send, thereby keeps the control to channel, until point to point communication finishes.
In one exemplary embodiment, can determine the maximum duration of channel occupancy.Guiding pilot tone 3430 after Rate Feedback 3425 and data 3435 are sent to response station STA 106B according to this Rate Feedback from initiator STA 106A.After data 3435, responder STA 106B sends guiding pilot tone 3440 and affirmation and speed control 3445.As response, initiator 106A sends guiding pilot tone 3450, and data 3455 are followed in the back.
This flow process can ad infinitum continue, and perhaps reaches at most the maximum time that channel access allows, and this depends on deployment cycle.Although do not show that in Figure 34 responder STA also can send data, and initiator also can sending rate control.These data segments can combine with those sections shown in Figure 34, so that maximizing efficiency (that is, SIFS needn't be inserted between these transmission).
When two or more BSS were overlapping, preferably adopting can be with the mechanism of coordination mode shared channel.The below provides several exemplary mechanism and exemplary operational process associated with it.These mechanism can combine use.
The exemplary mechanism of the first is dynamic frequency selection (DFS).Before establishing a BSS, WLAN need to search for this wireless medium and determine best frequency distribution (FA), so that establish the operation of BSS.In the process of search candidate FA, AP also can create neighbor list so that be redirected and AP between switch.In addition, WLAN can carry out mac frame sequential and neighbours BSS (below will further specify) synchronously.Can distribute BSS with DFS, synchronisation requirement minimizes between BSS thereby make.
The exemplary mechanism of the second is synchronous between BSS.In the DFS process, AP can obtain the sequential of neighbours BSS.Usually, preferably make all BSS (in one embodiment, on single FA, perhaps, in another embodiment, striding across a plurality of FA) synchronous, so that carry out switching between BSS.But, adopt this mechanism, work and synchronous its mac frame of approximating those BSS at identical FA at least.In addition, if be total to channel BSS overlapping (that is, AP can listen to the other side each other), then can there be it in newly arrived AP situation to inform original AP, and following formulation Resource Sharing Protocol.
The third exemplary mechanism is Resource Sharing Protocol.Overlapping BSS shared channel coequally on same FA.Mac frame is replaced between BSS according to certain predetermined way, thereby realize this point.Like this, the business among each BSS just can be used channel, and can not emit the risk of being disturbed by other BSS.Shared can be implemented between two overlapping BSS like this.For example, in the overlapping situation of 2 BSS, an AP uses the mac frame of even-numbered, and another AP uses the mac frame of odd-numbered.In the overlapping situation of 3 BSS, share and to realize for mould with 3.The embodiment that replaces can adopt the shared mechanism of any type.Control field in the BCH Overhead Message can indicate whether to carry out the type in resource-sharing and shared cycle.In this embodiment, the sequential of all STA is adjusted to the suitable shared cycle among the BSS.In this embodiment, in the overlapping situation of BSS, time-delay will increase.
The 4th kind of exemplary mechanism is auxiliary synchronous again of STA.This situation may occur: two BSS can't hear the other side each other, but a new STA in the overlapping region can hear they two.This STA can determine the sequential of these two BSS, and this is reported to them.In addition, this STA can determine time migration, and indicates which AP should change its frame sequential and what change.This information must be transmitted to all BSS that are connected with this AP, and they all must rebulid the frame sequential to realize synchronously.Can in BCH, announcing synchronously again of frame.This algorithm can be applied to process how unconscious overlapping BSS.
The below describes in detail and can be used for above-mentioned one or more machine-processed example process.
AP can realize synchronously when powering up or in other fixed times.By near the system search in all FA, can determine system sequence.For ease of synchronously, one group of orthogonal code can be used for assisting to distinguish different AP.For example, AP has the known beacon of repetition in each mac frame.These beacons can use Walsh sequence (for example, length is 16) to cover.Therefore, the equipment such as AP or STA can be carried out the pilot frequency intensity measuring (PSM) of local AP, to determine overlapping BSS.The below will further describe, and the movable STA that is associated with an AP can send echo, to assist synchronously.These echoes can use the sequential corresponding with AP overlay code (cover) and soverlay technique (covering).Therefore, when overlapping but these BSS AP separately of BSS can't detect signal from the other side, the STA echo can be received by neighbor AP, thus provide its AP for information about and neighbor AP can be synchronous signal.Note that the overlay code that on different FA, can reuse quadrature.
Can based on the set of undetected Walsh overlay code, finish to certainty the selection (that is, selecting a Walsh overlay code that does not detect in neighbor AP) of Walsh overlay code.If all overlay codes all exist, then the code corresponding with the most weak received signal level (RSL) can be reused by new AP.Otherwise, in one embodiment, can select to make the maximized code in working point (see also structuring power back-off (powerbackoff) mechanism that self adaptation is reused, the below also will be elaborated to this) of AP.
In this embodiment, interlaced with each other the coming of frame counter that is sent by each AP.The interlace mode that adopts is corresponding to Walsh overlay code label.Therefore, AP0 uses Walsh code 0.When AP0 frame counter=j, APj uses Walsh overlay code j, and its frame counter equals 0.
When powering up or will carry out the synchronous any time, AP monitors neighbor AP beacon and/or STA echo.If do not detect the neighbours system, then AP establishes its time reference.This can be arbitrarily, and is perhaps relevant with GPS, or any other local time reference.If detect individual system, then correspondingly establish local sequential.If AP detects two or more systems that do with the different time lineman, then AP can carry out with the system with peak signal synchronously.If these system works are distributed on (FA) in identical frequency, then AP can attempt to be associated with weak AP, thereby informs that it is operated near AP on the independent clock other.This new AP attempts weak AP is informed in synchronous two required time migrations in AP district.Weak district AP can adjust its sequential.For a plurality of neighbor AP, this can repeat.With the synchronous sequence of two or more systems, new AP can establish its sequential.If all neighbor AP all can not be synchronized to single sequential (no matter being what reason), then this new AP can be synchronized to any one neighbor AP.
AP can carry out dynamic frequency selection when powering up.As mentioned above, generally, preferably can select to make the overlapping minimum of BSS by DFS, thereby the quantity of BSS that need to be synchronous and any delay or the throughput reduction related with this locking phase are minimized (namely, compare the BSS that must share with one or more neighbours BSS these media, the BSS that can access whole media on a FA is more efficient).Synchronously, new AP can select to have the FA (that is, when measuring neighbor AP, or during echo) of minimum RSL.AP can periodically inquire STA, so that carry out the AP pilot measurement.Equally, AP can dispatch silence period, to assess the AP place by the level of interference that STA was caused from other districts (being neighbor bss S).If this RSL grade is excessive, then AP can attempt seeking another FA within the non-scheduled cycle, and/or formulates the power back-off strategy, and is as described below.
As mentioned above, can organize AP according to the pilot tone overlay code.In this embodiment, can to use length be 16 Walsh sequential covering code to each AP.Can use the arbitrarily code of a different length.The pilot tone overlay code is used for the signal at a super frame period internal modulation beacon.In this embodiment, super frame period equals 32 milliseconds (that is, 16 continuous N AC frame beacons).Then, STA can be in superframe interval integration coherently, with the pilot power of determining to be associated with a specific AP.As mentioned above, AP can select its Walsh code from undetected a plurality of available Walsh codes.If detect all codes (on identical FA), then AP can be according to they be ranked to the most weak inferior ordered pair from the strongest.AP can reuse the Walsh code corresponding with the most weak Walsh code that detects.
For ease of the identification neighbor AP, STA can be used for sending echo, to identify their corresponding AP.Therefore, as mentioned above, an AP who does not detect neighbor AP may detect corresponding STA echo, thereby identifies this AP and sequential thereof.Each AP can send configuration information in its beacon, and each STA can serve as repeater, so that retransmit AP configuration information and sequential to the neighbor AP of any reception.
When the order of receiving from AP, movable STA need to send a predetermined pattern, so that be operated in the existence that near AP on the identical FA detects this neighbours system.A kind of simple method is, a definition observation interval (for example, between FCH and RCH section) in mac frame, and it is not used for any business by AP.The duration of observation interval can be defined as long enough, with process the STA that is associated from this AP and with STA that neighbor AP is associated between maximum different propagation delays (for example, 160 chips, perhaps, 2 OFDM symbols).For example, the STA that is associated with the AP that uses Walsh overlay code j can be in its mac frame counter=0 o'clock sends echo.Be encoded with on this echo make neighbor AP detect existence and with adjacent AP district in the STA necessary information that coexists efficiently.
The structuring power back-off that can adopt self adaptation to reuse.When system is crowded must be reused near another AP to each FA the time, it is machine-processed preferably to apply a kind of structurized power back-off, so that the terminal in two districts is all with maximal efficiency work.When detecting when congested, can control to improve with power the efficient of system.That is to say, be not whenever all to send with total power, and AP can use a kind of structurized power back-off mechanism of mac frame counter synchronisation with them.
For example, suppose that two AP are operated on the identical FA.In case these AP detect this situation, they will formulate known power back-off strategy.For example, two AP use a kind of compensation scheme, itself so that: being total power Ptot at mac frame 0, is Ptot (15/16) at mac frame 1 ..., be Ptot/16 at mac frame 15.Because AP is synchronous and their frame counter interlocks, so, there is not the AP district to use simultaneously total power.This target is the compensation model that selection makes the STAs in each AP district work with highest-possible throughput.
Used compensation model of specific AP can be the function of the degree of disturbance that detects.In this embodiment, a specific AP can use maximum 16 known compensation models.AP can in BCH and in the echo that the STA that is associated by AP sends, transmit used compensation model.
Walton etc. make, exercise question is the United States Patent (USP) 6 of " Method and apparatus for controllingtransmissions of a communications systems ", 493, describe a kind of exemplary compensation scheme in 331 in detail, this patent has transferred assignee of the present invention.
Figure 53 shows another exemplary embodiment that can carry out with legacy system the technology of interoperability.There is shown an exemplary mac frame 1500, the above describes in detail it in conjunction with Figure 15.Also introduce a kind of time slot pattern, wherein defined slot time 5310.Slot time 5310 comprises MIMO pilot interval 5315 and time slot gap 5320.As shown in the figure, inserted pilot tone 5315, to reserve this channel, made it avoid the impact at other stations (comprising AP) of the rule work of basis such as EDCA.Improved mac frame 5330 consists essentially of mac frame 1500, has wherein inserted pilot tone 5315, so that keep the control to media.Figure 53 is illustrative, and this is apparent to those skilled in the art.The time slot pattern can combine with the mac frame of any type, describes its various examples here in detail.
In this embodiment, for ease of explanation, the mac frame of supposing traditional 802.11 systems use is 1.204 milliseconds integral multiple.Mac frame can be set as 2.048 milliseconds, so that synchronously.At target beacon transmitting time (TBTT), the announcement CFP duration is so that STA arranges its NAV.During CFP, the STA among the BSS should transmitted signal, unless polled.Alternatively, as previously mentioned, AP also can send RTS, and allows identical CTS of STA loopback, with further cleaning BSS.This CTS can be the synchronous transmission from all STA.In this embodiment, always start from 2.048 milliseconds of borders by guaranteeing mac frame, can eliminate shake.Like this, even if in the situation that TBTT shortens, also between adjacent/overlapping BSS, hold time synchronously.Above-described various other technologies can combine with the technology that the following describes.In case reserved media for amended mac frame 5330, just can use any available techniques, employing time slot pattern keeps the right of possession corporeal right to media, to prevent that traditional STA from disturbing the transmission of scheduling, thereby the throughput that has reduced potentially novel system increases (namely, use scheme shown in Figure 15 or Figure 53, other schemes of perhaps describing in detail here).
In this embodiment, new A P follows the CSMA rule and seizes channel.But before this, it should or listen to beacon or other STA, attempts to determine whether to exist another BSS.But, in order to realize fair resource-sharing, do not need synchronously.
In case detect neighbours BSS, this new A P just can seize channel by sending its beacon.In order to stop (lock out) other users, this new A P sends has the pilot tone of a certain frequency, thereby prevents that other STA from using this channel (that is, not having idling cycle to be longer than the PIFS=25 microsecond).
This new A P can arrange one can make it at the timer of determining to take in the fair fixedly duration this channel.Like this can be roughly synchronous with the beacon period of traditional AP, perhaps asynchronous (that is, per 200 milliseconds in 100 milliseconds).
This new A P can seize channel by any point in the interval that it allows, and this can be postponed by the traditional B session service user.If there is not business to serve, this new A P can abandon channel before its time expires.When this new A P occupied channel, it was restricted to a just time period with its use.In addition, the sequential of this new A P establishment can be consistent with traditional mac frame sequential.That is to say that novel beacon appears on 2.048 milliseconds of borders of new A P clock.Like this, New type of S TA can judge whether HTAP has occupied channel by observing these specific intervals, thereby keeps synchronously.
This new A P can announce its frame parameter in beacon.The part of frame parameter can comprise the pilot interval spacing, is used for the frequency of pilot transmission in this mac frame of expression.Note that this new A P can dispatch STA, so that its transmission is overlapping with periodic burst pilot.In this case, the overlapping STA of dispensing section knows this point, and ignores pilot tone within this cycle.Other STA do not know this point, therefore use a threshold supervision device, confirm what whether pilot tone sent in predetermined distance.
This situation: STA may occur and originally will send pilot signal by the moment that AP sends, perhaps, AP sends the guiding pilot tone to STA in this interval.Worsen its channel estimating in order to prevent other STA from using this pilot tone, the AP pilot tone can be used the Walsh overlay code with public guide frequency Walsh overlay code phase quadrature.Can adopt for the structure of distributing the Walsh overlay code.For example, when STA uses different Walsh overlay codes with AP, the Walsh space can comprise 2N overlay code, the overlay code of N is wherein reserved for AP, and other overlay code is to reserve for the STA that is associated with a specific AP, and the overlay code that these STA use is related with the Walsh overlay code of corresponding AP in a known way.
When this new A P sent assignment information to a STA, it expected that this STA sends to it in predetermined distance.This STA may not receive this assignment information, and in this case, PIFS is longer than at the interval that channel may not be used.In order to prevent this situation, AP can detect channel in t＜SIFS, and judges whether it is occupied.If unoccupied, then AP can by sending the pilot tone of corresponding phasing, seize channel immediately.
Novel channel allocation section time slot can be changed into the interval (16 microsecond) of SIFS.Like this, channel occupancy just can be protected, thereby refuses the legacy user in new exclusive in the cycle.
Must be designed to support interoperability to RCH, this is because the duration of RCH may surpass 16 microseconds.If can not provide at an easy rate this RCH In a particular embodiment, so, when novel MAC does not have the channel control (, under traditional mode, coexist), this RCH can be distributed into and be operated under the traditional mode.By allowing any time (that is, wait for 4 microseconds, and send 8 microseconds) of STA after pilot transmission to send access request, can hold F-RCH, shown in Figure 53.
Exemplary embodiment: enhancement 802.11MIMO WLAN
The exemplary embodiment that the below describes in detail illustrates above-mentioned various aspects and other aspects.In this embodiment, show the enhancement 802.11WLAN that uses MIMO.To describe various MAC in detail and strengthen, and, be used in corresponding data and message transferring structure on MAC layer and the physical layer.It will be recognized by those skilled in the art, only disclose an illustrative subset of WLAN function, and they can make the enlightenment here be applicable to the interoperability of 802.11 legacy systems, and with the interoperability of various other systems.
The function of the exemplary embodiment that the below describes in detail is the interoperability with traditional 802.11a, 802.11g STA, and with the interoperability of the ultimate criterion of 802.11e draft and expection.This exemplary embodiment comprises MIMO OFDM AP, and so name is in order to distinguish mutually with traditional AP.The below also will describe in detail, because backwards compatibility, traditional STA can be associated with MIMO OFDM AP.But if necessary, MIMO OFDMAP can refuse the association request from traditional STA clearly.The DFS process can be directed to the AP (can be traditional AP or another MIMO OFDM AP) that another supports traditional operation to unaccepted STA.
MIMO OFDM STA can or wherein not have the independent BSS (IBSS) of AP to be associated with 802.11a or 802.11g BSS.Therefore, for this operation, a such STA will realize all necessary functions of 802.11a, 802.11g and 802.11e expection final draft.
In BSS or IBSS, when sharing identical RF channel with MIMO OFDM STA, support various functions when traditional.The MIMO OFDM PHY spectrum mask (spectral mask) of advising is compatible with the spectrum mask of existing 802.11a, 802.11g, thereby, can not introduce additional adjacent-channel interference to traditional STA.The signal field backward compatibility of the signal field of the expansion in the PLCP header (following detailed description) and tradition 802.11.In traditional signal field not the rate value of usefulness be configured to define new PPDU type (below will describe in detail).Self adaptation coordination function (ACF) (below will describe in detail) can realize sharing arbitrarily of media between traditional and MIMOOFDM STA.802.11e the cycle of EDCA, 802.11e CAP and SCAP can be punctured into arbitrarily in any beacon interval, this is determined by the AP scheduler.
As mentioned above, need to use the effectively high data rate of balance MIMO WLAN physical layer support of high-performance MAC.The below describes the various attributes of this exemplary MAC embodiment in detail.The below is some exemplary attributes:
Utilized the capacity of mimo channel the self-adapted high-efficient of PHY speed and transmission mode.
The low delay service of PHY provides low end-to-end delay, the demand of using to solve high-throughput (for example, multimedia).When low load, adopt the MAC technology based on competition, perhaps when the heavy duty system, use centralized or distributed scheduling, can realize the low delay operation.Low delay has a lot of benefits.For example, low delay can be realized quick self-adapted, thereby makes the physical layer data rate maximization.Low delay can be realized cheap MAC by enough minibuffer devices, and needn't delay ARQ.Use for multimedia and high-throughput, low delay also makes end-to-end delay minimize.
Another attribute is high MAC efficient and low competition expense.In the MAC based on competition, when data rate is high, the time shorten that useful transmission takies, and incremental portion that should the time is wasted in expense, conflict and the idling cycle.By scheduling, and by a plurality of high layer packets (for example, IP datagram) are aggregated in the single mac frame, can reduce the in the media time of waste.Also can form aggregate frame, thereby lead code and training expense are minimized.
The high data rate that PHY supports can realize that the QoS that simplifies processes.
The exemplary MAC that the below describes in detail strengthens and can to keep the mode of backward compatibility with 802.11g and 802.11a, solve above-mentioned performance issue.In addition, support and the improvement of the function that comprises among the aforesaid draft standard 802.11e comprised following functions, such as TXOP and direct link agreement (DLP), and, optional piece affirmation mechanism.
In the description to following exemplary embodiment, for some concepts of introducing above, use new term.The mapping of new terminology is as shown in table 1:
Table 1. term mapping table
| The term that uses in the early stage term earlier paragraphs | Be mapped to the term that uses in the new term subsequent paragraphs |
| MUX PDU or MPDU | Mac frame |
| Part MPDU | The mac frame burst |
| MAC PDU | PPDU |
| Broadcast channel message (BCH) and control channel | SCHED message |
| Message (CCH) | |
| Control channel message subchannel | The CTRLJ section of SCHED message |
| TDD mac frame interval | Scheduling access period (SCAP) |
| F-TCH (forward traffic channel) | The AP-STA transmission of scheduling |
| R-TCH (reverse traffic channel) | The STA-AP of scheduling or STA-STA transmission |
| A-TCH (the point to point service, PTP channel of self-organizing) | Shielded EDCA or MIMO OFDM EDCA |
| PCCH (pointtopoint control channel) | PLCP header signal field |
| RCH | FRACH |
Flexibly frame aggregation
In this embodiment, flexibly frame aggregation is easy to realize.Figure 35 shows encapsulation one or more mac frames (or burst) in an aggregate frame.Frame aggregation can be encapsulated in one or more mac frames (or burst) 3510 in the aggregate frame 3520, wherein can add header-compressed, and the below will be elaborated to this.Polymerization mac frame 3520 formation PSDU (that is, and PLCPSDU) 3530, can be used as a PPDU and send.Aggregate frame 3520 can containing type be the frame (or burst) 3510 after the encapsulation of data, management or control.When the needs privacy, can be encrypted frame payload.The mac frame header of encrypted frame is " being under the plaintext state (in the clear) " transmission.
Aforesaid this mac layer frame polymerization can in the situation that does not have IFS or BIFS (burst interFrameGap, the below will further describe), be transferred to identical recipient STA with frame.In some applications, expectation makes AP not have in the situation of IFS a plurality of frames or aggregate frame to be sent to a plurality of recipient STA.Can realize this point by the SCHED frame that use the following describes.The time started of a plurality of TXOP of SCHED frame definition.When AP carries out back-to-back (back-to-back) transmission to a plurality of recipient STA, can be without lead code and IFS.This is called as the PPDU polymerization, to be different from the frame aggregation of MAC layer.
It is lead code that an exemplary polymerization mac frame transmission (being PPDU) begins the place, then be that MIMO OFDM PLCP header (comprises signal field, this signal field can comprise two fields: signal 1 and signal 2), the back is MIMO OFDM training symbol (if any) again.Further describe exemplary PPDU form below in conjunction with Figure 49-52.The polymerization mac frame neatly polymerization to send to one or more frames or the burst of identical recipient STA.(the SCHED message that describes in detail below allows the TXOP from AP to a plurality of recipient STA is carried out polymerization).For the quantity of polymerisable frame and burst, without limits.Full-size for the aggregate frame of establishing through consultation can be restricted.Typically, first frame in the aggregate frame and last frame may be the bursts that creates for efficient package.When the Frame after several encapsulation comprised in an aggregate frame, the mac header of data and QoS Frame can compress, and was as described below.
By using flexibly frame aggregation, transmit leg MAC can reduce PHY and PLCP expense and idling cycle as possible.Can be by frame being carried out polymerization eliminating interFrameGap and PLCP header, and frame burst flexibly, to take the free space among the TXOP fully, realize this point.In a kind of exemplary techniques, based on current data rate and distribute or based on duration of TXOP of competition, MAC calculates first the byte number that will offer PHY.Then, can be with the packing of the mac frame behind the complete sum burst, to take whole TXOP.
If complete frame can not be contained in the remaining space among the TXOP, then MAC can carry out burst with next frame, to take remainder bytes as much as possible among this TXOP.For package efficiently, can at random carry out burst to frame.In one exemplary embodiment, this any burst will be subject to the restriction of maximum 16 bursts of every frame.In the embodiment that replaces, can not need this restriction.The residue of mac frame (a plurality of) burst can send in next TXOP.In TXOP subsequently, if desired, MAC can give the not burst of the frame of complete transmission higher priority.
The polymerization header that the below describes in detail (being 2 bytes in this embodiment) is inserted into the mac header of each encapsulated frame (or burst), and encapsulated frame (or burst) is inserted in the aggregate frame.Length field in the polymerization header represents to encapsulate the length (unit is byte) of rear mac frame, and is used for extracting frame (and burst) by receiver from aggregate frame.The size (quantity of OFDM symbol) of the PPDU size field regulation MIMO OFDM PPDU transmission in the signal field of advising, and the length of the mac frame after each encapsulation is indicated by the polymerization header.
The header-compressed of encapsulated frame
Figure 36 shows a traditional mac frame 3600, and it comprises mac header 3660, and what follow later is frame 3650 (can comprise a variable number N byte) and frame check symbol (FCS) 3655 (in this embodiment, being 4 bytes).The prior art mac frame form is described in detail in 802.11e.Mac header 3660 comprises: frame control field 3610 (2 bytes), duration/id field 3615 (2 bytes), sequential control field 3635 (2 bytes) and QoS control field 3645 (2 bytes).In addition, also comprise four address fields: address 13620, address 23625, address 33630 and address 43640 (each is 6 bytes).Also these addresses can be called TA, RA, SA and DA.TA is transmitter station address, and RA is the destination address, and SA is source station address, and DA is the address, point of destination.
When comprising several encapsulation of data frame in the aggregate frame, the mac header of data and QoS Frame can be compressed.For example, Figure 37-39 shows the mac header after the compression of QoS Frame.Note that FCS calculates according to the mac header after the compression and (encryption or unencrypted) payload.
Shown in Figure 37-39, when sending frame with MIMO data PPDU (type 0000), in the mac header 3660 of mac frame 3600, introduce a polymerization header fields, thereby create the mac frame after the encapsulation, namely 3705,3805 or 3905.Mac header comprises the polymerization header fields, is called as the mac header (namely 3700,3800 or 3900) of expansion.Can be aggregated to the management after one or more encapsulation, control and/or Frame (comprising the QoS data) in the mac frame after the polymerization.When the usage data privacy, can the payload of data or QoS Frame be encrypted.
For each frame (or burst) that is inserted in the aggregate frame (being respectively 3705,3805 or 3905), insert polymerization header 3710.Header-compressed is indicated by the polymerization header type field of describing in detail below.The frame header of data and QoS Frame can compress, to eliminate redundant field.The aggregate frame 3705 that provides among Figure 37 shows a kind of unpressed frame, and it comprises all four addresses and duration/id fields.
After sending a unpressed aggregate frame, other aggregate frame just needn't identify dispatching station and destination address, because they are identical.Therefore, can omit address 13620 and address 23625.For the subsequent frame in the aggregate frame, needn't comprise duration/id field 3615.Duration can be used for setting NAV.Duration/id field as the case may be and by the heavy duty.In polling message, it comprises access ID (AID).In other message, identical field indicated for the duration of setting NAV.Corresponding frame 3805 has been shown among Figure 38.
When source address and address, point of destination comprise identical information, can provide further compression.In this case, address 33630 and address 43640 also can be omitted, thereby obtain frame shown in Figure 39 3905.
When field was removed, in order to decompress, receiver can will insert in this aggregate frame from the respective field of last header (after decompression).In this embodiment, the first frame in the aggregate frame always uses unpressed header.The deciphering of payload may be from some fields of mac header, and these fields may be removed for ease of header-compressed.After the decompression of frame header, can offer decryption engine to these fields.Length field is used for extracting frame (and burst) from aggregate frame by receiver.Length field indicates the length (unit is byte) of the frame with header compression.
After extracting, remove the polymerization header fields.Then, the frame after decompressing is delivered to decryption engine.In decrypting process, the field in (after the decompression) mac header need to be carried out the message integrity checking.
Figure 40 has provided an exemplary polymerization header 3710.For the one or more frames that in MIMO data PPDU, send (encryption, or unencrypted), be that each frame (or burst) header adds the polymerization header.This polymerization header comprises the polymerization header type field 4010 (be used for expression and whether adopted header-compressed and which kind of type) of 2 bits and the length field 4030 of 12 bits.Type 00 frame does not adopt header-compressed.Type 01 frame has been removed duration/ID, address 1 and address 2 fields.Class1 0 frame has the removal field identical with type 01 frame, has removed in addition address 3 and address 4 fields.Length field 4030 in the polymerization header indicates the length of the frame with header compression, and unit is byte.2 bits 4020 are reserved.Summed up the polymerization header type in the table 2.
Table 2. polymerization header type
| Bit 0 | |
The meaning |
| 0 | 0 | Not compression |
| 0 | 1 | Duration/ID, |
| 1 | 0 | Duration/ID, |
| 1 | 1 | Reserve |
In this exemplary embodiment, all management frames that encapsulate in the aggregate frame and control frame adopt unpressed frame header, and its polymerization header type is 00.Following management frames can be encapsulated in the aggregate frame with Frame together: related request, associated response, again related request, again associated response, probe requests thereby, probe response, disassociation, authentication and releasing authentication.Following control frame can be encapsulated in the aggregate frame with Frame: BlockAck (piece affirmation) and BlockAckRequest (piece is confirmed request).In other embodiments, can encapsulate the frame of any type.
The self adaptation coordination function
Self adaptation coordination function (ACF) is the extended version of HCCA and EDCA, and it can realize flexibly, the operation of efficient, low delay scheduling, is suitable for the operation of the high data rate supported by MIMO PHY.Figure 41 has provided an exemplary embodiment of the scheduling access period frame (SCAP) that uses in ACF.Use SCHED message 4120, AP can dispatch one or more AP-STA, STA-AP or STA-STATXOP simultaneously within the cycle of scheduling access period 4130 by name.These transmission through scheduling are identified as the transmission 4140 of having dispatched.SCHED message 4120 has replaced traditional HCCA poll of describing in detail above.In this exemplary embodiment, the maximum permissible value of SCAP is 4 milliseconds.
For ease of explanation, Figure 41 has provided exemplary scheduled transmissions 4140, and it comprises that AP transmits 4146 to AP transmission 4144 and STA to STA to STA transmission 4142, STA.In this embodiment, AP sends 4142A to STA B, then, sends 4142B to STA D, sends 4142C to STA G again.Note that between these TXOP and needn't introduce the gap that because for each frame, information source (AP) is identical.When information source changes, show gap between the TXOP (below exemplary clearance gap is described in further detail).In this embodiment, transmit after 4142 to STA at AP, STA C sends 4144A to AP, and then, behind a gap, STA G sends 4144B to AP, and through a gap, STA E sends 4144C to AP again.Then, a point-to-point TXOP 4146 is dispatched.In this case, STAE is information source (sending to STAF), so, if the STAE transmitting power is constant, then do not need to introduce the gap, otherwise, the BIFS gap can be used.Can other STA be dispatched to the STA transmission, but do not show these in this embodiment.According to any order, can dispatch any combination of TXOP.The order of shown TXOP type is exemplary convention.In order to reduce required gap number, expectation can be dispatched TXOP, and still, this not necessarily.
When only having MIMO STA, the NAV of SCAP can set by the duration field in the SCHED frame (following also the SCHED frame can be described in further detail).Alternatively, if wish protected traditional STA impact of avoiding, AP also can arrange CTS-to-Self 4110 before SCHED frame 4120, thereby was the SCAP establishment NAV at all STA places among the BSS.
In this embodiment, MIMO STA observes the SCAP border.Last STA that in SCAP, sends must be before SCAP finishes its TXOP of termination PIFS duration at least.MIMO STA also observes the TXOP border of scheduling, and finishes its transmission before the TXOP that distributes finishes.The STA of like this, follow-up scheduling just can begin its TXOP in for idle situation needn't detecting channel.
Can indicate in the ACF ability item scheduling that allows in the SCAP or based on the maximum length of the TXOP of competition.In this embodiment, the length of SCAP does not change in a beacon interval.This length can be at ACF ability item indicating.An exemplary ACF item comprises: SCAP length (10 bit), maximum SCAP TXOP length (10 bit), GIFS duration (4 bit) and FRACH response (4 bit).SCAP length represents the length of SCAP in the current beacon interval.This field is encoded take 4 μ s as unit.Maximum SCAPTXOP length represents that the maximum in the SCAP allows TXOP length.This field is encoded take 4 μ s as unit.The GIFS duration is continuous in the protection interval between the STA TXOP of scheduling.This field is encoded take 800ns as unit.The FRACH response represents take SCAP as unit.AP must use FRACH PPDU, by provide TXOP through scheduling to STA in FRACH response SCAP, response is made in the request of receiving.
Figure 42 has provided an example that SCAP and HCCA and EDCA is combined use.In any beacon interval (4210A-C represents with beacon), AP fully can be flexibly, will intert with 802.11e CAP, MIMO OFDM SCAP based on the duration of the access of EDCA competition adaptively and be in the same place.
Therefore, use ACF, AP can be as working among the HCCA, and still, it can also be the SCAP assignment period.For example, AP can distribute CAP as the operation that is poll among the HCCA as use CFP and CP among the PCF, perhaps, can distribute SCAP for the operation of scheduling.As shown in figure 42, in a beacon interval, AP can use any combination based on the cycle of access (EDCA) 4220A-F, the CAP 4230A-F of competition and SCAP 4100A-I.(for the sake of simplicity, the example among Figure 42 does not show any CFP.) AP is based on its dispatching algorithm and observed result that media are taken thereof, adjusts the ratio of the media that taken by dissimilar access mechanisms.Can adopt any dispatching technique.AP determines whether the QoS stream of admitting is satisfied with, and can use other observed results, comprises that the media of measuring take situation, adjust.
The above has described HCCA and related CAP thereof.Provided an illustrative CAP 4230 among Figure 42.That AP TXOP 4232 follows later is poll 4234A.HCCA TXOP4236A follows in poll frame 4234A back.Send another poll 4234B, that it is followed later is another corresponding HCCATXOP 4236B.
The above has described EDCA.Provided an illustrative EDCA 4220 among Figure 42.Show various EDCATXOP 4222A-C.Omitted CFP in this example.
The form that SCAP 4100 as shown in figure 42 can adopt Figure 41 to describe in detail comprises optional CTS-to-Self 4110, SCHED 4120 and scheduling access period 4130.
AP uses 802.11 business transferring Indication message (DTIM) message as described below to indicate scheduling operation.DTIM comprises the bitmap of access ID (AID), and another STA among this AP or the BSS has laid in data for it.Use DTIM, notify all STA that possess the MIMO ability after beacon, to keep wake-up states.In the BSS that traditional and MIMO STA exist, immediately following after beacon, dispatch first traditional STA.After conventional transmission, send immediately SCHED message, it shows the composition of dispatching access period.The STA that possesses the MIMO ability that does not dispatch in the particular schedule access period can sleep in remaining SCAP, then wakes up and monitors follow-up SCHED message.
Adopt ACF, can realize various other operator schemes.Figure 43 shows an exemplary operation, and wherein, each beacon interval comprises a plurality of SCAP 4100, wherein is interspersed with the access period 4220 based on competition.Under this pattern, shared medium wherein, is dispatched MIMO QoS stream during SCAP liberally, and the non-QoS stream of MIMO uses competing cycle with traditional STA (if present) simultaneously.The cycle of interting is realized the low delay service to MIMO and traditional STA.
As mentioned above, in SCAP, before the SCHED message CTS-to-Self can be arranged, for the protection of the impact of avoiding traditional STA.If there is no traditional STA does not then need CTS-to-Self (or other traditional cleaning signals).Beacon 4210 can be set a long CFP, avoids the impact of traditional STA of any arrival to protect all SCAP.CP when beacon interval finishes is so that newly arrived traditional STA can access media.
Use exemplary operation shown in Figure 44, in the situation that a large amount of MIMO STA are arranged, can realize the low delay operation of optimizing.In this embodiment, suppose that traditional STA (if any) only needs limited resource.AP sends a beacon, thereby sets up long CFP 4410 and short CP 4420.Beacon 4210 is followed later is any broadcast/multi broadcast message for traditional STA.Then, lean against privately SCAP 4100 is dispatched.This operator scheme also provides the power management of optimizing, because STA need to periodically be waken up in order to listen to SCHED message, and, if in current SCAP, be not scheduled, then can in the SCAP interval, sleep.
The FRACH that comprises in the scheduling access period 4130 by SCAP 4100 or MIMO EDCA cycle, provide the access based on protected competition that is used for MIMO STA.In CP 4420, traditional STA can carry out based on the access of competing media.
After the transmission of SCHED frame, can dispatch the transmission from the continuous scheduling of AP.The SCHED frame can send with lead code.Follow-up scheduling AP transmission can send in the situation of lead code not having.(can send the designator that whether comprises lead code for expression).The below describes in further detail an exemplary PLCP lead code.In this exemplary embodiment, the STA of scheduling transmission begins having in the situation of lead code.
Mistake is recovered
Recover in order to receive the mistake from SCHED, AP can use various processes.For example, if a STA can't decode to a SCHED message, then it can not utilize its TXOP.If the TXOP of a scheduling did not begin in the time started of distributing, send during PIFS after then beginning by the TXOP in the not scheduling of usefulness, AP can start recovery.AP can use the TXOP cycle of the not scheduling of usefulness as a CAP.In this CAP, AP can be to one or more STA transmitted signals, perhaps STA of poll.Poll can be for STA or another STA of the TXOP that has missed scheduling.Before next scheduling TXOP, this CAP finishes.
When the TXOP of a scheduling finishes too early, also can use identical process.Send during by the PIFS after last end of transmission in the TXOP of scheduling, AP can begin to recover.As mentioned above, AP can use scheduling TXOP do not use the cycle as CAP.
Shielded competition
As mentioned above, SCAP also can comprise: be exclusively used in the part of FRACH transmission and/or the part that MIMO STA can use the EDCA process therein.These access periods based on competition can be protected by the NAV that sets for SCAP.
Shielded competition is asked so that assistance AP dispatches by permission STA indication TXOP, thereby replenishes the low delay scheduling operation.In cycle, MIMOOFDM STA can use the access (avoiding and traditional STA competition) based on EDCA to send frame at shielded EDCA.Use conventional art, STA can ask or buffer state the 802.11e QoS control field indicating TXOP duration in mac header.But FRACH provides a kind of more efficient means of identical function.In cycle, STA can use the competition of the Aloha formula in gap at FRACH, accesses channel in the FRACH of fixed dimension time slot.FRACH PPDU can comprise that the TXOP duration asks.
In this exemplary embodiment, MIMO PLCP header is used in the transmission of MIMO frame, and the below will be elaborated to this.In the situation that has non-MIMO STA; because traditional 802.11b, 802.11a and 802.11g STA can only decode to signal 1 field (being described in detail below in conjunction with Figure 50) of MIMO PLCP header; so the MIMO frame must send having in the situation of protection.As tradition and MIMO STA when all existing, can protect with traditional RTS/CTS sequence with the STA of EDCA access procedure.Tradition RTS/CTS refers to traditional lead code, PLCP header and mac frame form and transmits RTS/CTS.
The protection mechanism that the MIMO transmission also can use 802.11e HCCA to provide.Therefore, use control access period (CAP), the transmission from AP to STA, the polled transmission of (using the direct link agreement) from STA to AP or from STA to STA can be protected.
AP also can use traditional CTS-to-Self, and protection MIMO scheduling access period (SCAP) is avoided the impact of traditional STA.
When an AP determines that all STA that exist among the BSS can both decode to MIMO PLCP header, indicate this point in its MIMO ability item in beacon.Such BSS is called as MIMO BSS.
In MIMO BSS, under EDCA and HCCA, according to the aging rule of MIMO OFDM training symbol, MIMO PLCP header and MIMO OFDM training symbol are used in the frame transmission.MIMO PLCP is used in transmission among the MIMO BSS.
The interFrameGap that reduces
The above describes the various technology that are generally used for reducing interFrameGap in detail.Here provide the example of the interFrameGap in this exemplary embodiment of several reductions.For scheduled transmission, the time started of TXOP indicates in SCHED message.The accurate time started that transmit leg STA can indicate in SCHED message, begin its scheduling TXOP, and needn't determine that media are idle.As mentioned above, the AP of the continuous scheduling in SCAP transmission is not have to send in the situation of minimum IFS.
In this exemplary embodiment, the STA of continuous scheduling transmission (from different STA) is to send in the situation of at least one GIFS at IFS.The default value of GIFS is 800ns.Can select larger value, reach at most the value of the burst IFS (BIFS) that defines below.The value of GIFS can indicate in ACF ability item, as mentioned above.Other embodiment can adopt any value of GIFS and BIFS.
Continuous N IMO OFDM PPDU transmission (TXOP burst) from identical STA is separated with BIFS.In the time of in being operated in the 2.4GHz frequency band, BIFS equals 10 μ s, and MIMO OFDM PPDU does not comprise the ofdm signal expansion of 6 μ s.In the time of in being operated in the 5GHz frequency band, BIFS is 10 μ s.In an alternative embodiment, BIFS can be set as large or smaller value, comprise 0.For recipient STA automatic gain control (AGC) can be changed, when the transmitting power of transmit leg STA changes, can use the gap greater than 0 between transmission.
Need to not send with MIMO OFDMPPDU from the at once frame of response of recipient STA.On the contrary, they send with conventional P PDU, that is, and and the clause 19 in the 2.4GHz frequency band or the clause 17 in the 5GHz frequency band.The below provides several examples, illustrates how tradition and MIMO OFDM PPDU to be multiplexed on the media.
At first, consider a traditional RTS/CTS, MIMO OFDM PPDU burst is followed in its back.This transfer sequence is as follows: traditional RTS-SIFS-traditional CT S-SIFS-MIMOOFDM PPDU-BIFS-MIMO OFDM PPDU.In 2.4GHz, traditional RTS or CTS PPDU use the ofdm signal expansion, and SIFS is 10 μ s.In 5GHz, do not have the OFDM expansion, but SIFS is 16 μ s.
Secondly, consider an EDCA TXOP who uses MIMO OFDM PPDU.This transfer sequence is as follows: MIMO OFDM PPDU-BIFS-traditional B lockAckRequest-SIFS-ACK.For suitable access style (AC), use the EDCA process to obtain EDCATXOP.As mentioned above, the access style of EDCA definition can use different parameters to each AC, such as AIFS[AC], CWmin[AC] and CWmax[AC].Traditional BlockAckRequest sends in the situation that signal extension or 16 μ s SIFS are arranged.If send in the aggregate frame of BlockAckRequest in MIMO OFDM PPDU, then do not have ACK.
The 3rd, consider the TXOP of continuous scheduling.Transfer sequence is as follows: STA A MIMOOFDM PPDU-GIFS-STA B MIMO OFDM PPDU.If the maximum that the PPDU transfer ratio is distributed allows the TXOP time short, so, after STA A MIMO OFDMPPDU transmission, may have one period free time.
As mentioned above, encoded decoding and the demodulation of OFDM transmission forced extra processing demands at recipient STA place.In order to solve this point, 802.11a and 802.11g allow recipient STA before must sending ACK to be arranged the additional time.In 802.11a, the SIFS time is set as 16 μ s.In 802.11g, the SIFS time is set as 10 μ s, but has introduced additional 6 μ s ofdm signals expansion.
According to identical logic, because decoding and the demodulation meeting of MIMO OFDM transmission cause more processing load, so, can design an embodiment who improves SIFS or ofdm signal expansion, this can further lower efficiency.In this exemplary embodiment, by piece ACK and the delay block affirmation mechanism of expansion 802.11e, for all MIMO OFDM transmission, needn't need ACK at once.What replace increase SIFS or signal extension is eliminated signal extension, and for a lot of situations, the required interFrameGap between the transmission to have obtained reducing or eliminating continuously, thereby raises the efficiency.
SCHED message
Figure 45 shows SCHED message, and the above introduces it in conjunction with Figure 41, and the below also will be described in further detail it.SCHED message 4120 is polling messages more than, and it distributes one or more AP-STA, STA-AP and STA-STATXOP within the duration of scheduling access period (SCAP).Use SCHED message, can reduce poll and competition expense, and, unnecessary IFS eliminated.
This exemplary mac header 4510 comprises: frame control 4535 (2 bytes), duration 4540 (2 bytes), BSSID 4545 (6 bytes), power management 4550 (2 bytes) and MAP 4555 (3 bytes).The bit 13-0 of duration field 4540 indicates the length of SCAP, and unit is microsecond.Duration field 4540 is used for setting NAV for the duration of SCAP by the STA that can carry out MIMO OFDM transmission.When having traditional STA among the BSS, AP can protect SCAP with other means, for example, and traditional CTS-to-Self.In this exemplary embodiment, the maximum of SCAP is 4 milliseconds.BSSID field 4545 sign AP.
The SCHED counting is a field (being 6 bits in this embodiment) that all increases progressively when each SCHED transmission.The SCHED counting resets when each beacon transmissions.The SCHED counting can be used for various purposes.For example, the electricity-saving function that uses the SCHED counting is described below.
The used transmitted power level of transmitting power field 4630 expression AP.In this exemplary embodiment, the following coding of this 4 bit field: the channel that indicates in the item of information for beacon, this value represent the quantity that transmitted power level is lower than the 4dB stride of maximum transmit power level (unit is dBm).
The received power level of received power field 4640 expression AP place's expectations.In this exemplary embodiment, the following coding of this 4 bit field: this value represents received power level and is higher than the minimum receiver sensitivity level (quantity of 4dB stride 82dBm).Based on the received power level at STA place, STA can followingly calculate its transmitted power level: STA transmitting power (dBm)=AP transmitting power (dBm)+AP received power (dBm)-STA received power (dBm).
In this exemplary embodiment, in the STA-STA transmission course of scheduling, control section sends with the launching electrical level that can decode at AP and recipient STA place.From the power control report of AP or the power management field 4550 in the SCHED frame, make STA can determine can be at the AP place to the control section required transmitted power level of decoding.The above has described this general aspect in conjunction with Figure 22.STA-STA transmission for scheduling when the required power of decoding at the AP place is different from the power of decoding required at recipient STA place, sends PPDU with the higher person in these two power levels.
Figure 48 shows the SCHED control frame that distributes for TXOP.Among 530 sections of CTRL0 4515, CTRL1 4520, CTRL2 4525 and the CTRL34 each has variable length, and each comprises 0 or a plurality of assignment item (being respectively 4820,4840,4860 and 4880).Each CTRLJ section is added with FCS (being respectively 4830,4850,4870 and 4890) and 6 tail bits (not shown)s of 16 bits.For CTRL0 section 4515, FCS is for mac header 4510 and any CTRL0 assignment item 4820 and calculate (so, show, before mac header is added on CTRL04515) in Figure 48.In this exemplary embodiment, even do not comprise assignment item in the CTRL0 section, also comprise the FCS 4830 of CTRL0 4515.
Just as this paper detailed description, AP sends the assignment information of AP-STA, STA-AP and STA-STA transmission in the SCHED frame.Assignment item to different STA sends in the CTRLJ section, is represented by the STA in the SCHED speed field of the PLCP header of its transmission.Note that CTRL0 to CTRL3 corresponding to the robustness of successively decreasing.Each STA begins the PLCP header of SCHED PPDU is decoded.Signal field indicates existence and the length thereof of CTRL0, CTRL1 among the SCHED PPDU, CTRL2 and CTRL3 section.When the STA receiver begins mac header and CTRL0 section are decoded, until FCS decodes, it continues decode CTRL1, CTRL2 and CTRL3 subsequently to each assignment item, can't the CTRLJ section place that its FCS verifies stopped.
As shown in table 3, defined five kinds of assignment item.Several assignment item can be bundled in each CTRLJ section.The maximum that each assignment item indicates the TXOP of time started of TXOP of transmit leg STA access ID (AID), recipient STAAID, scheduling and scheduling allows length.
Table 3. assignment item type
| Type (3 bit) | The assignment item type | Field (bit length) | Total bit length |
| 000 | Single worker AP-STA | Lead code existence (1) AID (16) start offset (10) TXOP duration (10) | 40 |
| 001 | Single worker STA-AP | AID (16) start offset (10) TXOP duration (10) | 39 |
| 010 | Duplex AP-STA | Lead code existence (1) AID (16) start offset (10) AP TXOP duration (10) STA start offsets (10) STA TXOP duration (10) | 60 |
| 011 | Single worker STA-AP | Send AID (16) and receive the maximum PPDU size of AID (16) start offset (10) (10) | 55 |
| 100 | Duplex STA-STA | AID 1 (16) AID 2 (16) STA, 1 start offsets (10) |
75 |
In the continuous transmission from AP, can eliminate lead code.If AP does not send lead code for the AP transmission of scheduling, then lead code existence bit is made as 0.For example, the benefit of eliminating lead code is, when AP has low bandwidth to several STA, low delay stream, for example, in the BSS with a plurality of ip voices (VoIP) stream.Therefore, the SCHED frame can be realized the polymerization (that is, above-mentioned PPDU polymerization) of the transmission from AP to several recipient STA.The frame that above-mentioned frame aggregation allows to mail to a recipient STA carries out polymerization.
The start offset field is the integral multiple of 4 μ s, is the time started of quoting from SCHED message lead code.AID is the access ID of (a plurality of) STA of distributing.
For all the assignment item types except the STA-STA transmission of scheduling, TXOP duration field is that the maximum of the TXOP of scheduling allows length, is the integral multiple of 4 μ s.The actual PPDU size of the PPDU that sends is pointed out (below will further describe) in signal 1 field of PPDU.
For the STA-STA transmission (assignment item type 011 and 100) of scheduling, maximum PPDU size field also is that the maximum of the TXOP of scheduling allows length, is the integral multiple of 4 μ s, still, also can use other rules.In this exemplary embodiment, for the STA-STA transmission of scheduling, TXOP only comprises a PPDU.Recipient STA uses the maximum PPDU size of assignment item indicating, determines the quantity (because the PPDU size field is replaced by the request field in the signal 1, describing in detail below in conjunction with Figure 51) of OFDM symbol among the PPDU.If STA-STA stream uses the OFDM symbol with standard protection interval (GI), then recipient STA sets the PPDU size of the TXOP of scheduling for the maximum PPDU size of distributing an indicating.Have the OFDM symbol that shortens GI if STA-STA stream uses, then recipient STA is by amplifying maximum PPDU size field and rounding up to determine that PPDU is big or small with the factor 10/9.Transmit leg STA can send and compare the short PPDU of maximum PPDU size that distributes.The PPDU size does not provide the length of mac frame after the polymerization to receiver.The length of encapsulated frame is included in the polymerization header of each mac frame.
Launch party and recipient STA are included in the assignment item, can make the STA power saving that in SCAP, is not scheduled and sends or receive.The SCHED count area of introducing above recalling.The maximum that each assignment information of being dispatched by SCHED message indicates the TXOP of time started of TXOP of transmit leg STAAID, recipient STA AID, scheduling and scheduling allows length.The SCHED counting increases progressively when each SCHED transmission, and resets when each beacon transmissions.STA can indicate power-save operation to AP, and therefore is provided concrete SCHED count value, and during this period, they can be distributed transmission with being scheduled or be received TXOP by AP.Then, STA can periodically wake up, and just monitors the SCHED message with suitable SCHED counting.
The PPDU form
Figure 49 shows traditional 802.11PPDU 4970, and it comprises afterbody 4950 and the elongated filling information 4955 of PLCP lead code 4975 (12 OFSM symbols), PLCP header 4910, elongated PSDU 4945,6 bits.The part 4960 of PPDU 4970 comprises: signal field (1 OFDM symbol) sends with speed=1/2 with BPSK; And elongated data field 4985, send with the modulation format that indicates in the signal 4980 and speed.PLCP header 4910 comprises the service field 4940 (be included in the data 4985, send according to this form) of signal 4980 and 16 bits.Signal field 4980 comprises: speed 4915 (4 bit), reserved field 4920 (1 bit), length 4925 (12 bit), parity bit 4930 and afterbody 4935 (6 bit).
The signal field (below will describe in detail) of the expansion in this exemplary PLCP header (below will describe in detail) keeps backward compatibility with the signal field 4980 of tradition 802.11.The not usefulness value of the speed field 4915 in traditional signal field 4980 is set, to define new PPDU type (following detailed description).
Several new PPDU types have been introduced.In order to keep backward compatibility with traditional STA, the speed field in the signal field of PLCP header is modified to speed/type field.Speed be not designated as the PPDU type with value.The PPDU type is existence and the length thereof of index signal field extension specification signal 2 also.The new value of speed/type field is defined in table 4.These values of speed/type field define for traditional STA.Therefore, traditional STA can abandon the decoding to PPDU after signal 1 field successfully being decoded and find undefined value in the speed field.
Perhaps, the reserved place in the legacy signal field can be made as " 1 ", mail to the MIMO OFDM transmission of a New type of S TA with indication.Recipient STA can ignore this reserved place, and continues to attempt signal field and remaining transmission are decoded.
Receiver can be determined based on the PPDU type length of signal 2 fields.FRACHPPDU has only occurred once in the specified portions of SCAP, and needs only to be decoded by AP.
Table 4.MIMO PPDU type
| Speed/type (4 bit) | | Signal | 2 field lengths (OFDM symbol) |
| 0000 | MIMO BSS IBSS or MIMOAP transmission (except the SCHED PPDU) | 1 | |
| 0010 | MIMO |
1 | |
| 0100 | MIMO |
2 |
Figure 50 shows the MIMO PPDU form 5000 for transfer of data.PPDU 5000 is called as PPDU type 0000.PPDU 5000 comprises: PLCP lead code 5010, signal 1 5020 (1 OFDM symbol), signal 25040 (1 OFDM symbol), training symbol 5060 (0,2,3 or 4 symbol) and elongated data field 5080.In this exemplary embodiment, PLCP lead code 5010 (if present) is 16 μ s.With PPDU control section speed and modulation format transmitted signal 1 5020 and signal 2 5040.Data 5080 comprise: service 5082 (16 bits); Feedback 5084 (16 bits); Elongated PSDU 5086; Afterbody 5088 (each stream has 6 bits) wherein, is used different convolution chnnel codings to each stream; Elongated filling information 5090.Send data 5080 with PPDU control section speed and modulation format.
The MIMO PLCP header of PPDU type 0000 comprises: signal (comprising signal 1 5020 and signal 2 5040), service 5082 and feed back 5084 fields.Compare with traditional 802.11, service field is constant, and is to send with this data segment speed and form.
The ES field is indicated preferred guidance method.In this exemplary embodiment, when the ES bit is set up, select characteristic vector guiding (ES), otherwise, spatial spread (SpatialSpreading, SS) selected.
Data rate vector feedback (DRVF) field provides feedback to station, equity side, but this feedback is about the supporting rate on each of maximum four spatial models.
Clear and definite Rate Feedback makes the station can be fast and make exactly the maximization of its transmission rate, thereby greatly improves system effectiveness.The feedback of low delay is desirable.But the feedback chance needs not to be synchronous.Can obtain transmission opportunity by any mode, for example, based on (being EDCA) of competition, (being HCF) or (being ACF) mode of scheduling of poll.Therefore, can between transmission opportunity and Rate Feedback, transmit the variable time amount.Based on the life-span of Rate Feedback, transmitter can be used avoidance mechanism, to determine transmission rate.
For the transport stream from STA A to STA B, the feedback that provided to STAA by STA B (front is described, for example, referring to Figure 24) is provided PPDU data segment rate adaptation.For ES or SS operator scheme, when STA B received the MIMOOFDM training symbol from STA A, it all will estimate attainable data rate on each spatial flow.Any subsequent transmission stream from STA B to STA A, STA B is included in this estimated value in the DRVF field of feedback 5084.The DRVF field sends with data segment 5080 speed.
When to the STAB transmitted signal, which kind of transmission rate the DRVF that STA A receives from STA B based on it determine to use, and required avoidance mechanism during optional considering delay.Signal field (following detailed description) comprises the DRV field 5046 of 13 bits, and this DRV field 5046 can be decoded to the frame that sends from STAA recipient STA B.DRV 5046 sends with control section speed.
The DRVF field is encoded, and it comprises: STR field (4 bit), R2 field (3 bit), R3 field (3 bit) and R4 field (3 bit).The STR field represents to flow 1 speed.Be the STR value shown in the table 5 with this code field.R2 represents to flow 1 STR value and flows difference between 2 the STR value.R2 value " 111 " expression stream 2 turn-offs.R3 represents to flow 2 STR value and flows difference between 3 the STR value.R3 value " 111 " expression stream 3 turn-offs.If R2=" 111 " then is made as R3 " 111 ".R4 represents to flow 3 STR value and flows difference between 4 the STR value.R4 value " 111 " expression stream 4 turn-offs.If R3=" 111 " then is made as R4 " 111 ".
When ES=0, namely during spatial spread, the another kind of DRVF coding is as follows: the speed (4 bit) of fluxion amount (2 bit), each stream.The speed field of each stream is encoded as above-mentioned STR value.Remaining 7 bits are reserved.
Table 5.STR coding
| The STR value | Encoding rate | Modulation format | The symbol of bit/each stream |
| 0000 | 1/2 | BPSK | 0.5 |
| 0001 | 3/4 | BPSK | 0.75 |
| 0010 | 1/2 | QPSK | 1.0 |
| 0011 | 3/4 | QPSK | 1.5 |
| 0100 | 1/2 | 16QAM | 2.0 |
| 0101 | 5/8 | 16QAM | 2.5 |
| 0110 | 3/4 | 16QAM | 3.0 |
| 0111 | 7/12 | 64QAM | 3.5 |
| 1000 | 2/3 | 64QAM | 4.0 |
| 1001 | 3/4 | 64QAM | 4.5 |
| 1010 | 5/6 | 64QAM | 5.0 |
| 1011 | 5/8 | 256QAM | 5.0 |
| 1100 | 3/4 | 256QAM | 6.0 |
| 1101 | 7/8 | 256QAM | 7.0 |
Except DRVF, STAB also provides power control feedback to transmit leg STAA.This feedback is included in the power control field, and also sends with data segment speed.This field is 2 bits, and expression increases power or reduction power or keep power constant.Resulting transmitted power level is designated as the data segment transmitted power level.
Table 6 shows exemplary power control word segment value.The embodiment that replaces can adopt the power control field of different sizes, and the power adjustment of replacing.
Table 6. power control word segment value
| The power control field | Implication |
| 00 | Unchanged |
| 01 | With increased |
| 10 | Power is reduced 1dB |
| 11 | Reserve |
For whole PPDU, transmitted power level remains unchanged.When data segment transmitted power level and open loop STA transmitting power (that is, AP is to the above-mentioned transport stream required power level of decoding) not simultaneously, send PPDU with the maximum in these two power levels.That is to say that the PPDU transmitted power level is the maximum in open loop STA transmitting power (dBm) and the data segment transmitting power (dBm).
In this exemplary embodiment, in the first frame of any frame turnaround sequence, the power control field is made as " 00 ".In follow-up frame, its expression increases or reduces power according to the step-length of 1dB.Recipient STA will use this feedback information in all subsequent frame transmission of mailing to this STA.
Signal 15020 comprises: the afterbody 5030 of speed/type field 5022 (4 bit), reserved place 5024, PPDU size/request 5026 (12 bits), parity bit 5028 and 6 bits.Signal 1 field 5020 is (in this exemplary embodiment, being 6Mbps) that send with control section speed and form.Speed/type field 5022 is set as 0000.Reserved place 5024 can be set as 0.
PPDU size/request 5026 has two effects, and this depends on transmission mode.In STA transmission and all AP transmission based on competition, this field represents the PPDU size.Under this first pattern, bit 1 expression PPDU has used the OFDM symbol of expansion, and bit 2 expression PPDU use has the OFDM symbol that shortens GI, and bit 3-12 represents the quantity of OFDM symbol.
In the non-AP STA transmission of scheduling, PPDU size/request 5026 expression requests.Under this second pattern, bit 1-2 represents SCHED speed.The SCHED rate representation can be used to send to STA the SCHED field of the numbering the highest (0,1,2 or 3) of an assignment information.Between the training symbol transmission period from AP, each non-AP STA estimates that it can receive from AP the speed of SCHED frame transmission healthy and strongly.In the follow-up scheduled transmission from STA, this maximum allows speed to be included in the SCHED speed field.This field is decoded by AP.AP comes the follow-up TXOP of STA is dispatched with this information, and definite CTRLJ (0,1,2 or 3), to be used for issuing these distribution to STA.
Under the second pattern, bit 3-4 represents qos field, the part of its sign TC 0 or 1 request (be 1/3rd multiple) (that is, 0%, 33%, 67%, 100%).Bit 5-12 represents the request length (in this exemplary embodiment, being the integral multiple of 16 μ s) of TXOP.
The existence of signal 2 fields 5040 and length thereof are indicated by the speed/type field 5022 in the signal 15020.Signal 2 fields 5040 are to send with control section speed and form.Signal 25040 comprises: reserved place 5042, training type 5044 (3 bit), data rate vector (DRV) 5046 (13 bit), parity bit 5048 and afterbody 5050 (6 bit).The training type field of 3 bits indicates length and the form of MIMO OFDM training symbol.Bit 1-2 represents the quantity (0,2,3 or 4 OFDM symbol) of MIMO OFDM training symbol 5060.Bit 3 is training type fields: 0 expression SS, 1 expression ES.DRV 5046 is provided for each the speed in maximum four spatial models.DRV 5046 is identical with the coded system that DRVF adopts (to be included in the feedback 5084, as mentioned above).Signal 2 fields 5040 are carried out verification by 1 parity bit 5048, and finish with 6 bit tail 5050 that are used for convolution coder.
Figure 51 shows SCHED PPDU 5100 (speed/type=0010).SCHEDPPDU 5100 comprises: PLCP lead code 5110, signal 15120 (1 OFDM symbol), signal 25140 (1 OFDM symbol), training symbol 5160 (0,2,3 or 4 symbol) and elongated SCHED frame 5180.In this embodiment, when PLCP lead code 5110 exists, be 16 μ s.Signal 15020 and signal 25040 are to send with PPDU control section speed and modulation format.SCHED frame 5180 can comprise the above-mentioned various speed of describing in conjunction with ACF.
Signal 15120 comprises: speed/type 5122 (4 bit), reserved place 5124, CTRL0 size 5126 (6 bit), CTRL1 size 5128 (6 bit), parity bit 5130 and afterbody 5132 (6 bit).Speed/type 5122 is set as 0010.Reserved place 5124 can be set as 0.CTRL0 size 5126 indicates take the segment length of the SCHEDPPDU of minimum speed limit (in this embodiment as 6Mbps) transmission.This section comprises: the service field of PLCP header, mac header and CTRL0 section 5126.In this embodiment, this value is to encode with the integral multiple of 4 μ s.5128 expressions of CTRL1 size are take the segment length of the SCHEDPPDU of next higher rate (in this embodiment as 12Mbps) transmission.In this embodiment, this value is to encode with the integral multiple of 4 μ s.The CTRL1 size is " 0 " expression: do not have corresponding CTRL1 section among the SCHED PPDU.Signal 1 field 5120 is carried out verification by parity bit 5130, and finishes with 6 bit tail 5132 that are used for convolution coder.
Signal 25140 comprises reserved place 5142, training type 5144 (3 bit), CTRL2 size 5146 (5 bit), CTRL3 size 5148 (5 bit), FCS 5150 (4 bit) and afterbody 5152 (6 bit).Reserved place 5142 can be set as 0.Training type 5144 and the same (the training type 5044) that be 0000 appointment of PPDU type.
The segment length of the SCHED PPDU that CTRL2 size 5146 the following flank speeds of expression (being 18Mbps in this embodiment) send.In this embodiment, this value is to encode with the integral multiple of 4 μ s.The CTRL2 size is " 0 " expression: do not have corresponding CTRL2 section among the SCHED PPDU.5148 expressions of CTRL3 size are take the segment length of the SCHED PPDU of flank speed (in this embodiment as 24Mbps) transmission.In this embodiment, this value is to encode with the integral multiple of 4 μ s.The CTRL2 size is " 0 " expression: do not have corresponding CTRL3 section among the SCHED PPDU.
Figure 52 shows FRACH PPDU 5200 (speed/type=0100).FRACHPPDU 5200 comprises: PLCP lead code 5210, signal 1 5220 (1 OFDM symbol) and signal 2 5240 (2 OFDM symbols).In this exemplary embodiment, PLCP lead code 5210 (when existing) is 16 μ s.Signal 1 5220 and signal 2 5240 are to send with PPDU control section speed and modulation format.During the FRACH cycle in MIMO scheduling access period, STA sends FRACH PPDU 5200.The FRACH cycle is established by AP, so be known (as above describing in detail) for it.
Signal 15220 comprises: speed/type 5222 (4 bit), reserved place 5224, request 5226 (12 bits), parity bit 5228 and afterbody 5230 (6 bit).Speed/type 5222 is set as 0100.Reserved place 5224 can be set as 0.Request field 5226 and the same (5000) that are 0000 appointment of PPDU type as above describe in detail.Signal 1 field 5220 is tested by parity bit 5228, and finishes with 6 bit tail 5230 that are used for convolution coder.
Signal 25240 comprises reserved place 5242, source AID 5244 (16 bit), purpose AID5246 (16 bit), FCS 5248 (4 bit) and afterbody 5250 (6 bit).Reserved place 5242 can be set as 0.The upper STA that sends of source AID 5244 sign FRACH.The purpose STA that purpose AID 5246 sign TXOP ask.In this exemplary embodiment, if destination party is AP, then the value of purpose AID field 5246 is set as 2048.The FCS 5248 of 4 bits calculates according to whole signal 1 and signal 2 fields.Before convolutional encoding, add the afterbody 5250 of 6 bits.
In this exemplary embodiment, STA can access channel with the Aloha of time slot, and sends a request message in FRACH.If successfully received by AP, then AP provides one through the TXOP of scheduling to requesting party STA in a rear scheduling access period.The FRACH timeslot number of current scheduling access period indicates N_FRACH in SCHED message.
STA can also keep a variable B_FRACH.After the transmission on the FRACH, if STA receives the TXOP assignment information from AP, its B_FRACH that resets then.If STA does not receive the TXOP assignment information from AP in the SCHED of predetermined quantity (FRACH_RESPONSE) transmission, then B_FRACH is increased by 1, reach at most maximum 7.Parameter F RACH_RESPONSE is included in the ACF item of beacon.In any FRACH, STA is with probability (N_FRACH)
-1* 2
-B_FRACHChoose a FRACH time slot.
If AP does not dispatch any FRACH cycle, then MIMO STA can use the EDCA rule, is at war with in the protected competing cycle in SCAP.
It will be appreciated by those skilled in the art that and to use multiple different technologies and method representation information and signal.For example, data, instruction, order, information, signal, bit, symbol and the chip of mentioning in the description on run through can represent with voltage, electric current, electromagnetic wave, magnetic field or particle, light field or particle or above-mentioned combination in any.
Those skilled in the art also can understand, various exemplary box, module, circuit and the algorithm steps of describing in conjunction with the disclosed embodiments here all can electronic hardware, computer software or the combination of the two realize.In order to be clearly shown that the interchangeability between the hardware and software, more than various exemplary assembly, frame, module, circuit and steps are all carried out generally description with its functional form.This functional be to realize or realize depending on the design constraint that specific application and whole system are applied with software with hardware.Those skilled in the art can realize for each specific application described functional in many ways, and still the result of this realization should not be construed as and causes deviating from scope of the present invention.
Utilize general processor, digital signal processor (DSP), application-specific integrated circuit (ASIC) (ASIC), field programmable gate array (FPGA) or other programmable logical devices, discrete gate or transistor logic, discrete hardware components or the combination in any among them, can realize or carry out various exemplary logic diagram, module and the circuit described in conjunction with embodiment disclosed herein.General processor may be microprocessor, but in another kind of situation, this processor may be processor, controller, microcontroller or the state machine of any routine.Processor also may be implemented as the combination of computing equipment, for example, and the combination of DSP and microprocessor, multi-microprocessor, one or more microprocessor or any other this kind structure in conjunction with the DSP core.
In conjunction with the step of the described method of embodiment disclosed herein or algorithm can directly be presented as hardware, the software module carried out by processor or the combination of these two.Software module may be present in the medium of RAM memory, flash memory, ROM memory, eprom memory, eeprom memory, register, hard disk, mobile disk, CD-ROM or any other form well known in the art.The coupling of a kind of typical storage media and processor, thereby so that processor can be from this medium reading information, and can be to this medium writing information.In the example of replacing, medium can be the part of processor.Processor and medium may be present among the ASIC.This ASIC may be present in the user terminal.In the example of replacing, the discrete assembly that processor and medium can be used as in the user terminal exists.
The title that this paper comprises is used for reference to and helps each joint of location.These titles are not to want to be limited in the thereafter protection range of described concept.These concepts go in full.
Provide the foregoing description of described disclosed embodiment can be so that those skilled in the art can realize or use the present invention.To those skilled in the art, the various modifications of these embodiment are apparent, and the general principles of definition here also can be applied to other embodiment on the basis that does not depart from the scope of the present invention with purport.Therefore, the present invention is not limited to shown here embodiment, but consistent with the widest scope that meets principle disclosed herein and novel feature.
Claims (32)
1. method of between one or more equipment that communicate according to the first transformat and one or more equipment that communicates according to the second transformat, carrying out interoperability on the transmission channel, described method comprises:
According to described the first transformat transmitted signal on described transmission channel, in order to described transmission channel is reserved one period duration;
The duration of wherein said reservation is corresponding to the interval according to described the first transformat, and comprises at least one interval according to described the second transformat; And
At the duration of described reservation, communicate according to described the second transformat.
2. the method for claim 1 also comprises: before sending the described signal that is used for reserving, according to described the first transformat contention access.
3. the method for claim 1 also comprises:
The described transmission channel of request access; And
Reception is in response to the distribution of described request.
4. the method for claim 1, wherein described signal is transmission opportunity (TXOP) according to IEEE 802.11 agreements.
5. the method for claim 1, wherein described signal has been established uncontended periods.
6. the method for claim 1, wherein transmitted signal is in order to comprise also that with one period duration of described transmission channel reservation sending a request sends (RTS) message, and described RTS message has been indicated the transmitting continuous time.
7. the method for claim 1, wherein transmitted signal is in order to comprise also that with one period duration of described transmission channel reservation sending one permits sending (CTS) message, and described CTS message has been indicated the transmitting continuous time.
8. the method for claim 1, wherein described the first transformat is the IEEE802.11 form.
9. the method for claim 1, wherein described the second transformat comprises time division multiplexing (TDD) frame period, and this time division multiplexing frame period comprises:
Pilot tone;
The poll that merges comprises a plurality of polls that are merged in the single message;
According to the zero of the poll of described merging or a plurality of access point frame to distant station;
According to the zero of the poll of described merging or a plurality of distant station frame to access point;
According to the zero of the poll of described merging or a plurality of distant station frame to distant station; And
Zero or a plurality of at random access section according to the poll of described merging.
10. the communication means on the transmission channel comprises:
Distributed for the first duration for communicating at transmission channel according to the first communication format in the multiple communication format; And
Distributed for the second duration for communicating at described transmission channel according to the second communication format in the multiple communication format,
Wherein said the first duration comprises described the second duration.
11. method as claimed in claim 10, wherein, at least a communication format in the described multiple communication format comprises spatial manipulation.
12. method as claimed in claim 11, wherein, the described communication format that comprises spatial manipulation in the described multiple communication format is multiple-input and multiple-output (MIMO) communication format.
13. method as claimed in claim 12, wherein, described MIMO communication format is the single output of many inputs (MISO) communication format.
14. method as claimed in claim 10, wherein, a kind of communication format in the described multiple communication format comprises time division multiplexing (TDD) frame period, and this time division multiplexing frame period comprises:
Pilot tone;
The poll that merges; And
One or more frames according to the poll of described merging.
15. method as claimed in claim 14, wherein, one or more frames comprise that access point is to the communication of distant station.
16. method as claimed in claim 14, wherein, one or more frames comprise that distant station is to the communication of access point.
17. method as claimed in claim 14, wherein, one or more frames comprise that distant station is to the communication of distant station.
18. method as claimed in claim 14, wherein, one or more frames comprise the at random access to described transmission channel.
19. method as claimed in claim 10, wherein, a kind of communication format in the multiple communication format is identical with the 802.11EDCA form.
20. method as claimed in claim 10, wherein, a kind of communication format in the multiple communication format is identical with the 802.11CAP form.
21. method as claimed in claim 10, wherein, a kind of communication format in the multiple communication format is identical with scheduling access period SCAP form.
22. method as claimed in claim 10, also comprise: distribute a series of one or more the 3rd duration for communicating at described transmission channel according to the first communication format in the described multiple communication format, and distribute a series of one or more the 4th duration according to the second communication format in the described multiple communication format for communicating at described transmission channel, described a series of the 3rd duration and a series of the 4th duration intert mutually.
23. method as claimed in claim 22 wherein, is selected described interting so that the maximum time interval between described a series of the 3rd duration to be provided.
24. method as claimed in claim 10, wherein, described the first duration comprises one or more scheduling access period SCAP interval.
25. method as claimed in claim 24, wherein, described the second duration comprises one or more 802.11EDCA interval.
26. method as claimed in claim 10 also is included as described the first duration establishment uncontended periods.
27. method as claimed in claim 10 also is included as described the second duration establishment competing cycle.
28. one kind is used for the method that communicates at transmission channel, comprises:
Send beacon according to the first communication protocol;
According to the described transmission channel of described the first communication protocol contention access;
Between the access periods that described competition is arrived, communicate at described transmission channel according to the second communication protocol,
Wherein said competition to access comprise and contain at least one according to the competing cycle at the interval of described second communication agreement.
29. method as claimed in claim 28 also comprises:
Establish uncontended periods; And
During described uncontended periods, distribute poll according to described the first communication protocol.
30. method as claimed in claim 28 also comprises:
Access for the second time described transmission channel according to described the first communication protocol competition; And
Between the access periods of competing the described second time, communicate at described transmission channel according to described the first communication protocol.
31. method as claimed in claim 29, wherein:
The first access point is established described uncontended periods; And
The second access point is according to described the first communication protocol contention access, and between the access periods that described competition is arrived, communicates according to described the second communication protocol and one or more distant station.
32. an equipment that operates with access point, described access point is established uncontended periods and competing cycle according to the first communication protocol, and described equipment comprises:
The contention access module is used for during described competing cycle according to described the first communication protocol contention access transmission channel;
Wherein said competition to access comprise and contain at least one according to the competing cycle at the interval of second communication agreement;
Transmitter, be used for described competition to access periods between send at described transmission channel according to described the second communication protocol; And
Receiver, be used for described competition to access periods between receive at described transmission channel according to described the second communication protocol.
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| TW200536306A (en) | 2005-11-01 |
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| TWI383302B (en) | 2013-01-21 |
| CN1894914A (en) | 2007-01-10 |
| BRPI0415426A (en) | 2006-12-05 |
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