CA1143439A - Mobile communication system - Google Patents
Mobile communication systemInfo
- Publication number
- CA1143439A CA1143439A CA000372615A CA372615A CA1143439A CA 1143439 A CA1143439 A CA 1143439A CA 000372615 A CA000372615 A CA 000372615A CA 372615 A CA372615 A CA 372615A CA 1143439 A CA1143439 A CA 1143439A
- Authority
- CA
- Canada
- Prior art keywords
- mobile
- channel
- radio
- access channel
- origination
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W68/00—User notification, e.g. alerting and paging, for incoming communication, change of service or the like
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2621—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using frequency division multiple access [FDMA]
Abstract
Abstract of the Disclosure There is provided a mobile transmission system wherein a plurality of radio zones, each including one radio base station, the base stations of all radio zones being controlled by a control center which controls a paging and an origination of a mobile, are arranged to form a service area, and each radio zone is provided with at least one mobile access channel and a single mobile paging channel assigned with a radio fre-quency common to all radio zones, thus enabling to establish speech channels for the mobiles. The frequency of the mobile access channel is made to be different for adjacent radio zones and one or more frequencies are allocated to each base station.
The control center is provided with means for controlling an origination of the mobile for selecting at least one channel among available channels allocated to a radio base station associated with the mobile, circuit switching means operatively connected to the origination control means, for establishing the mobile access channel, and means for broadcasting a channel number of the established mobile access channel to all radio zones through the mobile paging channel. Each mobile is pro-vided with a receiver for receiving the channel number of the mobile access channel, means for updating and storing the received channel number, and means for sequentially receiving radio waves transmitted through the stored access channel and for comparing received field intensities to select a mobile access channel adapted to send out an origination signal of the mobile.
The control center is provided with means for controlling an origination of the mobile for selecting at least one channel among available channels allocated to a radio base station associated with the mobile, circuit switching means operatively connected to the origination control means, for establishing the mobile access channel, and means for broadcasting a channel number of the established mobile access channel to all radio zones through the mobile paging channel. Each mobile is pro-vided with a receiver for receiving the channel number of the mobile access channel, means for updating and storing the received channel number, and means for sequentially receiving radio waves transmitted through the stored access channel and for comparing received field intensities to select a mobile access channel adapted to send out an origination signal of the mobile.
Description
3~39 This invention relates to a vehicle communication system comprising a number of radio zones.
In a mobile communication system in which a service area is constituted by a plurality of xadio ~ones each installed with a base station provided with a pluralit~ of channels, a common control channel system is generally used including a mobile paging channel ~P-CH) and a mobile access channel (A-CH) which are used to establish a speech channel (S-CH) so as to decrease the set-up time of a call connection and to efficiently utili~e fre~uencies.
The prior ar~ and the invention will be described in conjunction with the attached drawings in which:
Figs. 1 and 2 are charts showing exchan~e of various codes between a control center and a mobile at the time of paging and access before talking;
Fig. 3 is a block diagram of a prior art mobile communication system;
Fig. 4 is a block diagram showing details of a control center;
E'igs. 5 and 6 are flow charts showing the operation of a controller in the Fig. 4 control center;
Fig. 7 shows a connection of a voice transfer switch;
Fig. 8 is a block diagram showing one embodiment of this invention;
Fig. 9 shows details of hlocks ~6a, 47 and 48 shown in Fig. 8;
Fig. 10 is a block diagram showing one example of a mobile s-tation;
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Fig. 11 is a block diagram showing details of the Fig. 10 circuit;
Fig. 12 is a flow chart for explaining the operation of controller 94b shown in Fig. 11;
Fig. 13 is a block diagram showing a modified embodiment of this invention; and Fig. 1~ is a block diagram showing details of the elements 106a, 107 and 108 shown in Fig. 13.
As disclosed on pages 1172 - 1190 of "Review of Electrical Communication Laboratories" Vol. 25, Nos. 11-12, 1977 published by Nippon Telegraph and Telephone Puhlic Corporation, when making a mobile terminating call through a paging channel ~P-CH), a page code is sent from a control center to a mobile. Then the mobile sends out a page response code in response to the page code. In a case shown in Fig. 1, a control center CC sends the page code to both base stations BSl and BS2. Where a mobile is in a radio zone ~of the base station BSl, the page response code is sent back to the control center CC via the base station BS1.
Since the control center receives C~; mg/~,~ - 2 -.
: ' . ` . ~
- :
' ~3~39 the page response code from the mobile by way of the base station BSl, it sends an idle channel number among a number o~
channels allocated to the base station BSl by means of a channel assiyn code ~o the mobile. In the mobile, the channel is skipped to the assigned channel, and after checking the loop a bell is rung. Then the mobile subscriber station (MSS) permits a mobile subscriber to begin talking. In this system, many mobiles utilize the paging channel P-CH on the time di-vision basis to improve the utilization e~ficiency.
As shown in Fig. 2, the access channel is used at the time of a mohile originating call. ~ore particularlyr in the mobile, the channel is changed ~rom the paging channel P-CH to the access channel A-C~ through which an access-channel-mark code is sent outO Since the contro~ center CC receives the origination code ~rom the base station BSl, it selects an idle channel out of a number of channels allocated to the base station BSl for sending a channel assign code to the mobile through the access channel. The mobile sk.ips. to the assigned . : channel to make a loop.check and sends out a dial code.to begin talking.
. Reservation o~ an access channel is necessary because where an idle channel among a number of speech channels is selected to transmit an origination code therethrough and then . utilize the selected channel as a speech channel it takes a many time to search the idle channel~ Where the access channel is fixed, however, it can not con.ey traffics as many as tha~
'~' ` ' .
, ~343g of the paging channel because ;ndividual moblles simultaneously send origination codes at a high probability, resultin~ in a so-called call collisionO
In a most widely used vehicle communication system, as the channel exclusively usea as a paginy channel was provided for each base station a single channel havin~ a predetermined fre~uency common to all zones, whereas as control channels exclusively used for accessing were provided for each base station one or more channels having predetermined frequencies common to all zones, the number o channels being determined by a maximum expectant number of the m~bi7es moving into or out of the service area of each base station.
More particularl~, the frequency of the radio carrier signal and the phase of the modulated signal are adjusted in an overlapped zone to m;nimize interf~rence between these signals.
Thus, as shown in Fig. 3 in radio zones I and II, a frequèncy fl is allocated to the paging channel P-CH and frequencies f2 and f3 to the access channel A-CH.
In the mobile communication system described above, there is no problem in the mobile paging channel, but in the case of the mobile access channel, as it utilizes specific fre~uencies common to all zones, the number o~ transce;vers in each base station increases greatly, thus increasing the cost of installation as will be described later in more detail. On the other hand, when the number oE the transceivers is fixed, the number of the speech channels decreases proportionally.
.
~3~39 From the standpoint of the increase in the number of the speech channels where the traffic is busy, i-t is desirable to use the mobile access channel as a speech channel.
Summary of the Invention _ Accordingly, it is an object of this invention to provide a novel mobile communication system capable of providing much more speech channels with simple construction.
Another object of this invention is to provide a mobile communication system capable of utilizing all transceivers, except those used in a mobile paging channel, for speech channels without impairing the speech performance of the base station.
According to one embodiment there is provided a mobile communication system wherein a plurality of radio zones, each including one radio base station, the base stations oE all radio zones being controlled by a control center which controls a paging and an origination of a mobile, are arranged to form a service area, and each radio zone is provided with at least one mobile access channel and a single mobile paging channel assigned with a radio frequency common to all radio zones, thus enabling to establish speech channels for the mobiles, characterized in that the at least one mobile access channel of one radio zone is assigned with a radio frequency which is different from that assigned to adjacent radio zones, the common radio control station is provided with means for controlling an origination of the mobile for selecting at least one channel amon~ available channels allocated to a radio base station associated with the mobile, circuit switching means operatively connected to mg/é,r - 5 -:
3~3~
the origination control means, for establishing the mobile access channel, and means for broadcasting a channel ~umber of the established mobile access channel -to all radio zones through the mobile paging channel; and wherein each mobile is provided with a receiver Eor receiving the channel number of the mobile access channel, means for updating and storing the received channel number, and means for sequentially receiving radio waves transmitted through the stored access channel and for comparing received field intensities to select a mobile access channel adapted to send out an origination signal of the mobile.
Description of the Preferred Embodiments For the sake of simplicity, in Fig. 3 showing a prior art mobile communication system, only two base stations 1 and 2 are shown, and the number of radio transmitter and receivers or transceivers in each base sta-tion is 6. This communication system generally comprises radio zones I and II
within the range of the radio waves from the base stations 1 and 2, mobile units 3 and 4, and a control center 5 controlling all base stations. A paging control unit 6 and access control units 7 and 8 are provided in the control eenter 5.
Details of the control center 5 are shown in Fig. ~.
page encoder 201 of page channel connection signal transrnitting and system controlling seetion 6a is eonstituted by a parallel-in-serial-out type shift register and started by a start signal from a controller 203 to produce a page code to be sent to mobiles via a transfer switch 205. A
channel assign encoder 202 is also constituted by a B
. ...
mg/~jr~ - 6 -' ' :
parallel-in-serial-out type shift register and operates to transmit via the transfer switch 205 -the channel number of an idle speech channel stored in a channel memory device 204 to a mobile which has transmitted a page response.
Page response decoders 6b and 6c are constituted by ,~
mg/~r~ - 7 -serial-in-parallel-out type shift registers, and when they receive a page response code from a mobile, they inform this fact to the controller 203~
An origination code from a mobile in the radio zone I
is received by either one of serial-in-parallel-out type shift registers 7b and 8b which are selected by the mobile subscriber.
These shift registers act as origination decoders. In this example, it is assumed that the shift register 7b has been selected. Then the output of the shift register 7b is applied to a controller 207 of a section 7a. The controller 207 dis-criminates radio zones RZl and RZ2 ~in this example RZl) and requests the controller 203 to designate an idle channel. Then the controller 203 informs an idle speech channel stored in the channel memory device 204 to the controller 207. The control-ler 207 sets the channel number of the idle channel in a channel assign encoder 206 and sends out this channel number to the mobile as a channel assign code. Where the oirigination code is inputted to an origination decoder 7c associated with the radio zone II, the same operation is made except that the radio zone to be searched is different~ Where the orignation code is inputted to decoders 8b and 8c, simlllar processing is made with a similar controller in a decoder 8a.
The flow charts of the controllers 203 and 207 are shown in Figs. 5 and 6, respectively.
Each base station is provided with six radio transmit-ter-receivers 10-15 and 20-25 and the control center 5 is 3~39 provided with voice transfer switches 33-35 and 43-45.
Each of the switches 33-35 and 43-45, is used to interconnect an ordinary telephone line and an approach line and has a construction similar to a switch circuit shown in Fig. 7 utilized in a conventional telephone exchange.
Since the operation oE the mobile communication system shown in Fig. 3 is well known in the art and can be readily understood from the description o the embodiment of this invention, it will not be described here.
Simply~ except the frequency of radio transmitter-receivers 10 or 20 for the paging channel, since two frequencies are assigned to the access channel, each base station is provlded with two radio transmitter-receivers 11 and 17 and 21 and 220 As a consequence the number of channels that can be used as the speech channels in each base station is three as can be noted from the num~er of the voice transfer switches 33-35 or 43-45.
Considering the number of effective access channels o~
the communication system, the channel frequencies f2 and f3 of the channels are common to the entire system so that while these channel frequencies are used in the radio zone I, the other zones can not use them. ~ccordingly, when a mobile 3 in the radio zone I and a mobile 4 in the radio zone II wish to use a channel, irrespective of the presence of two transceivers in each base station, the available access channel is only one for each base station. When each of two mobiles 3a and 3b, for ~, ,~ ,!
_ 9 _ example, in the radio zone I wishes to use a channel, it is possible to utilize two channels. ~ut in this case in the other radio zone II, since these two channel can not be used, it is possible to use only one channel on the average. Thus, when it is desired to have two effective access channels, it is necessary to provide additional two line connection signal controllers. This reduces the number of the speech channels by two, leaving only one channel. The above-described data show an extreme case because the number of channels per one base 10 ~ station is small. Let us consider an actual example. Suppose now that the number of the radio zones is 8, that the number of the radio transmitter-receives of each radio zone is 100 (except tbe transceiver for the paging channel) and that the number of access channels necessary for each service area is 5. Then the total number of the access channel radio transmit-ter-receivers over all base stations is 5x8=40. Accordingly, the number of the encoders and decoders of the access channel controllers also becomes 5x8=40.
As can be noted from the foregoing description, when one attempts to use the access channel as the speech channel in one zone, such a channel can not be used neither as the access channel nor the speech channel in the remaining zone. In other words, installed transmitter-receivers are not used efficiently.
Fig. 8 illustrates a simplified block diagram of one embodiment of this invention. In this case, like Fig. 3, the number of the base stations is 2 and the number of the radio 3~
transmitter-receivers in each base station is 6. Ignoring the frequency, respective component elements are identical to those shown in Fig. 3 and reference numerals are equal to those used in Fig. 3 plus 40. The system shown in Fig. 8 is different from that shown in Fig. 3 in that transmission controllers 47 and 48 are connected to transmitters 51 and 61 respectively.
For this reason, the provision of an access line connecting signal receiver in individual base stations is dispensed with so that it is not necessary to divide it into a plurality of circuits designated by numerals with suffixes a, b and c. Such a system can operate satisfactory when the operation of the mobile units is adaptive ~o the system as will be described with reference to Fig. 10~ Of course, two access channels of at least two adjacent base stations should have different frequencies for the purpose of preventing interference there-between.
Details of blocks 46a and 47 shown in Fig. 8 is shown in Fig. 9 Although these blocks operates substantially in the same manner as the elements 6a and 7a shown in Fig. 4 they are different in that since controllers 227 and 228 are not required to discriminate radio zones I and II, it is not neces-sary to exchange a signal required for effecting such a dis-crimination. Blocks 47 and 48 operate in the same manner.
Fig. 10 is a block diagram showing one example of the construction of the electric circuit carried on a mobile. This electric circuit comprises an antenna 91, a duplexer 92, a ~3~L39 receiver 93, a data -transmitter-receiver 94 having capabilities of encoding, decoding and comparison o~ field intensities o~
signals as well as sequence control capability, a ~requency synthesizer 96, a transmitter 97 and a memory device 98 storing channel numbers (or letters or symbols) of all access channels and the corresponding field strength values. These channel numbers are sent from a mobile paging signal controller 4 through transceivers 50 and 60 as sys~em information to a mobile and stored in the memory device 98 via antenna 91, lO receiver 93 and data transmit~er-receiver 94. Reference numeral 99 denotes a microphone or loudspeaker.
In a mobile communication system constructed as shown in Figs. 8 and 10, the system information or a vehicle paging signal is simultaneously transmitted from the paging line signal transmitter 46a through radio transmitter-receivexs 50 and 60 and received by all mobiles, and a radio signal received by antenna 91 and duplexer 92 is demodulated by receiver 93 and is then decoded by data transmitter-receiver 94.
When the received signal is a paging code, a paged mobile transmits an up-linked paging response code of the same Erequency. Where the mobile is in the zone T, the sent back response signal .is received by a paging line connection signal receiver 46b via the transceiver 50. The paging line connection signal transmitter 46a capable of controlling the system judges ~5 that the mobile is in the radio zone I according to the re-ceived signal, thus designating a speech channel among idle . , .
channels o~ the radio zone I so as to send out the channel number of the speech channel. The mobile receiving the desig-nated channel number cornmences a conversation through a channel of that channel number.
When the received signal contains a channel nurnber of the access channel as the system information, the content of the memory device is updated by the channel number decoded by the data transmitter-receiver 9~.
When a mobile sends out an origination signal, the channel number alloca-ted as the access channel and stored in the memory device 98 is read out by the data transmitter-receiver 94 and channels are sequentially designated for the frequency synthesi~er 96 by using a radio frequency designator 95 so as to sequentially receive both of the transmitted wave (a transmission output of the radio transmitter-receiver 51 at a frequency f2~ of the access channel in the radio base station 1 and the transmitted wa~e (a transmission output oE the radio transmission-receiver 61 at a frequency f3) of the access channel in the radio base station 2 and to compare the field strengths of respective input signals at different frequencies f2 and f3, thus selecting a radio base station having stronger field (in this examp1e the field intensity of the transmitted wave oE the radio ~se station 1 is stronger than that oE the base station 2). The mobi~e sends out an origination signal through the access channel of the selected radio zone. The sent out signal i~ received by an A-CH encoder/recoder 47 via 3~3~
radio transmitter-receiver 51. Accordingly, a suitable line is selected from idle channels of the radio zone I so as to desig-nate the speech channel number through the radio transmitter-receiver 51 for the mobile which has sent out the origination signal~ The mobile which has received the designated channel number commences a conversation through a channel of that channel number.
Fig. 11 shows details of one example of the mobile unit circuit arrangement as shown in Fig. 10. This unit circuit arrangement comprises a transmitter-receiver including a frequency synthesizer of a well knwon phase locked loop (PLL) type.
Describing in more detail with this transmitter and receiver, where a controller 94b designates a channel number of a predetermined paging channel P-CH for a radio frequency designator 95t a local frequency of the frequency synthesizer 96 is supplied to receiver 93 and transmitter 97 and locked in the paging channel P-CH.
Under this condition, system information code from an antenna 91 is~demodulated by receiver 93 and then inputted to a data receiver 94a which is constituted by a serial-in-paralle-out type shift register so as to apply the received signal to the controller 94b as parallel signals. The control-ler 94b decodes the channel number that has designated an access channel among the system information codes thus storing the decoded channel namber in a memory device 98. Where the '' 1. .
3~
access channel is predetermined, it is prestored in the memory device 98.
When a mobile subscriber hooks-off, a signal from a hook switch 267 is applied to the controller 94b. At this time, the controller 94b commences to apply one of the access channel numbers stored in the memory device 98 to the frequency controller 95 to start reception of the first access channel.
Where an intermediate fre~uency amplifier 254 is made of the type CA308~ sold by RCA Corporation, a received field strength can be obtained and the controller 94b stores the field strength of t~le first access channel in the memory device 98 via an analogue-digital converter 268. Then the channel number of the second access channel is again designated for the fre-quency designator 95 for storing the field strength at that ~15 time in the memory device g8. In this manner, all access channels informed by the system information codes are scanned for storing respective field strengths in the memory device 98. Thereafter, the field strengths are compared with each ~ other for selecting an access channel having the largest field strength.
The cotroller 94b causes the frequency-synthesizer 96 to lock an access channel regarding the largest field so as to set an origination code in the data transmitter 94c of the parallel-in-serial-out type shift register, and activates a power amplifier 262 by a carrier on/off signal on line 269 produced by the controller 94b to send out an origination code.
.- - 15 -: .
.
A speech channel assigned by a control center via a base station as a response of the origination code is set in the frequency designator 95 via the data receiver 9~a and the controller 94b in the same manner as the reception of the system information code to switch the frequency of the mobile to the assigned channel.
Fig. 12 is a flow chart showing the operation of the controller 94b. Although the operation of mobile terminating call is not shown in Fig. 12, as it is not directly related to this invention, it is omitted.
The embodiment operates in a manner described above, but in the system shown in Fig. 8, among five channels that can-be used for communication, the access channel is one and the remaining ~our channels are used as the speech channels. If two channels are used as the access channels, the speech channels are 3, thus increasing the number of the speech channels than the system shown in Fig. 3. In an actual e~ample, where the number ~f the zones is 8, and where subscribers are distributed evenly in each zone, the number of the access channel transmitter and receiver is one for each zoneS the number of the access channel transmitters and receiverz for the entire zones is ~, and the numbers of the access channel encoders and decoders are 8 respectively.
Comparing these data with those of the prior art system shown in Fig. 3, the number of the radio transmitter and receivers is re~uced by 4 in each radio base station, meaning a ~3~3~
significant difference as the number of the zones increases.
Fig. 13 shows a simplified block diagram showing another embodiment of this invention, in which vehicles are omitted. In this modification, line connection transfer switches 101 and 102 are added to the system shown in Fig. 8, thereby adding the following per~ormances to the paging controller and access controllers which are designated by reference numerals 106, 107 and 108.
As can be noted from the construction of the line connection transfer switches 101 and 1~2, in the base station 1, transmitter-receiver 51 or channel ~ 51 is connected to the access controller 107 so that the channel CH 51 acts as an access channel, while the other channels CH 52 to CH 55 are connec~ed to voice transfer switches respectively to form speech channels. ~n the same manner, in the base station 2, a transmitter-rece~iver 62 participates in access channel and the other transmitter-receivers 61, 63-65 establish speech channels.
The channel numbers of these two access channels are always broadcasted from a paging line connection signal transmitter 106a to all zones. Thus all vehicles receive this signal to update the content of the memory device 38.
Fig. 14 shows details of the elements 106a, 107 and 108 shown in Fig. 13r more particularly paging channel encoder/
decoder 106 and access channel encoders/decoders 107 and 108.
At first, a controller 230 selects any idle speech channel from a memory device 204 for operating switch 101. In 3~3~
this example the access channel encoder/decoder 107 is con-nected to a channel CHSl, while the access channel encoder/
decoder 108 is connected to a channel CH62. Other channels are connected to switches 72-75 and ~1, 83-85. The ~act that the access channels are channels CH51 and CH62 is instructed to system information encoder 226. When a switch 231 is thrown to the side of the encoder 226, an access channel information code is sent to mobile units through line 210~
Where there is a vehicle termination call, switch 231 is thrown to the side of the page encoder 201 to send out a page code in the same manner as in Fig. 13.
In the same manner as in Fig. 13, the origination code ~:
from a mobile is applied to either one of origination decoders 229 and 232.
The operation thereafter is the same as that of Fig.
13 except that it is not necessary to discriminate the radio zones. Under these conditions, all speech channels (in this example CH 52-CH 55) are available for con~er~ation. When all the speech channels, except access channels, are under conver-sation, channel CH 51 is designated as a speech channel and then switch 101 i5 thrown to the side of switch 71 to use channel 51 as the speech channel. While this condition per-sists, when the speech of the channel 55 terminates, the switch 101 is transferred to connect the channel CH 55 to the access channel encoder/decoder 107, and the fact that the present access channels are channels 55 and 62 is designated for the 343~
system in~ormation encoder 226, this fact being informed to the vehicles via switch 231 and line 210.
Let us compare these advantages with those of the first embodiment ta~ing a case wherein the number of zones is 8, the number of channels is 100, and the number of mobile access channels is 8. It can be noted that one speech channel is increased for each base station, meaning an increase of g channels when compared with the conventional system shown in Fig. 3.
Although according to this embodiment, it is r~ecessary to use eight (corresponding to 101 and 102) line connection transfer switches and the performances of the paging controller 106 and origination controllers 107 and 108 become more or less complicated, these disadvantages do no~ present serious problems, and advantage of increasing 8 speech channels is much remarka-ble. Thus, according to this invention, the utili~ation per-centage o~ the available channels can be greatly increased.
In a mobile communication system in which a service area is constituted by a plurality of xadio ~ones each installed with a base station provided with a pluralit~ of channels, a common control channel system is generally used including a mobile paging channel ~P-CH) and a mobile access channel (A-CH) which are used to establish a speech channel (S-CH) so as to decrease the set-up time of a call connection and to efficiently utili~e fre~uencies.
The prior ar~ and the invention will be described in conjunction with the attached drawings in which:
Figs. 1 and 2 are charts showing exchan~e of various codes between a control center and a mobile at the time of paging and access before talking;
Fig. 3 is a block diagram of a prior art mobile communication system;
Fig. 4 is a block diagram showing details of a control center;
E'igs. 5 and 6 are flow charts showing the operation of a controller in the Fig. 4 control center;
Fig. 7 shows a connection of a voice transfer switch;
Fig. 8 is a block diagram showing one embodiment of this invention;
Fig. 9 shows details of hlocks ~6a, 47 and 48 shown in Fig. 8;
Fig. 10 is a block diagram showing one example of a mobile s-tation;
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' ~3~3~
Fig. 11 is a block diagram showing details of the Fig. 10 circuit;
Fig. 12 is a flow chart for explaining the operation of controller 94b shown in Fig. 11;
Fig. 13 is a block diagram showing a modified embodiment of this invention; and Fig. 1~ is a block diagram showing details of the elements 106a, 107 and 108 shown in Fig. 13.
As disclosed on pages 1172 - 1190 of "Review of Electrical Communication Laboratories" Vol. 25, Nos. 11-12, 1977 published by Nippon Telegraph and Telephone Puhlic Corporation, when making a mobile terminating call through a paging channel ~P-CH), a page code is sent from a control center to a mobile. Then the mobile sends out a page response code in response to the page code. In a case shown in Fig. 1, a control center CC sends the page code to both base stations BSl and BS2. Where a mobile is in a radio zone ~of the base station BSl, the page response code is sent back to the control center CC via the base station BS1.
Since the control center receives C~; mg/~,~ - 2 -.
: ' . ` . ~
- :
' ~3~39 the page response code from the mobile by way of the base station BSl, it sends an idle channel number among a number o~
channels allocated to the base station BSl by means of a channel assiyn code ~o the mobile. In the mobile, the channel is skipped to the assigned channel, and after checking the loop a bell is rung. Then the mobile subscriber station (MSS) permits a mobile subscriber to begin talking. In this system, many mobiles utilize the paging channel P-CH on the time di-vision basis to improve the utilization e~ficiency.
As shown in Fig. 2, the access channel is used at the time of a mohile originating call. ~ore particularlyr in the mobile, the channel is changed ~rom the paging channel P-CH to the access channel A-C~ through which an access-channel-mark code is sent outO Since the contro~ center CC receives the origination code ~rom the base station BSl, it selects an idle channel out of a number of channels allocated to the base station BSl for sending a channel assign code to the mobile through the access channel. The mobile sk.ips. to the assigned . : channel to make a loop.check and sends out a dial code.to begin talking.
. Reservation o~ an access channel is necessary because where an idle channel among a number of speech channels is selected to transmit an origination code therethrough and then . utilize the selected channel as a speech channel it takes a many time to search the idle channel~ Where the access channel is fixed, however, it can not con.ey traffics as many as tha~
'~' ` ' .
, ~343g of the paging channel because ;ndividual moblles simultaneously send origination codes at a high probability, resultin~ in a so-called call collisionO
In a most widely used vehicle communication system, as the channel exclusively usea as a paginy channel was provided for each base station a single channel havin~ a predetermined fre~uency common to all zones, whereas as control channels exclusively used for accessing were provided for each base station one or more channels having predetermined frequencies common to all zones, the number o channels being determined by a maximum expectant number of the m~bi7es moving into or out of the service area of each base station.
More particularl~, the frequency of the radio carrier signal and the phase of the modulated signal are adjusted in an overlapped zone to m;nimize interf~rence between these signals.
Thus, as shown in Fig. 3 in radio zones I and II, a frequèncy fl is allocated to the paging channel P-CH and frequencies f2 and f3 to the access channel A-CH.
In the mobile communication system described above, there is no problem in the mobile paging channel, but in the case of the mobile access channel, as it utilizes specific fre~uencies common to all zones, the number o~ transce;vers in each base station increases greatly, thus increasing the cost of installation as will be described later in more detail. On the other hand, when the number oE the transceivers is fixed, the number of the speech channels decreases proportionally.
.
~3~39 From the standpoint of the increase in the number of the speech channels where the traffic is busy, i-t is desirable to use the mobile access channel as a speech channel.
Summary of the Invention _ Accordingly, it is an object of this invention to provide a novel mobile communication system capable of providing much more speech channels with simple construction.
Another object of this invention is to provide a mobile communication system capable of utilizing all transceivers, except those used in a mobile paging channel, for speech channels without impairing the speech performance of the base station.
According to one embodiment there is provided a mobile communication system wherein a plurality of radio zones, each including one radio base station, the base stations oE all radio zones being controlled by a control center which controls a paging and an origination of a mobile, are arranged to form a service area, and each radio zone is provided with at least one mobile access channel and a single mobile paging channel assigned with a radio frequency common to all radio zones, thus enabling to establish speech channels for the mobiles, characterized in that the at least one mobile access channel of one radio zone is assigned with a radio frequency which is different from that assigned to adjacent radio zones, the common radio control station is provided with means for controlling an origination of the mobile for selecting at least one channel amon~ available channels allocated to a radio base station associated with the mobile, circuit switching means operatively connected to mg/é,r - 5 -:
3~3~
the origination control means, for establishing the mobile access channel, and means for broadcasting a channel ~umber of the established mobile access channel -to all radio zones through the mobile paging channel; and wherein each mobile is provided with a receiver Eor receiving the channel number of the mobile access channel, means for updating and storing the received channel number, and means for sequentially receiving radio waves transmitted through the stored access channel and for comparing received field intensities to select a mobile access channel adapted to send out an origination signal of the mobile.
Description of the Preferred Embodiments For the sake of simplicity, in Fig. 3 showing a prior art mobile communication system, only two base stations 1 and 2 are shown, and the number of radio transmitter and receivers or transceivers in each base sta-tion is 6. This communication system generally comprises radio zones I and II
within the range of the radio waves from the base stations 1 and 2, mobile units 3 and 4, and a control center 5 controlling all base stations. A paging control unit 6 and access control units 7 and 8 are provided in the control eenter 5.
Details of the control center 5 are shown in Fig. ~.
page encoder 201 of page channel connection signal transrnitting and system controlling seetion 6a is eonstituted by a parallel-in-serial-out type shift register and started by a start signal from a controller 203 to produce a page code to be sent to mobiles via a transfer switch 205. A
channel assign encoder 202 is also constituted by a B
. ...
mg/~jr~ - 6 -' ' :
parallel-in-serial-out type shift register and operates to transmit via the transfer switch 205 -the channel number of an idle speech channel stored in a channel memory device 204 to a mobile which has transmitted a page response.
Page response decoders 6b and 6c are constituted by ,~
mg/~r~ - 7 -serial-in-parallel-out type shift registers, and when they receive a page response code from a mobile, they inform this fact to the controller 203~
An origination code from a mobile in the radio zone I
is received by either one of serial-in-parallel-out type shift registers 7b and 8b which are selected by the mobile subscriber.
These shift registers act as origination decoders. In this example, it is assumed that the shift register 7b has been selected. Then the output of the shift register 7b is applied to a controller 207 of a section 7a. The controller 207 dis-criminates radio zones RZl and RZ2 ~in this example RZl) and requests the controller 203 to designate an idle channel. Then the controller 203 informs an idle speech channel stored in the channel memory device 204 to the controller 207. The control-ler 207 sets the channel number of the idle channel in a channel assign encoder 206 and sends out this channel number to the mobile as a channel assign code. Where the oirigination code is inputted to an origination decoder 7c associated with the radio zone II, the same operation is made except that the radio zone to be searched is different~ Where the orignation code is inputted to decoders 8b and 8c, simlllar processing is made with a similar controller in a decoder 8a.
The flow charts of the controllers 203 and 207 are shown in Figs. 5 and 6, respectively.
Each base station is provided with six radio transmit-ter-receivers 10-15 and 20-25 and the control center 5 is 3~39 provided with voice transfer switches 33-35 and 43-45.
Each of the switches 33-35 and 43-45, is used to interconnect an ordinary telephone line and an approach line and has a construction similar to a switch circuit shown in Fig. 7 utilized in a conventional telephone exchange.
Since the operation oE the mobile communication system shown in Fig. 3 is well known in the art and can be readily understood from the description o the embodiment of this invention, it will not be described here.
Simply~ except the frequency of radio transmitter-receivers 10 or 20 for the paging channel, since two frequencies are assigned to the access channel, each base station is provlded with two radio transmitter-receivers 11 and 17 and 21 and 220 As a consequence the number of channels that can be used as the speech channels in each base station is three as can be noted from the num~er of the voice transfer switches 33-35 or 43-45.
Considering the number of effective access channels o~
the communication system, the channel frequencies f2 and f3 of the channels are common to the entire system so that while these channel frequencies are used in the radio zone I, the other zones can not use them. ~ccordingly, when a mobile 3 in the radio zone I and a mobile 4 in the radio zone II wish to use a channel, irrespective of the presence of two transceivers in each base station, the available access channel is only one for each base station. When each of two mobiles 3a and 3b, for ~, ,~ ,!
_ 9 _ example, in the radio zone I wishes to use a channel, it is possible to utilize two channels. ~ut in this case in the other radio zone II, since these two channel can not be used, it is possible to use only one channel on the average. Thus, when it is desired to have two effective access channels, it is necessary to provide additional two line connection signal controllers. This reduces the number of the speech channels by two, leaving only one channel. The above-described data show an extreme case because the number of channels per one base 10 ~ station is small. Let us consider an actual example. Suppose now that the number of the radio zones is 8, that the number of the radio transmitter-receives of each radio zone is 100 (except tbe transceiver for the paging channel) and that the number of access channels necessary for each service area is 5. Then the total number of the access channel radio transmit-ter-receivers over all base stations is 5x8=40. Accordingly, the number of the encoders and decoders of the access channel controllers also becomes 5x8=40.
As can be noted from the foregoing description, when one attempts to use the access channel as the speech channel in one zone, such a channel can not be used neither as the access channel nor the speech channel in the remaining zone. In other words, installed transmitter-receivers are not used efficiently.
Fig. 8 illustrates a simplified block diagram of one embodiment of this invention. In this case, like Fig. 3, the number of the base stations is 2 and the number of the radio 3~
transmitter-receivers in each base station is 6. Ignoring the frequency, respective component elements are identical to those shown in Fig. 3 and reference numerals are equal to those used in Fig. 3 plus 40. The system shown in Fig. 8 is different from that shown in Fig. 3 in that transmission controllers 47 and 48 are connected to transmitters 51 and 61 respectively.
For this reason, the provision of an access line connecting signal receiver in individual base stations is dispensed with so that it is not necessary to divide it into a plurality of circuits designated by numerals with suffixes a, b and c. Such a system can operate satisfactory when the operation of the mobile units is adaptive ~o the system as will be described with reference to Fig. 10~ Of course, two access channels of at least two adjacent base stations should have different frequencies for the purpose of preventing interference there-between.
Details of blocks 46a and 47 shown in Fig. 8 is shown in Fig. 9 Although these blocks operates substantially in the same manner as the elements 6a and 7a shown in Fig. 4 they are different in that since controllers 227 and 228 are not required to discriminate radio zones I and II, it is not neces-sary to exchange a signal required for effecting such a dis-crimination. Blocks 47 and 48 operate in the same manner.
Fig. 10 is a block diagram showing one example of the construction of the electric circuit carried on a mobile. This electric circuit comprises an antenna 91, a duplexer 92, a ~3~L39 receiver 93, a data -transmitter-receiver 94 having capabilities of encoding, decoding and comparison o~ field intensities o~
signals as well as sequence control capability, a ~requency synthesizer 96, a transmitter 97 and a memory device 98 storing channel numbers (or letters or symbols) of all access channels and the corresponding field strength values. These channel numbers are sent from a mobile paging signal controller 4 through transceivers 50 and 60 as sys~em information to a mobile and stored in the memory device 98 via antenna 91, lO receiver 93 and data transmit~er-receiver 94. Reference numeral 99 denotes a microphone or loudspeaker.
In a mobile communication system constructed as shown in Figs. 8 and 10, the system information or a vehicle paging signal is simultaneously transmitted from the paging line signal transmitter 46a through radio transmitter-receivexs 50 and 60 and received by all mobiles, and a radio signal received by antenna 91 and duplexer 92 is demodulated by receiver 93 and is then decoded by data transmitter-receiver 94.
When the received signal is a paging code, a paged mobile transmits an up-linked paging response code of the same Erequency. Where the mobile is in the zone T, the sent back response signal .is received by a paging line connection signal receiver 46b via the transceiver 50. The paging line connection signal transmitter 46a capable of controlling the system judges ~5 that the mobile is in the radio zone I according to the re-ceived signal, thus designating a speech channel among idle . , .
channels o~ the radio zone I so as to send out the channel number of the speech channel. The mobile receiving the desig-nated channel number cornmences a conversation through a channel of that channel number.
When the received signal contains a channel nurnber of the access channel as the system information, the content of the memory device is updated by the channel number decoded by the data transmitter-receiver 9~.
When a mobile sends out an origination signal, the channel number alloca-ted as the access channel and stored in the memory device 98 is read out by the data transmitter-receiver 94 and channels are sequentially designated for the frequency synthesi~er 96 by using a radio frequency designator 95 so as to sequentially receive both of the transmitted wave (a transmission output of the radio transmitter-receiver 51 at a frequency f2~ of the access channel in the radio base station 1 and the transmitted wa~e (a transmission output oE the radio transmission-receiver 61 at a frequency f3) of the access channel in the radio base station 2 and to compare the field strengths of respective input signals at different frequencies f2 and f3, thus selecting a radio base station having stronger field (in this examp1e the field intensity of the transmitted wave oE the radio ~se station 1 is stronger than that oE the base station 2). The mobi~e sends out an origination signal through the access channel of the selected radio zone. The sent out signal i~ received by an A-CH encoder/recoder 47 via 3~3~
radio transmitter-receiver 51. Accordingly, a suitable line is selected from idle channels of the radio zone I so as to desig-nate the speech channel number through the radio transmitter-receiver 51 for the mobile which has sent out the origination signal~ The mobile which has received the designated channel number commences a conversation through a channel of that channel number.
Fig. 11 shows details of one example of the mobile unit circuit arrangement as shown in Fig. 10. This unit circuit arrangement comprises a transmitter-receiver including a frequency synthesizer of a well knwon phase locked loop (PLL) type.
Describing in more detail with this transmitter and receiver, where a controller 94b designates a channel number of a predetermined paging channel P-CH for a radio frequency designator 95t a local frequency of the frequency synthesizer 96 is supplied to receiver 93 and transmitter 97 and locked in the paging channel P-CH.
Under this condition, system information code from an antenna 91 is~demodulated by receiver 93 and then inputted to a data receiver 94a which is constituted by a serial-in-paralle-out type shift register so as to apply the received signal to the controller 94b as parallel signals. The control-ler 94b decodes the channel number that has designated an access channel among the system information codes thus storing the decoded channel namber in a memory device 98. Where the '' 1. .
3~
access channel is predetermined, it is prestored in the memory device 98.
When a mobile subscriber hooks-off, a signal from a hook switch 267 is applied to the controller 94b. At this time, the controller 94b commences to apply one of the access channel numbers stored in the memory device 98 to the frequency controller 95 to start reception of the first access channel.
Where an intermediate fre~uency amplifier 254 is made of the type CA308~ sold by RCA Corporation, a received field strength can be obtained and the controller 94b stores the field strength of t~le first access channel in the memory device 98 via an analogue-digital converter 268. Then the channel number of the second access channel is again designated for the fre-quency designator 95 for storing the field strength at that ~15 time in the memory device g8. In this manner, all access channels informed by the system information codes are scanned for storing respective field strengths in the memory device 98. Thereafter, the field strengths are compared with each ~ other for selecting an access channel having the largest field strength.
The cotroller 94b causes the frequency-synthesizer 96 to lock an access channel regarding the largest field so as to set an origination code in the data transmitter 94c of the parallel-in-serial-out type shift register, and activates a power amplifier 262 by a carrier on/off signal on line 269 produced by the controller 94b to send out an origination code.
.- - 15 -: .
.
A speech channel assigned by a control center via a base station as a response of the origination code is set in the frequency designator 95 via the data receiver 9~a and the controller 94b in the same manner as the reception of the system information code to switch the frequency of the mobile to the assigned channel.
Fig. 12 is a flow chart showing the operation of the controller 94b. Although the operation of mobile terminating call is not shown in Fig. 12, as it is not directly related to this invention, it is omitted.
The embodiment operates in a manner described above, but in the system shown in Fig. 8, among five channels that can-be used for communication, the access channel is one and the remaining ~our channels are used as the speech channels. If two channels are used as the access channels, the speech channels are 3, thus increasing the number of the speech channels than the system shown in Fig. 3. In an actual e~ample, where the number ~f the zones is 8, and where subscribers are distributed evenly in each zone, the number of the access channel transmitter and receiver is one for each zoneS the number of the access channel transmitters and receiverz for the entire zones is ~, and the numbers of the access channel encoders and decoders are 8 respectively.
Comparing these data with those of the prior art system shown in Fig. 3, the number of the radio transmitter and receivers is re~uced by 4 in each radio base station, meaning a ~3~3~
significant difference as the number of the zones increases.
Fig. 13 shows a simplified block diagram showing another embodiment of this invention, in which vehicles are omitted. In this modification, line connection transfer switches 101 and 102 are added to the system shown in Fig. 8, thereby adding the following per~ormances to the paging controller and access controllers which are designated by reference numerals 106, 107 and 108.
As can be noted from the construction of the line connection transfer switches 101 and 1~2, in the base station 1, transmitter-receiver 51 or channel ~ 51 is connected to the access controller 107 so that the channel CH 51 acts as an access channel, while the other channels CH 52 to CH 55 are connec~ed to voice transfer switches respectively to form speech channels. ~n the same manner, in the base station 2, a transmitter-rece~iver 62 participates in access channel and the other transmitter-receivers 61, 63-65 establish speech channels.
The channel numbers of these two access channels are always broadcasted from a paging line connection signal transmitter 106a to all zones. Thus all vehicles receive this signal to update the content of the memory device 38.
Fig. 14 shows details of the elements 106a, 107 and 108 shown in Fig. 13r more particularly paging channel encoder/
decoder 106 and access channel encoders/decoders 107 and 108.
At first, a controller 230 selects any idle speech channel from a memory device 204 for operating switch 101. In 3~3~
this example the access channel encoder/decoder 107 is con-nected to a channel CHSl, while the access channel encoder/
decoder 108 is connected to a channel CH62. Other channels are connected to switches 72-75 and ~1, 83-85. The ~act that the access channels are channels CH51 and CH62 is instructed to system information encoder 226. When a switch 231 is thrown to the side of the encoder 226, an access channel information code is sent to mobile units through line 210~
Where there is a vehicle termination call, switch 231 is thrown to the side of the page encoder 201 to send out a page code in the same manner as in Fig. 13.
In the same manner as in Fig. 13, the origination code ~:
from a mobile is applied to either one of origination decoders 229 and 232.
The operation thereafter is the same as that of Fig.
13 except that it is not necessary to discriminate the radio zones. Under these conditions, all speech channels (in this example CH 52-CH 55) are available for con~er~ation. When all the speech channels, except access channels, are under conver-sation, channel CH 51 is designated as a speech channel and then switch 101 i5 thrown to the side of switch 71 to use channel 51 as the speech channel. While this condition per-sists, when the speech of the channel 55 terminates, the switch 101 is transferred to connect the channel CH 55 to the access channel encoder/decoder 107, and the fact that the present access channels are channels 55 and 62 is designated for the 343~
system in~ormation encoder 226, this fact being informed to the vehicles via switch 231 and line 210.
Let us compare these advantages with those of the first embodiment ta~ing a case wherein the number of zones is 8, the number of channels is 100, and the number of mobile access channels is 8. It can be noted that one speech channel is increased for each base station, meaning an increase of g channels when compared with the conventional system shown in Fig. 3.
Although according to this embodiment, it is r~ecessary to use eight (corresponding to 101 and 102) line connection transfer switches and the performances of the paging controller 106 and origination controllers 107 and 108 become more or less complicated, these disadvantages do no~ present serious problems, and advantage of increasing 8 speech channels is much remarka-ble. Thus, according to this invention, the utili~ation per-centage o~ the available channels can be greatly increased.
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a mobile communication system wherein a plurality of radio zones, each including one radio base station, the base stations of all radio zones being controlled by a control center which controls a paging and an origination of a mobile, are arranged to form a service area, and each radio zone is provided with at least one mobile access channel and a single mobile paging channel assigned with a radio frequency common to all radio zones, thus enabling to establish speech channels for the mobiles, the improvement wherein said at least one mobile access channel of one radio zone is assigned with a radio frequency which is different from that assigned to adjacent radio zones, said control center is provided with means for controlling an origination of said mobile for selecting at least one channel among available channels allocated to a radio base station associated with said mobile, circuit switching means operatively connected to said origination control means, for establishing said mobile access channel, and means for broadcasting a channel number of said established mobile access channel to all radio zones through said mobile paging channel; and wherein each mobile is provided with a receiver for receiving said channel number of the mobile access channel, means for updating and storing said received channel number, and means for sequentially receiving radio waves transmitted through said stored access channel and for comparing received field intensities to select a mobile access channel adapted to send out an origination signal of said mobile.
2. A mobile communication system according to claim 1 wherein said circuit switching means is controlled by said origination control means, for said operative connection.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3012780A JPS56126339A (en) | 1980-03-10 | 1980-03-10 | Mobile communication system |
| JP30127/'80 | 1980-03-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143439A true CA1143439A (en) | 1983-03-22 |
Family
ID=12295103
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000372615A Expired CA1143439A (en) | 1980-03-10 | 1981-03-10 | Mobile communication system |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4392242A (en) |
| JP (1) | JPS56126339A (en) |
| AU (1) | AU526469B2 (en) |
| CA (1) | CA1143439A (en) |
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| US3663762A (en) * | 1970-12-21 | 1972-05-16 | Bell Telephone Labor Inc | Mobile communication system |
| JPS5241082B2 (en) * | 1973-03-28 | 1977-10-17 | ||
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| JPS5547745A (en) * | 1978-08-25 | 1980-04-04 | Nec Corp | Mobile communication system |
-
1980
- 1980-03-10 JP JP3012780A patent/JPS56126339A/en active Granted
-
1981
- 1981-03-05 US US06/240,937 patent/US4392242A/en not_active Expired - Lifetime
- 1981-03-10 CA CA000372615A patent/CA1143439A/en not_active Expired
- 1981-03-10 AU AU68199/81A patent/AU526469B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU526469B2 (en) | 1983-01-13 |
| JPS56126339A (en) | 1981-10-03 |
| US4392242A (en) | 1983-07-05 |
| AU6819981A (en) | 1981-10-29 |
| JPS6145905B2 (en) | 1986-10-11 |
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