WO2003067889A2

WO2003067889A2 - Multicarrier downstream communication

Info

Publication number: WO2003067889A2
Application number: PCT/IB2003/000353
Authority: WO
Inventors: Petrus A. M. Van Grinsven; Henricus J. C. Kuijpers
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2002-02-06
Filing date: 2003-01-31
Publication date: 2003-08-14
Also published as: WO2003067889A3; AU2003202733A1; AU2003202733A8

Abstract

A transmission system has a primary station and at least one secondary station, which stations are coupled through a transmission medium. The stations each comprise means for transmission between the respective stations. The primary station comprises a multicarrier unit coupled to the transmission medium. On each carrier downstream frequency there are data streams, whose content is user controlled by transmission means which are common transmission medium modems. In particular the control information is meant for controlling data payload at the one or more carriers. The transmission medium comprises a partially fibre, partially coax medium. An improved flexibility at reduced cost is achieved with common cable modems when supplying user services, such as video on demand, pay per view, special television, such as high definition television services, WEB services, data, voice, or the like.

Description

Multicarrier downstream communication

The present invention relates to a transmission system having a primary station and at least one secondary station, which primary and secondary stations are coupled through a transmission medium, whereby the primary and secondary stations each comprise means for transmission between the respective stations, and the primary station further comprises a multicarrier unit coupled to the transmission medium.

The present invention also relates to a primary station and secondary station for application in the transmission system, to a method for exchanging downstream and upstream signals between the primary station and at least one secondary station respectively in a partially fibre, partially cable transmission medium, and to signals for application in the transmission system and its stations, and to signals for applying the method.

Such a transmission system and method are known from WO 00/79794. The known transmission system has a primary station and one or more secondary stations. The primary and secondary stations are coupled through a transmission medium in the form of a Hybrid Fibre Coax (HFC) medium. The primary and secondary stations each comprise means for transmission between the respective stations. The secondary station has transmission means embodied by Set Top Boxes (STB). The primary station further comprises a multicarrier unit in the form of a QAM array having QAM units coupled to the transmission means. Each QAM unit transmits its own always present television programs at a carrier frequency which is different from the carrier frequency of another QAM. A user of the television set needs to have his own STB tuner if he wants to tune to a television channel present at another QAM frequency and transmitted by another QAM unit. In that case even two tuners are being used, that is one in the television set and one in the STB. It is a disadvantage of the known transmission system that it can hardly be used effectively to meet the wishes of an increasing demand in flexibility respecting the transmission of all sorts, amounts, formats and speeds of for example TN programs, data, gaming, networking, video, or IP related data from the Internet, and other kinds of data. It is an object of the present invention to provide a more flexible transmission system and method capable of providing large quantities of data, such as video on a more cost effective and current way. Thereto the transmission system according to the invention is characterized in that multicarrier unit is capable of effecting user controlled carrier downstream communication by transmission means which are common transmission medium modems.

Correspondingly the method according to the invention is characterized in that the downstream signal which comprises several carriers effects selective carrier downstream communication by common transmission medium modems.

It is an advantage of the transmission system and method according to the present invention that users or user groups at the at least one secondary stations serviced by the primary station mainly control the data content at the carrier frequencies. This means that a majority of the data space available at all carriers is occupied by data, which is actually used by the user or group of users. Data which is not actually requested for at that moment by a particular user or group of users is not transmitted to the secondary stations over one or more carriers where these secondary stations are tuned to. This in turn means optimum effective use of available transmission capacity and provides a reduction of the cost per data quantity transferred over the transmission system according to the invention. Furthermore it is an advantage of the invention that for the transfer for video and/or data only common transmission medium modems can be used, that is to say that in a cable environment a single current cable modem can do the job, without the need for additional investments in Set Top Boxes, containing another tuner and demodulator.

An embodiment of the transmission system according to the invention is characterized in that the modem in the at least one secondary station is arranged for upstream transmitting control information for controlling downstream payload at the one or more carriers generated by the multicarrier unit.

The actual user control is such that the data space saved at a carrier frequency can be filled up with additional data payload, such as for example Video On Demand (VOD) or other larger or smaller, faster or slower data types.

The user control can simply be effected through communication of required control information through any desired upstream path to the primary_/ station. The upstream control information may even originate from a group of users, which has the advantage that the large asymmetry between downstream and upstream data commumcation is reduced. A further embodiment of the transmission system according to the invention is characterized in that the transmission system comprises frame means for copying control information into each frame associated with the one or more carriers.

This way the necessary control information is always available in the generated frames at every carrier.

A still further embodiment of the transmission system according to the invention is characterized in that if the transmission medium comprises a fibre medium one or more carriers present in the multicarrier signal is/are exchanged over the fibre medium between the primary and the at least one secondary station. In case of a fibre transmission medium between the primary and secondary station(s) the fibre medium allows a simultaneous transfer of different carriers carrying the requested data at different carrier frequencies (Frequency Division Multiplexing) or optical wavelengths (Wavelength Division Multiplexing) or using a combination of FDM and WDM. The user selected data requested by the secondary stations can now be spread out over all available carriers, which creates empty space per carrier that can be occupied by other data.

Another further embodiment of the transmission system according to the invention is characterized in that if the transmission medium comprises a coax medium a subset of the carriers present in the multicarrier signal is exchanged over the coax medium then present between the primary and the at least one secondary station.

In case of a coaxial cable as transmission medium between the primary and secondary station(s) only the carriers carrying the user requested data is sent over the cable. For example real time video over IP address (Video on IP) is now possible with an already existing common cable modem, which is usually already present at home. Advantageously the transmission system according to the invention is characterized in that the transmission medium comprises a partially fibre, partially coax medium.

This is called a well known HFC medium, wherein the transmission system and its stations is embedded both at the level of the fibres and the coaxial cables. Other detailed embodiments of the invention are set out in the remaining claims.

At present the transmission system and method according to the invention will be elucidated further together with their additional advantages, while reference is being made to the appended drawing, wherein similar components are being referred to by means of the same reference numerals.

In the drawing:

Fig. 1 shows a general outline of a transmission system according to the prior art embedded in a Hybrid Fibre Coax (HFC) transmission medium having primary and secondary stations;

Fig. 2 shows details of a primary station for application in the transmission system according to the invention; and

Fig. 3 shows respective data streams e.g. on dedicated carriers present in the transmission system according to the invention.

Fig. 1 shows a general outline of a transmission system 1 implemented in

Hybrid Fibre Coax (HFC) technology. The transmission system 1 has a primary station 2 and at least one secondary station 3. The primary station 2 is typically located in the Head-End (HE) or Hub or maybe even in the Fiber Node (FN). The HE, Hub and FN are connected by a glass fibre transmission medium 4. The HE services for example 50,000-200,000 homes and a Hub typically services 10,000 - 20,000 homes. A Fibre Node (FN) typically services 500- 2,000 homes. The right part of Fig. 1 reflects the transmission medium as a cable 4, generally a coax cable. The cable 4 couples the signal from the primary station or stations 2 via the FN 2 and the coax branches to the Network Terminals (NT) 3 at the homes of the users or at the homes of a group of lets say 5-10 users. Hereinafter with the above in mind general reference will be made to the mutually communicating stations as primary station 2 and secondary station 3. The primary and secondary stations 2 and 3 respectively each comprise transmission means 5 for effecting transmission between the stations 2, 3. These transmission means 5 (only schematically shown) are embodied by Cable Modem Termination Systems (CMTS), sometimes called Interactive Network Adapter (INA) depending on the standard used in the system 1. On the user level every user has its own common in home cable modem as transmission means 5, which may be a built in cable modem.

Fig. 2 shows details of the primary station 2 for application in the fibre part of the HFC as shown in Fig. 1. In particular it shows that the primary station 2 has several downstream paths D and one or more an upstream paths U. The primary station 2 comprises a so called layer two switch 6 for processing the down and upstream signals sent to and by the secondary stations 3. The station 2 comprises a multicarrier unit 7 coupled to the switch 6 and via the downstream paths D to the transmission glass fibre medium 4. The multicarrier unit 7 is capable of effecting user controlled multicarrier downstream commumcation. Given the fully packed data stream to be transmitted to the secondary stations, such as the schematically indicated stream S shows in Fig. 3 it is proposed to tear apart the stream S into N dedicated carrier streams (where N=3 in this example) SI, S2 and S3. Thereto the station 2 comprises Network Interfaces (NT) 8, which are generally integrated into the switch 6. Each upstream path U of the station 2 comprises in succession an IF/RF stage 9, (burst) receiver 10, and a return link subsystem (RLS) 11. From the received upstream signal control information, including user controlled information, is being derived, which information is named: Medium Access Control (MAC) in stream S of Fig. 3. The station 2 comprises a frame means 12 coupled to the RLS 11. Several in the case as shown three parallel downstream branches each further comprise in succession a Forward Link Subsystem, also acting as Data Inserters (DI's) 13, a modulator 14, and IR/RF stages 9. Each of the DI's 13 is coupled to the frame means 12, which generates frames containing the control information, which will be the MAC protocol related data, which is being copied into each of the dummy frames. The dummy frames are forwarded to the DI's 13. The stream S comprises Data packages IP1, IP2 and IP3 in stream S as shown in Fig. 3, which packages are distributed over the respective stream SI, S2 and S3 in the parallel downstream branches. The tearing apart of packed stream S creates empty data spaces in the partial streams SI, S2 and S3, which may be filled by for example Video On Demand (VOD) data or other user requested payload data. Examples of other data are: Pay per view data, video in IP, special television data, such as high definition television services, WEB services or the like. Through the fibre medium 4 each of the respective carrier modulated streams SI, S2 and S3 may be sent to the secondary stations 3 for example modulated on different colors of light transmitted by glass fibre laser sources. The transmission means 5 in the fibre part of the system 1 may be common transmission medium modems of the Cable Modem Termination System (CMTS) type.

What is explained above for the fibre part, also holds for the cable part on a lower level in the transmission system 1 , with the exception that it is <jnly possible to transmit a limited number of streams over the cable. So in order to be able to create enough empty space in the transmitted stream, the stream should virtually only be occupied by data packages like IP1, IP2, EP3, that are actually being used by the users or user group.

Of course the built up of a station for the cabled part of the system 1 may be somewhat different from the embodiment shown in Fig. 2. Essential elements will roughly be the same, save for the frequency transmission spectrum involved. In an HFC system the available upstream bandwidth is typically 60 MHz, that is 5-65 MHz in European networks and 37 MHz, that is 5-42 MHz in North American networks. Downstream bandwidth for cables range from 70-870 MHz. Examples of modulation schemas are QPSK, 16QAM, 32QAM, 64QAM, 256QAM. Because generally there is a high degree of asymmetry between the downstream traffic and the upstream traffic, the upstream paths TJ of a group of for example (100 - 200) users can be grouped together. This way a multi user upstream communication is linked to the multicarrier downstream system for the same group of users.

The method explained above can be implemented within the framework of the Data Over Cable System Interface Standard (DOCSIS) of CableLabs (USA) or its European counterpart Euro-DOCSIS, or the DVB-RC standard.

Claims

CLAIMS:

1. A transmission system having a primary station and at least one secondary station, which primary and secondary stations are coupled through a transmission medium, whereby the primary and secondary stations each comprise means for transmission between the respective stations, and the primary station further comprises a multicarrier unit coupled to the transmission medium, characterized in that the multicarrier unit is capable of effecting user controlled carrier downstream communication by transmission means which are common transmission medium modems.

2. The transmission system according to claim 1, characterized in that the modem in the at least one secondary station is arranged for upstream transmitting control information for controlling downstream payload at the one or more carriers.

3. The transmission system according to claim 2, characterized in that the transmission system comprises frame means for copying control information into each frame associated with the one or more carriers.

4. The transmission system according to one of the claims 1-3, characterized in that if the transmission medium comprises a fibre medium one or more carriers present in the multicarrier signal is/are exchanged over the fibre medium between the primary and the at least one secondary station.

5. The transmission system according to one of the claims 1-4, characterized in that if the transmission medium comprises a coax medium a selected one of the carriers present in the multicarrier signal is exchanged over the coax medium then present between the primary and the at least one secondary station.

6. The transmission system according to one of the claims 1-5, characterized in that the transmission medium comprises a partially fibre, partially coax medium.

7. Primary station for application in the transmission system according to one of the claims 1-6, the transmission system having a primary station and at least one secondary station, which primary and secondary stations are coupled through a transmission medium, whereby the primary and secondary stations each comprise means for transmission between the respective stations, and the primary station further comprises a multicarrier unit coupled to the transmission medium, characterized in that the multicarrier unit is capable of effecting user controlled carrier downstream communication by transmission means which are common transmission medium modems.

8. Secondary station for application in the transmission system according to one of the claims 1-6, the transmission system having a primary station and at least one secondary station, which primary and secondary stations are coupled through a transmission medium, whereby the primary and secondary stations each comprise means for transmission between the respective stations, and the primary station further comprises a multicarrier unit coupled to the transmission medium, characterized in that the multicarrier unit is capable of effecting user controlled carrier downstream communication by transmission means which are common transmission medium modems.

9. A method for exchanging downstream and upstream signals between a primary station and at least one secondary station respectively in a partially fibre, partially cable transmission medium, characterized in that the downstream signal which comprises several carriers effects selective carrier downstream communication by common transmission medium modems.

10. The method according to claim 9, characterized in that the transmission medium may range form a full fibre to a full cable medium.

11. The method according to claim 9 or 10, characterized in that the upstream signals comprises control information for controlling downstream payload at the one or more carriers.

12. The method according to claim 11, characterized in tha control information is being copied into each of the frames associated with the one or more carriers.

13. The method according to one of the claims 9-12, characterized in that the carriers apart from a possible fixed payload at least comprises user controlled payloads.

14. The method according to one of the claims 9-13, characterized in that the user controlled payloads may comprise video on demand, pay per view, video in IP, special television, such as high definition television services, WEB services, data, voice, or the like, which may for example be packed in a video over IP in DOCSIS format, or video in MPEG- TS having separate Program Identifier.

15. Signals for application in the transmission system according to one of the claims 1-6, the primary station according to claim 7, the at least one secondary station according to claim 8, and/or for applying the method according to one of the claims 9-14, which primary and secondary stations are coupled through a transmission medium, whereby the primary and secondary stations each comprise means for transmission between the respective stations, and the primary station further comprises a multicarrier unit coupled to the transmission medium, characterized in that the multicarrier unit is capable of effecting user controlled carrier downstream communication by transmission means which are common transmission medium modems.