WO2003001826A2 - Procede et appareil permettant de transmettre des donnees - Google Patents

Procede et appareil permettant de transmettre des donnees Download PDF

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Publication number
WO2003001826A2
WO2003001826A2 PCT/EP2002/004858 EP0204858W WO03001826A2 WO 2003001826 A2 WO2003001826 A2 WO 2003001826A2 EP 0204858 W EP0204858 W EP 0204858W WO 03001826 A2 WO03001826 A2 WO 03001826A2
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WO
WIPO (PCT)
Prior art keywords
data
compression
data stream
previous
link
Prior art date
Application number
PCT/EP2002/004858
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English (en)
Other versions
WO2003001826A3 (fr
Inventor
Stephen Hill
Stephen John Barrett
Stephen Aftelak
Original Assignee
Motorola Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Motorola Inc filed Critical Motorola Inc
Publication of WO2003001826A2 publication Critical patent/WO2003001826A2/fr
Publication of WO2003001826A3 publication Critical patent/WO2003001826A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/04—Protocols for data compression, e.g. ROHC

Definitions

  • This invention relates to a method and apparatus for transmitting data over a shared resource in a communication network.
  • each of the remote terminals communicates with typically a fixed base station. Communication from the remote terminal to the base station is known as uplink and communication from the base station to the remote terminal is known as downlink.
  • the total coverage area of the system is divided into a number of separate cells, each predominantly covered by a single base station. The cells are typically geographically distinct with an overlapping coverage area with neighbouring cells.
  • FIG. 1 illustrates a cellular communication system 100.
  • a base station 101 communicates with a number of remote terminals 103 over radio channels 105.
  • the base station 101 covers users within a certain geographical area 107, whereas other geographical areas 109, 111 are covered by other base stations 113, 115.
  • the communication link will change from being between the remote terminal and the base station of the first cell, to being between the remote terminal and the base station of the second cell.
  • This is known as a handover.
  • some cells may lie completely within the coverage of other larger cells.
  • All base stations are interconnected by a fixed network.
  • This fixed network comprises communication lines, switches, interfaces to other communication networks and various controllers required for operating the network.
  • a call from a remote terminal is routed through the fixed network to the destination specific for this call. If the call is between two remote terminals of the same communication system the call will be routed through the fixed network to the base station of the cell in which the other remote terminal currently is. A connection is thus established between the two serving cells through the fixed network.
  • PSTN Public Switched Telephone Network
  • the call is routed from the serving base station to the interface between the cellular mobile communication system and the PSTN. It is then routed from the interface to the telephone by the PSTN.
  • PSTN Public Switched Telephone Network
  • a cellular mobile communication system is allocated a frequency spectrum for the radio communication between the remote terminals and the base stations. This spectrum must be shared between all remote terminals simultaneously using the system.
  • CDMA Code Division Multiple Access
  • DS-CDMA Direct Sequence CDMA
  • the signals are prior to being transmitted multiplied by a high rate code whereby the signal is spread over a larger frequency spectrum.
  • a narrowband signal is thus spread and transmitted as a wideband signal.
  • the original narrowband signal is regenerated by multiplication of the received signal with the same code.
  • a signal spread by use of a different code will at the receiver not be de-spread but will remain a wide band signal.
  • the majority of interference caused by interfering signals received in the same frequency spectrum as the wanted signal can thus be removed by filtering.
  • CDMA communication systems are IS 95 standardised in North America and the Universal Mobile Telecommunication System (UMTS) currently under standardisation in Europe.
  • UMTS Universal Mobile Telecommunication System
  • GPRS General Packet Radio Service
  • GSM Global System for Mobile communication
  • bursty data streams where the instantaneous data rate may vary significantly.
  • An example of such a bursty data stream is a video signal where a source encoder typically will have an output data rate that varies significantly for the same quality level dependent on the nature of the picture being encoded. For example, a fast moving image with high level of detail will generate a much higher data rate than a relatively static image with low level of detail. As the nature of the image typically changes during a transmission the data rate may vary by several orders of magnitude.
  • One method for allocating resource to a bursty service is by providing resource allocation sufficient to allow for the maximum data rate. However, this would clearly be inefficient as for most of the time only a fraction of the allocated resource would be used.
  • Another method is to packetise the data stream and allocate part of a shared resource to the service.
  • the packetising may result in varying data packet sizes and/or varying intervals between transmission of packets.
  • statistical multiplexing results in an improved efficiency in the utilisation of the resource.
  • the quality of service for example in terms of dropped packets due to interference from other services
  • This complicates providing a guaranteed quality of service because this is dependent upon the statistics of all the packet streams. These statistics may be difficult to obtain, and the admission control decision is computationally complex to implement.
  • a method for transmitting data over a shared resource in a communication network comprising the steps of : receiving a data stream having a varying data rate; provisioning from the shared resource, a circuit switched data link having a link data rate below the maximum data rate of the data stream; compressing the data stream to a compressed data stream having a compressed data rate not higher than the link data rate using variable data compression; and transmitting the compressed data stream over the circuit switched data link.
  • variable data compression is such that a minimum compression factor is used and the data stream and compressed data stream comprise a plurality of data packets.
  • variable data compression comprises both lossy and non-lossy compression dependent on the compression level required to compress the data stream.
  • an apparatus for transmitting data over a shared resource in a communication network comprising: means for receiving a data stream having a varying data rate; means for provisioning from the shared resource, a circuit switched data link having a link data rate below the maximum data rate of the data stream; means for compressing the data stream to a compressed data stream having a compressed data rate not higher than the link data rate using variable data compression; and means for transmitting the compressed data stream over the circuit switched data link.
  • the advantages of the invention includes the provision of efficient data communication while allowing the resource for transmitting data to be independent of other data services being supported. It also includes the advantage of data compression having a low complexity and computational resource requirement as it enables compression to be as low as possible to provide for data communication at the link data rate.
  • FIG. 1 is an illustration of a cellular communication system according to prior art
  • FIG. 2 illustrates a block diagram of an apparatus for transmitting data in accordance with an embodiment of the invention
  • FIG. 3 illustrates a packetised data stream having a varying data rate
  • FIG. 4 illustrates how the data packets of FIG. 3 are affected by the data compressor in accordance with an embodiment of the invention.
  • Fig. 2 illustrates a block diagram of an apparatus for transmitting data 200 in accordance with an embodiment of the invention.
  • a data source 201 generates data to be transmitted.
  • a specific example is a video data source, which records a picture and digitises these.
  • the digitised signal is fed to a source encoder 203 which generates a digital video signal based on the digitised signal from the data source.
  • the output of the source encoder 203 is connected to a data segmenter 205 which receives a data stream (the digital video signal) having a varying data rate from the source encoder 203 and separates this data stream into discrete data packets.
  • the data segementer 205 is connected to a data compressor 207.
  • the data compressor 207 is also connected to a resource provisioner 209 for provisioning a circuit switched data link from a shared resource, such as a shared common channel on the air interface. Alternatively, the total air interface resource may be seen as the shared resource from which a circuit switched data link is provisioned.
  • the circuit switched data link is provisioned such that the link data rate is below the maximum data rate of the data stream from the data segmenter 205.
  • the data compressor 207 compresses the data stream to a compressed data stream having a compressed data rate not higher than the link data rate. This compression is done by use of variable data compression.
  • the data compressor 207 is connected to a transmitter 211 which transmits the compressed data stream over the circuit switched data link provisioned by the resource provisioner 209.
  • the transmitted compressed data stream is received by a receiver 213, which is connected to a de-compressor 215.
  • the de-compressor 215 decompresses the received data output from the receiver in a process that reverses the function of the compressor 207.
  • the data stream output by the de-compressor 215 is then processed in a conventional fashion.
  • a data source for a speech may consist in a microphone, an analog amplifier and a digital to analog converter, which samples the amplified microphone signal at a fixed resolution and at fixed intervals. This generates a fixed data rate signal, which is however a very inefficient representation of the signal. The signal is therefore fed to the source encoder which encodes the microphone signal as a digital speech signal.
  • This encoding is based on knowledge of speech signals, as is well known in the art, and therefore provides a highly efficient signal containing sufficient information to regenerate a speech signal at the receiver.
  • variable source encoding include video signals where the data rate depends on the level of detail and changes in the picture.
  • the output of the source encoder is fed to a data segmenter, which segments the data into discrete packets.
  • the source encoder directly outputs data in discrete packets.
  • FIG. 3 illustrates a packetised data stream having a varying data rate.
  • the data stream represents the output of the data segmenter, which is fed to the data compressor, hi this example, each data packet has a fixed duration but the data size and thereby the data rate of each packet varies. Thus packet 301 has a higher data rate than packet 303.
  • the maximum data rate of the packetised data stream is given by data packet 307. The minimum data rate is zero as for some time intervals no data packets are generated (e.g. corresponding to the silence periods for a speech signal).
  • Transmission of a varying data rate data stream such as shown in FIG. 3 is problematic.
  • One option is to allocate a circuit switched link between transmitter and receiver.
  • conventional approaches require that a link is provisioned which has a data capacity equal or larger than the maximum data rate. It is clear that for the majority of the time this data link will not be fully utilised and therefore that a significant loss in capacity is incurred.
  • the resource provisioner provisions a circuit switched data link.
  • this provisioning is such that the data capacity of the link is below the maximum data rate of the varying data stream.
  • the resource provisioner allocates a lower resource level so that the link data rate is below the maximum data rate of the data stream.
  • the exact data rate of the provisioned link can depend on many factors such as the quality required, the cost of the resource, the available bandwidth, the complexity requirements for compressing etc. It may dynamically be determined or may be predetermined for a given service, hi the preferred embodiment, a given service has a predetermined link data rate dependent on the service determined to give a reasonable quality level, for example if a speech signal is to be transmitted the link data rate is set to 4 kbps and if a video signal is transmitted it is set to 384 kbps. Hence, in this embodiment, the resource provisioner is informed or detects that a speech signal is to be transmitted and consequently it provisions a 4 kbps circuit switched link.
  • circuit switched link can be done according to any known method or system for resource allocation without detracting from the current invention.
  • the varying data rate data stream is transmitted over this link.
  • the data compressor uses variable data rate compression to generate a compressed data stream having a compressed data rate not higher than the link data rate using variable data compression.
  • variable compression is in response to the link data rate and the current rate of the varying data rate.
  • this is such that a minimum of available compression is used which will result in a compressed data rate below the link data rate.
  • FIG. 4 illustrates how the data packets of FIG. 3 are affected by the data compressor in accordance with an embodiment of the invention.
  • the dashed line 401 illustrates the link data rate (or circuit bandwidth) of the provisioned circuit switched link.
  • Data packets 309, 311 and 315 all have a data rate, which is below the link data rate. They can therefore be transmitted using the circuit switched link without any requirement for compression and they are therefore left unaffected by the data compressor.
  • Data packets 303 and 305 have a data rate, which is higher than the link data rate, and therefore the variable data compression is applied to these packets.
  • the data compressor comprises means for operating a plurality of different compression algorithms having different compression factors.
  • compression algorithms which provides higher compression factors will be more complex than for lower compression factors and therefore require higher computational resources.
  • Data compression can either be lossy or loss-free. For loss free compression no information is lost and the original data stream can be recovered. For lossy data compression some information is lost and consequently the quality of the underlying signal (e.g. speech or video signal) may be degraded. Typically, the higher the compression factor the higher the degradation in quality.
  • the data compressor comprises functionality for running both lossy and loss-free compression algorithms with different compression factors.
  • the data rate of the data packets 303 and 305 is of such magnitude that the compression factor required to reduce the data rate to that of the link data rate can be achieved by a loss-free data compression algorithm.
  • the data compressor therefore selects an appropriate loss-free compression algorithm and applies it to the data packets (note different compression algorithms and factors are used for the two data packets in the given example). Consequently, the compressed data packets 303 and 305 can now be transmitted over the circuit switched link.
  • the data rate of data packets 301 , 307 and 313 exceed the link data rate by a significant margin.
  • a loss-free compression algorithm is chosen to achieve the required compression factor.
  • an appropriate lossy compression algorithm is chosen and applied to the whole data packet.
  • a combination of two or more compression algorithms are used such that part of the data packet is compressed using a lossy data compression algorithm and part of the data is compressed using a loss-free data compression algorithm, h the example of FIG. 4, both loss-free and lossy data compression is used.
  • variable data rate compression technique including any compression or combination of compression algorithms
  • the receiver is a conventional receiver and the de-compressor reverses the function of the compressor.
  • the de-compressor can automatically determine the compression scheme used by the data compressor from the received compressed data stream but in the preferred embodiment the data compressor embeds signalling information in a data packet header. This information contains information on which compression algorithm(s) have been used on which data. The receiver decodes this information before de-compression and uses the information to select the appropriate de-compression algorithm(s).
  • the output to the data compressor is packetised and is transmitted in packets over the air interface.
  • the data compressor compresses these packets or segments individually. The compression is thus performed on a per data packet basis such that each packet is compressed independently of other data packets.
  • a plurality of data packets from the data segmenter is combined into a single data packet on the air interface and in this case the compression may be done individually for each input data packet to the data compressor or may be done individually for each air interface data packet only.
  • the decompression performed at at the receiver can then be performed individually and independently for each received data packet resulting in low complexity receivers as well as a high immunity to errors as transmission errors will only affect small units of data (i.e. a single data packet).
  • the data source, source encoder, data segmenter and data compressor may be implemented as a single functional entity and the intermediate signals described in the above embodiment may not be present.
  • the data source and source encoder may not be separable but be a single functional unit.
  • the sampling of a signal may be controlled according to the content of the underlying signal e.g. by reducing the sample rate of a speech signal during quiet periods or reducing the sampling resolution during high signal levels.
  • the source encoder comprises functionality for directly generating a signal having a data rate below the link data rate of the switched circuit link. In this case the data compression is an integral and inseparable part of the source encoding process.
  • the preferred embodiment is especially applicable to a cellular mobile communication system such as GSM or UMTS.
  • the apparatus and method may be embedded in the User Equipment such as a mobile phone, user terminal or subscriber unit, or may equally well be used in the fixed network and specifically in a base station. It is thus equally applicable to uplink and downlink.
  • the invention therefore provides a number of advantages including: Providing a method of guaranteeing a quality of service, which is independent of other users.

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  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé et un appareil permettant de transmettre des données. Un dispositif de codage de source (203) reçoit des données d'une source de données (201). Ce dispositif de codage de source (203) produit un flux de données qui possède un débit binaire variable. Ce flux est amené à un dispositif de segmentation de données (205), qui met en paquets le flux de données avant de l'amener à un dispositif de compression de données (209). Ce dispositif de compression de données (207) compriment le flux de données de manière qu'il puisse être transmis dans une liaison commuté de circuit continu, laquelle possède un débit binaire de liaison inférieur au débit binaire maximum du flux de données. La compression est variable, de façon que seuls les paquets de données possédant des débits binaires supérieurs au débit binaire de liaison soient comprimés. Une telle compression est soit une compression avec perte soit une compression sans perte, en fonction du niveau de compression requis. Les données comprimées sont émises à l'aide d'un émetteur conventionnel (211) et reçues à l'aide d'un récepteur conventionnel (213). Cette invention peut être appliquée à des systèmes de communication cellulaires.
PCT/EP2002/004858 2001-06-22 2002-04-29 Procede et appareil permettant de transmettre des donnees WO2003001826A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0115397.2 2001-06-22
GB0115397A GB2376849B (en) 2001-06-22 2001-06-22 Method and apparatus for transmitting data

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WO2003001826A2 true WO2003001826A2 (fr) 2003-01-03
WO2003001826A3 WO2003001826A3 (fr) 2003-12-04

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GB0314793D0 (en) * 2003-06-25 2003-07-30 Hewlett Packard Development Co Controlled download of data

Citations (4)

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US5611038A (en) * 1991-04-17 1997-03-11 Shaw; Venson M. Audio/video transceiver provided with a device for reconfiguration of incompatibly received or transmitted video and audio information
WO2000051307A1 (fr) * 1999-02-26 2000-08-31 Telefonaktiebolaget Lm Ericsson (Publ) Compression d'en-tetes adaptative pour la communication par paquets
WO2000079764A1 (fr) * 1999-06-18 2000-12-28 Telefonaktiebolaget L M Ericsson (Publ) Codage delta robuste dote d'informations historiques
US20020099829A1 (en) * 2000-11-27 2002-07-25 Richards Kenneth W. Filter proxy system and method

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Publication number Priority date Publication date Assignee Title
GB2325376B (en) * 1997-05-14 2001-09-19 Dsc Telecom Lp Allocation of bandwidth to calls in a wireless telecommunications system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5611038A (en) * 1991-04-17 1997-03-11 Shaw; Venson M. Audio/video transceiver provided with a device for reconfiguration of incompatibly received or transmitted video and audio information
WO2000051307A1 (fr) * 1999-02-26 2000-08-31 Telefonaktiebolaget Lm Ericsson (Publ) Compression d'en-tetes adaptative pour la communication par paquets
WO2000079764A1 (fr) * 1999-06-18 2000-12-28 Telefonaktiebolaget L M Ericsson (Publ) Codage delta robuste dote d'informations historiques
US20020099829A1 (en) * 2000-11-27 2002-07-25 Richards Kenneth W. Filter proxy system and method

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Title
CASNER S, JACOBSON V: "RFC 2508 Compressing IP/UDP/RTP Headers for Low-Speed Serial Links" NETWORK WORKING GROUP IETF, February 1999 (1999-02), XP002121319 *
HUI ZHANG: "Service Disciplines for Guaranteed Performance Service in Packet-Switchng Networks" PROCEEDINGS OF THE IEEE, vol. 83, no. 19, 10 October 1995 (1995-10-10), XP002230587 cited in the application *

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Publication number Publication date
GB0115397D0 (en) 2001-08-15
GB2376849A (en) 2002-12-24
GB2376849B (en) 2003-08-27
WO2003001826A3 (fr) 2003-12-04

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