EP1068694A1 - Codage d'entrelacement de blocs dans un systeme de commutation par paquets - Google Patents

Codage d'entrelacement de blocs dans un systeme de commutation par paquets

Info

Publication number
EP1068694A1
EP1068694A1 EP99914865A EP99914865A EP1068694A1 EP 1068694 A1 EP1068694 A1 EP 1068694A1 EP 99914865 A EP99914865 A EP 99914865A EP 99914865 A EP99914865 A EP 99914865A EP 1068694 A1 EP1068694 A1 EP 1068694A1
Authority
EP
European Patent Office
Prior art keywords
packet
blocks
interleaving
time period
block
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.)
Withdrawn
Application number
EP99914865A
Other languages
German (de)
English (en)
Inventor
Maria Gustafsson
Magnus Persson
Erik Dahlman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
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 Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of EP1068694A1 publication Critical patent/EP1068694A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0071—Use of interleaving
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/27—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/63—Joint error correction and other techniques
    • H03M13/6306—Error control coding in combination with Automatic Repeat reQuest [ARQ] and diversity transmission, e.g. coding schemes for the multiple transmission of the same information or the transmission of incremental redundancy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0078—Avoidance of errors by organising the transmitted data in a format specifically designed to deal with errors, e.g. location
    • H04L1/0083—Formatting with frames or packets; Protocol or part of protocol for error control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0033—Systems modifying transmission characteristics according to link quality, e.g. power backoff arrangements specific to the transmitter
    • H04L1/0034—Systems modifying transmission characteristics according to link quality, e.g. power backoff arrangements specific to the transmitter where the transmitter decides based on inferences, e.g. use of implicit signalling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1803—Stop-and-wait protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1806—Go-back-N protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1809—Selective-repeat protocols

Definitions

  • the present invention is directed towards a packet switched network, and more particularly towards a method of interleaving data associated with a packet so as to optimize transmission of the packet.
  • GSM systems provide a circuit switched data service, which can be used to interconnect with external data networks.
  • the circuit switched data service is used for both circuit switched as well as packet switched data communication.
  • GPRS General Packet Radio Services
  • GPRS will support both connectionless protocols (e.g., IP) as well as a connection-oriented protocols (X.25).
  • IP connectionless protocols
  • X.25 connection-oriented protocols
  • One of the advantages with- a packet switched data communication protocol is that a single transmission resource can be shared between a number of users.
  • a timeslot on a radio-frequency carrier can be utilized by several mobile users for reception and transmission of data.
  • FDMA frequency division multiple access
  • TDM A time division multiple access
  • Capacity in a TDMA system is increased by compressing the transmission signal into a shorter time slot. As a result, the information must be transmitted at a correspondingly faster bit rate which increases the amount of occupied spectrum proportionally.
  • FDMA or TDMA systems or a hybrid FDMA/TDMA system
  • code division multiple access (CDMA) or wideband CDMA systems which supports bandwidths of up to 12 times that of standard CDMA systems, allow signals to overlap in both time and frequency. Thus, all CDMA signals share the same frequency spectrum.
  • CDMA code division multiple access
  • wideband CDMA systems which supports bandwidths of up to 12 times that of standard CDMA systems
  • the multiple access signals appear to be on top of each other.
  • the information data stream to be transmitted is first coded or spread using a unique spreading code and then combined with a long PN-sequence or a shorter scrambling-sequence.
  • the scrambling-sequences are planned from cell to cell so that neighboring cells use different scrambling-sequences or scrambling-masks.
  • the information data stream and the PN-sequence or the scrambling sequence can have the same or different bit rates.
  • the information data stream and the PN-sequence or the scrambling-sequence are combined by multiplying the two bit streams together.
  • a plurality of coded information signals are transmitted on radio frequency carrier waves and jointly received as a composite signal at a receiver.
  • Each of the coded signals overlaps all of the other coded signals, as well as noise related signals, in both frequency and time.
  • a corresponding information signal is isolated and decoded.
  • a base station 100 will receive a data packet containing, for example, a sequence of digital data from a data source 110, such as a telephone network.
  • the base station will then encode, through the use of an encoder 105, and interleave, through the use of an interleaver 106, the data packet for transmission to a mobile unit 120.
  • Encoder 105 herein performs channel coding, e.g., convolutional coding, as opposed to forward error correction coding described below.
  • the interleaving process reorders the bits in the data packet. For example, assume that the data packet included four bits that were originally ordered as follows: Al, A2, A3, A4. The interleaving process would reorder the data bits to produce, by way of example, a result such as A3, A2, A4, Al.
  • deinterleaver 125 When the interleaved and encoded data packet is received by the mobile unit 120, it is deinterleaved by deinterleaver 125. Deinterleaver 125 places the data bits back into their original order. For the example given above, deinterleaver would receive the data bits in the order of A3, A2, A4, Al and would reorder the bits back -4-
  • the deinterleaved, encoded data packet is then forwarded to decoder 126 where it is decoded back into its original form.
  • the data packet is then sent to a processing unit, such as an audio component, for processing.
  • Interleaving in conjunction with some type of encoding method, operates to lower burst error rates by spreading in time the effects of any burst errors.
  • a burst error is simply a grouping of errors that occur over a short period of time and which affect consecutive bits in a transmitted data packet. When the packet is deinterleaved, the burst error will be spread in time giving a higher likelihood that the coding can be used to correct errors.
  • the packet is disturbed during its transmission from the base station to the mobile unit, for example by a collision with another packet, by an increase in the interference level or bad channel conditions, e.g., fading, and must be retransmitted by the base station.
  • the base station has to retransmit the packet until a successful transmission is accomplished which is indicated by an acknowledgment from the mobile unit that the packet has been received correctly.
  • the error correction information For the mobile unit to be able to determine whether a packet has been correctly received, the error correction information, which was added to the packet, must be considered.
  • the forward error correction (FEC) coding can, for example, be provided in the form of a cyclic redundancy check (CRC).
  • ARQ Automatic Repeat Query
  • acknowledged are stored for retransmission, and are only then deleted from the storage when they have been acknowledged.
  • the packets are provided with a packet number so that the destination can acknowledge the correct packet numbers.
  • Examples of ARQ methods that use packet numbering and do not wait for an acknowledgment before they transmit the next packet are selective ARQ and (cumulative) go-back-N ARQ. These methods provide higher throughputs especially on connections which contain a certain amount of delay.
  • a block is the smallest part of the packet which is re- transmittable over the air interface.
  • the blocks are individually encoded and interleaved and are provided with overhead information, such as CRC bits and block numbers.
  • Figure 2 illustrates a conventional packet where the blocks are individually encoded and interleaved.
  • packet transmissions are subject to burst errors.
  • a system designer would desire a large interleaving period. That is, one skilled in the art would readily recognize that the larger the interleaving period, the more spread out the burst errors would be when the packet is eventually deinterleaved at the receiver. By spreading in time the effects of the burst errors, the effectiveness of the forward error correction coding operation is increased.
  • the instant invention overcomes the above deficiencies by providing a technique which provides both a good interleaving scheme and an efficient ARQ protocol.
  • a packet is divided into a plurality of blocks. Each block is individually encoded and inner- block interleaved. The blocks are then interleaved again over a longer period of time.
  • the second interleaving operation is referred to herein as "outer-block interleaving.”
  • the present invention allows for the size of a packet block to be optimized, which increases the effectiveness of the ARQ protocol, and provides greater interleaving of the packet's data elements so as to minimize the effects of burst errors.
  • Figure 1 illustrates a conventional interleaving and encoding scheme
  • Figure 2 illustrates a conventional method of dividing and interleaving the blocks of a packet
  • Figure 3 illustrates an exemplary cellular mobile radio telephone system within which the techniques according to the present invention can be implemented
  • Figure 4 illustrates a method of dividing and interleaving the blocks of a packet according to the present invention
  • Figure 5 illustrates a simulation result of the interleaving scheme according to the present invention for a mobile speed of 120 km/h.
  • Figure 6 illustrates a simulation result of the interleaving scheme according to the present invention for a mobile speed of 50 km/h.
  • FIG. 3 illustrates an exemplary cellular mobile radio telephone system within which the techniques according to the present can be implemented.
  • the cellular mobile radio telephone system includes a base station 300 and a mobile unit or remote unit 320. It is well understood by those skilled in the art that a typical cellular system comprises a plurality of base stations and a plurality of mobile units, but for the sake of simplicity Figure 3 only illustrates one base station and one mobile unit. While the discussion below involves the transfer of packets from a base station to a mobile unit, one skilled in the art will recognize that the techniques of the instant invention applies equally well to communications from the mobile unit to the base station.
  • the base station 300 includes a packet divider 304, an encoder 305, and an interleaver 306.
  • the mobile unit 320 includes a deinterleaver 325, a decoder 326, and processmg unit 327. -8-
  • the sending unit receives a data packet from a source 110, such as a telephone network.
  • the base station 300 first divides the packet into a plurality of blocks through the use of packet divider 304. Each block may then have overhead information, e.g., CRC bits and a block number, added thereto.
  • the blocks are then individually encoded by encoder 305.
  • the overhead information can be encoded in a manner different than the payload data, e.g., using a separate encoder.
  • the encoded blocks are then transferred to interleaver 306 which performs the interleaving scheme of the instant invention.
  • the interleaved and encoded data packet is then sent synchronously or asynchronously over the link.
  • the destination i.e., the mobile station 320 checks the correctness of the blocks and sends either an acknowledgment signal (ACK) or a non-acknowledgment signal (NAK) dependent upon whether the blocks have been successfully or unsuccessfully received, respectively.
  • ACK acknowledgment signal
  • NAK non-acknowledgment signal
  • the source can respond with a retransmission of the block which was not successfully received.
  • non-acknowledgment signals are not used. Instead, the sender waits during a time-out period and if an acknowledgment signal is not received within the time-out period, the sender automatically retransmits the block.
  • ARQ Automatic Repeat Query
  • the mobile unit 320 deinterleaves the packet with deinterleaver 325.
  • the encoded packet is then decoded by decoder 326 to thereby obtain the original packet.
  • the packet is then processed by the receiving unit in a well known manner. For example, the packet may be transferred to an audio component for processing.
  • each packet is divided into blocks when it is received in the base station.
  • the blocks are then individually encoded and overhead information, such as CRC bits and block numbers, is added to each block.
  • the blocks are then individually interleaved, i.e., they are inner-block interleaved.
  • the blocks are then interleaved again, except over a longer time period. This second interleaving process is known as "outer-block interleaving.”
  • the resulting packet could, by way of example, be represented as follows:
  • the packet is then interleaved again, except over a longer time period. If the time period is selected to be the size of two blocks, then a possible resulting packet could be represented as:
  • Selection of the size of the outer-block interleaving period is dependent upon such factors as buffer size and channel conditions.
  • interleaving process performed by interleaver 306, would require temporary buffering of the blocks to be interleaved. Therefore, it is evident that the larger the outer-block interleaving period that is chosen, the larger the buffer size that is needed. Similar buffers would be needed for deinterleaving as well. By choosing a shorter outer-block interleaving period, one can minimize the buffer requirement.
  • a second factor to consider in selecting the outer-block interleaving period is the channel condition. Due to a variety of time-varying factors, including position of the mobile station and environmental conditions, the condition of the transmission channel could be poor (i.e., it could be prone to burst errors or nulls which extend over a large time period). Moreover, interference to any given connection is also time varying. In order to compensate for such poor channel conditions, a larger outer-block interleaving period would be desirable whereby the effects of such burst errors would be more greatly dispersed over time. Alternatively, when transmission conditions are good, a shorter outer-block interleaving period could be chosen. Thus, the outer-block interleaving can be dynamically variable, e.g., if the incidents of requests for retransmission increase beyond a threshold, then the outer-block interleaving period can be increased.
  • the size of the outer-block interleaving period is selected to be equal to the packet length, there will inevitably be some delay if there are blocks to be retransmitted. This is evident from the fact that the packet's data elements would be interleaved throughout the packet, requiring the entire packet to be received in order for all the elements of a block to be received. If, however, the outer-block -11-
  • interleaving period is chosen to be less than or greater than the packet length, then there will be no significant delay for retransmissions. Although the block delay is increased, the overall performance of the system is not affected.
  • Figures 5 and 6 set forth results of simulations for an exemplary wideband CDMA system which were performed for mobile speeds of 120 km/h and 50 km/h.
  • the information bit rate was selected as 240 kbps and the speed of the mobile unit was chosen as 120 km/h which is equivalent to a Doppler frequency of 213 Hz if a 1.9 GHz test spectrum is used.
  • Three interleaving periods were selected: one block (1.25 ms), one frame (10 ms) and two frames (20 ms).
  • the speed of the mobile unit was decreased to 50 km/h which is equivalent to a Doppler frequency of 93 Hz.
  • the same information bit rate of 240 kbps was also used.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Probability & Statistics with Applications (AREA)
  • Theoretical Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Error Detection And Correction (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

La présente invention concerne un procédé et un système d'entrelacement de blocs d'un paquet qui permet de réduire au minimum les effets dus à des paquets d'erreurs, et en même temps d'améliorer l'efficacité du protocole ARQ. Un paquet est d'abord divisé en plusieurs blocs. Chaque bloc est ensuite codé individuellement et entrelacé de façon interne. Après quoi les blocs sont entrelacés sur une plus longue période temporelle. Par la mise en oeuvre de deux étapes d'entrelacement, la présente invention permet de maintenir au minimum la taille d'un bloc de paquets, ce qui accroît l'efficacité du protocole ARQ et permet d'obtenir un plus grand entrelacement des éléments de données de paquet de façon à réduire au minimum les effets dus à des paquets d'erreurs.
EP99914865A 1998-03-30 1999-03-26 Codage d'entrelacement de blocs dans un systeme de commutation par paquets Withdrawn EP1068694A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US5012598A 1998-03-30 1998-03-30
US50125 1998-03-30
PCT/SE1999/000485 WO1999050990A1 (fr) 1998-03-30 1999-03-26 Codage d'entrelacement de blocs dans un systeme de commutation par paquets

Publications (1)

Publication Number Publication Date
EP1068694A1 true EP1068694A1 (fr) 2001-01-17

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ID=21963509

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99914865A Withdrawn EP1068694A1 (fr) 1998-03-30 1999-03-26 Codage d'entrelacement de blocs dans un systeme de commutation par paquets

Country Status (6)

Country Link
EP (1) EP1068694A1 (fr)
JP (1) JP2002510902A (fr)
AR (1) AR018814A1 (fr)
AU (1) AU3351499A (fr)
CA (1) CA2325993A1 (fr)
WO (1) WO1999050990A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6965916B1 (en) * 2000-12-14 2005-11-15 Bellsouth Intellectual Property Corp. System and method for data distribution and recovery
JP4685787B2 (ja) * 2003-10-08 2011-05-18 デジタル ファウンテン， インコーポレイテッド Ｆｅｃベース信頼度制御プロトコル
US8009758B2 (en) 2007-06-20 2011-08-30 Samsung Electronics Co., Ltd Apparatus and method for channel-interleaving and channel-deinterleaving data in a wireless communication system
KR100957430B1 (ko) 2007-06-20 2010-05-11 삼성전자주식회사 무선통신 시스템에서 인터리빙 장치 및 방법

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JPH04233840A (ja) * 1990-07-05 1992-08-21 American Teleph & Telegr Co <Att> データ通信システム、データ信号処理方法及び移動体無線電話トランシーバ
JPH0817485B2 (ja) * 1991-01-29 1996-02-21 三洋電機株式会社 Ｍｕｓｅ音声デコーダ
US5392299A (en) * 1992-01-15 1995-02-21 E-Systems, Inc. Triple orthogonally interleaed error correction system
SE504396C2 (sv) * 1994-04-28 1997-01-27 Ericsson Telefon Ab L M Detektering av felaktigt mottagna dataramar i ett kommunikationssystem
US5583889A (en) * 1994-07-08 1996-12-10 Zenith Electronics Corporation Trellis coded modulation system for HDTV

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Also Published As

Publication number Publication date
CA2325993A1 (fr) 1999-10-07
AU3351499A (en) 1999-10-18
AR018814A1 (es) 2001-12-12
WO1999050990A1 (fr) 1999-10-07
JP2002510902A (ja) 2002-04-09

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