WO1997038549A1 - Procede et dispositif de correction d'erreurs sans voie de retour de signaux numeriques transmis dans des reseaux - Google Patents

Procede et dispositif de correction d'erreurs sans voie de retour de signaux numeriques transmis dans des reseaux Download PDF

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Publication number
WO1997038549A1
WO1997038549A1 PCT/EP1997/001500 EP9701500W WO9738549A1 WO 1997038549 A1 WO1997038549 A1 WO 1997038549A1 EP 9701500 W EP9701500 W EP 9701500W WO 9738549 A1 WO9738549 A1 WO 9738549A1
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Prior art keywords
cells
cell
fec
data
frame
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PCT/EP1997/001500
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English (en)
Inventor
Georg Carle
Gehard KRÜGER
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Universität Karlsruhe (Th)
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Publication of WO1997038549A1 publication Critical patent/WO1997038549A1/fr

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    • 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
    • H04L1/0057—Block codes
    • 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
    • H04L1/0085—Formatting with cells
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/46—Interconnection of networks
    • H04L12/4604—LAN interconnection over a backbone network, e.g. Internet, Frame Relay
    • H04L12/4608—LAN interconnection over ATM networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0478—Provisions for broadband connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5638—Services, e.g. multimedia, GOS, QOS
    • H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
    • H04L2012/5647—Cell loss
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5638—Services, e.g. multimedia, GOS, QOS
    • H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
    • H04L2012/5652—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly

Definitions

  • FEC Forward Error Correction
  • FEC schemes may be very beneficial in cases where retransmissions by a higher layer protocol lead to low QoS and an inefficient use of network resources and in cases in which delay requirements make the use of retransmissions impossible.
  • An FEC scheme can be used for real-time services, and for reliable non-real-time service.
  • the present invention comprises a novel FEC scheme which is designed for the Service Specific Convergence Sublayer (SSCS) of the standardized AAL Type 5 (AAL5, [1.363]) .
  • SSCS Service Specific Convergence Sublayer
  • AAL5 AAL5, [1.363]
  • the presented FEC scheme uses a method and an apparatus to encode frame-level protocol inform ⁇ ation into Protocol Data Units (PDUs) of the Common Part Convergence Sublayer (CPCS) of AAL5. Furthermore, the presented FEC scheme uses a method and an apparatus to encode and decode the required redundant information. By use of the present mvention the amount of redundant information can be adjusted according to the application requirements in a specific communication scenario.
  • PDUs Protocol Data Units
  • CPCS Common Part Convergence Sublayer
  • the present invention relates to a method and an apparatus for data communication and, more particularly, to protocol mechan- isms for error control in a particular type of networks: fast packet switched networks using short packets of fixed size called cells.
  • the Broadband Integrated Services Digital Network (B-ISDN) under standardization by the International Telecom ⁇ munications Union (ITU, [1.121] ) is the most popular network of this network type.
  • B-ISDN is based on the Asynchronous Transfer
  • ATM Cell Payload
  • Upcoming applications e.g. distributed multimedia systems, computer-supported cooperative work (CSC ) applications, and virtual shared memory systems, require reliable high per ⁇ formance pomt-to-point and point-to-multipoint communication services.
  • Quality of service (QoS) issues of importance are not only throughput, delay, and delay ⁇ itter but also differences of ⁇ elay and reliability within the group.
  • QoS Quality of service
  • a key problem that must be solved to provide a reliable multipoint service is the recovery from cell losses due to congestion in the switches. The probability for cell loss may vary over a wide range depending on the strategy for usage parameter control (UPC) and call admission control which is applied.
  • UPC usage parameter control
  • bit errors In addition to cell loss due to congestion in several scenarios the service quality may also be affected by bit errors.
  • networks with non-negligible bit error rates are customer premises networks with low-cost physical layers such as unshielded twisted pair (UTP) cables.
  • UTP unshielded twisted pair
  • the intro ⁇ duction of wireless ATM networks will give another example for a physical layer that may cause significant bit error rates.
  • Bit errors in the ATM header that cannot be recovered by the CRC of the ATM Header Error Control (HEC) may lead to cell loss or cell misdelivery. This makes them subject to AAL error control procedures. Bit errors in the ATM payload are also subject to AAL error control.
  • Ohta and Kitami [0hKi91] study the performance of an FEC scheme that is applied on Virtual Paths.
  • the payload of cells remains untouched. They arrange cells into matrices generating one redundant cell per row and one red ⁇ undant cell per column.
  • the redundant cells per row are used for error detection.
  • the present invention differs from the NTT scheme by the fact that it uses Cell Sequence Numbers for error detection while the NTT scheme uses redundant cells per row instead as well as by the fact that the NTT scheme uses only a single matrix for cell loss recovery.
  • McAuley [McA90] describes an FEC scheme which is applicable for any packets size, including AAL frames, and ATM cells. This scheme is based the generation of a fixed number of redundancy packets for a given number of user data packets applying a modified Reed-Solomon burst erasure code(RSE) . The code is able to recover any h cells lost out of k+h cells.
  • RSE Reed-Solomon burst erasure code
  • Rosensack [Bie93] presents a performance evaluation.
  • Zhang and Sarkies [ZhSa91] have studied the performance of a two-dimensional FEC scheme which is applicable for virtual paths. In this scheme Reed-Solomon codes are used for detection of bit errors and for recovery of lost cells.
  • LANs Local Area Networks
  • QoS parameters associated with the cell loss ratio may be negotiable and depend also on the service type. For some service classes, e.g. UBR, a cell loss rate suffi ⁇ ciently low to achieve a satisfying application level QoS may not be expected.
  • the current AAL types for data transfer i.e. AAL5 and AAL3/4 [1.363], do not provide an error correction scheme. Rather, they only perform error detection and rely on the error correction capability of the transport layer protocol, e.g. TCP.
  • TCP transport layer protocol
  • complete AAL PDUs are discarded if a bit error or a cell loss has been detected.
  • the error correc ⁇ tion capability of the transport layer is typically based on retransmissions from the sender, for example TCP uses a variant of the go-back-N retransmissions scheme.
  • the transport layer or network layer e.g. IP
  • IP does not have a cell-based error correction capability.
  • complete packets must be retransmitted even if received packets have only a single bit error.
  • go-back-N schemes not only the packet in error but a full -ransmission window has to be retransmitted.
  • a data-unit of 64 Kbytes i.e. the maximum ⁇ ata-unit size of AAL5
  • the probaoility that the received data-unit has any bit error is expected to be about 5x10 " , for uncorrelated errors with a bit error ratio (BER) of 10 ⁇ Q .
  • BER bit error ratio
  • the resulting packet error rate is approximately 1x10 .
  • MTU Maximum Transmission Unit
  • the expected packet error probability due to bit errors will be linearly increased for a growing number of receivers. This means that for a large scale reliable multicast service, e.g. interactive games over the Internet, it is difficult to provide a service with satisfying throughput and latency performance without an FEC scheme.
  • TSDUs transmission service data units
  • RRC1626 transmission service data units
  • CLR cell loss ratio
  • the loss rate of higher layer packets may grow linearly for a growing number of cells composing a packet as shown in [Rom93] .
  • the response time of a transport protocol that provides a reliable service in ATM networks using packet-level error control is also degrading very fast for growing cell loss.
  • the present invention which describes a new FEC scheme for AAL5 comprises the following parts.
  • the first part is used for encoding and decoding of redundant information.
  • This is the FEC method and apparatus of the present invention which will be referred to as Double Matrix Interleaving XOR scheme.
  • This scheme allows for the efficient generation of redundant inform ⁇ ation at the transmitter and for efficient error recovery at the receiver.
  • the second part which will be referred to as protocol encoding method and apparatus, allows for distingui ⁇ shing of different cells, for decoding of protocol information, and for error detection at the receiver.
  • the present invention allows to exploit the potential benefits of an AAL level forward error correction (FEC) scheme for reliable data transmission services in ATM networks.
  • FEC forward error correction
  • the following conditions for successful integration of FEC schemes into the Service Specific Convergence Sublayer of AAL5 are fulfilled by use of the present invention: (1) Compatibility with existing AAL type 5 is important.
  • AAL-SDUs of variable length e.g. IP packets
  • the parameter of the FEC would be the size and the structure of the appended redundant information. The purpose of this requirement is to give a possibility for optimization of the transmission efficiency, i.e. to minimize redundant data transmission and to achieve a media/service independence.
  • Tr.e processing costs of the FEC scheme in lossless state, i.e. without cell loss or bit error, should be as small as poss ole. Without loss or error in the CPCS-PDUs carrying the user ⁇ ata no FEC decoding should be required. Similarly, reordering of data should be avoided in the lossless state. O 97/38549 PC ⁇ 7EP97/01500
  • frames will be transmitted without ceil losses or Dit errors with a very high probability . This case has to be optimized for low processmg costs and low overhead.
  • partic ⁇ ular exploit special properties of ATM networks.
  • special properties of the data formats of the ATM header, where one bit called AUU is used, and of the trailer of AAL5 frames are exploited.
  • a particular bit of these 3 bits allows to distinguish two types of cells.
  • the AUU-bit can be used to mark the last cell of a sequence of cells thus defining a so-called Adaptation Layer Frame (AAL-frame) .
  • AAL-frame Adaptation Layer Frame
  • AAL5-UU AAL5 ⁇ ser-to-User-Indication
  • CPI Common Part Indicator
  • the present invention is designed to use the available two bytes of the AAL5 trailer efficiently.
  • the FEC method and apparatus for encoding and decoding of redundant data could be based on the well known Reed-Solomon- Codes [McAu90], [Fel93] .
  • Reed-Solomon Codes have the advantage of a nigh error correcting capabilities but the disadvantage of a fairly high implementation complexity, i.e. high processing costs. Therefore, the present invention comprises a novel method and an apparatus for an FEC scheme which is referred to as the Double Matrix Interleaving XOR scheme. This scheme allows simple implementation both in hardware and in software.
  • the FEC scheme of the present invention uses either one or two redundancy blocks. If two redundancy blocks are used, the first block is called the primary redundancy block and the second block is called the secondary redundancy block.
  • redundancy block consists of a number of redundancy cells which are calculated from the data cells of an ATM Adaptation Layer Service Data Unit (AAL-SDU) .
  • AAL-SDU ATM Adaptation Layer Service Data Unit
  • the redundancy cells are arranged into a matrix.
  • the matrices used for encodmg the redundancy are different.
  • Figure 1 shows a suitable FEC encoder for the h cells calculated over the columns.
  • Figure 2 depicts a suitable decoder. Please note that m all Figures D( ⁇ ) is used as a synonym of D x . Both encoder and decoder are based on simple XOR-functions described by ⁇ .
  • a lost cell per column For decoding an arbitrary lost cell per column can be decoded by performing an XOR-operation on all but the missing cell of the column together with the redundancy cell of this column.
  • a secondary redundancy block can be used to regenerate the original data cells.
  • the data cells D ⁇ D m are arranged into a Matrix with h s columns.
  • the second ⁇ ary redundancy matrix has [m/2] columns, whereby [m/2] equals the Ceiling of m/2.
  • Decoding for a column of the primary redundancy block with two missing cells (D x and D y ) comprising the steps of:
  • Double Matrix Interleaving XOR scheme Comparing with known schemes for error recovery at the receiver the Double Matrix Interleaving XOR scheme has a superior ratio of the error recovery capability versus the number of operations required for this error recovery. Further, in comparison with known schemes for protocol encoding the present invention is particularly efficient in partitioning the information required by the receiver for error detection as well as recovery in protocol fields per cell and protocol fields oer frame. Description of the Drawings
  • Fig. 1 is a block diagram of an FEC encoder
  • Fig. 2 is a block diagram of an FEC decoder
  • Fig. 3 is a block diagram of a frame format with an FEC code of data from a previous frame
  • Fig. 4 is a block diagram of Cell Format Type 1;
  • Fig. 5 is a block diagram of Cell Format Type 2;
  • Fig. 9 is a block diagram of an AAL5 CPCS trailer
  • Fig. 10 is a block diagram of a format for the CPCS-UU
  • Fig. 11 is a block diagram of another format for the CPCS- UU;
  • Fig. 12 is a block diagram of an extended format for the CPCS-UU;
  • Fig. 13 is a block diagram of an Error Protocol Format with Cell Format Type 1
  • Fig. 14 is a block diagram of an Error Protocol Format with Cell Format Type 2
  • Fig. 15 is a block diagram of an Error Protocol Format with Ceil Format Type 3 in the case of Variant B
  • One embodiment of the present invention comprises a method and an apparatus for encodmg an arbitrary number of redundancy cells, i.e. h primary redundancy cells, from cells of an AAL5- CPCS-PDU of variable length.
  • This has the advantage that the apparatus based on the invention can generate redundancy cells with .Little delay.
  • Another advantage of this embodiment is that a relatively small integrated circuit can be used to implement the apparatus for generating primary redundancy cells.
  • Another embodiment of the invention comprises a method and an apparatus for recovering missing data cells by using the primary redundancy cells. This has the advantage that a receiving apparatus can start to regenerate corrupted or missing cells directly after the first redundancy cell is received, thus allowing error correction with little delay.
  • Another advantage of this embodiment is that a relatively small integrated circuit can be used to implement the apparatus for recovering errors by decoding redundancy cells.
  • Another embodiment of the invention comprises a method and an apparatus for encoding additional redundancy cells, the secondary redundancy cells, of an AAL5-CPCS-PDU of variable length.
  • This has the advantage that a receiver can correct certain errors of corrupted or missing cells which could not be recovered without.
  • Another advantage of this embodiment is that additional redundancy cells can be qenerated with little delay and a relatively small integrated circuit can be used to imple ⁇ ment the apparatus for generating secondary redundancy cells.
  • another embodiment of the mvention comprises a method and an aDparatus for recovering corrupted or missing data cells ov using both the primary redundancy cells and the secondary red ⁇ undancy cells. This has the advantage that certain errors can be corrected now which cannot be corrected without the present invention.
  • This also has the advantage that very little delay is introduced at the receiver in case there are no errors or in case all errors can be corrected using only the primary red ⁇ undancy cells. Another advantage of this embodiment is that this error correction can be performed with little delay and a relatively small integrated circuit can be used to implement the apparatus at the receiver.
  • An FEC Scheme for AAL5 needs an appropriate protocol format for cells and frames to allow error detection and error correction.
  • the protocol format to be defined can be partitioned into a cell format and mto a frame format to be called as 'per-cell protocol information' .
  • Two possible solutions for an FEC scheme for the SSCS of AAL5 are presented. Thereby, a scheme is de ⁇ fined which allows simpler implementation by fewer functions and fewer fields per cell as well as higher efficiency by better error control properties and less protocol overhead.
  • One requirement for the scheme is that for simplicity all user data of an SSCS-SDU has to be in the same CPCS-PDU. In this case no per-cell protocol information needs to be used to identify the first cell or the last cell of an SSCS-SDU.
  • Solution 1.2 is mdependent from the previous Solution 1.1.
  • the B/E bit allows to detect a loss of the last data cell or last redundancy cell. However, this loss is also detected by the cell sequence number and the length field of the AAL5 trailer.
  • Example 2 The last cell of the AAL5 PDU will contain 40 bytes of padding when the CPCS-SDU ends with an FEC cell. How could this be avoided?
  • FEC cells are sent in a separate CPCS-PDU which is not of AAL5 format
  • the AUU-bit in the ATM cell header which usually indicates the last cell of a AAL5 CPCS-PDU, is used to mark the last FEC cell.
  • This cell does not contam an AAL5 trailer.
  • AAL5 CPCS SDU one or several FEC cells of an FEC frame are followed by data cells of the subsequent FEC frame. This leads to the data structure depicted in Figure 3.
  • CRC is only performed on a AAL5 CPCS-PDU basis using CRC-32 m the trailer. This case is appropriate for low bit error rates.
  • Cells do not need a CF field to indicate their Cell Format. Rather, the cell format can either be constant per VC, e.g. indicated by signaling, or indicated by a Cell Format field per frame.
  • Cell Format Type 3 ⁇ CF 3; cells with individual CRC)
  • the previous cell format has the disadvantage that CRC field is located in the cell header.
  • This format for the last cell of the CPCS-PDU is shown in Figure 7 and called Cell Format Type 3 Variant A.
  • the cell sequence number is not necessary because the length field of the AAL5 trailer allows to detect such a loss.
  • Including a field with CRC-10 mto the last cell of a AAL5 CPCS-PDU is not very useful either because CRC-32 would indicate bit errors with very high probaDility.
  • Example 3 The most common case will be a lossless system. How can processing be simplified for this case?
  • This ident ⁇ ifier is preferably placed in the AAL5 CPCS-PDU trailer in the fields CPCS-UU or CPI or in an SSCS header or trailer.
  • the AAL5 trailer format is shown in Figure 9.
  • the CPI field currently has no defined purpose except to pad the trailer to 8 bytes. It is proposed to use this field of 1.363 in future versions. Therefore, it is preferable to use the CPCS user-to-user (CPCS-UU) indication byte for additional identifier.
  • CPCS-UU CPCS user-to-user
  • Send one AAL5 CPCS-PDU which comprises both FEC cells and data cells.
  • Use either a predefined number of FEC ceils cr use a field per PDU indicating where to separate data and FEC cells.
  • a predefined offset is part of a parameter agreement by signaling during call set-up.
  • An identifier is placed in the AAL5 CPCS-PDU trailer in the fields CPCS-UU or in an SSCS header or trailer.
  • CPCS- UU to indicate the number of cells at the beginning of the frame which are FEC cells of the previous CPCS-PDU allows for minimal padding. This method is considered as a particularly preferable solution.
  • the receiver needs to be informed about the number of primary redundancy cells and the number of secondary redundancy cells.
  • the application and the number of secondary redundancy cells could be indicated to the receiver during call setup by using special signaling messages. It is also possible to specify that certain bits in the AAL5-CPCS-trailer represent the number of secondary redundancy cells directly encoded.
  • a special b t for synchronization m every cell allows to identify the first cell of a larger unit. Such a bit allows to identify the beginning of an AAL SDU and to segment this SDU mto several CPCS-PDUs.
  • a sequence number per frame is provided together with an identification of the last CPCS-PDU of a block.
  • the sequence number is called 'Frame Sequence Number' (FSN) .
  • FSN allows to detect and identify missing CPCS-PDUs. Sequence numbers are used in one of the following ways:
  • Incrementing FSNs modulo the FSN numbering space avoids a limit for the maximum number of segments of an AAL SDU. In this case an additional indication is required m order to identify the last CPCS-PDU of a block.
  • the CPCS-UU byte of the AAL5 CPCS-Trailer is used for the sequence number. If 4 bits of the CPCS-UU byte are used for the f ⁇ e_ ⁇ #RedCells, a FSN field of 4 bits is possiole.
  • the CPI-byte is used for identifying the last frame of a bloc ⁇ either oy reserving one bit (LastF) or Dy reserving a special value of the CPI-byte for this purpose. In combination witn solution 3.2 this leads to the data format for the CPCS-UU byte shown in Figure 12.
  • a sequence number per frame is used. This number is decremented and the last CPCS PDU carries sequence number 0.
  • an AAL SDU may be segmented mto a maximum number of CPCS-PDUs according to the FSN numbering space. FSNs of 4 bit would allow segmenting into 8 frames; FSNs of 8 bit would allow segmenting into 256 frames. In the framework of the present invention, however, Solution 4.3 is recommended.
  • One embodiment of the present mvention provides for a method and an apparatus for transmitting redundancy cells m combination with AAL5-PDUs which contam user data by using Solution 2.1. It has the advantage that no additional bandwidth overhead is required for transmission of redundancy cells. Further, receivers which are able to process AAL5-PDUs but which do not have a separate apparatus for processmg of the redundancy cells automatically discard all redundancy cells and therefore only deliver user data to the higher layer, as re ⁇ quired. Thus, the present invention is capable to be applied in combination with existing apparatus for the processmg of AAL5- PDUs.
  • Another embodiment of the present invention provides for a method and an apparatus for transmitting redundancy cells in AAL5-PDUs m combination with user data cells by use of Solu ⁇ tion 2.2.
  • This has the advantage that the user data is seg ⁇ mented into frames in a way that very little or no padding is required thus leading to a very little bandwidth overhead.
  • Another advantage of the present invention is that it is very easy for the receiver to separate the redundancy cells and tne cells with user data. Further, the user data and the corres ⁇ ponding redundancy cells are transported in different AAL5-PDUs thus allowing to check the integrity of the user data and the redundancy data independently.
  • Another advantage is that the apparatus for decoding at the receiver introduces only little additional delay and it can be implemented with a small integrated circuit .
  • Another embodiment of the invention provides for a method and an apparatus for encodmg per-cell protocol information for detection of missing cells and identification of redundancy cells oy using Cell Format Type 1. This has the advantage that only very little bandwidth is required for transporting the per-cell protocol information to the receiver. Furthermore, the apparatus for encodmg introduces only little additional delay and if can be implemented with a small integrated circuit.
  • Another embodiment of the present invention provides for a method and an apparatus for encodmg per-cell protocol informa ⁇ tion for the detection of corrupted cells and missing cells and for the identification of redundancy cells by the application of Cell Format Type 2.
  • This has the advantage that the receiver easily detects corrupted cells and very little additional band- width is required for this capability as well as for the per- cell protocol information.
  • the apparatus for encoding introduces only little additional delay and it can be imple ⁇ mented with a small integrated circuit.
  • Another embodiment of the present invention provides for a method and an apparatus for encodmg per-cell protocol informa ⁇ tion for the detection of corrupted cells and missing cells as well as for the identification of redundancy cells by the use of Cell Format Type 3.
  • This has the advantage that the sender can start transmitting a cell prior to completing the evalua- tion cf the cyclic redundancy check CRC-10 thus reducing the overall delay. Further, the receiver easily detects corrupted cells and very little additional bandwidth is required for this capability as well as for transporting the per-cell protocol information to the receiver.
  • This has the further advantage that the apparatus for encoding introduces only little addi ⁇ tional delay and it can be implemented with a small integrated circuit.
  • Another embodiment of the present invention provides for a method and an apparatus for distinguishing data cells from red- undancy cells by applying Solution S3.1. This has the advantage of reducing the processmg requirements the absence of errors .
  • Another embodiment of the present invention provides for a method and an apparatus for transmitting redundancy cells by applying Solution 3.2. This has the advantage of reducing the processing requirements of a lossless system. Further, only l ⁇ tt_e additional bandwidth is required for padding bytes.
  • Another embodiment of the present invention provides for a method and an apparatus for segmenting and reassembling large AAL-SDUs by application of Solution 4.1. This has the advantage that the method and the apparatus for segmenting and reassemb ⁇ ling large AAL-SDUs is easy and the apparatus can be implement ⁇ ed with a small integrated circuit.
  • Another embodiment of the present invention provides for a method and an apparatus for segmenting and reassembling large AAL-SDUs by applying solution 4.2. This has the advantage that the method and the apparatus for segmenting and reassembling large AAL-SDUs is easy and very little bandwidth is required for this method. Further, the apparatus can be implemented with a small integrated circuit.
  • Another embodiment of the present invention provides for a method and an apparatus for segmenting and reassembling large AAL-SDUs by the use of solution 4.3.
  • This has the advantage of introducing additional error detection capability which allows to detect and identify missing and missequenced CPCS-PDUs.
  • the method for segmenting and reassembling large AAL- SDUs is simple, little bandwidth is required, and the apparatus can be implemented with a small integrated circuit.
  • Another method for segmenting and reassembling large AAL- SDUs makes use of Solution 4.4.
  • This has the advantage of introducing additional error detection capability which allows to detect and identify missing and missequenced CPCS-PDUs. Furtner, the method for segmenting and reassembling large AAL- SDUs is simple, little bandwidth is required, and the apparatus can oe implemented with a small integrated circuit.

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Abstract

Méthode de correction d'erreurs sans voie de retour (FEC), basée sur la cellule, située dans la couche d'adaptation MTA (AAL) et conçue pour la sous-couche de convergence spécifique à un service de AAL standardisée de type 5. Cette méthode FEC code l'information de protocole au niveau de la cellule sous forme d'unités de données de protocole de la sous-couche de convergence de partie commune de AAL5 et code, puis décode l'information redondante nécessaire par une méthode XOR d'entrelacement à double matrice. Ces procédés et dispositifs peuvent être utilisés dans des réseaux dans lesquels sont nécessaires des services de communications extrêmement efficaces, point à point et point à multipoint, par exemple des réseaux numériques de services intégrés à bande large, des systèmes multimédia répartis, des applications de tâches coopératives assistées par ordinateur et des systèmes virtuels à mémoire partagée.
PCT/EP1997/001500 1996-04-05 1997-03-25 Procede et dispositif de correction d'erreurs sans voie de retour de signaux numeriques transmis dans des reseaux WO1997038549A1 (fr)

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US60/015,147 1996-04-05

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WO1999030462A2 (fr) * 1997-12-12 1999-06-17 3Com Corporation Systeme de correction aval des erreurs pour media en temps reel a base de paquets
GB2336270A (en) * 1998-04-07 1999-10-13 Northern Telecom Ltd AAL5 data communication
WO2000036755A1 (fr) * 1998-12-15 2000-06-22 Tiernan Communications, Inc. Procede et systeme de correction d'erreurs a compatibilite amont dans une liaison de communication en temps reel
US6145109A (en) * 1997-12-12 2000-11-07 3Com Corporation Forward error correction system for packet based real time media
US6170075B1 (en) 1997-12-18 2001-01-02 3Com Corporation Data and real-time media communication over a lossy network
US6226769B1 (en) 1997-12-12 2001-05-01 3Com Corporation Forward error correction system for packet based real time media
US6243846B1 (en) 1997-12-12 2001-06-05 3Com Corporation Forward error correction system for packet based data and real time media, using cross-wise parity calculation
WO2002058245A2 (fr) * 2001-01-17 2002-07-25 Koninklijke Philips Electronics N.V. Procede et appareil pour proteger la transmission sans perte d'un flux de donnees
KR100354745B1 (ko) * 1998-11-02 2002-12-18 삼성전자 주식회사 비디오코딩및디코딩방법
EP1512228A1 (fr) * 2002-06-10 2005-03-09 Harris Corporation Procede et systeme de correction d'erreurs sans voie de retour destines a la transmission fiable de donnees en temps reel sur un reseau a commutation de paquets
EP1244238A3 (fr) * 2001-03-23 2006-08-30 Siemens Information and Communication Networks S.p.A. Protection des données de représentation du mode de transmission dans un système de transmission du type point-multipoints
WO2008049341A1 (fr) * 2006-10-24 2008-05-02 Hangzhou H3C Technologies Co., Ltd. Procédé de traitement de messages, dispositif de transmission de messages et dispositif de réception de messages
US8185795B1 (en) 2008-06-27 2012-05-22 Emc Corporation Side channel for forward error correction used with long-haul IP links
EP2532109A4 (fr) * 2010-03-05 2016-04-20 Samsung Electronics Co Ltd Logiciel intégré fec - couche applicative pour wigif
US9973215B1 (en) 2013-01-28 2018-05-15 EMC IP Holding Company LLC Controlled multipath data packet delivery with forward error correction

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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6226769B1 (en) 1997-12-12 2001-05-01 3Com Corporation Forward error correction system for packet based real time media
WO1999030462A3 (fr) * 1997-12-12 1999-09-02 3Com Corp Systeme de correction aval des erreurs pour media en temps reel a base de paquets
US6487690B1 (en) 1997-12-12 2002-11-26 3Com Corporation Forward error correction system for packet based real time media
US6243846B1 (en) 1997-12-12 2001-06-05 3Com Corporation Forward error correction system for packet based data and real time media, using cross-wise parity calculation
US6145109A (en) * 1997-12-12 2000-11-07 3Com Corporation Forward error correction system for packet based real time media
WO1999030462A2 (fr) * 1997-12-12 1999-06-17 3Com Corporation Systeme de correction aval des erreurs pour media en temps reel a base de paquets
US6170075B1 (en) 1997-12-18 2001-01-02 3Com Corporation Data and real-time media communication over a lossy network
GB2336270A (en) * 1998-04-07 1999-10-13 Northern Telecom Ltd AAL5 data communication
KR100354745B1 (ko) * 1998-11-02 2002-12-18 삼성전자 주식회사 비디오코딩및디코딩방법
US6744816B1 (en) 1998-11-02 2004-06-01 Samsung Electronics Co., Ltd. Video coding and decoding methods
WO2000036755A1 (fr) * 1998-12-15 2000-06-22 Tiernan Communications, Inc. Procede et systeme de correction d'erreurs a compatibilite amont dans une liaison de communication en temps reel
WO2002058245A2 (fr) * 2001-01-17 2002-07-25 Koninklijke Philips Electronics N.V. Procede et appareil pour proteger la transmission sans perte d'un flux de donnees
WO2002058245A3 (fr) * 2001-01-17 2002-10-10 Koninkl Philips Electronics Nv Procede et appareil pour proteger la transmission sans perte d'un flux de donnees
EP1244238A3 (fr) * 2001-03-23 2006-08-30 Siemens Information and Communication Networks S.p.A. Protection des données de représentation du mode de transmission dans un système de transmission du type point-multipoints
EP1512228A1 (fr) * 2002-06-10 2005-03-09 Harris Corporation Procede et systeme de correction d'erreurs sans voie de retour destines a la transmission fiable de donnees en temps reel sur un reseau a commutation de paquets
EP1512228A4 (fr) * 2002-06-10 2008-08-20 Harris Corp Procede et systeme de correction d'erreurs sans voie de retour destines a la transmission fiable de donnees en temps reel sur un reseau a commutation de paquets
WO2008049341A1 (fr) * 2006-10-24 2008-05-02 Hangzhou H3C Technologies Co., Ltd. Procédé de traitement de messages, dispositif de transmission de messages et dispositif de réception de messages
US8127207B2 (en) 2006-10-24 2012-02-28 Hangzhou H3C Technologies Co., Ltd. Method for processing packets, an apparatus for transmitting packets, and an apparatus for receiving packets
US8185795B1 (en) 2008-06-27 2012-05-22 Emc Corporation Side channel for forward error correction used with long-haul IP links
EP2532109A4 (fr) * 2010-03-05 2016-04-20 Samsung Electronics Co Ltd Logiciel intégré fec - couche applicative pour wigif
US9973215B1 (en) 2013-01-28 2018-05-15 EMC IP Holding Company LLC Controlled multipath data packet delivery with forward error correction

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