WO2000005918A1 - Procede pour determiner des paquets de donnees contenus dans un flux de donnees continu - Google Patents

Procede pour determiner des paquets de donnees contenus dans un flux de donnees continu Download PDF

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Publication number
WO2000005918A1
WO2000005918A1 PCT/DE1999/001963 DE9901963W WO0005918A1 WO 2000005918 A1 WO2000005918 A1 WO 2000005918A1 DE 9901963 W DE9901963 W DE 9901963W WO 0005918 A1 WO0005918 A1 WO 0005918A1
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WO
WIPO (PCT)
Prior art keywords
last
bits
data
atm
synchronization information
Prior art date
Application number
PCT/DE1999/001963
Other languages
German (de)
English (en)
Inventor
Klaus Hünlich
Original Assignee
Siemens Aktiengesellschaft
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 Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2000005918A1 publication Critical patent/WO2000005918A1/fr

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Classifications

    • 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
    • H04L2012/5652—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
    • H04L2012/5653—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly using the ATM adaptation layer [AAL]
    • H04L2012/5656—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly using the ATM adaptation layer [AAL] using the AAL2
    • 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
    • H04L2012/5672—Multiplexing, e.g. coding, scrambling
    • H04L2012/5674—Synchronisation, timing recovery or alignment
    • 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
    • H04L2012/5672—Multiplexing, e.g. coding, scrambling
    • H04L2012/5675—Timeslot assignment, e.g. TDMA

Definitions

  • a known data transmission method for high transmission bit rates is the so-called Asynchronous Transfer Mode (ATM).
  • ATM Asynchronous Transfer Mode
  • ATM cells In the transmission technology known as asynchronous transfer mode (ATM), data packets of fixed length, so-called ATM cells, are used for the data transport.
  • An ATM cell is composed of a five-byte long cell header containing the switching data relevant for the transport of an ATM cell, the so-called ⁇ header 'and a 48-byte long user data field, the so-called ⁇ payload'.
  • ⁇ header a five-byte long cell header containing the switching data relevant for the transport of an ATM cell
  • ⁇ payload' a 48-byte long user data field
  • the ATM data format is adapted to this - often referred to in the literature as ⁇ ATM layer (layer 2) Network layer (layer 3) according to the OSI reference model (Open Systems I_connection).
  • the first byte of the user data area of an ATM cell is defined as a pointer that points to the first substructure element arranged in the user data area, ie it is the start address of the first in User data area located cell header of a substructure element stored. Using this pointer, it is possible to restore the synchronization between transmitter and receiver in the event that one or more ATM cells have been lost, for example due to a transmission error.
  • patent application GR 98 P 2136 (internal file number), which has the same priority, suggests switching ATM cells, which are subdivided into substructure elements according to the ATM adaptation layer AAL type 2, by means of an ISDN switching system by means of an arrangement arranged therein to implement time slot-oriented switching matrix module.
  • the packet-oriented ATM data format in accordance with the ATM adaptation layer AAL type 2 is converted to a time slot-oriented data format in accordance with the TDM method (Time Division Multiplex).
  • TDM method Time Division Multiplex
  • 32 user channels are available for data transmission, which are designed as ISDN-oriented B channels (Integrated Services Digital Network) with a transmission bit rate of 64 kbit / s each.
  • the object of the present invention is to specify a method by which the detection of boundaries between individual data packets for an extraction from into a continuous Inserted data packets is enabled.
  • a substructure element according to the ATM adaptation layer AAL type 2 is composed of a 3-byte long cell header and a user data area of variable length (0 to 64 bytes).
  • the cell header of a substructure element is subdivided into an 8-bit channel identification CID (Channel I_dentifier), a 6-bit length identification LI (Length Indicator), and a 5-bit transmitter-receiver identification UUI (User-to -User Indication) and a 5 bit Ze11kopf checksum HEC (Header Error Control).
  • the cell head checksum HEC - often referred to in the literature as a block check string - is determined in a so-called cyclic block check - often referred to in the literature as code-independent error protection and abbreviated as CRC (Cyclic Redundancy Check) - and is used to check the correctness of the first 19 bits transmitted in the cell header of a substructure element.
  • CRC Cyclic Redundancy Check
  • the binary characters of the data block to be saved - i.e. the first 19 bits transmitted in the cell header of a substructure element - serve as a coefficient. of a so-called basic polynomial.
  • a basic polynomial "x 18 + x 12 + x 7 + x 3 + 1" results from a data block "1000001000010001001”.
  • This basic polynomial is divided by a so-called generator polynomial "x 5 + x 2 + 1" (standardized by ITU-T 1.362) modulo-2. The remainder remaining after the division corresponds to the cell head checksum HEC.
  • An essential advantage of the method according to the invention is that it enables data packets inserted into a continuous data stream to be recovered without transmitting additional information which marks the beginning of a data packet.
  • An advantage of embodiments of the invention defined in the subclaims is, inter alia, that by inserting filler cells or filler data into a substructure element when converting a packet-oriented data format into a time slot-oriented data format, a mediation of compressed data (with a variable transmission bit rate) is possible without previous decompression. This prevents a loss of quality when transmitting compressed data.
  • 1 a structural diagram for the schematic representation of the conversion of the packet-oriented ATM data format into the time slot-oriented TDM data format according to a first conversion mode
  • 2 shows a structural diagram for the schematic representation of the conversion of the packet-oriented ATM data format into the time slot-oriented TDM data format according to a second conversion mode
  • 3 a structural diagram for the schematic representation of a TDM channel with associated time stamps.
  • FIG. 1 shows a schematic illustration of a conversion of the packet-oriented ATM data format according to the ATM adaptation layer AAL type 2 (ATM adaptation layer) into the time slot-oriented data format according to the TDM method (Time Division Multiplex) according to a first conversion mode of a conversion unit UE.
  • Data is transmitted in the context of the packet-oriented ATM data format via ATM cells ATM-Zl, ATM-Z2.
  • An ATM cell ATM-Zl, ATM-Z2 is composed of a cell header H which contains the switching data relevant for the transport of an ATM cell ATM-Zl, ATM-Z2 and a 48-byte useful data field.
  • the ATM adaptation layer AAL type 2 it is possible to subdivide the useful data area of an ATM cell ATM-Zl, ATM-Z2 into substructure elements SE.
  • a substructure element SE according to the ATM adaptation layer AAL type 2 is composed of a 3-byte long cell header and a user data area I of variable length (0 to 64 bytes).
  • the cell header of a substructure element SE in turn is subdivided into an 8-bit channel identification CID (Channel Identifier), a 6-bit length identification LI (Length Indicator), a 5-bit transmitter-receiver identification UUI ( User-to-User Indication) and a 5 bit long cell header checksum HEC (Header Error Control).
  • CID Channel Identifier
  • LI Length Indicator
  • UUI User-to-User Indication
  • HEC Header Error Control
  • VCI value Virtual Channel I_dentifier
  • substructure elements SE which are defined on the basis of different channel identifications CID in the cell header 0, ..., 3 of the substructure elements SE.
  • Elements SE a user data field I of variable length (0 to 2 ° byte) can be defined, so that data transmission with variable transmission bit rate can be realized for the different logical connections.
  • each substructure element SE of an ATM cell ATM-Zl defined for the transmission of user data is ATM-Z2 a TDM channel
  • K0, ..., K3 assigned to the time slot-oriented data format according to the TDM method.
  • An assignment of a substructure element SE to a TDM channel K0, ..., K3 takes place in a signaling phase preceding the user data transmission.
  • the conversion of the packet-oriented data format according to the ATM adaptation layer AAL type 2 to the time slot-oriented data format in accordance with the TDM method must additionally adapt the - possibly variable - transmission bit rate of the packet-oriented data format resulting from the size and arrival of substructure elements SE to the constant transmission bit rate of 64 kbit / s of the time slot oriented data format. This is achieved in the context of the first conversion mode of a conversion unit UE by inserting so-called filler cells FZ of variable length into the continuous TDM data stream.
  • substructure elements SE received and packaged in ATM cells ATM-Zl, ATM-Z2 are unpacked via a packet-oriented data transmission link.
  • so-called filler cells FZ are converted to the substructure containing the useful data for the conversion of the - possibly variable - transmission bit rate resulting from the size and arrival of the substructure elements SE to the constant transmission bit rate of 64 kbit / s of the time slot-oriented data format.
  • SE elements added.
  • the length of a fill cell FZ is determined by a so-called fill cell header FZH.
  • the length of a fill cell FZ is chosen so that the total transmission bit rate of a substructure element SE and a fill cell FZ results in an integer multiple of 64 kbit / s.
  • the transmission bit rate of a substructure element SE is greater than 64 kbit / s - that is, greater than the transmission bit rate of a TDM channel K1, ..., K4 - the user data transmitted in a substructure element SE are transferred to several TDM channels K1,. .., K4 divided.
  • FIG. 2 shows a schematic illustration of a conversion of the packet-oriented ATM data format according to the ATM adaptation layer AAL type 2 (ATM adaptation layer) into the time slot-oriented data format according to the TDM method (Time Division Multiplex) according to a second conversion mode of the conversion unit UE.
  • ATM adaptation layer AAL type 2 ATM adaptation layer
  • TDM method Time Division Multiplex
  • FIG. 3 shows a schematic illustration of a TDM channel TDM with substructure elements SE packed therein.
  • the octet-oriented TDM data stream of the TDM channel passes through a test unit PE, in which a test - in the following with
  • Designated cell header check - the received data is carried out for a specific bit sequence which characterizes the start of a substructure element SE.
  • This cell head check is carried out on the basis of the cell head checksum HEC transmitted in the cell head SEH of a substructure element SE.
  • the binary characters of a data block to be secured - in this case the first 19 bits transmitted in the cell header SEH of a substructure element SE - are used as coefficients of a so-called basic polynomial as part of a cyclic block check.
  • This basic polynomial is called a generator polynomial "X 5 + x 2 + 1" (standardized by ITU-T 1.362) divided modulo-2. The remainder remaining after the division corresponds to the cell head checksum HEC.
  • Test unit PE received bytes in a shift register - often also referred to as a FIFO (First In First Out) memory
  • the 3 temporarily stored bytes are the characteristic bit sequence searched for and a time mark Z which is synchronous with the beginning of the cell header is set. Then the byte first stored in the shift register is deleted from the shift register and a new byte - the last one received at the test unit PE - is written into the shift register for a new division.
  • This characteristic bit sequence is repeated with each cell head SEH of a substructure element SE.
  • the characteristic bit sequence occurs anywhere in the continuous data stream due to a random bit configuration.
  • an additional check is carried out in addition to the cell header check
  • distance check - carried out.
  • the length of a substructure element SE is filled up with Filling data FD adapted to the required constant transmission bit rate of a TDM channel - so the scope of the distance check merely checks whether the characteristic bit sequence occurs at the same distance. If the character teristic bit sequence three times in a row at the same distance, the detection is considered synchronous. If a characteristic bit sequence occurs at a distance that deviates from the distance interval, the detection becomes asynchronous. The recognition is synchronized again after recognizing the characteristic bit sequence three times at the same distance. With the aid of the length identification LI transmitted in the cell header SEH of such a substructure element SE, the transmitted user data can be separated from the filler data FD.
  • substructure elements SE with different lengths occur - the lengths of the respective substructure elements SE and Lengths of the respective filler cells FZ can be different - the distance check is carried out taking into account the length identification LI transmitted in the cell header SEH of a substructure element SE. If the characteristic bit sequence occurs three times in succession at the distance specified by the length identification LI, the detection is considered to be synchronous. If a characteristic bit sequence occurs at a distance that is not predetermined by the length identification LI, the detection becomes asynchronous. The recognition becomes synchronous again after recognizing the characteristic bit sequence three times at the distance specified by the length identification LI.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

Selon l'invention, les paquets de données (SE) présentent chacun une tête de cellule de longueur l constante, constituée de données de tête de cellule (CID, LI, UUI) et d'une somme de contrôle de tête de cellule finale (HEC). Une unité de contrôle (PE) divise les dernières données reçues à partir du flux de données continu (TDM) par un polynôme générateur qui sert de base au calcul de la somme de contrôle de tête de cellule (HEC) à partir des données de tête de cellule (CID, LI, UUI), et lorsque le reste de la division est égal à zéro, une marque temporelle (Z) indiquant le début d'un paquet de données (SE) est mise en place.
PCT/DE1999/001963 1998-07-22 1999-07-01 Procede pour determiner des paquets de donnees contenus dans un flux de donnees continu WO2000005918A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1998132998 DE19832998A1 (de) 1998-07-22 1998-07-22 Verfahren zur Ermittlung von in einem kontinuierlichen Datenstrom enthaltenen Datenpaketen
DE19832998.9 1998-07-22

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10159911A1 (de) * 2001-12-06 2003-06-26 Rohde & Schwarz Verfahren zur gezielten Annahme von Datenabschnitten
US7431923B2 (en) 2005-01-03 2008-10-07 Arius Research Inc. Cytotoxicity mediation of cells evidencing surface expression of CD63
US7442777B2 (en) 2000-11-29 2008-10-28 Arius Research Inc. Cytotoxicity mediation of cells evidencing surface expression of CD63
US7534429B2 (en) 2000-11-29 2009-05-19 Hoffmann-La Roche Inc. Cytotoxicity mediation of cells evidencing surface expression of CD63

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5570362A (en) * 1994-03-16 1996-10-29 Fujitsu Limited System for transferring variable length cells under ATM
US5768274A (en) * 1994-03-31 1998-06-16 Hitachi, Ltd. Cell multiplexer having cell delineation function
US5774469A (en) * 1996-04-01 1998-06-30 Telefonaktiebolaget Lm Ericsson Combined minicell alignment and header protection method and apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5570362A (en) * 1994-03-16 1996-10-29 Fujitsu Limited System for transferring variable length cells under ATM
US5768274A (en) * 1994-03-31 1998-06-16 Hitachi, Ltd. Cell multiplexer having cell delineation function
US5774469A (en) * 1996-04-01 1998-06-30 Telefonaktiebolaget Lm Ericsson Combined minicell alignment and header protection method and apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DODDS D E ET AL: "ATM framing acquisition", IEEE WESCANEX 93. COMMUNICATIONS, COMPUTERS AND POWER IN THE MODERN ENVIRONMENT CONFERENCE PROCEEDINGS (CAT. NO.93CH3317-5), SASKATOON, SASK., CANADA, 17-18 MAY 1993, 1993, New York, NY, USA, IEEE, USA, pages 56 - 60, XP000380229, ISBN: 0-7803-1319-4 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7442777B2 (en) 2000-11-29 2008-10-28 Arius Research Inc. Cytotoxicity mediation of cells evidencing surface expression of CD63
US7534429B2 (en) 2000-11-29 2009-05-19 Hoffmann-La Roche Inc. Cytotoxicity mediation of cells evidencing surface expression of CD63
DE10159911A1 (de) * 2001-12-06 2003-06-26 Rohde & Schwarz Verfahren zur gezielten Annahme von Datenabschnitten
DE10159911B4 (de) * 2001-12-06 2005-12-22 Rohde & Schwarz Gmbh & Co. Kg Verfahren zur gezielten Annahme von Datenabschnitten
US7431923B2 (en) 2005-01-03 2008-10-07 Arius Research Inc. Cytotoxicity mediation of cells evidencing surface expression of CD63

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