Multiplexing traffic into structure blocks in ATM cells

Details Multiplexing traffic into structure blocks in ATM cells Multiplexing traffic into structure blocks in ATM cells

1998-06-01

2001-05-01

Kizou, Hassan (Department: 2662)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S474000

Reexamination Certificate

active

06226294

ABSTRACT:

This invention relates to telecommunications networks and in particular to a system and method for asynchronous transfer mode (ATM) transmission of traffic.
BACKGROUND OF THE INVENTION
A recent development in telecommunications technology has been the introduction of the asynchronous transfer mode (ATM) transmission technique. The asynchronous transfer mode (ATM) technology is a flexible form of transmission which allows various types of service traffic, e.g. voice, video or data, to be multiplexed together on to a common means of transmission, the traffic being carried in cells each having a header indicating its destination. The service traffic is adapted typically into 53 byte cells comprising 5 byte headers and 48 byte payloads such that the original traffic can be reconstituted at the far end of the ATM network. This form of adaptation is performed in the ATM adaptation layer (AAL). The technique allows large volumes of traffic to be handled reliably and efficiently.
Specification No EP-A1-0,225,714 describes a communications network comprising a number of nodes and in which short delay limits are met by creating composite packets carrying information for more than one call. A call is allocated one or more octets at a given location in packets having a given connection number. A description of voice transport in an ATM broad band network is given by W O Covington in “Communications Technology for the 1990's and Beyond, Dallas, Nov. 27-30, 1989, Volume 3, 27 November 1989, IEEE, pages 1921-1925.
A limiting factor in the introduction of ATM is the difficulty of interfacing new broad band ATM networks not only with existing narrow band networks, commonly referred to as legacy networks, but also with the newly emerging narrow band cellular and wireless networks. In an attempt to address the latter-mentioned part of this problem, ANSI committee T1S1.5 has recently issued a baseline document containing proposals for a new ATM Adaptation Layer (AAL) that encapsulates and transports short user packets (called AAL-SDUs) inside an ATM cell stream. The new AAL is intended to be applicable to both fixed and variable length short packets and has been named ‘Small Multiplexed ATM Adaptation Layer’ (SMAAL). SMAAL is intended to support applications such as low bit rate-compressed voice, both with and without silence suppression, leading to both constant bit rate and variable bit rate user information. A consequence of these applications can be the unacceptably long voice packetisation delay that can occur in filling a complete ATM cell with the resulting user information from a single source. The purpose of SMAAL is to permit multiple short packets of user information from one or more users to be multiplexed inside a single ATM cell, thereby alleviating the packetisation delay problems. While this facilitates the transmission of short packets within the ATM network, it does not provide an effective means of interfacing with existing legacy networks, neither basic 64 kbit/s narrow band networks nor narrow band voice networks employing compression and silence suppression techniques.
SUMMARY OF THE INVENTION
The object of the invention is to minimise or to overcome these disadvantages.
A further object of the invention is to provide an improve apparatus and method for the transport of narrow band communications traffic.
According to the invention there is provided a method of transporting traffic between first and second narrow band networks across an asynchronous transfer mode ATM) network, the method including multiplexing traffic from users of the first narrow band network into structured blocks within ATM cells, providing each cell with a respective single control information field (CIF) and a header, transmitting the cells across the ATM network to the second narrow band network, and demultiplexing the user traffic from the transmitted cells, characterised in that said control information field incorporates a length indicator (LI) indicative of the size of the structured blocks within that cell whereby to define the demultiplexing process, that changes in structured block size are signalled via a change indicator (Cl) contained in the control information field, and that transport of user information or of signalling information is denoted by a single bit information/signalling (I/S) indicator contained in the control information field.
According to another aspect of the invention there is provided an arrangement for transporting traffic between first and second narrow band networks across an ATM network, the arrangement including means for multiplexing traffic from users of the first narrow band network into structured blocks within ATM cells, means for providing each cell with a respective single control information field and a header, means for transmitting the cells across the ATM network to the second narrow band network, and means for demultiplexing the user traffic from the transmitted cells, characterised in that said control information field incorporates a length indicator indicative of the size of the structured blocks within that cell whereby to define the demultiplexing process, that changes in structured block size are signalled via a change indicator (CI) contained in the control information field, and that transport of user information or of signalling information is denoted by a single bit information/signalling (I/S) indicator contained in the control information field.
The method and arrangement provide for the transport across ATM networks of narrow band 64 kbit/s channels as required for interworking between legacy networks. A single unified transport capability is made available to fulfil the requirements for the ATM trunking of narrow band services, whether constant bit rate or piece wise constant bit rate (as for compressed voice with silence suppression) in character.


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patent: 5761343 (1998-06-01), Haruma et al.
patent: 5774469 (1998-06-01), Wirkestrand
patent: 5805933 (1998-09-01), Takahashi
patent: 6021135 (2000-02-01), Ishihara et al.
patent: 0 225 714 (1987-06-01), None
Ohta, “A Technique To Detect And Compensate Consecutive Cell Loss In ATM Network”, IEEE Infocom '91, 4/91, pp. 781-790.
Covington, “Voice Transport On An ATM Broadband Network”, IEEE Globecom '89, pp 1921-1925.

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