Multiplex communications – Pathfinding or routing – Through a circuit switch
Patent
1997-05-15
2000-02-08
Ngo, Ricky Q.
Multiplex communications
Pathfinding or routing
Through a circuit switch
370395, 370465, H04Q 1104
Patent
active
060234652
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCES TO RELATED APPLICATIONS
Attention is here directed to our co-pending applications Ser. No. 08/737,818 and Ser. No. 08/737,817 which relate to integrated broad band and narrow band access arrangements.
FIELD OF THE INVENTION
This invention relates to digital communications systems and in particular to systems embodying asynchronous transfer mode (ATM) technology.
BACKGROUND OF THE INVENTION
The asynchronous transfer mode (ATM) technology is a flexible form of transmission which allows any type of service traffic, voice, video or data, to be multiplexed together on to a common means of transmission. In order for this to be realised, the service traffic must first be 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 an ATM network. This form of adaptation is performed in the ATM adaptation layer (AAL). Five types of adaptation layer have been defined. This invention relates to adaptation layer 1 which is used to adapt constant bit rate traffic to the ATM standard.
BRIEF SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided n arrangement for adapting a non-blocking broad band asynchronous transfer mode (ATM) switch having a plurality of ports to provide a switching function for narrow band traffic, the arrangement including adaptive virtual junctors one attached to each said switch port to provide ingress to and egress from the switch and each having means for assembly and disassembly of ATM payloads, wherein each said adaptive virtual junctor has a virtual connection with every other adaptive virtual junctor, each said virtual connection comprising a number of virtual circuits, and means associated with each said adaptive virtual junctor for controlling on a call by call basis the number of virtual circuits on each virtual connection associated with that adaptive virtual junctor.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying drawings in which:-
FIG. 1 is a schematic diagram illustrating the narrow band and broad band interworking requirements;
FIG. 2 illustrates the structure of the ATM adaptation layer 1;
FIG. 3 illustrates flexible interworking unit functionality;
FIG. 4 illustrates the use of ATM as the basis for a narrow band switching fabric;
FIG. 5 is a schematic diagram of an adaptive virtual junctor;
FIG. 6 illustrates the use of ATM transmission to link a number of ATM based narrow band switching fabrics;
FIGS. 7 and 8 illustrate respectively interworking unit egress and ingress process architecture; and
FIG. 9 is a schematic diagram of a transmission adaptation device.
DETAILED DESCRIPTION OF THE INVENTION
The basic requirements for an inter-working unit between a narrow band (11) and a broad band (12) public network switch via an interworking unit (13) are illustrated in FIG. 1. The interworking unit provides the adaptation function. The most basic form of inter-working is for voice applications in which a POTS line or an ISDN B-Channel must be adapted to a Virtual Circuit using ATM Adaptation Layer 1 providing 64 kb/s connectivity between the two networks; this is required to work with voice services on an ATM workstation. The cell assembly delay for such a connection is typically 6 milliseconds which can cause potential voice echo problems in many applications; echo cancellation to overcome such problems is well understood but is rather expensive to implement. The more general inter-working case is for a P.times.64 kb/s service typically used for H320 video conference where a value of P=6 is typical. Time slot sequence integrity is a special requirement of this application. The AAL1 can be used for unstructured data transfer in which a synchronous bit stream is passed transparently through an ATM network and reconstituted at the far end. For the flexible handling of 64 kb/s channels, the structured data transfer mode in which phase information identify
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Brueckheimer Simon Daniel
Dean Robert John
Mauger Roy Harold
Oliver Allen William
Ngo Ricky Q.
Northern Telecom Limited
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