Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Patent
1997-02-28
1999-04-13
Jung, Min
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
370420, 370429, 370465, H04L 1256
Patent
active
058944770
DESCRIPTION:
BRIEF SUMMARY
This invention relates to digital communications systems and in particular to systems embodying asynchronous transfer mode (ATM) technology.
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.
The construction of a host interface for an ATM network is described in specification No. WO-A-92 22034. An arrangement for operating an asynchronous packet transmit bus is described in specification No. EP-A-0 523 874.
An ATM exchange may support POTS or ISDN services as well as B-ISDN services. The H320 Video conference standard is a typical user of an n.times.64 Kb/s service, this may well be embedded within a B-ISDN workstation and can also be supported by the N-ISDN. In an ATM exchange with 2 Mb/s trunk circuits with independent calls on each 64 kb/s channel it is desirable that traffic once adapted to ATM should remain in ATM up to the destination narrowband port. It is further desirable that a physical trunk at e.g. 155 Mb/s should be able to carry logical routes to more than one destination as 155 Mb/s is generally too large a capacity for trunking within a narrowband service network. If the logical routes are of n.times.64 kb/s where n.gtoreq.6 then the cell assembly delay is reduced to the point that echo cancellation is no longer necessary. The cell assembly delay of a single 64 kb/s circuit is 6 msec which requires echo cancellation for interworking with the existing narrowband network.
According to the invention there is provided an integrated broadband and narrowband access arrangement, including a passive optical network, a multiplexed ATM adapter, an ATM core associated with the multiplexed adapter, wherein the ATM core terminates a broadband access system and a narrowband access system whereby to deliver ATM cells to a SDH/ATM trunk or to the adapter, wherein the narrow band access system comprises a plurality of line cards providing narrow band services which are connected to a common STM backplane, wherein the services comprising the narrowband system are terminated each by a respective adapter providing an individual virtual circuit connection to the multiplexed adapter, the narrowband services within that virtual circuit having permanently assigned timeslots whereby to retain timeslot sequence integrity throughout the adaptation process, wherein each said ATM adapter provides an interface between the backplane and the passive optical network, wherein the multiplexed adapter allows any channel within any virtual circuit to be connected to any channel on the backplane, and wherein the storing and distribution processes are controlled by a chain structure, each link in the chain comprising two bidirectional pointers and an address in the egress or ingress frame memory, there being one link per channel in each of the egress or ingress chains.
According to another aspect of the invention there is provided a method of transmitting traffic in an integrated broadband and narrowband access arrangement comprising a multiplexed ATM adapter and an ATM core associated with the multiplexed adapter, wherein the ATM core terminates a broadband access system and a narrowband access system whereby to deliver ATM cells to a SDH/ATM trunk or to the adapter, the method including terminating the services comprising the narrowband system each by a respective adapter providing an individual virtual circuit connection to the multiplexed adapter, and providing the narrowband services within that vir
REFERENCES:
patent: 5490140 (1996-02-01), Abensour et al.
patent: 5583863 (1996-12-01), Darr, Jr. et al.
patent: 5623491 (1997-04-01), Skoog
Brueckheimer Simon Daniel
Mauger Roy Harold
Jung Min
Northern Telecom Limited
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