Multiplex communications – Pathfinding or routing
Reexamination Certificate
2000-07-20
2003-05-27
Nguyen, Steven (Department: 2665)
Multiplex communications
Pathfinding or routing
C370S401000, C370S395300
Reexamination Certificate
active
06570868
ABSTRACT:
BACKGROUND TO THE INVENTION
This invention relates, in general, to a system and method for establishing a communication connection and is particularly, but not exclusively, applicable to network architectures that support differing resource capabilities and which combine narrowband call control, services and routing with broadband connectivity.
SUMMARY OF THE PRIOR ART
Globally, telecommunication systems are, generally, in a transitional phase between first generation, narrowband digital networks (such as the Global System for Mobile (GSM) cellular communication system) and future, multi-media digital networks (such as the Universal Mobile Telecommunication System (UMTS)) having broadband capabilities. This transition is necessarily required to support higher data rate communications, including video and internet applications, that are presently being both considered and made available. Unfortunately, this transitional phase also presents system operators with several dilemmas, and also prejudices immediate implementation of such broadband systems. For example, until such a time when a free-standing broadband system becomes an accepted and freely available standard for all subscriber terminals (such as cellular telephones and data transmission devices), system operators are reticent to write-off their significant investments in current narrowband infrastructure technology. Indeed, such narrowband infrastructure technology already provides a rich set of services and service creation environments which would have to be re-implemented to be deployed in broadband networks. Consequently, present-day narrowband systems must be adapted to accommodate both narrowband and broadband users; with this statement particularly relevant to call establishment and interworking procedures between these different forms of network.
For an effective migration between narrowband and broadband systems (for the transitional phase), system operators must particularly consider an interworking scenario when all subscribers connect to a. narrowband network, but one or more intermediate broadband networks are used to relay information between these narrowband subscribers.
In more detail, telecommunication networks comprise nodes connected by communication resources (usually termed “links”), with a particular network technology characterised by the means of transmission of user and control information along these links and also by the routing and relaying functions embodied in the nodes. The term routing is used to describe the process of determining the path the information will take through the network, while relaying is the process of transferring information from one link to another, i.e. the information is merely passed, without alteration, from one channel resource to another.
Taking GSM as an exemplary form of a narrowband digital network, user and control information (or “data”) is interleaved, using time division multiplexing (TDM), on a 52 kbit per second (kbps) pulse code modulated (PCM) bearer channel. Indeed, these bearer channels can each framed to support four voice calls of 16 kbps, comprised from 13 kbps of sampled and encoded speech and 3 kbit/s of ancillary information, such as parity check and correction bits (and the like) and synchronisation information. Data is then relayed across a node by some form of synchronous TDM switching fabric, often of the ‘time-space-time’ type. Control information (e.g. call set up and tear down messages) logically follows the same path (although not always the same physical path) through the network as user information, and is terminated in each node for routing purposes. Routing is conventionally performed, in each node, on a ‘hop-by-hop’ basis using long lived routing tables, i.e. the node is sufficiently intelligent to determine an optimum route for the succeeding network connection.
Control information is regulated by a signalling scheme that is distinctive to the type of network employed. Particularly, public signalling systems are used between nodes of a public network and between public networks of different operators. Signalling System No. 7 is the only important example of a public signalling system. Access signalling systems are used between subscribers and edge nodes of public networks, e.g. between a radiotelephone and a base station subsystem (BSS). In fact, the most common digital access signalling schemes are Common Channel Signalling Systems, such as the Integrated Service Digital Network (ISDN) DSSS1 signalling schemes (and its predecessors) and Channel Associated Signalling schemes that are both derived from analog signalling. Private schemes are generally derived from access schemes but provide richer functionality within personal networks, such as within a secure private branch exchange (PBX).
On the other hand, broadband digital networks are characterised in that user and control information is transmitted in fixed or variable length ‘packets’, with these packets prepended with headers that contain bearer channel identification. In contrast with narrowband systems, user information is relayed across a node via an asynchronous switching fabric that examines each packet in turn (using some kind of fairness algorithm) and directs it to the appropriate output link in response to the input link and bearer channel identification. Routing and control information transmission is, however, similar to that for the narrowband case, and differs only inasmuch as the signalling schemes are technology specific.
To facilitate use of broadband networks and the migration of communication networks to high data rate technologies (e.g. the 2 Mbps rate envisaged within UMTS), there is a need to provide an effective mechanism for interconnecting narrowband networks through a transparent broadband ether. In other words, the broadband ether must accommodate and support narrowband signalling schemes without affecting either data integrity or in any way inhibiting data flow or interconnection.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a method of establishing a communication connection across a broadband network from a first terminal in a first narrowband network to a second terminal in a different narrowband network, the broadband network having a signalling protocol dissimilar to those provided in the respective first and second narrowband networks, the method comprising the steps of: at the first narrowband network and on a first communication circuit, receiving an incoming call request from the first terminal, the incoming call request containing an address of the first terminal and a destination address associated with the second terminal; selecting a phantom trunk different to the first communication circuit, the phantom trunk having a circuit identity and being arranged to support a narrowband communication between the first narrowband network and the second narrowband network; in a first message, sending the destination address and the circuit identity from the first narrowband network to the second narrowband network; in a second message, sending the circuit identity and the address of the first terminal to the second narrowband network; identifying the presence of the circuit identity in both the first message and the second message to establish that the communication connection is between the first terminal and the second terminal; and establishing the communication connection through the broadband network.
In a second aspect of the present invention there is provided a communication system having a broadband network and a plurality of narrowband networks each containing at least one communication device, the narrowband networks having differing signalling protocols to those of the broadband network and wherein the narrowband networks are interconnected through the broadband network, the communication system arranged to establish a communication connection between a calling communication device in a first narrowband network and a receiving communication device in a different narrowband network, e
Ashworth Mark
Cable Julian Frank Barry
Mauger Roy Harold
Shields James
Barnes & Thornburg
Nguyen Steven
Nortel Networks Limited
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