System and method for establishing a communication connection

#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.

#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.

#An exemplary embodiment of the present invention will now be described with reference to the accompanying drawings, in which:

#FIG. 1 is a block diagram illustrating an abstract model of a narrowband communication node;

#FIG. 2 is a block diagram illustrating, in accordance with a preferred embodiment of the present invention, the interconnection of subscriber terminals between narrowband and broadband networks;

#There are, apparently, two principal ways of implementing the interconnection of narrowband subscribers units through an intermediate broadband network, such as an asynchronous transmission mode (ATM) architecture; either an interworking function can be implemented at each boundary between the narrowband and broadband networks (in which a dedicated and reversible coding transposition is applied to the respective narrowband/broadband information), or narrowband information can be encapsulated over a broadband subnet whereby the narrowband information is packaged with a broadband frame structure (so entirely maintaining the integrity and format of the original encoded narrowband information). In relation to user information, e.g. encoded speech or specific data traffic, the present invention has identified that both the interworking function and encapsulation mechanisms are possible and merely represent an additional process step that complicates and extends the requirements for coding within communication systems, generally. However, in relation to control information (which is required to establish and maintain a connection), there are a number of penalties and benefits associated with both of the above approaches. Specifically, encapsulation allows existing services to be supported, even though these services may not independently be sustained by the broadband network. Furthermore, encapsulation is simple to implement. On the other hand, interworking requires only a local view at each interworking point (i.e. at the narrowband/broadband boundary), and also provides a mechanism that can support the participation of narrowband and broadband subscribers in a single call. The present invention utilises an inventive combination of both the interworking and encapsulation mechanisms to provide enhanced and synergistic system capabilities that are not provided by the straightforward use of either base mechanism.

#Referring to FIG. 1, a block diagram illustrating an abstract model of a narrowband communication node 10 is shown. A number of subscriber terminals 12, such as landline telephones or modems, are coupled, typically, to a plurality of line interfaces 14-15 (although only one need be supplied for an operational system). The plurality of line interfaces 14-15 are each connected to a switching fabric 16 that is arranged to route an input of the switching fabric 16 to an appropriate output thereof, as will readily be appreciated. The plurality of line interfaces 14-15 are also coupled (usually on an individual basis) to a call server 18 arranged to administer and control, for example, the set-up and tear-down of calls across the narrowband network 10. The call server 18 is further coupled to the switching fabric 18. A trunk signalling interface 20, that acts to decode and interpret signalling schemes used within the narrowband network 10, is coupled between the call server 18 and the switching fabric 16. Outputs from the switching fabric 16 are coupled to a plurality of trunk interfaces 22-24 (although only one need be supplied for an operational system). The plurality of trunk interfaces are further coupled to secondary exchanges 26, such as PBXs or BSSs, within the narrowband network 10.

#As will be appreciated, the term “subscriber terminal” is used merely to describe a particular endpoint connection for a line or trunk interface.