Wide-band speech teleconferencing over an integrated network
There is a lot of interest at present in the provision of an integrated network which can carry both voice and data traffic. The recent emergence of asynchronous transfer mode (ATM) networks has made this desire a reality. The Unison project built a network consisting of local area networks (LANs) and exchange LANs connected at local and remote sites by an ATM-Iike backbone network. This extends the facilities of the LAN to a wider area. The Unison network is also an intelligent network, because it provides a service to the user (such as dynamic data-bases, which ease call set-up and facilitate user migration). An important feature of the Unison network is also the provision of applications which demonstrate the suitability of the network to carry both voice and data traffic, and which exploit the intelligent network features. This thesis describes a very important application: the provision of a two- and three-party wide-band speech teleconferencing system. The first part of the thesis deals with the provision of a two-party teleconferencing system, based on a wide-band speech codec. The codec is interfaced to the Unison Network via transputers (parallel processors). This thesis considers in detail the voice protocols which make up part of the network interface. The work includes the set-up and control benefits gained from interaction with a desk-top workstation, which can also be used to guide other multi-media services (such as video). A topic which has been greatly under-stressed in other similar research (i.e. the acoustic aspects of the system) is also investigated. The second part of the thesis deals with the logical expansion of the two-party system to a three- or more party scenario across the Unison network. Towards this end, a bridge has been designed and implemented based on transputers. The problems associated with matching the DSP algorithm used in the codecs with that implemented in the bridge is also discussed. The same systems considerations addressed by the two-party version are expanded to operate with the three-party teleconferencing system.