The future of IP-PSTN interworking

As the Internet continues to grow at a phenomenal rate, there is art emerging desire for it to be able to support voice communications, sometimes referred to as voice over LP (VolP). Although the Internet is some way from being able to support carrier-class voice quality, interworking of PSTN and VolP is currently receiving much attention. The approach being adopted at the moment is the use of a media gateway box, which enables carrier PSTN standards to be interworked with VoIP protocols. In the longer term, however and depending upon the actual traffic mix and volumes, such an approach may lead to an expensive and unscalable global telephony service. The particular issue addressed by this paper is the need to understand the technical and economic pros and cons associated with interworking different telephony service standards rather than, developing a new single global standard. The aspects this paper concentrates on include: the current approach of VoIP provisioning based on gateway/gatekeeper interworking and the limitations presented to the network in terms of cross-network signalling. It will compare the cost and complexity to other evolving networks such as public and corporate PSTN and mobile networks. The paper will examine how the current growth trends, which are being fuelled by data traffic, may influence future network architectures and protocols and hence the VoIP implementation options.