Fixed / Mobile Convergence : Aspects and Evolution of End-to-end Voice Performance in an Integrated Fixed and Mobile Network

IP-transport is a vehicle for integration of networks of different origins into a single entity. A new step in this evolution is the integration of fixed and mobile networks, not just at the service layer, but also at the infrastructure layer. Where such an integration for packet-based, non-real-time services looks evident, concerns exist about backward compatibility. In particular, the potential support of voice traffic between such integrated fixed and mobile network with sufficient quality is a remaining issue. If a codec robust to packet loss is used the parameter determining quality is the delay for interactive voice communications. In this paper we evaluate the end-to-end delay for different combinations of calls originating and terminating in either the mobile or fixed network, by investigating the delay budgets in different fixed or mobile ingress/egress networks and over different backbones. The end-to-end delays for voice are found to be asymmetric and below the maximum allowed endto-end delay for voice, but slightly above the interactivity bound provided that the packet-based voice traffic gets sufficient priority and bandwidth over the packet-based network over which it is transported.