1 Chapter # MOBILE MULTICAST Group communications in a wireless Internet Elias C. Efstathiou and George C. Polyzos Mobile Multimedia Laboratory, Athens University of Economics and Business 1. INTRODUCTION During the late-1990s, the popularity of Internet applications like B2C (business-to-consumer) e-commerce and web-browsing led traditional network operators to seek ways which allowed their customers to access these new services. Today (2002), IP-based packet switching technology has finally matured enough to replace the circuit-switched backbones of telecommunication carriers. Convergence on the IP protocol is now happening and it will continue to happen throughout this decade. It is obvious that this one common protocol will ease the management of all wired and wireless data networks. IP will also fuel the deployment of novel applications. An important feature these applications will expect from an all- IP internetwork is full support for multipoint communications. Multipoint, or group, communications are best described by the term multicast, a term associated with network support for efficient data delivery to more than one interested recipients. Multicast’s objective is to place the least amount of burden on network and end-host resources. Applications that could exploit this feature include conferencing, on-line games, software distribution, and others. Although multicast can be emulated by letting the data sources themselves send packet copies to all intended destinations, this “multi- unicast” solution offers no scalability as resources on both the source host and its local network would eventually be depleted. Today, the many players involved in what is a rapid expansion of the Internet still place “all-IP” convergence several years away. All of these players are, in one way or another, focusing on Internet protocols, with 3G