ATM LAN EMULATION FOR MOBILE CELLULAR NETWORKS

In this paper, the design issues of ATM LAN emulation (LANE) in a mobi le environment are addressed and investigated. One of the most importa nt issues is to support the transparent services for mobile stations. We show that the wireline LANE model, defined by the ATM Forum, for th e legacy LANs (Ethernet/FDDI/token ring) is not efficient enough to ha ndle a handoff. On occurring a handoff, the ATM network has to maintai n network connections and reroute data to the new location of mobile s tations. Combined with the conventional cellular handoff schemes, the wireline LANE-based data rerouting is performed at the base station. A s a result, a communication path between two mobile stations may becom e inefficient when the station moves, e.g., the path elongates and inc urs extra processing overheads. To overcome this problem, we suggest m aintaining a separate connection for each pair of mobile stations inst ead of each pair of LANs (as defined in the ATM Forum). Following on t his suggestion, an extensive cellular handoff scheme is proposed for a n ATM-based wireless network. In the proposal, the rerouting decision is furnished at the ATM switch. It shows that this scheme not only mee ts the basic handoff requirements (data continuity and transparency), but also offers smaller handoff latency and a shorter path. A path mig ration scheme is also suggested to migrate an inefficient path to a be tter one, if any. The effectiveness of the proposed handoff scheme for the wireless LAN emulation service is evaluated by analysis. Some imp lementation issues and the cost/performance tradeoffs between addition al connections (one for each pair of mobile stations) required and ban dwidth waste caused by path elongation are studied.