ABSTRACT
SUMMARY In this paper, the design issues of ATM LAN emulation (LANE) in a mobile environment are addressed and investigated. One of the most important issues is to support the transparent services for mobile stations. We show that the wireline LANE model, defined by the ATM Forum, for the legacy LANs (Ethernet/FDDI/token ring) is not efficient enough to handle a handoff. On occurring a handoff, the ATM network has to maintain network connections and reroute data to the new location of mobile stations. Combined with the conventional cellular handoff schemes, the wireline LANE-based data rerouting is performed at the base station. As a result, a communication path between two mobile stations may become inefficient when the station moves, e.g., the path elongates and incurs extra processing overheads. To overcome this problem, we suggest maintaining a separate connection for each pair of mobile stations instead of each pair of LANs (as defined in the ATM Forum). Following on this suggestion, an extensive cellular handoff scheme is proposed for an ATM-based wireless network. In the proposal, the rerouting decision is furnished at the ATM switch. It shows that this scheme not only meets the basic handoff requirements (data continuity and transparency), but also offers smaller handoff latency and a shorter path. A path migration scheme is also suggested to migrate an inefficient path to a better one, if any. The effectiveness of the proposed handoff scheme for the wireless LAN emulation service is evaluated by analysis. Some implementation issues and the cost/performance tradeoffs between additional connections (one for each pair of mobile stations) required and bandwidth waste caused by path elongation are studied.
