Crossover switch discovery for wireless ATM LANs

The emergence of Wireless Local Area Networks (WLANs) has brought about the possibility of mobile computing. In order to maintain connectivity to Mobile Hosts (MHs), a handover mechanism is needed as MHs migrate from one Base Station's (BS) wireless cell to another. Current handover schemes are mainly catered for connectionless WLANs (example Mobile IP) which do not have the ability to support Quality of Service (QoS) for continuous media traffic. Hence, mobility for connection-oriented WLANs (example Wireless ATM) should be considered. The problem faced in a connection-oriented WLAN is the ability to provide a fast, efficient and continuous handover mechanism. Mechanisms that can meet most of these requirements are the Incremental and Multicast Based Re-establishment handover schemes. In particular, the incremental re-establishment scheme relies on the presence of a ‘Crossover Switch’ (CX) to establish the new partial circuits to the new BS. In this paper, five CX discovery schemes are proposed to compute and select the optimised new partial path such that both the set-up latency and network resource consumption associated with the handover are small. The proposed CX discovery schemes (Loose Select, Prior Path Knowledge, Prior Path Optimal, Distributed Hunt and Backward Tracking) are suitable for wireless ATM LANs employing either the centralised or distributed connection management approach with either distance-vector or link-state-like minimumhop routing schemes. Simulation results obtained from a trace-driven mobile network simulator on four different network topologies (Random, Star, Tree and Hierarchical Redundancy) reveal that the Prior Path Knowledge and Distributed Hunt discoveries outperform the other schemes in various aspects. Finally, using the IBM PARIS Gigabit Network as an example, we show how CX discovery is incorporated with routing, connection management and QoS.