Design of an ATM switch for handoff support

In a wireless ATM system, a network must provide seamless services to mobile users. To support this, mobility function should be added to existing ATM networks. Through a handoff operation, a mobile user can receive a service from the network without disconnecting the communication. A handoff results in connection path rerouting during an active connection. To avoid cell loss during a handoff, cell buffering and rerouting are required in the network. A handoff switch is a connection breakdown point on an original connection path in the network from which a new connection sub-path is established. It performs cell buffering and rerouting during a handoff. Cell buffering and rerouting can introduce a cell out-of-sequence problem. In this paper we propose a handoff switch architecture with a shared memory. The architecture performs cell buffering and rerouting efficiently by managing logical queues of virtual connections in the shared memory and sorting head-of-line cells for transmission, thus achieving in-sequence cell delivery during a handoff. We also present simulation results to understand the impacts of handoffs on switch performance.