(A) new scheme for seamless handoffs in wireless ATM networks using the 2-layered cluster concept

Abstract

In this thesis, we propose a new handoff scheme using the 2-layered cluster concept for the seamless handoffs between clusters in cellular wireless ATM networks. In wireless ATM networks, the seamless handoff schemes between cells or clusters are needed to support various QoSs for each class of service. The handoff between the cells whose corresponding base stations are connected to a same ATM switch, i.e. intra-cluster handoff can operate without the path rerouting and the handoff delay is negligible. But when an intra-cluster handoff occurs, it needs to reroute communication path and some delay-sensitive connections are forced to be terminated by the long handoff delay. To solve this problem, many schemes to reduce inter-cluster handoff delay has been suggested. But the shorter the path rerouting time, the larger waste of network resources and computing power. With the proposed 2-layered cluster concept, the networks are clustered into two layers. In this proposed scheme, one base station is connected to two different ATM switches, and then one cell belongs to two clusters each of them belongs to different cluster layers respectively. The network with this concept can support seamless inter-cluster handoff regardless of path rerouting time, reduce the pingpong effects at the border of clusters, and increase the channel efficiency of wired channel. Such advantageous features of 2-layered network neither incur any increase of inter-cluster handoff rate nor requires additional ATM switches.