An improved handoff scheme for ATM-based LEO satellite systems

In future wireless personal communication networks (PCNs), asynchronous transfer mode (ATM) based satellite (SATM) on low earth orbit (LEO) constellation shows its potential advantages not only because of its ability of dramatically extending the boundaries of the existing public multimedia networks, but also because of its global coverage and possibilities of QoS guaranteed broadband applications, which is very important in PCNs. In this paper, we introduce a group of handoff schemes which utilize ATM virtual path connections (VPC) and virtual circuit connections (VCC) concepts in defining the connections between all pairs of end satellites (nodes) for a predefined inter/intra satellite link (ISL) sub-network. Then, we apply kinds of matrices, such as shortest path, least traffic and certain bandwidth in finding an appropriate path. The paper also proposes a handoff scheme by defining some of the predefined satellite nodes as key nodes that a thoroughly path optimizing processing is required to make current suboptimal path optimized when a path is via these key nodes. By this scheme, we can keep the selected path optimized from time to time and avoid both long handoff delay and frequent resource reallocation at the same time. Finally, a handoff scheme combined of all above schemes, including paths selecting, extending, rerouting, and optimizing in an ATM-based satellite system is recommended. To evaluate the proposed schemes, a simulation based on the Iridium system has been performed, and results are shown in the paper.