Similar to a mobile-user in the cell-based GSM, a satellite in a LEO system constantly circulate8 along its predesigned obit. Satellites' movement causes their visibility change, and thus a user's call needs to be handed over among satellites from time to time. The handovers may occur frequently Without handling those calls well, the system performance will degrade. This paper dealt with call admission conwl and considered a multiservice LEO system allocating various bandwidths for different calls (so-called multirate). A novel guard-channel policy that reserves appropriate channels for various types of handover calls was proposed. It applied SMDP theory to find optimal channel reservation, on the premise of COS guarantee to handover calls. The result? manifested that under various traffic conditions, this SMDP-based guardehannel policy performed better than coordinak-convex and ordinary SMDP-based policies.

This paper focuses on the issues of admission control and rerouting for LEO satellite networks providing multimedia services. The issues includes resource allocation and routing for intersatellite links (ISLs), load balance amongst links. and satellite handover and rerouting caused by satellites ' dynamic characteristics. Applying Markov Decision Process (MDP) theory and generic policy-iteration formulation. a distributed routing scheme, called adaptive cost routing (ACR), is proposed. Comparing the performance of ACR with other routing schemes in terms of system throughput and blocking rate, the ACR presented itself with not only a better routing performance, but also less connection setup time and easier to be implemented in contrast to most centralized routing algorithms.