Leo Satellite Communication Channel Transmission System Characteristics And Location Management Strategy

Mobile satellite communication system is a necessary part of next generation wireless communication system. During the work, planning and designing modern mobile communication systems which are based on satellites, the study of propagating characteristics of the satellite mobile channel is one of the most important factors. And another important aspect of the mobile satellite network is to manage the location of all users. Many network signal flows and database updates and queries are required to accomplish such a task. There are two basic operations that are elemental to track mobile users: location update and paging. Associated with each one of these operations there is a certain cost. For instance, frequent updates cause high power consumption at the mobile terminals and heavy loads to the network, increasing one cost leads to a decrease in the other one. We should find a trade-off between these two problems.In this paper, I study some key technologies such as channel model simulation, channel coding and interleaving firstly, and then propose two strategies for location management in LEO satellite network. The main contents are followed:In chapter 2, a simulation model for the broadband satellite attenuation channel is presented. I both study the concatenated code and interleaving technologies, analyze the impact of different code and interleaving depth on bit error rate (BER) of the system, and the corresponding conclusion is drawn. In practical project designs, we must consider the factors about system performance, complexity to choose the codes and interleaving depths.In chapter 3, I propose a terminal aided two-step pointer forwarding strategy for location registration in LEO satellite network which avoids bottleneck in home location register (HLR). Simulation results indicate that our strategy significantly decreases the location update cost, the average paging time and cost, particularly for the satellite networks where there exit frequent flip-flop effects.In chapter 4, I propose a distributed HLR mechanism of location management, to deal with the mobility of roam user far away from his resident HLR in a LEO network. Compared with the traditional method, the registration and cancellation cost can be reduced since the roam user's information was recorded in HLR's special memory. The proposed scheme can greatly reduce long distance signaling traffic and degree of HLR bottleneck, and is very suitable for subscribers with low call-to-mobility ratio (CMR). The method is feasible since memory's cost decreases gradually.