| Summary: | Low earth orbit mobile satellite system (LEO-MSS) is the major system to provide communication support for the regions beyond the coverage of terrestrial network systems. However, passive handover happens frequently caused by the quick movement of LEO satellites in LEO-MSS. It not only causes the waste of radio resource, but also makes it hard to guarantee the quality of service (QoS), especially for user groups in hot-spot regions. To tackle this problem, we propose an extensible multi-layer network architecture to reduce the handover rate, especially group handover rate by introducing high-altitude platforms (HAPs) and terrestrial relays (TRs) to this system. We then propose a multi-layer handover management framework and also design different handover procedures based on handover forecast for different kinds of handovers according to the proposed architecture and framework to reduce handover delay and signalling cost. Furthermore, we propose a dynamic handover optimization to reduce the dropping probability and guarantee the QoS of mobile terminals. Numerical results show that the proposed architecture reduces group handovers significantly. The proposed handover procedures also provide better performance on delay and signalling cost compared with traditional handover protocols. With the proposed dynamic handover optimization, the proposed handover procedures provide better performance on dropping probability and throughput. The proposed dynamic handover optimization has an excellent performance on dropping probability while guaranteeing the QoS of mobile terminals.
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