Research And Simulated Implementation Of QoS-Based Dynamic Multicast Routing Mechanism For Satellite Internet

As a newly arising network technology, satellite Internet provides "wherever and whenever, whoever can communicate with whomever by whatever means". It is a scheme to provide the users spread all over the world with Internet service. At the same time with the enhancement of new real-time multimedia applications appear continuously, such as distant education and video conference. The infrastructure of Internet should provide high communication bandwidth and guarantee QoS for these multimedia multicast applications. As a critical component of the next generation Internet (NGI), an important issue for satellite Internet is to consider how to provide QoS support effectively.The issue of QoS-based dynamic multicast routing mechanism is mainly studied by analyzing the structure and movement characteristics of satellite Internet. Smooth and rapid handoff is guaranteed by adopting soft handoff and setting handoff priorities; on the other hand, the multicast routing algorithm is designed to reduce the occurrence of handoffs as much as possible. The purpose of the multicast routing algorithm is to maximize the life cycle, meanwhile considering QoS requirements. To resolve this NP-comleteness, Lagrangean relaxation modern optimal algorithm is employed in this thesis. The improved PRIM algorithm works out the multicast tree that satisfies the QoS requirements based on subgradient optimization. Moreover, redundant paths are used to provide further QoS guarantee in this algorithm.In order to verify this algorithm, it is simulated on NS2 simulation platform, and is adjusted according to the simulation results. Iridium constellation is adopted as the simulated network model architecture. The performances of this algorithm are analyzed and compared. Simulation results show that this algorithm significantly prolongs the life cycle of the multicast tree, reduces the occurrence of handoffs, and provides reliable QoS guarantee, therefore it is feasible and effective.