Research On Key Techniques Of Distributed Mobility Management In Satellite Networks

The development of Internet has greatly contributed to the advance of satellite technologies.Providing Internet services by satellite networks is becoming a popular trend with many advantages,such as the large coverage,not subject to geographical conditions and flexible deployment.Nevertheless,the high-speed movement of satellites causes the constant changing of the terminal's access location with high frequency,which brings great challenges to mobility management in satellite networks.As a result,designing efficient mobility management schemes becomes an important issue in satellite networks.Existing work on mobility management in satellite networks,mainly borrows the idea from that of the terrestrial counterpart,and is all based on the centralized management architecture.With the increase of the network scale and mobile traffic,this centralized management scheme has exposed many shortcomings,such as the non-optimal routes,lack of scalability and single point of failure.Therefore,the Internet Engineering Task Force(IETF)proposes Distributed Mobility Management to avoid the above issues by deploying the distributed mobility anchor.This thesis explores key techniques of the Distributed Mobility Management in satellite networks.The content of this paper is concluded as follows:(1)A Distributed Mobility Management architecture for Satellite networks(DMMS)is proposed.DMM-S removes the centralized binding from the mobile terminal to the fixed mobility anchor and adopts the dynamic binding strategy.Based on this idea,each terrestrial gateway realizes regional mobility management for terminals within their own management area.The global location management is accomplished through the synchronization of the distributed terrestrial gateways.Both terrestrial gateways and satellites support the forwarding management.Comparing with existing centralized management schemes,DMM-S can greatly reduce non-optimal routes,and has better scalability and flexibility.Simulation results show that DMM-S is an efficient scheme with preferable scalability in both management cost and routing efficiency.(2)Distributed location management schemes based on terrestrial gateways are explored.Three location management schemes are proposed and analyzed: loose location management,precise location management,and the grouping location management.Theoretical analysis is conducted to evaluate the total cost including the query cost and the management cost.The cost of the loose location management can be equal to that of the precise location management for the query frequency within given range.Starting from the above analysis,we speculate and prove the existence of the optimum scheme in grouping location management under the same condition.Simulation results validate the analysis and present more features on the query latency,which provide a valuable insight into the design of the distributed location management in satellite networks.(3)An optimized forwarding management scheme based on the Lowest Common Ancestor(LCA)during the handover process is proposed.Firstly,we analyze the applicability of existing forwarding schemes in satellite networks.Based on this analysis,to decrease the cost of non-optimal routes during the handover process,we propose an optimized forwarding management scheme based on LCA.In this method,a tree with shortest path is constructed from the accessed satellite of the source terminal to that of the destined mobile terminal.The LCA of the old and the new accessed satellites of the mobile terminal is chosen as the forwarding node during the handover process.Simulation results show that this method can greatly reduce the non-optimal routes during the handover process with acceptable increase in management cost,and the cost can be equal to that of the traditional one when irrespective of the processing limitation on satellites.(4)An optimized scheme for reliable transport of location information for mobile networks based on network coding is proposed.In the mobility management scheme for mobile networks in DMM-S,the Geostationary Earth Orbit(GEO)satellite is utilized to broadcast the location information of mobile networks to speed up the location update process.Considering the lossy Ground-Satellite Link(GSL)on the GEO satellite,network coding is utilized to optimize the reliable transport.In this method,an array for packet loss is maintained at the sender and network coding is adopted to encode the packets during the retransmission stage.Theoretical analysis is conducted in typical processing models of satellite networks with different reliable mechanism in transport.Simulation results show that this method can greatly reduce the bandwidth usage while achieving comparable latency with better scalability.