Research On Strategy Of Handover In Hybrid Satellite-Terrestrial Networks

Terrestrial mobile communication system has been well developed and owns the advantages as high quality of communication,low cost and a respectively small coverage radius.While the satellite communication system provides global coverage and can be used to provide communication service in the area out of terrestrial wireless networks'coverage.At the same time,access to a satellite network when the terminal is moving at a very high speed helps to reduce the handover frequency and the call drop rate,thus improving the user experience.Therefore,it is imperative to build a hybrid satellite and terrestrial network integrating the advantages of both systems.In the hybrid network system,energy consumption of the satellite system needs to be specifically considered.Satellite power resources are limited and valuable,so it is important to minimize system power consumption under the premise of a good quality of service.The handover process in hybrid network system involves both network access selection and resource release and distribution,so the handover strategy not only has a direct impact on the user communication experience,but also affects the distribution of power and other network resources.To solve these problems,this paper comes up with two vertical handover strategies in HSTNs aiming at satellite power optimization.These two strategies reduced the static and dynamic power consumption in satellite system in indirect and direct ways respectively.The main achievements of this paper are divided into two parts:First,a classified discussion about both of the HSTNs scenario and the handover scenarios of high-speed mobile terminals is carried out.Aiming at the problem of very limited resource in satellite networks,this paper proposed the thought of restricting the access to satellite networks only under certain conditions and connecting to terrestrial networks most of the time by dividing the motion patterns of mobile terminals.Based on this designing thought,the motion pattern of terminals is modeled and analyzed in detail and a handover scheme based on motion patterns in HSTNs is brought up,named HSMP-HSTNs.Finally,we carried out a simulation analysis and verification of the scheme.According to the results,the proposed scheme indirectly decreases the energy dissipation under the scenarios mentioned above as well as guaranteeing a good quality of service.Second,to further minimize the power consumption of satellite network,an improved Markov decision algorithm for vertical handover,namely SPO-MDP(A Satellite Power Optimized Markov Decision Progress),is brought up.In this algorithm,the handover decision process during a user's conversation is modeled as a Markov decision sequence.The objective function for handover decision is set based on the optimization of satellite network power consumption along with the assurance of user experience during the handover process.The Simulation results show that the proposed algorithm can lead to a lower power consumption and fewer handoff times in satellite systems compared to several existing schemes and meanwhile keeps the call drop rate at a respectively low level.