Research On The Channel Allocation Scheme Of LEO Satellite Mobile Communications

As a key national fundamental communication establishment and component of global mobile communications, satellite mobile communication systems are widely used in national security, emergent succor, internet, remote education, satellite broadcasting and personal mobile communications. The new generation wideband satellite communication system is an indispensable technique for global seamless coverage and high-speed"sky-internet". The new technologies of satellite communication are developed quickly. Especially, the development and applications of low earth orbit satellite mobile communications are strategic consequence of countries in the world. Due to the costliness and scarceness of the satellite wireless channel, the wireless resource management is a crucial issue in the research of satellite mobile communications. In this dissertation, channel allocation and spotbeam handover management are studied, which are the hardcore of the wireless resources management.Firstly, a dynamic channel allocation scheme is proposed. In allusion order to tackle the problems of frequently spotbeam handovers and high handover call dropping probabilities, the predictive formulas of mean and variance of the spotbeam traffic are deduced. And then, the channel occupation distribution is predicted. A global traffic Prediction and Stochastic Control based Channel Allocation scheme (PSCCA) is designed according to the character of LEO satellites. The simulations are performed and the results reveal the validity of the scheme. Comparing with the termination location based handover scheme, PSCCA shows its strong control capability on handover call dropping probabilities. Because PSCCA need not the information of the termination location, it has lower system complexity and signaling overheads.Secondly, a utility function based adaptive channel allocation scheme is proposed and the corresponding mathematical model is established. Nowadays, providing multi-type services is the trend of the wideband satellite communications. With the character of variable service bandwidth, the utility function is used to express the relationship between bandwidth and user's satisfaction and a handover call admission control scheme is designed. And then, a novel utility function based adaptive channel allocation scheme is brought forth based on the premise of the establishment of the constrained nonlinear programming model which aims at maximizing the system user's satisfaction. The proposed scheme has the lower handover call probability at the cost of little utility.In succession, two intelligent computing algorithms are proposed to solve the constrained nonlinear programming problem in the proposed adaptive channel allocation scheme. Genetic algorithm and particle swarming optimization algorithm are designed respectively. Genetic algorithm is a general optimization algorithm by which the proposed adaptive channel allocation scheme is validated. While the utilization of the particle swarming optimization algorithm can improve the efficiency of the solving procedure further. The advantages of the designed particle swarming optimization algorithm consist in that the nonlinear inertia weight improves the convergence speed and the check of feasible of particles is introduced for constrains handling. The simulation results show that the proposed adaptive channel allocation scheme can adapt to the change of the traffic by dynamically adjusting the bandwidth of the calls and overcomes the defect of the lower channel utilization of the reservation channel scheme.Fourthly, a structure of integrated LEO satellite and terrestrial communication system is presented. It is necessary to integrate the LEO satellite communication systems and terrestrial mobile communication systems for improving the capacity and efficiency, achieving global seamless coverage. Based on the analysis of satellite network traffic and the characteristic of traffic sources distribution, an integrated structure of LEO-land non-infrastructure communication system is proposed. The load balancing scheme based on the land repeaters which is used to connect the terminations around it. And the corresponding call control protocols are designed.Finally, the main contributions of this dissertation are summarized and some suggestions and directions for the future work in this field are given.