Research On Hybrid Satellite-terrestrial Cooperative Communications

Satellite-terrestrial communications have received widespread attention because of its wide geography scope and long communication distance and other advantages.However,its performance has been greatly limited because of the intricate channel and masking effect between satellite and earth station.Satellite-terrestrial cooperative communications systems have developed rapidly in order to adapt the variable satellite-terrestrial communications environment and improve the reliability of communication and other requirements.Satellite-terrestrial cooperative communications are studied in this paper,the main works and contributions are summarized as following:(1)An overview of the knowledge of satellite-terrestrial communications.The common ways of signal transmission and the influencing factors are summarized.Four common probability density functions of propagation characteristics of the satellite-terrestrial channel are provided.The applications of LDPC codes in communication and the construction methods and decode algorithms of binary rate-compatible LDPC codes are given.The advantages and disadvantages of three kinds of satellite-terrestrial cooperative communications systems are discussed based on LDPC codes.Simulation results on the performance of different cooperative communications systems are given and compared the performance of cooperative systems with using LDPC codes of different parameters(2)A new satellite-terrestrial fading channel model is designed,and the simulator structure is given based on the theory of weighted sine sum.The parameters of the new model are derived.The new model can describe a variety of satellite-terrestrial fading models and solve the problem that the traditional models were difficult to analyze the second-order statistics of the satellite-terrestrial channel.The simulation results show that the second-order statistics of the proposed model are very similar to the measured data.(3)Aimed at solving the problem of performance loss of traditionalsatellite-terrestrial communications systems caused by changeable channel states.The Hybrid Automatic Repeat reQuest(HARQ)protocol is introduced to the three-node satellite-terrestrial cooperative communication system.The expressions of the maximum transmission rate at the receiving terminal and outage probability of the system are derived in the incremental retransmission and chase combining modes for HARQ-II mechanism.The comparison results show that the performance of the communications system with a copy of the incremental retransmission scheme is better than others.Designed a novel satellite-terrestrial channel-adaptive coded cooperation scheme by combined the incremental retransmission mode with the rate-compatible LDPC codes.In this new scheme,the satellite and terrestrial relay can determine the retransmission rates according the channel condition,the code rates at the relay and terrestrial terminal could be nonlinearly growth.The expressions of outage probability and throughput are derived and compared.Simulated and compared the performance of this novel scheme with other schemes,the results show that the novel satellite-terrestrial cooperation communications scheme can reduce the bit error rate and outage probability in any kinds of satellite-terrestrial fading channels.