Research On Coding Techniques Of Satellite Ground Wireless Communications

With the continuous improvement of the mobile communication and the increasing massive demand of wireless service,the existing satellite communication cannot well satsify the requirements of broadband,high speed and high reliability satellite service.It is urgent to introduce new technologies to improve the system capacity and transmission rate.Multiple-input and multiple-output(MIMO)can achieve high-speed data transmission and improve spectrum efficiency without increasing bandwidth and transmit power.Therefore,the introduction of MIMO technology into satellite communications has become an important research topic.In this work,a dual-satellite dual-polarized satellite MIMO communication system consisting of two dual-polarization geostationary satellites is introduced.The Markov chain is used to simulate the transition of different channel states.After considering the effects of time correlation,Doppler effect,shadow effect,multipath effect,polarization diversity and spatial diversity on the channel,a detailed channel modeling algorithm is proposed.Based on the estiablished MIMO satellite channel,the wireless transmission technology is studied.By using orthogonal space-time block code(OSTBC)and quasi-orthogonal space-time block code(QOSTBC),the bit error rate performance of MIMO satellite communication systems is simulated.For the scenario where a single multi-beam satellite serves multiple terrestrial users,user grouping algorithm in unicast transmission is studied in this work.For the unicast transmission,each satellite beam serves only one user.All users are divided into multiple groups,where users in the same group are simultaneously served by space-division multiple access(SDMA)and different groups of usres are served in different time slots via time-division multiple access(TDMA).Under this framework,a sum-rate maximization user grouping(SMUG)algorithm is proposed in this work.All users are sequentially added to different groups until the sum rate can not increase any more.However,in the above algorithm,some users may not be served by the satellite.To improve the fairness so that all the users can be served,a sum-rate maximization user grouping with user fairness(SMUG-UF)algorithm is proposed in this work.In addition,the multicast precoding design for multibeam satellite is also studied in this work.Under the constraints of total satellite power and user quality of service(QoS),we aim at maximizing energy efficiency by designing the satellite precoding.With sequential convex approximation(SCA)and the Charnes-Cooper transform,the original non-convex fractional programming problem is transformed into a convex optimization problem.Finally,the effectiveness of the proposed algorithm is verified by our simulations.