Enhancement Technique For Satellite Ground Wireless Communications

Satellite communication system has many advantages,such as wide coverage,long communication distance,large channel capacity and no geographical restrictions.It is widely applied in television broadcasting,personal mobile communications,military communications and other fields.With the increasing demand for satellite communications and the continuous development of satellite communication services,satellite communications are currently undergoing scientific research and industrial production with the aiming at large capacity and high data rates.The application of the beneficial technology in terrestrial wireless communications to satellite communications to achieve the enhancement of satellite ground wireless communications is the focus of this work.By introducing the spatial dimension,the multi-input multi-output(MIMO)technique is capable of increasing the system capacity and spectral effeciency without consuming additional bandwidth and power.Therefore,one method to enhance the performance of satellite ground wireless communications is to study how to build the MIMO satellite links.In this work,two satellite ground MIMO communication systems are presented.The first system includes a single dual-polarized geostationary earth orbit(GEO)satellite and some ground users,while the second system includes two single-polarized GEO satellites and some ground users.Then the statistical channel models based on multi-state transitional Markov chain are investigated.The temporal correlation and Doppler effect involved in the statistical channel modeling are analyzed.The correlations of MIMO channels introduced by polarization diversity and spatial diversity are on focus.The detailed channel modeling algorithms as well as the steps for implementation are given.Subsequently,the diversity gain is obtained by applying the spacetime coding to the established satellite ground MIMO communication systems.In addition,the characteristics of the MIMO channels,the system outage capacity and the bit error rate performance for Alamouti space-time coding are simulated,which verifies the effectiveness of the space-time coding in enhancing the performance of the established systems.The precoding technique preprocesses the transmitted signal according to the channel state information,which can reduce or eliminate the multi-user interference.The power allocation can improve the system spectral efficiency(SE)and energy efficiency(EE)by optimizing the power of the signal transmitted to different users.As another method to enhance the performance of satellite ground wireless communications,this work studies the SE or EE maximization problem for multi-beam GEO satellites with full frequency reuse.Under the constraints of total power and quality of service(QoS),a joint precoding and power allocation optimization algorithm based on sequential convex approximation(SCA)is designed to maximize the SE of the satellite ground wireless communication system.On the other hand,aiming at maximizing the EE of satellite ground wireless communication systems under the constraints of total power and QoS,a power allocation algorithm based on zero forcing(ZF)precoding and a joint precoding and power allocation optimization algorithm based on SCA are presented,respectively.The effectiveness of these algorithms is verified in simulations.