Performance Analysis For Multi-user Transmission In Broadband Satellite Communication Systems

Due to its advantages of wide coverage,high capacity,and flexibility,satellite communication is considered as an effective approach to provide broadband access to the users in remote areas where base stations are difficult to be deployed,making it as an essential supplement to the terrestrial cellular network and as one of the key parts in future communication infrastructure.This dissertation mainly analyzes the performance of the multi-user satellite communication system under several typical application scenarios,so as to provide guidelines and basis for the system design.The main contributions of this dissertation are summaried as follows:1.For the multi-user satellite forward link transmission system based on the amplify-and-forward(AF)protocol,the outage probability(OP)and ergodic capacity(EC)of the system are investigated under the opportunistic scheduling scheme.Firstly,considering the effects of antenna gain and path loss,the maximum output signal-to-noise ratio(SNR)expression of the system exploiting the opportunistic scheduling scheme is obtained.Then,by assuming that satellite links experience double-lognormal fading,the analytical expressions of OP and EC of the considered system are derived.Finally,the simulation results are given to validate the theoretical analysis and reveal the influence of the user numbers,different fading scenarios,and outage thresholds on system performance.2.For the satellite communication system that exploits both the uplink non-orthogonal multiple access(NOMA)scheme and the downlink NOMA scheme based on the decode-and-forward(DF)protocol,the EC of the system is studied.Firstly,the satellite communication system using uplink NOMA scheme and downlink NOMA scheme is modeled by taking the effects of antenna gain and path loss.Next,use the successive interference cancellation(SIC)technology on both the satellite and the users,the expression of user output signal-to-noise ratio based on the DF protocol is obtained.Then,the closed expression of EC is derived where both uplink and downlink experience Shadowed-Rician fading.Finally,the simulation results not only verify the correctness of the theoretical analysis,but also prove that the NOMA scheme can achieve higher system capacity compared with the orthogonal multiple access scheme.3.For the multi-beam satellite downlink transmission system exploiting layered division multiplexing(LDM)technology,the ergodic capacity is analyzed.By considering path loss and satellite antenna gain,a multi-beam satellite downlink transmission system model is obtained.Firstly,the satellite adopts LDM technology to delivers multicast and unicast signal simultaneously for multiple users on the ground,and use successive interference cancellation technology at the users to decode the multicast and unicast signal respectively to obtain the expressions of its output signal-to-interference-to-noise ratio(SINR).Then,utilizing the statistical channel state information of the satellite link,under the condition of maximizing the output SINR,the transmit beamforming weight vector of the satellite is obtained.Further,the closed expression of the EC is derived based on the condition that the satellite links experience Shadowed-Rician distribution.Finally,the simulation results verify the correctness of the theoretical analysis,and reveal the influence of typical parameters on the system performance.