| Spatial modulation(SM),as a widely used multi-antenna transmission technology,can effectively solve the problems of inter-channel interference and multi-antenna synchronization compared with the traditional multi-input multi-output(MIMO)technology.SM technology increases the spatial dimension,extends the traditional 2-dimensions digital modulation to 3-dimensions,and transmits information through antenna selection and constellation mapping.Quadrature spatial modulation(QSM)is further evolved from SM,adding an additional modulation spatial dimension,which means that the transmitter can send the in-phase and orthogonal components of the modulation symbol separately.Through two antenna selections,QSM can transmit twice as many index bits as SM,thereby improving system spectral efficiency and obtaining higher transmission diversity.In the beyond 5th generation(B5G)wireless communication,the reliable information transmission of users in high-speed mobile scenes has been challenged.Orthogonal time frequency spatial(OTFS)modulation technology emerged at the historic moment,which can shift digital modulation to the delay Doppler domain.The sparsity of the delay-Doppler channel can effectively counter the Doppler effect in high-mobility communication,thus achieving the reliable transmission of information in the rapidly time-variant channels.The joint design of QSM technology and OTFS system can ensure reliable transmission of information in high-mobility communication,fully utilizing diversity in spatial,time,and frequency domains,and achieving better performance.Based on the above research analysis,this thesis mainly conducts joint design research on QSM technology and OTFS system,and provides corresponding low complexity detection algorithms and scheme design optimization design to achieve efficient and reliable communication.The specific research contents are as follows:1)The system design of OTFS based on QSM(QSM-OTFS)and a low complexity enhanced minimum mean square error(EMMSE)detection algorithm consisting of antenna detection and symbol detection are proposed.The theoretical average bit error rate(ABER)of QSM-OTFS system is derived based on the joint boundary theorem,moment generating function,and the Laplace transform pair.The simulation results verify the effectiveness of the theoretical derivation of QSM-OTFS system,and under the same spectral efficiency,the proposed QSM-OTFS system has higher transmission reliability than traditional SM based OTFS(SM-OTFS)systems,while EMMSE detection can achieve a good compromise between detection performance and complexity.2)Based on the QSM-OTFS system,we propose an generalized quadrature spatial modulation based OTFS(GQSM-OTFS)efficient communication system.In this scheme,the number of antennas sending the real and imaginary part of the transmission information symbol at the transmitter is set to be multiple,and the corresponding antenna activation mode of the real and imaginary part is formed,thereby increasing the number of index bits for antenna selection and improving the spectral efficiency of the system.The theoretical ABER performance and detection complexity of the GQSM-OTFS system are deduced and analyzed in this thesis.The simulation results show that the proposed GQSM-OTFS scheme contributes to improve the spectral efficiency and reliability of the system.3)Based on the GQSM-OTFS system and the idea of antenna grouping,a new GQSM-OTFS communication system based on antenna grouping is designed,and the corresponding low complexity detection algorithm is provided.In the proposed scheme,the transmitter antenna is divided into several groups,and two of them are selected to activate for independent QSM-OTFS modulation transmission.By increasing the index bit of the activated antenna group and number of activated antennas,the spectral efficiency is improved compared with QSM-OTFS system.The simulation results show that the GQSM-OTFS scheme based on antenna grouping not only improves the transmission reliability on the basis of the QSM-OTFS scheme,but also its detection complexity is far less than that of GQSM-OTFS scheme when the number of antennas is large. |
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