Research On Signal Detection And Secure Transmission Scheme For Spatial Modulation

With the mobile communication develop to the 5G,5G communication network puts forward higher requirements for data transmission rate,transmission delay,energy consumption and spectrum utilization of communication system.MIMO technology transmits data by multiple antennas,which not only improves the spectrum efficiency of the System,but also brings problems such as inter-channel interference,inter-antenna synchronization and high energy consumption.Spatial modulation technology can solve these problems very well.In spatial modulation system,on the one hand,the existing signal detection algorithms have poor detection performance,and new detection methods with excellent performance and low complexity are needed;on the other hand,the physical layer security transmission scheme in MIMO system can not be directly applied to spatial modulation system.Therefore,due to the above problems and needs,this paper carries out research from the following two aspects.Based on the study of classical signal detection algorithms,two improved signal detection algorithms are designed in this paper.Firstly,aiming at the high complexity of ML algorithm,a low complexity spatial modulation detection algorithm with weight factor is designed.The algorithm gives a weighting factor whose subscript corresponds to the antenna serial number of the transmitter,and then arranges the values of the weighting factor in descending order.Several antenna serial numbers corresponding to the values are selected to form the antenna candidate set.At last,the transmit antenna and the modulation symbol are searched jointly in the candidate set.Secondly,aiming at the problem of too many searches in distance based detection algorithm,an improved distance based detection algorithm based on threshold is designed.The algorithm also introduces the idea of antenna candidate set.When the joint estimation of the active transmit antenna sequence number and the transmit symbol is made,the search is terminated immediately when the calculation result is less than the threshold value.The simulation results show that the BER performance of the two improved algorithms is close to that of the maximum likelihood algorithm,and their complexity is low.In addition,the problem of secrecy communication in spatial modulation system is studied.Aiming at the problem that existing secure transmission schemes can not provide good secrecy capability,an enhanced secure transmission scheme with artificial noise is designed.The channel state information of legitimate users is used to transform the transmit antenna index and constellation symbol index,then the bit information is mapped into new index and the secrecy capability of the system is also analyzed.Secondly,in the secure transmission system of spatial modulation,when the number of transmitting antennas is not ainteger power of 2,it involves the problem of transmit antenna selection.Based on the perspective of instantaneous secret mutual information,a transmit antenna selection scheme based on cou-off rate is designed.The simulation results show that the proposed scheme is superior to the existing antenna selection scheme,and can improve the secrecy rate of the system,while maintaining good bit error rate performance.