Research On Signal Transmission And Detection Based On Index Modulation And Intelligent Reflecting Surface

With the development of information technology,B5G(Beyhond 5-th Generation)and 6G(6-th Generation)put forward higher requirements on spectrum utilization rate,system throughput,delay and other aspects.Traditional signal transmission technology has been unable to meet the real-time and efficient business needs of multi-users in emerging industries,and cannot provide technical support for the realization of the Internet of everything in the true sense.Therefore,Index Modulation(IM)and Reconfigurable Intelligent Surface(RIS),as key technologies for future wireless networks,attract wide attention in the academic circle.The existing IM technology mainly realizes signal transmission in the frequency domain and the space domain,which can improve the resource utilization rate of the system.In frequency-domain IM technology,information is divided into modulation bits and index bits for transmission by dynamically activating subcarriers.IM,also known as Spatial Modulation(SM),is used for signal transmission by dynamically activating the state of the antenna.RIS technology,by reshaping wireless channels,improves the disadvantages of traditional wireless communication,which is easily affected by the surrounding environment,so as to improve signal transmission quality.This thesis focuses on using IM and RIS technology to optimize the signal transmission of communication system and improve the spectrum utilization rate and the quality of signal detection.Firstly,in this thesis,the Orthogonal Frequency Division Multiplexing(OFDM)systems enhanced by IM are studied,and the semi-blind channel estimation of systems using pilot is proposed.Aiming at the problem that the traditional signal detection method of IM-based transmission system is too complicated,an intelligent signal detection method based on Complex Deep Neural Network(C-DNN)and Complex Convolution Neural Network(C-CNN)is proposed.Simulation results show that these two methods can reduce the Bit Error Rate(BER)of the transmission system and accelerate the convergence speed.Secondly,in order to improve system capacity and spectrum efficiency,this thesis studies RIS system signal transmission scheme,RIS and Non-orthogonal Multiple Access(NOMA)technology are combined to improve the communication coverage and communication quality of uplink scenarios.In order to deal with the problem of spatial correlation,a new constellation optimization method is proposed in the system combining RIS and NOMA.The simulation results show that the new constellation optimization method can solve the singularity problem and improve the accuracy of signal detection effectively.Finally,this thesis combines RIS with IM technology to realize spatial IM,namely SM,to further improve the spectral efficiency and the quality of signal detection.Considering the spatial correlation of reflection elements in RIS array in uplink scenario,two new spatial correlation compensation technologies without control link are proposed.The first one uses static phase compensation to introduce phase shift independent of index information bit.The second method uses dynamic phase compensation to introduce phase shift dependent on the activation mode.Simulation results verify that in RIS system aided Spatial Modulation(RIS-SM)with strong spatial correlation,the two phase compensation techniques proposed can also accurately detect transmitted data bits and index bits.