Signal Detection Based On Sphere Decoding In Differential Spatial Modulation System

As a newly emerging multiple-input multiple-output(MIMO)technique,spatial modulation(SM)improves spectral efficiency by introducing a spatial dimension,it has no inter-channel interference compared with the conventional MIMO technique.Moreover,only a single radio frequency chain is needed and the receiver has low complexity.However,the spatial modulation system needs to know the channel state information when demodulating,so the channel estimation must be performed at the receiver.The introduction of channel estimation error will bring about unavoidable performance loss,while the channel estimation also increases the complexity of the receiver.Based on this,a derivative spatial modulation technique,Differential Spatial Modulation(DSM)is proposed.Compared with SM system,DSM technique introducing a time dimension while activating one antenna per time slot so that avoiding channel estimation problems while maintaining the advantages of SM technology.The thesis focuses on the signal detection algorithm of DSM system at the receiver and try to find a DSM signal detection algorithm with lower complexity.Sphere decoding(SD)detection algorithm has the best error rate performance and lower complexity than the maximum likelihood(ML)detection algorithm.It has important application in SM systems.The existing literature has pointed out that the SD algorithm in the DSM system has more relative complexity reduction than the SD algorithm in the SM system.Therefore,the thesis focuses on how to optimize and improve the traditional SD detection algorithm in the DSM system.This thesis analyzes the defects of the traditional SD detection algorithm in the search logic,initial radius and search space.After that,several improved sphere decoding detection algorithms with low complexity are proposed in a targeted manner.The main research work and achievements are summarized as follows:(1)An algorithm called Ordered Sphere Decoding(O-SD)is proposed to solve the problem of the searching order of elements in the lattice in DSM system.(2)An algorithm called Radius-optimized and Ordered Sphere Decoding(R-O-SD)is proposed to solve the problem of the initial radius of the O-SD detection algorithm in the DSM system.(3)After comparing and analyzing the size of search space of SM and DSM system.An algorithm called Pretreated and Ordered Sphere Decoding(P-O-SD)is proposed to solve the problem that the size of search space is too large in DSM system.Simulation results show that O-SD algorithm and R-O-SD algorithm can effectively reduce the computational complexity of the traditional sphere decoding while ensuring Bit Error Rate(BER),while P-O-SD algorithm achieves a great complexity reduction with a small BER performance loss.