| In multiple input and multiple output(MIMO)systems,spatial modulation(SM)technology is considered to be a new transmission technology that can achieve higher spectral efficiency,energy utilization,and have a simple system structure.It achieves the balance between energy efficiency,complexity and hardware cost in a brand new way,which has been received widespread attention since it was put forward.However,with the development of wireless communication technology,SM can not obtain the transmit diversity gain and multiplexing gain of multiple antennas due to its special transmission structure,so it is not suitable for high-speed and high-capacity scenarios,especially in the future massive MIMO structure.In order to solve this problem,two new SM techniques based on precoding are proposed by improving and optimizing the conventional SM in this thesis.The two schemes are aimed at the transmit SM(TSM)and receive SM(RSM)modes respectively,which bring additional beamforming gain on the basis of the existing spatial modulation,thereby greatly improving the performance of the systems.Firstly,this thesis has a thoroughly survey of the existing spatial modulation technology by analyzing its defects,limitation scenarios of application.Then,various SM optimization scheme with channel state information(CSI)assistance at transmitter in the existing literature are studied,including offset spatial modulation(OSM),phase alignment assisted spatial modulation(SM-P)in TSM mode,and a variety of precoding aided spatial modulation in RSM mode.Performance comparison and theoretical analysis are also presented in this thesis.Then,two new spatial modulation schemes,zero forcing assisted single layer beamforming for spatial modulation(SZF-SM)and a simplified beamforming(SBF)assisted spatial modulation,are proposed.The proposed SZF-SM utilizes zero forcing(ZF)precoding method and CSI to construct a special spatial signal,which can make the system convey all information bits in a single data stream for transmission after the ZF operation at transmitter.This structure can avoid the interferences caused by conventional MIMO multi-streams transmission,and not only achieves beamforming gain at the transmitter,but also obtains receive diversity gain by performing joint detection with all receive antennas.Furthermore,the upper bounds of the theoretical bit error rate(BER)for SZF-SM systems,including multiple input and single output(MISO)and MIMO structures,are derived.Simulation results vadidate the theoretical analysis.It is also shown the proposed scheme performs better than the conventional MIMO systems in highly correlated channels,showing its the advantages in some special scenarios by laying some of the bits in spatial domain.For the proposed SBF transmission scheme,where the correlation matrix of the channel at the transmitter is utilized to construct its spatial transmission signal for beamforming,is able to obtain the beamforming gain and simplify the complexity of detection at the receiver.Accordingly,a low complexity linear blind detection is proposed for SBF,which does not require accurate CSI at the receiver,but only the power of the received signal to detect and recover the information bits.In addition,this thesis also analyzes and derives the transmit-receive diversity of SBF systems in small-scale and large-scale MIMO scenarios,showing that the performance of the blind detection method is close to the optimal ML detection in massive MIMO configuration.Finally,the proposed SZF-SM,SBF transmission schemes are compared with various SM technologies and conventional MIMO precoding systems from BER performance and computational complexity.The simulation results and complexity analysis show that the novel schemes have advantages both on performance and complexity in MIMO systems,providing a new structure and practical for the future massive MIMO systems. |
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