Research On Non-constant Envelope Differential Spatial Modulation

Spatial Modulation(SM)is an emerging highly efficient MIMO technology.By activating only one antenna element at a time and encoding part of the information into the antenna index as spatial information,the SM technology effectively reduces the number of RF chains in the MIMO system and eliminates inter-channel interference.More importantly,SM improves both spectral and energy efficiency of MIMO system.However,the coherent detection of SM relies heavily on acquisition of the channel state information(CSI),which consumes extra time-frequency resources and is subject to estimation error in practice,which in turn affects detection performance.In order to circumvent issues related to CSI acquisition,the idea of Differential Spatial Modulation(DSM)was proposed.DSM shares most of the physical features with SM but employs less complex differential processing in detection such that CSI is not required.However,the differential processing may introduce severe error accumulation,especially to the signal's amplitude,which is unfavorable when using higher order modulation with non-constant envelope.In this thesis,some issues with using non-constant envelope constellation and massive MIMO for DSM are investigated1)To solve the problem of error accumulation to amplitude in non-constant envelope signals for DSM,this thesis proposes a scheme which based on normalizing the signal power.DSM can transmit any form of constellation symbols by exploit this scheme.Further,this paper analyzes the error propagate problem of the proposed scheme and proposes a multi-ring constellation scheme to mitigate this problem.Simulation results show that the proposed non-constant envelope transmission scheme can eliminate the amplitude accumulation and enable DSM to transmit any non-constant envelope signal.In addition,compare with Quadrature Amplitude Modulation(QAM),the proposed multi-ring constellation scheme has better robustness.2)To solve the problems of downlink massive MIMO-DSM,such as the waste of antenna resources,spectral efficiency loss,and difficult to achieve channelconditions,this thesis proposes an uplink massive MIMO-DSM scheme,In this way,the advantage of DSM and massive MIMO can be incarnate at the same time.In our scheme,we employ the symbol by symbol detection by the cross-covariance matrix of the two adjacent space time matrixes when the channel vectors become orthogonal.The simulation results show that the proposed detection scheme has similar bit error rate(BER)performance with Zero Forcing(ZF)detection,and the computational complexity is lower than ZF.3)This thesis proposes two schemes to solve the problem of non-constant envelope signal transmission of uplink Massive MIMO-DSM,one of which is the existing scheme to massive MIMO-DSM,and the second is extend the proposed scheme to massive MIMO-DSM.Both schemes use the proposed detector to detect the signal.The simulation results show that the proposed scheme is superior to the existing large-scale MIMO differential non-constant envelope transmission scheme,but exist air floor effects.To solve this problem,this paper proposed an advanced detection scheme.The simulation results show that the advanced detection scheme decrease the air floor effect and improves the detection performance at the cost of increasing complexity a little bit.