Joint Design Of Non-orthogonal Codebook And Precoding In Multi-user Mimo Transmission

In the fifth generation of cellular networks(5G),non orthogonal multiple access(NOMA)has great potential as a multiple access method which can realize large-scale access and high-frequency spectral efficiency.Multiple input multiple output(MIMO)system can use space resources to improve the spectral efficiency and transmission rate.Therefore,by combining MIMO with NOMA,the base station can serve multiple users and improve the system capacity.For downlink multi-user MIMO(MU-MIMO),because users can not cooperate with each other,it is necessary to do precoding at the base station transmitter to eliminate or reduce inter-antenna interference.Firstly,precoding algorithms and space time block coding(STBC)in downlink multi antenna system are studied.One is to study the implementation and performance analysis of ZF and MMSE precoding algorithms in MU-MIMO system.The second is to study the coding and detection of STBC in multiple input single output(MISO)system.Both the detection of STBC and the precoding of MU-MIMO need the accurate acquisition of channel state information(CSI).Then,this paper studies the design of non orthogonal codebook for downlink.The system models based on single antenna and dual antenna are proposed.Firstly,the process of non orthogonal codebook multiplexing is given,the codebook design scheme based on constellation rotation and unique translatable mapping(UDM)is proposed,and the maximum likelihood(ML)detection and message passing algorithm(MPA)are given at the receiver.The space-time structure of the downlink non orthogonal codebook is proposed in the scenario of dual antenna transceiver,and the detection of the receiver is realized in the fading channel.Finally,the precoding and detection algorithms are studied in the classical antenna scenario,and then a more universal downlink MU-MIMO system combined with non orthogonal space-time codebook is proposed.When the number of antennas at the transmitter is less than the total number of antennas at the receiver,but greater than each receiver,the objective function following minimum sum mean square error(Min-SMSE)criterion is given.Then a non orthogonal codebook design scheme based on cyclic layered space time architecture(CLST)is proposed to make good use of the characteristics of spacetime structure.Because the channel matrix is singular to both the transmitter and the receiver,the interference between antennas can not be completely eliminated by precoding and detection.A combined precoding and detection algorithm are proposed.Finally,we add multi-user channel coding and design iterative decoding algorithm combined with Viterbi decoder of convolutional code.The goal is to reach the BER performance in the order of 10-3 while Eb/N0=30dB.