Research And Implementation Of Sparse Code Division Multiple Access Algorithm

The traditional orthogonal multiple access technology,the number of connections is limited by the number of orthogonal resources,has been unable to adapt to the requirements of current the 5th Generation communication(5G).Therefore,Non-orthogonal Multiple Access(NOMA)technology came into being.NOMA technology can connect more users under the premise of the same total amount of resources,so NOMA technology has attracted extensive attention in the academic field.Sparse Code Multiple Access(SCMA),as a code domain NOMA technology,can show better link performance than other code domain NOMA technologies.Because the performance of SCMA system is mainly determined by SCMA codebook and multi-user detection algorithm,so there are many SCMA codebook design methods and multi-user detection algorithms.First,this thesis proposes a SCMA codebook design method based on constellation distance for Additive White Gaussian Noise(AWGN)channel,this codebook design method transforms the traditional codebook design problem into the optimization problem of multi-dimensional user constellation superimposed on resource blocks,the optimization criterion is to minimize the average energy of the resource block constellation points when the distance between each constellation point superimposed on the resource block exceeds a certain threshold.In this thesis,the optimization problem is modeled as a nonconvex optimization problem,and the optimal solution of the optimization problem is obtained by Feasible Point Pursuit and Successive Approximation(FPP-SCA)algorithm,the final designed codebook has better bit error performance than Huawei codebook and Liangyan codebook in AWGN channel.Secondly,this thesis proposes a SCMA codebook design method based on Mothflame Optimization(MFO)algorithm,the codebook design method firstly designs a complex domain user codeword with parameters,so as to obtain a SCMA codebook with parameters,the design criteria to judge the quality of the codebook are to minimize the bit error rate(Min-BER),minimize the average peak-to-average power ratio(Min-APAPR)and maximize the lower bound of mutual information(Max-AMIL).In this thesis,MFO algorithm is used to solve the three codebook design criteria,can obtain the codebook with better performance,and the algorithm is suitable for different overload rates and channels.The final Min-BER codebook has better bit error performance than the Huawei codebook under different channels.After adding Turbo code,the performance of the MinAPAPR codebook and Max-AMIL codebook is better than other literature codebooks and Min-BER codebooks better.Finally,this thesis implements the Max-Log-Message Passing Algorithm(Max-LogMPA)for the SCMA system with fifteen users and six resource blocks in hardware.Firstly,this thesis uses the fixed-point result with less precision to design the top-level architecture of the algorithm,and then designs the architecture of each module.In order to improve the throughput,this thesis adopts two-way spatial parallel and four-stage pipeline processing,and the throughput rate can reach 3.256 Mbps.Finally,this thesis carries out the FPGA board-level test,and the test results show the correctness of the hardware implementation.