SCMA系统多用户检测算法研究
发布时间：2019-04-22 22:00
【摘要】：稀疏码多址接入(Sparse Code Multiple Access,SCMA),作为一个前景广阔的5G无线空口技术,是一种基于码本的频谱效率较优的非正交多址接入技术,现有的SCMA多用户检测算法主要是消息传递算法(Message Passing Algorithm,MPA),MPA算法是一种接近最优的最大后验概率检测算法性能的次优的多用户检测算法,该算法在迭代过程中,函数节点与变量节点的消息在因子图中并行传递,即首先更新函数节点消息,然后更新变量节点消息,本质上该算法是基于并行策略的思想。本文针对现有的SCMA系统接收端基于并行传递的MPA算法(Parallel MPA,PMPA)存在信息收敛不理想以及算法复杂度过高的问题,从提升误比特率(Bit Error Ratio,BER)性能和降低算法复杂度两个角度改进PMPA算法,得到两类改进算法,即基于串行策略的MPA算法(Serial MPA,SMPA)和基于残差的动态消息调度策略的MPA算法(Residual Dynamic MPA,R-DMPA)。SMPA算法以函数节点或变量节点为序,具体地提出基于函数节点串行更新的MPA算法(Function Node Serial MPA,FN-SMPA)和基于变量节点串行更新的MPA算法(Variable Node Serial MPA,VN-SMPA),SMPA算法按串行方式进行消息更新与传递,保证更新消息能够立即进入当前迭代过程,改善了消息传递的收敛速率;R-DMPA算法引入了残差的概念对节点更新的顺序进行排序,优先更新残差值大的节点消息,相较于PMPA和SMPA算法,R-DMPA算法的收敛速率更快,已更新的消息能够更快地融入到当前迭代过程。仿真结果验证了EXIT图分析的正确性。最后通过外信息转移图(Extrinsic Information Transfer,EXIT)这一数学工具从理论上分析MPA算法的收敛特性。首先将SCMA接收机检测器分为函数节点译码器和变量节点译码器,然后给出译码器EXIT图的理论分析,最后通过比较PMPA算法、VN-SMPA算法和R-DMPA算法的EXIT曲线估算出达到收敛状态所需的迭代次数。理论与仿真结果表明,R-DMPA算法的收敛速率最快。
[Abstract]:Sparse Code multiple access (Sparse Code Multiple Access,SCMA), as a promising 5G wireless air port technology, is a non-orthogonal multiple access technology based on codebook with better spectrum efficiency. The existing SCMA multi-user detection algorithms are mainly message passing algorithm (Message Passing Algorithm,MPA), MPA algorithm is a sub-optimal multi-user detection algorithm which approaches the optimal performance of the maximum posterior probability detection algorithm. The message of function node and variable node is passed in parallel in factor graph, that is to say, the message of function node is updated first, then the message of variable node is updated. In essence, the algorithm is based on the idea of parallel strategy. In this paper, aiming at the existing MPA algorithm based on parallel transmission (Parallel MPA,PMPA) in the receiver of SCMA system, the convergence of information is not ideal and the complexity of the algorithm is too high, from raising the bit error rate (Bit Error Ratio,). BER) improves PMPA algorithm from two aspects: performance and complexity reduction. Two kinds of improved algorithms are obtained, that is, MPA algorithm based on serial policy (Serial MPA,SMPA) and MPA algorithm based on residual dynamic message scheduling strategy (Residual Dynamic MPA,). R-DMPA) .SMPA algorithm takes function node or variable node as order, specifically proposes MPA algorithm (Function Node Serial MPA,FN-SMPA based on serial update of function node and MPA algorithm (Variable Node Serial MPA,VN-SMPA based on serial update of variable node). The SMPA algorithm updates and passes messages in serial mode, which ensures that the update messages can enter the current iterative process immediately, and improves the convergence rate of message delivery. R-DMPA algorithm introduces the concept of residual to sort the sequence of node update, and first updates the node message with large residual value. Compared with PMPA and SMPA algorithm, R-DMPA algorithm converges faster. Updated messages can be incorporated more quickly into the current iteration process. The simulation results verify the correctness of EXIT diagram analysis. Finally, the convergence characteristics of the MPA algorithm are analyzed theoretically by means of the external information transfer graph (Extrinsic Information Transfer,EXIT), which is a mathematical tool. Firstly, the SCMA receiver detector is divided into function node decoder and variable node decoder, and then the theoretical analysis of the decoder EXIT diagram is given. Finally, the PMPA algorithm is compared. The EXIT curves of VN-SMPA algorithm and R-DMPA algorithm are used to estimate the number of iterations needed to reach the state of convergence. Theoretical and simulation results show that the convergence rate of R-DMPA algorithm is the fastest.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5
本文编号：2463231
[Abstract]:Sparse Code multiple access (Sparse Code Multiple Access,SCMA), as a promising 5G wireless air port technology, is a non-orthogonal multiple access technology based on codebook with better spectrum efficiency. The existing SCMA multi-user detection algorithms are mainly message passing algorithm (Message Passing Algorithm,MPA), MPA algorithm is a sub-optimal multi-user detection algorithm which approaches the optimal performance of the maximum posterior probability detection algorithm. The message of function node and variable node is passed in parallel in factor graph, that is to say, the message of function node is updated first, then the message of variable node is updated. In essence, the algorithm is based on the idea of parallel strategy. In this paper, aiming at the existing MPA algorithm based on parallel transmission (Parallel MPA,PMPA) in the receiver of SCMA system, the convergence of information is not ideal and the complexity of the algorithm is too high, from raising the bit error rate (Bit Error Ratio,). BER) improves PMPA algorithm from two aspects: performance and complexity reduction. Two kinds of improved algorithms are obtained, that is, MPA algorithm based on serial policy (Serial MPA,SMPA) and MPA algorithm based on residual dynamic message scheduling strategy (Residual Dynamic MPA,). R-DMPA) .SMPA algorithm takes function node or variable node as order, specifically proposes MPA algorithm (Function Node Serial MPA,FN-SMPA based on serial update of function node and MPA algorithm (Variable Node Serial MPA,VN-SMPA based on serial update of variable node). The SMPA algorithm updates and passes messages in serial mode, which ensures that the update messages can enter the current iterative process immediately, and improves the convergence rate of message delivery. R-DMPA algorithm introduces the concept of residual to sort the sequence of node update, and first updates the node message with large residual value. Compared with PMPA and SMPA algorithm, R-DMPA algorithm converges faster. Updated messages can be incorporated more quickly into the current iteration process. The simulation results verify the correctness of EXIT diagram analysis. Finally, the convergence characteristics of the MPA algorithm are analyzed theoretically by means of the external information transfer graph (Extrinsic Information Transfer,EXIT), which is a mathematical tool. Firstly, the SCMA receiver detector is divided into function node decoder and variable node decoder, and then the theoretical analysis of the decoder EXIT diagram is given. Finally, the PMPA algorithm is compared. The EXIT curves of VN-SMPA algorithm and R-DMPA algorithm are used to estimate the number of iterations needed to reach the state of convergence. Theoretical and simulation results show that the convergence rate of R-DMPA algorithm is the fastest.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5
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