SCMA系統(tǒng)多用戶檢測算法研究
發(fā)布時間：2019-04-22 22:00
【摘要】：稀疏碼多址接入(Sparse Code Multiple Access,SCMA),作為一個前景廣闊的5G無線空口技術(shù),是一種基于碼本的頻譜效率較優(yōu)的非正交多址接入技術(shù),現(xiàn)有的SCMA多用戶檢測算法主要是消息傳遞算法(Message Passing Algorithm,MPA),MPA算法是一種接近最優(yōu)的最大后驗概率檢測算法性能的次優(yōu)的多用戶檢測算法,該算法在迭代過程中,函數(shù)節(jié)點與變量節(jié)點的消息在因子圖中并行傳遞,即首先更新函數(shù)節(jié)點消息,然后更新變量節(jié)點消息,本質(zhì)上該算法是基于并行策略的思想。本文針對現(xiàn)有的SCMA系統(tǒng)接收端基于并行傳遞的MPA算法(Parallel MPA,PMPA)存在信息收斂不理想以及算法復(fù)雜度過高的問題,從提升誤比特率(Bit Error Ratio,BER)性能和降低算法復(fù)雜度兩個角度改進PMPA算法,得到兩類改進算法,即基于串行策略的MPA算法(Serial MPA,SMPA)和基于殘差的動態(tài)消息調(diào)度策略的MPA算法(Residual Dynamic MPA,R-DMPA)。SMPA算法以函數(shù)節(jié)點或變量節(jié)點為序,具體地提出基于函數(shù)節(jié)點串行更新的MPA算法(Function Node Serial MPA,FN-SMPA)和基于變量節(jié)點串行更新的MPA算法(Variable Node Serial MPA,VN-SMPA),SMPA算法按串行方式進行消息更新與傳遞,保證更新消息能夠立即進入當(dāng)前迭代過程,改善了消息傳遞的收斂速率;R-DMPA算法引入了殘差的概念對節(jié)點更新的順序進行排序,優(yōu)先更新殘差值大的節(jié)點消息,相較于PMPA和SMPA算法,R-DMPA算法的收斂速率更快,已更新的消息能夠更快地融入到當(dāng)前迭代過程。仿真結(jié)果驗證了EXIT圖分析的正確性。最后通過外信息轉(zhuǎn)移圖(Extrinsic Information Transfer,EXIT)這一數(shù)學(xué)工具從理論上分析MPA算法的收斂特性。首先將SCMA接收機檢測器分為函數(shù)節(jié)點譯碼器和變量節(jié)點譯碼器,然后給出譯碼器EXIT圖的理論分析,最后通過比較PMPA算法、VN-SMPA算法和R-DMPA算法的EXIT曲線估算出達到收斂狀態(tài)所需的迭代次數(shù)。理論與仿真結(jié)果表明,R-DMPA算法的收斂速率最快。
[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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.5
本文編號：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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.5
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