一種改進基于門限的稀疏碼多址接入低復雜度多用戶檢測算法
doi: 10.11999/JEIT170647
基金項目:
國家重點研發(fā)計劃(2016YFC0801800),國家自然科學基金(51474015)
An Improved Threshold-based Low Complexity Multiuser Detection Scheme for Sparse Code Multiple Access System
Funds:
The National Key Research and Development Program of China (2016YFC0801800), The National Natural Science Foundation of China (51474015)
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摘要: 稀疏碼多址接入(Sparse Code Multiple Access, SCMA)作為一種基于多維碼本的非正交多址技術(shù),能有效滿足5G的巨連接、高頻譜效率和毫秒級時延需求。針對基于門限的消息傳遞算法(Message Passing Algorithm, MPA)存在低門限時誤比特率(Bit Error Rate, BER)較高的問題,該文提出一種改進的SCMA多用戶檢測算法。所提出的算法在基于門限MPA的基礎(chǔ)上,增加了對用戶節(jié)點穩(wěn)定性必要條件的判決,即只有符合門限條件并通過用戶節(jié)點穩(wěn)定性必要條件判決的用戶才能被提前解碼。這提高了提前判決碼字的可靠性并減少了因變相硬判的檢測機制造成的后驗軟信息損失。與基于門限的MPA相比,所提出的算法可使消息在低門限時迭代得更加充分,從而在低門限時仍然能夠使SCMA用戶獲得較好的BER性能。仿真結(jié)果表明,在低門限時采用該文所提出的算法SCMA用戶BER性能明顯好于僅采用基于門限的MPA的BER性能。Abstract: Sparse Code Multiple Access (SCMA) is a non-orthogonal multiple access technology based on multi-dimensional codebook, which can effectively address challenges in 5G such as massive connectivity, high spectral efficiency and millisecond delay. For the problem that threshold-based Message Passing Algorithm (MPA) has a high Bit Error Rate (BER) when the threshold is low, an improved SCMA multiuser detection scheme is proposed in this paper. Based on the threshold MPA scheme, the proposed scheme adds a judgment on the necessary conditions of user node stability. The users who not only satisfy the threshold criterion but also pass the judgment on the necessary conditions of user node stability can be decoded in advance. This improves the reliability of codeword which is judged in advance and reduces the loss of posterior soft information caused by the detection mechanism similar to the hard decision. Compared with the threshold-based MPA scheme, the proposed scheme allows the messages to be iterated more fully at low thresholds, which makes SCMA users achieve better BER performance at low thresholds. The simulation results show that better BER performance is achieved with the proposed scheme than that with the threshold-based MPA scheme for SCMA users.
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