稀疏码分多址（SCMA）是一种新型非正交多址技术，具有过载通信的特点。在高信噪比（Eb/N0）场景下基于消息传递（MPA）的译码算法，误比特率性能不理想。因此，提出一种部分响应与稀疏码分多址联合调制译码模型，方案继承了SCMA在译码端的低复杂性和部分响应的高容错性。为进一步降低联合译码的误比特率，将部分响应的Viterbi译码级联至MPA迭代译码过程中，即每次迭代过程中变量节点都会进行一次Viterbi译码，从而组成新型联合译码模块。仿真结果表明，改进后联合编译码模型能够有效降低系统对Eb/N0的需求，同时保持较低的误比特率。
Sparse code multiple access (SCMA) is a new type of non-orthogonal multiple access technology with overload communication. In the high signal to noise ratio(Eb/N0)scenario, based on the message passing (MPA) decoding algorithm, the bit error rate performance is not ideal. Therefore, a joint modulation and decoding model based on partial response and sparse code division multiple access is proposed. The scheme inherits the low complexity of SCMA at the decoding end and the high fault tolerance of partial response. In order to further reduce the bit error rate of the joint decoding, the Viterbi decoding of the partial response is cascaded into the MPA iterative decoding process, that is, the variable node performs a Viterbi decoding during each iteration, to form a new joint decoding module. The theoretical and simulation results show that the improved joint coding and decoding model effectively reduces the system’s demand for Eb/N0 and maintains a low bit error rate.
[1] Dai L, Wang B, Yuan Y, et al. Non-orthogonal multiple access for 5G:solutions, challenges, opportunities, and future research trends[J]. IEEE Communications Magazine, 2015, 53(9):74-81.
[2] Ma Z, Zhang Z Q, Ding Z G, et al. Key techniques for 5G wireless communications:network architecture, physical layer, and MAC layer perspectives[J]. Science China:Information Sciences, 2015, 58(4):1-20.
[3] Benjebbour A, Saito Y, Kishiyama Y, et al. Concept and practical considerations of non-orthogonal multiple access (NOMA) for future radio access[C]//2013 International Symposium on Intelligent Signal Processing and Communication Systems. IEEE, 2013:770-774.
[4] Nikopour H, Baligh H. Sparse code multiple access[C]//2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). IEEE, 2013:332-336.
[5] Kihara K, Nishimura T, Ohgane T, et al. Signal detection with belief propagation in faster-than-Nyquist signaling[C]//2017 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference (APSIPA ASC). IEEE, 2017:1790-1794.
[6] Zhang S, Xu X, Lu L, et al. Sparse code multiple access:an energy efficient uplink approach for 5G wireless systems[C]//2014 IEEE Global Communications Conference. IEEE, 2014:4782-4787.
[7] Ghaffari A, Leonardon M, Cassagne A, et al. Toward high-performance implementation of 5G SCMA algorithms[J]. IEEE Access, 2019, 7:10402-10414.
[8] Liu J, Wu G, Li S, et al. On fixed-point implementation of Log-MPA for SCMA signals[J]. IEEE Wireless Communications Letters, 2016, 5(3):324-327.
[9] Mu H, Ma Z, Alhaji M, et al. A fixed low complexity message pass algorithm detector for up-link SCMA system[J]. IEEE Wireless Communications Letters, 2015, 4(6):585-588.
[10] Wang Y, Qiu L. Edge selection-based low complexity detection scheme for SCMA system[C]//2016 IEEE 84th Vehicular Technology Conference (VTC-Fall). IEEE, 2016:1-5.
[11] Forney G. Maximum-likelihood sequence estimation of digital sequences in the presence of intersymbol interference[J]. IEEE Transactions on Information theory, 1972, 18(3):363-378.
[12] Rusek F. Partial response and faster-than-Nyquist signaling[D]. Lund:Lund University,2007.
[13] Taherzadeh M, Nikopour H, Bayesteh A, et al. SCMA codebook design[C]//2014 IEEE 80th Vehicular Technology Conference (VTC2014-Fall). IEEE, 2014:1-5.
[14] Pan Z, Li E, Wen L, et al. Joint iterative detection and decoding receiver for polar coded SCMA system[C]//2018 IEEE International Conference on Communications Workshops (ICC Workshops). IEEE, 2018:1-6.
[15] 张弩天.极化码的译码算法研究及其应用[D].成都:电子科技大学, 2018.
[16] 符杰林,张剑波,王俊义.SCMA与极化码的联合检测译码技术[J].计算机应用研究,2019(9):1-6.
[17] Pan Z, Li E, Zhang L, et al. Design and optimization of joint iterative detection and decoding receiver for uplink polar coded SCMA system[J]. IEEE Access, 2018, 6:52014-52026.
