scholarly journals An Efficient SCMA Codebook Optimization Algorithm Based on Mutual Information Maximization

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Chao Dong ◽  
Guili Gao ◽  
Kai Niu ◽  
Jiaru Lin
Keyword(s):  
Mutual Information ◽  
Optimization Algorithm ◽  
Message Passing ◽  
Multiple Access ◽  
Signal Model ◽  
Message Passing Algorithm ◽  
Continuous Output ◽  
Information Maximization ◽  
Multiuser Channels ◽  
The Relationship

An efficient codebook optimization algorithm is proposed to maximize mutual information in sparse code multiple access (SCMA). At first, SCMA signal model is given according to superposition modulation structure, in which the channel matrix is column-extended. The superposition model can well describe the relationship between the codebook matrix and received signal. Based on the above model, an iterative codebook optimization algorithm is proposed to maximize mutual information between discrete input and continuous output. This algorithm can efficiently adapt to multiuser channels with arbitrary channel coefficients. The simulation results show that the proposed algorithm has good performance in both AWGN and non-AWGN channels. In addition, message passing algorithm (MPA) works well with the codebook optimized according to the proposed algorithm.

scholarly journals SCMA Codebook Design Based on Decomposition of the Superposed Constellation for AWGN Channel

Electronics ◽  
2021 ◽  
Vol 10 (17) ◽  
pp. 2112
Author(s):  
Zhaoyang Hou ◽  
Zheng Xiang ◽  
Peng Ren ◽  
Bohao Cao
Keyword(s):  
Message Passing ◽  
Multiple Access ◽  
Euclidean Distance ◽  
Additive White Gaussian Noise ◽  
Factor Graph ◽  
Codebook Design ◽  
Awgn Channel ◽  
Message Passing Algorithm ◽  
Different Dimensions ◽  
Better Than

In this study, we propose a method named decomposition of the superposed constellation (DCSC) to design sparse code multiple access (SCMA) codebooks for the additive white Gaussian noise (AWGN) channel. We prove that the power of the user symbols (USs) is accurately determined by the power of the superposed constellation (SC). Thus, we select quadrature amplitude modulation (QAM) constellations as the SC and decompose the SC into several groups of USs with power diversity. The minimum Euclidean distance (MED) between superposed symbols (SS-MED) in the receiver is determined by the selected QAM and MED between the multi-dimensional codewords (CW-MED) is optimized by matching the symbols on different dimensions. We propose a simplified DCSC (S-DCSC) by modifying the factor graph and avoiding the transmission of USs with low power, which greatly reduces the complexity of the message passing algorithm (MPA). The simulations show that the SS-MEDs of DCSC and S-DCSC are larger than those in previous papers and the BER performance of the proposed codebooks is better than others.

Overview of Sparse Graph for Multiple Access in Future Mobile Networks

Frequenz ◽  
2017 ◽  
Vol 71 (11-12) ◽  
Author(s):  
Jing Lei ◽  
Baoguo Li ◽  
Erbao Li ◽  
Zhenghui Gong
Keyword(s):  
Wireless Communications ◽  
Mobile Networks ◽  
Message Passing ◽  
Multiple Access ◽  
Low Density ◽  
Sparse Graph ◽  
Extrinsic Information ◽  
Promising Technique ◽  
Satisfactory Performance ◽  
Message Passing Algorithm

AbstractMultiple access via sparse graph, such as low density signature (LDS) and sparse code multiple access (SCMA), is a promising technique for future wireless communications. This survey presents an overview of the developments in this burgeoning field, including transmitter structures, extrinsic information transform (EXIT) chart analysis and comparisons with existing multiple access techniques. Such technique enables multiple access under overloaded conditions to achieve a satisfactory performance. Message passing algorithm is utilized for multi-user detection in the receiver, and structures of the sparse graph are illustrated in detail. Outlooks and challenges of this technique are also presented.

scholarly journals A Threshold-Based Max-log-MPA Low Complexity Multiuser Detection Algorithm

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1016
Author(s):  
Guanghua Zhang ◽  
Zonglin Gu ◽  
Qiannan Zhao ◽  
Jingqiu Ren ◽  
Weidang Lu
Keyword(s):  
Computational Complexity ◽  
Multiuser Detection ◽  
Message Passing ◽  
Multiple Access ◽  
Low Complexity ◽  
Detection Algorithm ◽  
Necessary Condition ◽  
Threshold Condition ◽  
Message Passing Algorithm ◽  
The Stability

Sparse Code Multiple Access (SCMA) technology is a new multiple access scheme based on non-orthogonal spread spectrum technology, which was proposed by Huawei in 2014. In the algorithm application of this technology, the original Message Passing Algorithm (MPA) has slow convergence speed and high algorithm complexity. The threshold-based MPA has a high Bit Error Ratio (BER) when the threshold is low. In the Maximum logarithm Message Passing Algorithm (Max-log-MPA), the approximation method is used, which will cause some messages to be lost and the detection performance to be poor. Therefore, in order to solve the above problems, a Threshold-Based Max-log-MPA (T-Max-log-MPA) low complexity multiuser detection algorithm is proposed in this paper. The Maximum logarithm (Max-log) algorithm is combined with threshold setting, and the stability of user nodes is considered as a necessary condition for decision in the algorithm. Before message updating, the user information nodes are judged whether the necessary conditions for the stability of the user node have been met, and then the threshold is determined. Only users who meet the threshold condition and pass the necessary condition of user node stability can be decoded in advance. In the whole process, the logarithm domain MPA algorithm is used to convert an exp operation and a multiplication operation into a maximum value and addition operation. The simulation results show that the proposed algorithm can effectively reduce the computational complexity while ensuring the BER, and with the increase of signal-to-noise ratio, the effect of the Computational Complexity Reduction Ratio (CCRR) is more obvious.

scholarly journals Nonuniform Code Multiple Access

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Cheng Yan ◽  
Ningbo Zhang ◽  
Guixia Kang
Keyword(s):  
Message Passing ◽  
Multiple Access ◽  
Sparse Code ◽  
Rate Performance ◽  
Initial Information ◽  
Codebook Design ◽  
Constellation Design ◽  
Message Passing Algorithm ◽  
Sum Of Distances

For sparse code multiple access advanced (SCMAA), the quality of initial information on each resource node and the convergence reliability of the detected user in each decision process were unsatisfactory at the message passing algorithm (MPA) receiver. Driven by these problems, this paper proposes a nonuniform code multiple access (NCMA) scheme. In the codebook design of NCMA, different transmitted layers are generated from different complex multidimension constellations, respectively, and a novel basic complex multidimension constellation design is proposed to increase the minimum intrapartition distance. Then a novel criterion of permutation set is proposed to maximize the sum of distances between interfering dimensions of transmitted codewords multiplexed on any resource node, where the number of nonzero elements of transmitted codewords is more than 1. On the other side, an advanced MPA receiver is proposed to improve the reliability of detection on each transmitted layer of NCMA. Simulation results show that the block error rate performance of NCMA outperforms SCMAA and sparse code multiple access (SCMA) under the same spectral efficiency.

Demonstration of Pattern Division Multiple Access With Message Passing Algorithm for Multi-Channel mmWave Uplinks via RoF Mobile Fronthaul

2020 ◽  
Vol 38 (21) ◽  
pp. 5908-5915
Author(s):  
Shuyi Shen ◽  
You-Wei Chen ◽  
Qi Zhou ◽  
Jeff Finkelstein ◽  
Gee-Kung Chang
Keyword(s):  
Message Passing ◽  
Multiple Access ◽  
Message Passing Algorithm

scholarly journals Efficient Sparse Code Multiple Access Decoder Based on Deterministic Message Passing Algorithm

2020 ◽  
Vol 69 (4) ◽  
pp. 3562-3574 ◽  
Author(s):  
Chuan Zhang ◽  
Chao Yang ◽  
Xu Pang ◽  
Wenqing Song ◽  
Wei Xu ◽  
...  
Keyword(s):  
Message Passing ◽  
Multiple Access ◽  
Sparse Code ◽  
Message Passing Algorithm
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