Open Access

ARTICLE

Low Complexity Decoding Algorithm for Uplink SCMA Based on Aerial Spherical Decoding

Xiaohong Ji¹, Junjun Du¹, Guoqing Jia^1,*, Weidong Fang^2,3

1 Qinghai Nationalities University, Xining, 810007, China
2 Science and Technology on Micro-system Laboratory, Shanghai Institute of Micro-System and Information Technology, Chinese Academy of Sciences, Shanghai, 201800, China
3 University of Chinese Academy of Sciences, Beijing, 100049, China

* Corresponding Author: Guoqing Jia. Email:

Intelligent Automation & Soft Computing 2021, 27(3), 737-746. https://doi.org/10.32604/iasc.2021.013009

Received 30 August 2020; Accepted 13 October 2020; Issue published 01 March 2021

Abstract

As a new non-orthogonal multiple access technology for 5G massive machine type communication scenario, the sparse code multiple access (SCMA) has greatly improved the spectrum efficiency due to the high connection density. SCMA combines QAM (Quadrature Amplitude Modulation) modulation and sparse spreading into a codebook set to obtain forming gain. The user binary bit data is directly mapped into multi-dimensional codewords in the transmitter. The receiver uses the message passing algorithm (MPA) for multi-user detection to achieve efficient decoding. However, MPA is a good solution for SCMA, though its high complexity limits the application in practical systems. In order to reduce the complexity of MPA, this paper proposed a low-complexity decoding algorithm based on the serial spherical decoding message passing algorithm (SSD-MPA), which greatly enhanced the practicability of the SCMA system. The SSD-MPA took into account the distribution characteristics of the Gaussian noise and the reliability of the constellation points, and only updates the trusted constellation point messages of nodes within the spherical radius. At the same time, it used a serial strategy to speed up the convergence rate. The simulation results have shown that when the radius sets properly, the algorithm reduces the complexity by about 2/3 compared with the original MPA, and the performance was almost lossless.

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Citations