Improved JMPA multi-user detection algorithm in MIMO-SCMA system

• 1、College of Information Science and Engineering, Xinjiang Key Laboratory of Signal Detection and Processing, Xinjiang University, Urumqi 830046

Abstract：Although multiple-input multiple-output (MIMO) and sparse code multiple access (SCMA) are two effective ways to support high spectral efficiency and large-scale connection, they will lead to the decline of bit error performance, and more antennas will increase the cost of calculation. At present, there are few studies on joint message passing algorithm (JMPA) in the MIMO-SCMA system.Therefore, this paper proposes an improved joint iterative message passing algorithm (JMPA). Therefore, three aspects of improvement are made to the spherical JMPA algorithm whose radius R is 2σ: first, the Euclidean distance of the constellation points outside the decoding radius is multiplied by weight q to reduce their probability density and increase the probability of constellation points around the received signal being decoded. The other is to multiply an impact factor α in the update formula of the resource node message to make up for the information loss caused by the calculation of the resource node information. Finally, the log-likelihood ratio (LLR) value is multiplied by a maximum message value to improve the likelihood ratio and increase the effective likelihood information. Simulation results show that the improved algorithm can effectively improve detection performance and keep the same convergence rate. It is shown that the proposed algorithm can reduce the message loss caused by the original JMPA calculation and improve the detection performance of the receiver of the MIMO-SCMA system.

Keywords： multiple-input multiple-output(MIMO) sparse code multiple access(SCMA) joint message passing algorithm probability density impact factor