Performance Analysis of Uplink Sparse Code Multiple Access in Rician Fading This paper investigates the error performance of uplink sparse code multiple access (SCMA) over Rician fading channels, with the assumption of joint maximum likelihood multiuser detection. We provide an expression for the pairwiseerror probability of SCMA codewords, for multiuser signaling in the presence of additive white Gaussian noise and independent Rician fadings. Based on the derived codeword pairwiseerror probability, a tight upper bound on the average codeword error probability is then developed by using multiuser union bound estimation, which gives an accurate evaluation of the error performance of uplink SCMA. Simulations are carried out for different Rician channel scenarios, to verify the effectiveness of the analysis.

A ThresholdBased MaxlogMPA Low Complexity Multiuser Detection Algorithm Sparse Code Multiple Access (SCMA) technology is a new multiple access scheme based on nonorthogonal 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 thresholdbased MPA has a high Bit Error Ratio (BER) when the threshold is low. In the Maximum logarithm Message Passing Algorithm (MaxlogMPA), 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 ThresholdBased MaxlogMPA (TMaxlogMPA) low complexity multiuser detection algorithm is proposed in this paper. The Maximum logarithm (Maxlog) 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 signaltonoise ratio, the effect of the Computational Complexity Reduction Ratio (CCRR) is more obvious.