Design of A Low-Complexity Receiver for Uplink SCMA with Multiple Receive Antennas

Sparse Code Multiple Access (SCMA) has been proposed as a potential scheme to increase the spectral efficiency in overloaded scenarios. Most SCMA receivers are based on the Message-Passing Algorithm (MPA) because of the intrinsic graph structure of the resource allocation. In this paper, we discuss two low-complexity receivers that reduce the MPA complexity order. The first is a threshold-based edge-selection, which is an extension of results from a previous work to systems with multiple receive antennas. The second is a selection of receive antennas that minimizes the signal-to-interference ratio of the observed signal during the MPA calculations. Numerical simulation results show that each technique has its own advantages depending on the system parameters and signal-to-noise ratio (SNR) range of operation.