Gaussian Approximation-Based Belief Propagation Receiver for Uplink SCMA Systems With Imperfect CSIR

For uplink sparse code multiple access (SCMA) systems, a channel estimation is required to support a multi-user detection in practice. Motivated by the conventional detection, called a Gaussian approximation-based belief propagation (GA-BP) with matched filtering, we propose an efficient receiver suitable for the uplink SCMA systems when exact channel state information is not available. By estimating matched filtered channels (rather than explicitly estimating actual channels), the proposed methods efficiently support the second-stage GA-BP detector with negligible increment of complexity. The simulation results show that the proposed receiver achieves the similar estimation and detection performance to the state-of-the-art receiver while the required complexity can be drastically reduced.