Joint list multistage decoding with sphere detection for polar coded SCMA systems

A reduced complexity sphere detection (SD) scheme for sparse code multiple access (SCMA) is presented, which employs an MMSE estimate of the transmitted vector to reduce the number of visited tree nodes. Simulation results show that the complexity of this method is lower compared to sphere decoding based on QR factorization, as well as message passing algorithm (MPA). Furthermore, joint list decoding algorithm for polar coded SCMA system is proposed, which provides better performance compared to the conventional sequential user partitioning method with independent list successive cancellation decoding.