SCMA Receiver Design for Cellular Uplink Transmission Coexisted with D2D

Sparse code multiple access (SCMA) is one of the most concerned non-orthogonal multiple access schemes in 5G communication system. Meanwhile, device-to-device (D2D) communication is also one of the key technologies for 5G network to improve the spectral efficiency. In cellular systems with SCMA, the non-orthogonal nature renders resource blocks support for more users so that an overloaded system can be achieved. To further improve the system capacity, a D2D and uplink cellular coexisting network is proposed in this paper. The interference between D2D and cellular users are handled. Since conventional message passing algorithm (MPA) has the exponential complexity, the receiver for cellular users is based on some low complexity methods and that for D2D users is also associated with this method. Simulation results show that the proposed hybrid network has an acceptable BER performance loss compared to the general uplink SCMA system, while the proposed SCMA receiver can reduce the decoding complexity significantly compared to the conventional MPA.