Antenna-Resource-Based SCMA in Downlink Multiuser Transmission Systems

Sparse code multiple access (SCMA) is an appealing non-orthogonal multiple access technique, which transmits superimposed signals through various resources, such as frequency and time. It is known that multiple-input multiple-output (MIMO) has been widely used in wireless communications to improve the system performances by taking full advantages of fading channels. Regarding appealing feature of MIMO, this paper focuses on the SCMA system that exploits antennas (or space) as parallel resources to transmit superimposed signals, and this type is named as antenna-resource-based SCMA (AR-SCMA) systems. Unlike the classical frequency-resource-based SCMA (FR-SCMA), the received signals consist of both the superimposed multiple users' signals and interference from other antenna resources. To eliminate the antenna interference and separate users, we propose a joint zero-forcing (ZF-) and/or minimum mean square error (MMSE-) message passing algorithm (MPA). Simulation results show that our proposed AR-SCMA can improve the bit error rate (BER) performances, and achieve a higher channel capacity than the classical FR-SCMA system.