Spatial Modulation Aided Cooperative NOMA: Implementation and Achievable Rate Analysis

Abstract

In this paper, spatial modulation (SM) aided cooperative non-orthogonal multiple access (NOMA) is studied and its spectral efficiency is analyzed. Specifically, we extend the SM-aided NOMA with bit allocation (BA) proposed recently to cooperative NOMA system, and the resulted scheme is named SM-C-NOMA-BA. Both half-duplex cooperation and full-duplex cooperation are considered. In broadcast phase of the proposed half-duplex SM-C-NOMA-BA, information bits intended for strong and weak users are taken as amplitude-phase modulation (APM) bits and active antenna index bits, respectively, which are used to form the SM transmit signal at base station (BS). In cooperative phase, strong user decodes both APM bits and index bits and forwards index bits to weak user, and weak user decodes the index bits after receiving the signals from both BS and strong user in the two phases. In the full-duplex SM-C-NOMA-BA, strong user receives the BS signal and forwards the information of weak user simultaneously. Furthermore, the achievable rates with finite alphabet inputs are analyzed. Finally, numerical results are provided to demonstrate the performance of the proposed scheme.