Low Complexity Constellation Rotation-based SIC Detection for IM-NOMA Schemes

Abstract

With the expected explosive growth in the user density in wireless networks, recent works have investigated the integration of index modulation (IM) with multiple access schemes, namely the non-orthogonal multiple access (NOMA) scheme. IM-based NOMA schemes have shown appealing advantages in terms of error performance and power efficiency. However, the advantages come with higher detection complexity as an inherited disadvantage of applying IM. In this paper, we propose a constellation rotation-based approach to reduce the detection complexity of the successive interference cancellation (SIC) algorithm. Specifically, we assume two orthogonal constellations to be utilized for transmission. Hence, the introduced rotated-constellations result in orthogonality in the users' signals space which reduces the inter-user interference domains. Therefore the SIC detection complexity is reduced as well. The proposed approach is shown to have a 50% average reduced complexity as compared to classical SIC. Numerical simulations show a significant improvement in terms of error performance as compared to IM-NOMA scheme.