Iterative SIC-Based Multiuser Detection for Uplink Heterogeneous NOMA System

Abstract

This paper considers an uplink non-orthogonal multiple access (NOMA) system that shares spectrum between two groups of heterogeneous mobility users, modulated by orthogonal frequency division multiplexing (OFDM) and orthogonal time frequency space (OTFS), respectively. To eliminate multiuser interference (MUI), we propose an efficient iterative multiuser detection algorithm based on successive interference cancellation (SIC). In particular, the receiver applying our proposed algorithm incorporates two component detectors: one adopts simple frequency-domain equalization (FDE) for low-mobility user group with OFDM, and the other utilizes low-complexity message passing (MP) algorithm for high-mobility user group with OTFS. Those detectors iteratively exchange their outputs of symbol decisions, which are used in the SIC process. Moreover, we analyze the convergence performance of our proposed iterative detection algorithm by the extrinsic information transfer (EXIT) chart. The analysis verifies the algorithm's rapid convergence and potential to achieve the same performance as the detection with ideal SIC in high signal-to-noise ratio (SNR) region. Simulation results demonstrate that the proposed iterative SIC detection algorithm exhibits superior error performance than the existing FDE approach with SIC.