Fast generalized threshold‐based signal detection for multiuser downlink NOMA systems with arbitrary power allocation

Abstract

Summary Non‐orthogonal multiple access (NOMA) is a technique to improve spectral efficiency. Based on the constellation relationship (CR) between the superposition‐coded signal and individual user's signals, in the literature, a simple detection scheme threshold‐based signal detection has been proposed for the two‐user downlink NOMA (DL‐NOMA) system with specific power allocations, not arbitrary power allocation. Furthermore, the average symbol error probability (ASEP) with squared M‐ary quadrature amplitude modulation for two‐user DL‐NOMA systems has also been derived based on this CR. Based on the threshold‐based signal detection for the two‐user DL‐NOMA systems with specific power allocation, in this paper, a generalized threshold‐based signal detection is proposed for all users in the multiuser DL‐NOMA systems with arbitrary power allocation, and then a fast generalized threshold‐based signal detection is further proposed. The generalized ASEP for each individual user in the multiuser DL‐NOMA system is further derived in Rayleigh fading channels. Both theoretical ASEP and simulated symbol error rate results validate the fast generalized threshold‐based signal detection scheme and the generalized ASEP for multiuser DL‐NOMA systems with arbitrary power allocations.