Transceiver design for an uplink asynchronous NOMA using MSK-type signals

Abstract

The time offset is intentionally introduced into non-orthogonal multiple access (NOMA) to decrease inter-user interference and enhance performance. Recently, minimum shift keying type (MSK-type) signals suitable for power-efficient nonlinear amplifiers have been considered into the uplink asynchronous NOMA (ANOMA), but it is only for the capacity analysis. In this paper, the transceiver design for an uplink ANOMA using MSK-type signals is our concern. Following the maximum likelihood (ML) criterion under successive interference cancellation (SIC), we first propose a Viterbi algorithm (VA)-based detector. By the eigenvalue decomposition (ED) of Hermitian-Toeplitz matrices, an ED-based transceiver scheme is also given. Further, considering the asymptotic behavior of banded-Toeplitz matrices and the limitations of SIC-based transceivers, we propose a DFT matrix diagonalization (DFTD)-based transceiver scheme for joint ML (JML) detection. Finally, the complexity analysis of several detectors is provided. Numerical results reveal that the maximum sum throughput can be achieved by setting half the bit interval, and the time offset can bring a performance gain of 4 dB or 7.5 dB for SIC-based transceivers and 8 dB for JML-based transceivers. The relationship between bit-error-rate (BER) performance and different channel differences, and modulation formats is also shown by simulation.