Improvement of EVM for Downlink NOMA with Blind Nonlinear Compensation Scheme

Non-Orthogonal Multiple Access (NOMA) is expected to enhance spectrum utilization in 5G and beyond 5G mobile communication systems. Since NOMA multiplexes signals for multiple users into one radio resource, there is an issue that the influence of nonlinear distortion caused by radio frequency circuits becomes more severe. In this paper, we propose to mitigate the effects of nonlinear distortion by a blind nonlinear compensation technique in the receiver side. The improvement effect is evaluated by Error Vector Magnitude (EVM) of the received signal. From the computer simulation results, it is confirmed that the proposed method can effectively suppress the deterioration of downlink NOMA received signal that is affected by nonlinear distortion. As a result, it is possible to apply high-level modulation such as 256QAM in NOMA under such environments.