Multistate Digital Predistortion of Nonlinear Effect in PD-NOMA System

Power domain nonorthogonal multiple access (PD-NOMA) is an effective technique to improve spectral efficiency. When the power allocation strategy changes, the power of the signals synthesized by multiple users will change accordingly. This leads to a change in the nonlinear characteristics of the power amplifier (PA) and a deterioration of the bit error rate (BER) of the PD-NOMA system. Current methods cannot achieve real-time predistortion at low complexity and cannot dynamically track power state changes. To address this issue, a multistate digital predistortion (MS-DPD) method at the transmitter is proposed, which can quickly and dynamically adapt to different states. The experimental results indicate that the proposed MS-DPD method has a low BER and fast convergence speed within multiple power ratio states.