Distortion-aware beamforming design for multi-beam satellite communications with nonlinear power amplifiers

Hardware components can cause different impairments, including power amplifier (PA) non-linearities, which inevitably impact the system performance of satellite communications (SATCOM). In this work, we consider a multi-beam SATCOM downlink system and investigate the distortion-aware beamforming scheme with the characteristics of PA non-linearities. Notably, we aim to maximize the resource efficiency (RE), defined as the weighted sum of energy efficiency (EE) with spectral efficiency (SE), to obtain a flexible EE-SE tradeoff while accounting for the characteristics of PA distortion and the total power constraints. Given that the optimization objective is a sum of ratios and the high non-convexity involved in constraints, we propose an efficient approach that exploits the quadratic transformation, the Lagrange multiplier method, and the gradient ascent approach to handle this issue. Simulation results demonstrate the effectiveness of the distortion-aware beamforming approach in achieving the EE-SE tradeoff and exhibit a substantial RE performance gain over the conventional approach with ideal linear PAs assumed at the satellite transmitters.