Effect of Nonlinear Amplifier in Companded OFDM with Application to 802.11n WLAN

It is a well known fact that orthogonal frequency division multiplexing (OFDM) suffers from high peak to average power ratio (PAPR). The nonlinear distortion introduced by a high PAPR OFDM signal through practical amplifiers can further degrade the system performance. In this paper, we analyze the performance of a M-ary quadrature amplitude modulation (M-QAM) OFDM system which is subject to distortions from nonlinear high power amplifiers (HPAs) in a Rayleigh fading channel. In order to reduce the nonlinear distortion caused by HPAs, we propose a new companding technique to reduce the PAPR and a novel receiver structure to minimize the degradation effects from the decompander. For the purpose of simulation, we extend the analytical model to be in compliance with the IEEE 802.11n standard. The theoretical results are verified with the simulation.