Evaluation of channel estimation error inflicted by nonlinear amplification and of its recovery by the means of iterative algorithm

When high power amplifiers are in OFDM transmitters employed in the area of their nonlinear characteristics, the transmitters became more energy efficient and their consumption decreases. However, transmitted signal is nonlinearly amplified and therefore subject to nonlinear distortion. When assuming perfect channel state information present at the receiver, only data symbols are nonlinearly distorted, what results in a decreased performance. However, real world devices must obtain channel state information through estimation process, which is usually based on insertion of pilot symbols into transmission and subsequent pilot symbols channel estimation. In this case, also transferred pilot symbols are subject to nonlinear amplification and distortion, which lowers the accuracy of channel estimation process, and further decreases the transmission performance. This article concerns with evaluation of channel estimation error in a situation of nonlinear amplification, and with an improvement of channel estimation error by iterative algorithm of nonlinear distortion estimation, cancellation and channel reestimation.