Iterative Algorithm for Channel Re-Estimation and Data Recovery in Nonlinearly Distorted OFDM Systems

This paper presents a new algorithm for the nonlinear distortion cancellation andchannel re-estimation in an iterative manner for the OFDM transmission systems. Whereasin practical OFDM systems, where nonlinear amplifiers are used in the transmitter, data aswell as pilot symbols are nonlinearly distorted. As perfect channel state information is oftenassumed in many papers, the effect of the nonlinear distortion of the pilot symbols isusually not accounted for, and the data symbols are considered only. However, as the pilotsymbols are used to obtain the channel state information, the distortion caused to pilotsymbols by the nonlinear amplification is of the great importance, and for this reason thiseffect should be taken into account. To address this issue, in this paper, an efficientalgorithm will be introduced for joint data recovery and channel re-estimation in aniterative manner for OFDM transmission system. This algorithm iteratively estimates thenonlinear distortion due to nonlinear high power amplifier of the transmitter and then ituses it to compensate for this nonlinear distortion of the data and the pilot symbols, whichare subsequently used for subsequent and more precise channel re-estimation. As is shownin this paper, the proposed algorithm can be used to reduce nonlinear distortions even insituations when highly nonlinear amplifiers are applied.