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 and channel re-estimation in an iterative manner for the OFDM transmission systems. Whereas in practical OFDM systems, where nonlinear amplifiers are used in the transmitter, data as well as pilot symbols are nonlinearly distorted. As perfect channel state information is often assumed in many papers, the effect of the nonlinear distortion of the pilot symbols is usually not accounted for, and the data symbols are considered only. However, as the pilot symbols are used to obtain the channel state information, the distortion caused to pilot symbols by the nonlinear amplification is of the great importance, and for this reason this effect should be taken into account. To address this issue, in this paper, an efficient algorithm will be introduced for joint data recovery and channel re-estimation in an iterative manner for OFDM transmission system. This algorithm iteratively estimates the nonlinear distortion due to nonlinear high power amplifier of the transmitter and then it uses it to compensate for this nonlinear distortion of the data and the pilot symbols, which are subsequently used for subsequent and more precise channel re-estimation. As is shown in this paper, the proposed algorithm can be used to reduce nonlinear distortions even in situations when highly nonlinear amplifiers are applied.