Iterative Channel Estimation for Multiuser OFDM Systems in the Presence of Power Amplifier Nonlinearities

This paper proposes a new channel estimation approach for MIMO-OFDM systems subject to power amplifier nonlinearities. The harmful effect of nonlinear distortion on the system performance can be reduced by applying an iterative distortion cancellation technique. However, such an approach requires accurate channel estimates to yield good performance. In our approach, initial channel estimation is carried out in frequency domain (FD) followed by time domain (TD) processing of the received signal. In the TD step, the equalized signals from the FD processing is used to remove the nonlinear distortion and to improve the initial channel estimate. Simulations verify that the combined channel estimation and nonlinear cancellation strategy has a performance close to the case of perfectly known channel. Furthermore, a substantial improvement in the system performance is achieved with the proposed technique when compared with conventional methods in terms of mean square error and BER