Iterative channel estimation for OFDM with clipping

Estimating a channel that is subject to frequency selective Rayleigh fading is a challenging problem in an orthogonal frequency division multiplexing (OFDM) system with a nonlinear amplifier, e.g., clipping. We propose an iterative algorithm to efficiently estimate the channel impulse response (CIR) of a clipped OFDM system operating in an environment with a multipath fading channel and additive white Gaussian noise (AWGN). A tight lower bound on the mean square error (MSE) of channel estimation is given both by analysis and simulation. The iterative channel estimation algorithm is capable of improving the channel estimate by making use of pilot tones or using the channel estimate of the previous frame to obtain the initial estimate for the iterative procedure. In each iteration, nonlinear distortion is estimated and compensated assuming the nonlinear characteristic is known. Simulation results show that the bit error rate (BER) and MSE of the channel estimate can be significantly reduced by this algorithm.