SUMMARYLarge peak-to-average power ratio (PAPR) of multicarrier communication systems is a widely discussed topic in the literature and remains the major drawback of the orthogonal frequency division multiplexing (OFDM) modulation. Deliberate amplitude clipping has been found as a suitable way to reduce output signal peaks at the transmitter side. Unfortunately, it also causes numerous degradations. In this paper, we propose a study of nonlinearities led by the clipping process and a comparison of iterative receivers derived from the turbo-principle and devoted to the system performance restoration under severe clipping ratio (CR) constraint.

A soft decision aided suboptimal maximum likelihood detection algorithm for clipped COFDM transmissions is presented. Then clipping mitigation is performed by means of an iterative fashion receiver. Here the goal is to provide a posteriori code word bits soft decision instead of observed channel signal correction. From the channel decoder output information, a reduced set of channel neighbour signals is built aiding the maximum likelihood-based detection. Furthermore, we investigate the receiver performance for both non-coded and coded transmission schemes as well as over a frequency-selective channel scenario. Numerical results show that the proposed receiver is able to perform very close to the linear case even at severe clipping ratio.