A robust OFDM transmission scheme using a constellation index precoding technique over frequency-selective fading

In this paper, we consider an interesting precoding technique for orthogonal frequency-division multiplexing (OFDM) in order to enhance system performance for either uncoded or coded transmissions over a frequency-selective fading channel. The signaling mechanism of the proposed scheme is to map an information-carrying symbol block technically into another short block of symbols, which are taken out of an expanded constellation set, while the diversified symbols are interleaved prior to being modulated each by a specified subcarrier of an OFDM system. It can be found that not only the multipath diversity advantage across the subcarriers but also the coding gains can be achieved by the considered scheme at the receiver. The design of the considered precoding technique can be treated as a finite-dimensional optimization problem with entries taken by a specific modulus where the approximated error probability is minimized. We provide a set of efficient searching rules to find good spreading codes and demonstrate the performance comparisons among our proposed scheme and the existing precoded OFDM systems such as spreading transform OFDM and linear constellation precoded OFDM to verify the advantage of the proposed scheme. Copyright (C) 2015 John Wiley & Sons, Ltd.