Antipodal paraunitary precoding for OFDM application

Paraunitary (PU) matrices have found many applications. In this paper, a special class of PU matrices, namely the antipodal PU (APU) matrices, is used as precoding matrices for OFDM systems. Both the zero-forcing and MMSE receivers will be derived for precoded OFDM systems with APU precoding matrices. The performance of such precoded OFDM systems will be analyzed. We will show that using a APU precoding matrix, we are able to average the noise variance in both the time and frequency domains, and this obtains time and frequency diversity. Experiments show that precoded OFDM systems with MMSE receivers have a much better bit error rate performance than the conventional OFDM system.