OFDM-CPM signals for wireless communications

Abstract

A class of orthogonal frequency division multiplexing-continuous phase modulation (OFDM-CPM) signals is introduced in which the binary data sequence is mapped to complex symbols using the concept of correlated phase states of a CPM signal. A multiple-symbol-observation receiver is used to decode the received sequence, and an investigation of bit error rate over typical wireless multipath channels with additive white Gaussian noise is presented. The performance of a variety of OFDM-CPM signals is presented and analyzed. Performance is a function of parameter h and the observation interval, both of which are at the disposal of the system designer. It is shown that OFDM-CPM is a promising signalling scheme in multipath fading channels. Results for multi-h and asymmetric OFDM-CPM signals are also presented. The peak-to-average power ratio (PAPR) performance of these signals is also presented, and an algorithm to reduce PAPR is proposed that is based on a multi-amplitude CPM constellation. It is shown through numerical simulations that the proposed algorithm reduces the PAPR of a 128-carrier OFDM-CPM signal by more than 4 dB.