Novel Low-Complexity Receivers for Constant Envelope OFDM

Constant Envelope OFDM provides a solution to the issue of high peak-to-average power ratio in OFDM by using angle modulation to transform the OFDM signal to a constant envelope signal. The modulation index of Constant Envelope OFDM controls this transformation. In this paper, we develop novel receiver structures for Constant Envelope OFDM based on the Taylor series expansion, alleviating the need for angle demodulation at the receiver. This results in immunity from phase cycle slips due to phase wrapping and the threshold effect which would otherwise cause performance degradation. These receivers allow for a simpler implementation without the need to compute the arctangent at the receiver. We show that these novel receivers perform well when compared to the conventional arctangent based receiver for small and moderate modulation indices (2 pi h <= 0.7)for the cases of additive white Gaussian noise and multipath fading. For frequency selective fading, we show that the application of a frequency domain equalizer results in good performance when these novel receivers are employed. Finally, we study the performance of these new receivers when error correction coding is employed and show that they not only provide excellent performance but also significantly outperform the conventional arctangent based receiver for coded Constant Envelope OFDM performance.