Constant envelope DCT- and FFT-based OFDM systems with frequency modulation in flat fading channels

In this paper Discrete Cosine Transform and Fast Fourier Transform based Orthogonal Frequency Division Multiplexing (DCT-OFDM and FFT-OFDM) systems with frequency modulation are examined. Frequency modulation is used in both systems to achieve constant envelope (CE) signals and hence 0 dB PAPR; well-suited for efficient power amplification. The performances of such systems are examined over flat fading channels for transmission of data using M-ary Pulse Amplitude Modulation (MPAM) mapper. Closed-form expressions for bit error rate over flat Ricean and Rayleigh channels are derived. The parameters that affect error performance are identified and illustrated. Results show that CE-DCT-OFDM system outperforms CE-FFT-OFDM system from the viewpoint of BER and has several advantages as well.