Constant envelope DCT- and FFT-based OFDM systems with continuous phase chirp modulation over fading channels

Orthogonal Frequency Division Multiplexing (OFDM) systems with Continuous Phase Chirp Modulation (CPCM) are considered. In these systems, this modulation is used to realize constant envelope OFDM signals. Both Discrete Cosine Transform (DCT)- and Fast Fourier Transform (FFT)-based OFDM systems are considered and their Bit Error Rate (BER) performances over AWGN and fading channels are presented. Expressions for BER over Ricean and Rayleigh channels are derived and illustrated as function of modulation parameters. Results indicate that use of DCT instead of FFT in an OFDM system with CPCM results in better BER performance.