Constant modulus orthogonal frequency division multiplexing

Orthogonal frequency domain multiplexing (OFDM) is the signal format of choice for spectrally efficient communications over time-invariant, frequency-selective channels. OFDM has a large peak-to-average power ratio, however, which makes it incompatible with transmitter non-linearities (e.g., saturated power amplifiers (PAs)). Conversely, single-carrier constant envelope modulations can be used with a saturated PA, but exhibit limited spectral efficiency and requiring more complex receiver processing (i.e., channel equalization). This paper presents a method of modulation coding that results in an OFDM signal with constant modulus (CM-OFDM). A method of decoding this modulation code is developed and the resulting CM-OFDM system performance is compared to that of OFDM via simulation. The results suggest that CM-OFDM may provide a waveform uniquely qualified for some operational scenarios.