Computing the Optimal Amount of Constellation Distortion in OFDM Systems

Abstract

The primary disadvantage of orthogonal frequency-division multiplexing (OFDM) is the high time-domain peak-to-average power ratio (PAR) that severely limits the transmitter power efficiency. The PAR can be globally minimized by distorting the OFDM constellation subject to a constraint on the error vector magnitude (EVM). In this paper, we demonstrate that an optimal amount of EVM exists for minimizing the transmitter power consumption while maintaining a constant bit error rate (BER) at the receiver. Alternatively, the EVM value may be chosen to maximize the channel capacity while maintaining a constant power consumption at the transmitter. Both EVM levels are only a function of the required signal-to-noise ratio at the OFDM receiver.