Optimal subcarrier power allocation for OFDM in peak-power-limited channels

A major disadvantage of the orthogonal frequency division multiplexing (OFDM) system is the large dynamic range of its time-domain waveforms, making OFDM vulnerable to nonlinearities (including clipping effects) of the power amplifier (PA). The effects are nonlinear distortions as well as low DC to RF power conversion efficiency. The peak-to-average power ratio (PAR) is commonly used to characterize a signal´s dynamic range. In the recent literature, the distribution of the PAR of OFDM signals is revealed to be dependent on the power allocation among subcarriers. In this paper, the effect of different power allocation schemes on the power efficiency of peak-power constrained OFDM transmitters is investigated. Optimization problems are formulated to determine the optimal power allocation with respect to the power efficiency, power consumption and system throughput performance in AWGN channels.