Optimal constellation distortion for PAR reduction in OFDM systems

The high peak-to-average-power ratio (PAR) of orthogonal frequency division multiplexing (OFDM) transmission systems significantly reduces the power efficiency or performance of such systems, and many techniques have been proposed to deal with this problem. Recently, the active constellation extension (ACE) algorithm has received much attention, where the main idea is to reduce the PAR by introducing a perturbation of the transmit constellation that does not reduce the constellationpsilas minimum-distance. In this paper, a different approach is taken where the constellationpsilas minimum-distance is reduced to lower the PAR but the constellation perturbation is done in an optimal way to improve the system performance. The problem of optimally trading off PAR reduction and constellation distortion is shown to be a convex optimization problem that could be solved very efficiently. The proposed idea has no data-rate loss and does not require the transmission of side-information.