Peak-to-average power ratio reduction in OFDM with blind selected pilot tone modulation

Orthogonal Frequency Division Multiplexing (OFDM) is a spectrally efficient multicarrier modulation technique for high speed data transmission over multipath fading channels. However, the price paid for the high spectral efficiency is low power efficiency. OFDM signals suffer from high peak-to-average power ratios (PARs) which lead to power inefficiency in the RF portion of the transmitter. Selected mapping (SLM) is a promising distortionless technique to reduce the PAR of an OFDM signal. In this paper, we propose a novel technique which links the index of the phase rotation sequence in SLM to the location of the pilot tones that are used to estimate the channel. Each pilot tone location - phase sequence selection can lead to a different PAR value for the time-domain OFDM signal, and the signal with the lowest PAR value is transmitted. Our proposed method is "blind" in the sense that the "optimum" pilot tone location - phase sequence index is not transmitted as side information. We describe a novel technique to blindly detect the optimum index at the receiver by taking advantage of the disparity between the pilot tone and information signal powers. PAR reduction performance as well as BER performance of the proposed method in frequency selective fading channels are illustrated.