Abstract
Orthogonal frequency division multiplexing (OFDM) plays a vital role as a physical layer technology. However, its inclusion in fifth-generation wireless systems is under threat due to its low power efficiency caused by a high peak-to-average power ratio (PAPR). Attempting to solve this problem, we propose a new spectrally efficient PAPR reduction scheme in this paper. We change pilot symbols' positions among the data symbols iteratively, maintaining all the conditions required for accurate channel estimation. The particular combination of pilot and data symbols giving the lowest PAPR is transmitted. Although the pilots' locations are varied from frame to frame, no side information (SI) is sent to the receiver to convey information about the pilot symbols' locations. The pilot symbols, rather, are detected blindly at the receiver, utilizing only the equidistance and large-power properties of the pilot symbols, having detection accuracies of 95% and 85% over additive white Gaussian noise (AWGN) and fading channels at 0 dB signal-to-noise ratio, respectively. This facilitates bandwidth saving since the reservation of part of the available bandwidth to send SI to the receiver is no longer required. PAPR is found to be reduced up to 2.2 dB at a clipping probability of 10-2 by the proposed scheme. The pilot detection accuracy as well as the corresponding bit error rate (BER) of the proposed system are investigated over both AWGN and fading channels, and a significant improvement in BER is observed in the presence of a high-power amplifier at the transmitter. The reduced PAPR of the proposed system culminates in power saving of up to 2.6 W. This makes the proposed OFDM system a spectrally and energy-efficient physical layer technology.
