Adaptive PAPR reduction using tone reservation and clipping in OFDM transmission over fading channels

The high peak-to-average power ratio (PAPR) inherent in orthogonal frequency-division multiplexing (OFDM) signals forces the high-power amplifier (HPA) to operate with substantial input back-off (IBO) value, severely degrading transmitter power efficiency. This paper investigates the joint application of adaptive tone reservation (TR) and clipping for PAPR reduction in OFDM transmission over frequency-selective fading channels. The adaptive TR scheme employs channel state information to dynamically allocate reserved tones to subcarriers that experience poor signal-to-noise ratio (SNR) and are therefore of limited utility for data transmission. Four configurations have been systematically compared: a baseline without PAPR reduction, clipping only, adaptive TR only, and the proposed joint adaptive TR and clipping scheme. Simulations for the case of a measurement-based underwater acoustic channel with a hard-limiter HPA model demonstrate that adaptive TR alone achieves a 2.8 dB SNR gain over the baseline at a target bit error rate of 10−3, without introducing in-band distortion. The joint scheme yields a total SNR gain of 4.6 dB, combining the benefits from distortionless peak suppression by TR with the aggressive clipping action. Relative to clipping-only operation, the joint scheme decreases out-of-band emission by 3.5 dB and compresses the 99.5% occupied bandwidth by 40%. These results confirm that the combination of SINR-based adaptive TR and clipping provides simultaneous improvements in power efficiency and spectral containment, making it a compelling solution for communication systems subject to both power and spectral mask constraints.