Modified Gamma Correction Companding for PAPR Reduction in OFDM Systems Considering Solid-State Power Amplifier and Wireless Channels

摘要

Orthogonal frequency division multiplexing is a special form of multicarrier modulation and suffers from a very high peak-to-average power ratio (PAPR) that degrades overall performance of the system. In this article, a modified gamma correction companding (MGCC) is proposed that provides a significant reduction in PAPR when compared with existing gamma correction companding and other nonlinear companding methods available in the literature for PAPR reduction. Additionally, with the introduction of and A parameter, the proposed companding can provide more flexibility in PAPR reduction and therefore achieves better trade-offs among PAPR gain, bit error rate (BER) and power spectral density (PSD) levels. MGCC provides an additional immunity from noise by enlarging the small amplitudes of the signal selectively, while subcarriers with the large amplitudes are moderately amplified to reduce PAPR of the signal. Moreover, MGCC improves the BER and PSD performances by minimizing the nonlinear companding distortion. The proposed MGCC improves signal-to-noise ratio (SNR) degradation and total degradation performances by 2.0 and 2.3dB, respectively, with an input back-off power of 2.5dB when a practical solid-state power amplifier is considered. Computer simulations reveal that the MGCC can be applied to any modulation scheme and with arbitrary number of subcarriers (N) while it does not increase computational complexity when compared with existing schemes of companding.