Non Linear Companding Transform to Mitigate PAPR in DCT Based SC-FDMA System

Discrete cosine transform (DCT) based single carrier frequency division multiple access (SC-FDMA) system outperforms discrete Fourier transform based SC-FDMA (DFT SC-FDMA) system in terms of bit error rate (BER) performance. However, the peak-to-average power ratio (PAPR) of the DCT SC-FDMA system is slightly higher than that of the DFT SC-FDMA system. In this paper, a companding transform is proposed by approximating the distribution of magnitudes of DCT SC-FDMA signal and thereby transforming it into a triangular distribution. Proposed companding transform effectively reduces PAPR by maintaining the average power of companded signal. By clipping the companded signal to a specific threshold, PAPR can be reduced further. Moreover, the proposed technique causes fewer spectrum side-lobes than µ law and absolute exponential companding techniques. Simulated results ensure that proposed companding followed by clipping offers better PAPR and BER performances than the absolute exponential companding technique.