Companding technique for PAPR reduction in OFDM systems based on an exponential function

Abstract

In this paper, a new non-linear companding technique, called "exponential companding", is proposed to reduce the high peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. Unlike the /spl mu/-law companding scheme, which enlarges only small signals so that increases the average power, the schemes based on exponential companding technique adjust both large and small signals and can keep the average power at the same level. By transforming the original OFDM signals into uniformly distributed signals (with a specific degree), the exponential companding schemes can effectively reduce PAPR for different modulation formats and sub-carrier sizes. Moreover, many PAPR reduction schemes, such as /spl mu/-law companding scheme, cause spectrum side-lobes generation, but the exponential companding schemes cause less spectrum side-lobes. Computer simulations, which consider a baseband OFDM system with additive white Gaussian noise (AWGN) channels and a solid state power amplifier (SSPA), show that the proposed exponential companding schemes can offer better PAPR reduction, bit error rate (BER), and phase error performance than the /spl mu/-law companding scheme.