Peak-to-Average Power Ratio Suppression using Companding schemes in OFDM Systems

The reduction of the high signal peak-to-average-power-ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems limits the clipping-induced non-linear harmonic distortions caused by power amplifiers. In this paper, the characteristics of the circuits implemented in subthreshold CMOS are employed to perform companding-based PAPR reduction for OFDM signals. Simulation results confirm that the tanh-companding amplifiers are capable of reducing the PAPR of OFDM signals through the careful control of their design parameters.

I. Introduction

Orthogonal frequency division multiplexing (OFDM) is one of the spectrally efficient multi-carrier (MC) transmission techniques. In OFDM-based systems, a large number of independent narrowband signals are simultaneously transmitted over a set of orthogonal carriers whose frequencies are closely spaced in the frequency domain. The high spectral utilization offered by OFDM transmission is one of the reasons behind its adoption as the core system of many air-interface standards. These standards include, but not limited to, worldwide interoperability for microwave access (WiMAX), terrestrial digital video broadcasting (DVB-T) and the IEEE 802.11a standard for wireless local area networks (WLANs). Moreover, due to its robustness against multipath propagation effects in high-mobility environments, OFDM has been widely adopted for 4G communications. Moreover, the immunity of OFDM to impulsive noise has also recommended its use in wire-line applications, such as power line communications (PLC) and digital subscriber lines (DSL) [1].