M-QAM-OFDM system performance in the presence of a nonlinear amplifier and phase noise

The orthogonal frequency-division multiplexing (OFDM) modulation format has been proposed in Europe as the standard for broadcasting both audio and television digital signals and for wide-band wireless communication systems (e.g., HIPERLAN II). The performance of the OFDM scheme is severely affected by the nonlinearity of the high-power amplifier at the transmitter end and by the phase noise of the oscillators. In this paper, we investigate the joint effects induced on the OFDM signal by the amplifier nonlinearity and by the phase noise. An accurate statistical description of each contribution to the signal distortion is provided. Theoretical results show perfect agreement with those obtained by simulation and they can be used to derive the OFDM system performance, without the need to run extensive simulations.

I. Introduction

Orthogonal frequency-division multiplexing (OFDM) systems have been developed in the framework of the digital audio broadcasting (DAB) and digital video broad-casting-terrestrial (DVB-T) programs [1], [2]. More recently, OFDM has been employed for fixed-wire applications in the asynchronous digital subscriber line (ADSL) and high-bit-rate DSL (HDSL) systems [3], [4], and it has also been suggested for power-line communications [5]. OFDM has been shown to be very efficient in the use of the available bandwidth and in combating multipath fading [10]. Therefore, it is currently being considered the most promising transmission technique to support future wireless multimedia communications in frequency-selective channels [6], [7], and its application in conjunction with the code-division multiple access technology (CDMA) is under significant investigation [8]. Meanwhile, OFDM has been adopted as a standard for new high-rate wireless local area networks (WLANs), such as IEEE802.11, HIPERLAN II, as well as the Japanese Multimedia Mobile Access Communications (MMAC) [9].