Nonlinear Multicarrier Transmitter System With Signal Clipping: Measurement, Analysis, and Optimization

Signal clipping is a well-established method employed in orthogonal frequency division multiplexing (OFDM) systems to mitigate peak-to-average power ratio. The utilization of this technique is widespread in electronic devices with limited power or resource capabilities due to its high efficiency and low complexity. While clipping effectively diminishes nonlinear distortion stemming from power amplifiers (PAs), it introduces additional distortion known as clipping distortion. The optimization of system performance, considering both clipping distortions and the nonlinearity of PAs, remains an unresolved challenge due to the intricate modeling of PAs. In this article, we undertake an analysis of PA nonlinearity utilizing the Bessel–Fourier PA model and simplify its power expression through intermodulation product analysis. We mathematically derive expressions for the receiver signal-to-noise ratio and system symbol error rate (SER) for nonlinear clipped OFDM systems. Using these derivations, we explore the optimal system configuration required to achieve the lower bound of SER in practical OFDM systems, taking into account both PA nonlinearity and clipping distortion. The results and methodologies presented in this article contribute to an improved comprehension of system-level optimization in nonlinear OFDM systems employing clipping technology.

I. Introduction

Power amplifiers (PAs) exhibit nonlinear characteristics when faced with high-power input signals, which is commonly referred to as PA nonlinearity [1], [2], [3], [4]. The rapid progress of multiple-input and multiple-output (MIMO) technology, coupled with the growing number of subcarriers, has resulted in a significant rise in the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) devices. This increase in PAPR poses a major challenge in practical OFDM systems, as it can lead to reduced power efficiency, degraded system performance, and potential distortion in the transmitted signals. PA's nonlinearity has become a vital concern, as it may cause significant performance degradation when faced with high PAPR [5], [6]. To ensure system linearity, designers are compelled to reduce the input power of the amplifier, albeit at the cost of energy efficiency [7]. As a result, reducing PAPR has emerged as a critical problem in OFDM systems and has attracted significant research attention.