Digital pre-distortion of power amplifier impairments in spectrally agile transmissions

In this paper, we present an investigation into the performance of digital pre-distortion (PD) techniques designed to compensate for power amplifier (PA) impairments that occur during the transmission of spectrally agile waveforms. Spectrally agile transmission techniques, such as non-contiguous orthogonal frequency division multiplexing (NC-OFDM), have been receiving an increasing amount of attention recently within the wireless research community as a potential solution for enabling dynamic spectrum access (DSA), which is an approach for utilizing wireless spectrum more efficiently and mitigating the spectrum scarcity issue currently faced by modern society. Although there has been substantial research efforts into designing transceiver architectures for spectrally agile communication systems, there exists numerous opportunities to further improve upon the performance of these systems by focusing on the compensation of the non-linear impairments resulting from the radio frequency (RF) front-ends of the communication system, especially the PA component. To better understand the impact of this component on system performance, we characterize the physical behavior of the PA with respect to the transmission of a spectrally agile waveform using a software-defined radio (SDR) platform in order to obtain realistic results. The hardware experimental results show that pre-distortion can effectively suppress the out-of-band (OOB) emissions caused by both nonlinearities of PA and high peak-to-average power ratio (PAPR) of spectrally agile transmission.