Power Reduction in OFDM based Cognitive Radio Systems

The increasing demand for wireless communication introduces efficient spectrum utilization challenge. To address this challenge, cognitive radio has emerged as the key technology, which enables opportunistic access to the spectrum. The main potential advantages introduced by cognitive radio are improving spectrum utilization and increasing communication quality. In this paper, we consider the high peak-to-average power ratio (PAPR) problem of orthogonal frequency division multiplexing (OFDM) signals in cognitive radio systems. A high PAPR can lead to saturation in the power amplifier (PA) of secondary users (SUs) and consequently increase spectral spreading, and cause interference to adjacent primary users (PUs).Simulation results illustrates the performance of the system under Additive White Gaussian Noise (AWGN) and further evaluation is done for comparing the proposed companding technique with previous techniques. The power spectral density (PSD) and bit error rate (BER) are evaluated at the output of the nonlinear PAs to provide a realistic performance comparison.