Outage performance of cooperative amplify-and-forward OFDM systems with nonlinear power amplifiers

Cooperative diversity and orthogonal frequency division multiplexing (OFDM) are two key technologies for future wireless communication systems. One of the main problems of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted signals, which may cause the introduction of intercarrier interference due to the presence of nonlinear power amplifiers (PAs). In this paper, a theoretical analysis of the outage probability of an amplify-and-forward (AF) cooperative diversity OFDM system accounting for nonlinear distortions introduced by a nonlinear PA is developed. It is assumed a frequency-selective Rayleigh fading and a downlink transmission, with the base station having a linear PA and the relay having a nonlinear PA. Our analysis shows how the PA parameters affects the outage probability for different SNR levels. The validity of the proposed outage analysis is verified by means of computer simulations.