Performance analysis of cooperative amplify-and-forward orthogonal frequency division multiplexing systems with power amplifier non-linearity

Orthogonal frequency division multiplexing (OFDM) is considered as a key technology for future wireless communication systems. One of the main disadvantages of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted signals. When a non-linear power amplifier (PA) is present, the high PAPR may cause the introduction of non-linear distortions. On the other hand, cooperative communications have emerged as a promising technology for wireless networks. A theoretical analysis of an amplify-and-forward OFDM system taking into consideration the non-linear distortions introduced by a PA is done. More specifically, approximate analytical expressions for the outage probability and average symbol error rate (SER) are derived and studied under several special situations. The performance analysis sheds light on the influence of PA non-linearity on the outage probability and the average SER of an OFDM system. Particularly, it is shown that the non-linear PA has a more significant effect over the average SER for medium and high signal-to-noise ratio (SNR) values and for small-order constellations. The analytical results are validated by means of computer simulations for different system configurations and SNR levels.