Outage Probability Analysis of an AF Cooperative Multi-Relay Network with Best Relay Selection and Clipped OFDM Transmission

Outage probability analysis of a multi-path cooperative communication system with single relay selection, amplifyand- forward (AF) relaying and clipped orthogonal frequency division multiplexing (OFDM) transmission is addressed. The clipping technique is the simplest approach to overcome the high peak-to-average power ratio (PAPR) of OFDM transmitted signals, but it may give rise to in-band distortion as well as out-of-band interference. In this work, the nonlinear distortions introduced by the clipping process at the source are modeled as the aggregate of an attenuation factor and clipping noise. The magnitude squared of the signal scaled by the clipping factor can be modeled by an exponential distribution. The twohop wireless transmission is modeled in the time domain as an Erlang distribution function. As a result of this model, the outage probability with the clipped OFDM signal transmitted over multipath fading channel of length L and an arbitrary number of relay nodes M with best single relay selection is calculated. Moreover, the analytical expressions for the cumulative density function (CDF) of the end-to-end signal-to-noise ratio (SNR) are obtained. In addition, the analysis shows how the clipping operation affects the outage probability for different clipping ratio levels (mu). Finally, the theoretical results are compared with simulated results to confirm the validity of the analysis.