Performance of hybrid relaying in cooperative wireless systems in the presence of impulsive noise

Hybrid relaying combines the merits of both Decode-and-forward (DF) and Amplify-and- forward (AF) by forwarding clean packets in DF if decodes correctly and forwarding soft represented packets in AF if decodes incorrectly. In this paper a hybrid relaying scheme in a cooperative communication system in the presence of impulsive noiseis proposed. In this method, the relay is considered to be decode-and-forward (DF) or amplify-and-forward (AF) or silent based on comparing the signal to noise ratio (SNR) at the relay with two thresholds. If the SNR at the relay is higher than the first threshold, the relay is considered as DF. If the SNR at the relay lies between the two thresholds, the relay is considered as AF. Finally, if the SNR at the relay is lower than the second threshold, the relay is considered as silent. The relays forward their signals to the destination and the destination combines these signals. The performance of the proposed hybrid relaying system is evaluated for perfect and estimated channel and is compared with the performance of DF and AF. It is found that DF always plays more important role than AF in improving the error performance of the hybrid system. The channel is estimated using the sign algorithm and the performance of channel estimation algorithm is measured in terms of mean square error.