Asymptotic BER Analysis of Threshold Digital Relaying Schemes in Cooperative Wireless Systems

In uncoded cooperative wireless networks, error propagation due to the detection errors at the relay limits the performance of cooperative digital relaying. Threshold relaying is a simple and effective technique to mitigate error propagation without any reliance on the channel coding. This paper analyzes the asymptotic end-to-end (e2e) bit error rate (BER) of threshold digital relaying in a network with a single relay and links experiencing independent Rayleigh fading. It is shown that the optimal threshold that minimizes the e2e BER increases as log(SNR) as the average link signal-to-noise ratios are increased simultaneously. The resulting e2e BER decreases as log(SNR)/SNR² , thereby achieving dual diversity.