Signal-to-Noise Ratio Comparison of Amplify-Forward and Direct Link in Wireless Sensor Networks

We compare the signal-to-noise ratio performances of an amplify-forward relay link and a direct link in a wireless sensor network. For a slow Rayleigh fading channel, an exact expression for the probability that the SNR of an amplify-forward relay link exceeds the SNR of a direct link is obtained. For a Rician fading channel, an upper bound for the corresponding probability is obtained. Numerical results indicate that, among the two fading channels considered, Rayleigh fading is more detrimental to the SNR performance of the amplify-forward relaying scheme.

I. Introduction

In cooperative relaying, the availability of relay channels between a source (sensor) and a destination is exploited by appropriately combining signals arriving via various relay channels. A summary of cooperative diversity along with a chronological order of developments is provided by Laneman et al. in [1]. In a two-part paper, Sendonaris and Aazhang have provided the concept and the implementation aspects of cooperative diversity for wireless networks of mobile users [2]–[3].