Published in Viswanathan, R. (2007). Signal-to-noise ratio comparison of amplify-forward and direct link in wireless sensor networks. 2nd International Conference on Communication Systems Software and Middleware, 2007 (COMSWARE 2007), 1-4. doi: 10.1109/COMSWA.2007.382467 ©2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.


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.