Energy Efficiency of Cooperative SIMO Schemes -Amplify Forward and Decode Forward

In this paper, we quantify and compare the energy efficiency of amplify-and-forward (AF) and decode-and- forward (DF) schemes on a basic three node cooperative network. Total energy is calculated considering circuit energy as well as transmission energy. For AF and DF schemes, we set a target symbol error probability (SEP) and evaluate the minimum transmission energy for achieving the target SEP. In this process we first derive an approximation for SEP at high SNR for DF with possible error in relays. Next, we formulate energy calculation as a convex optimization problem and present the theoretical solution. The result is used to compare the total energy consumption of AF and DF for various relay positions: relay near source and relay near destination. The results illustrate significant dependence on (1) circuit energy for short distances where DF has lower energy efficiency and, (2) transmission energy at larger distances (between source and destination) where AF has lower efficiency.