Relay Selection from a Battery Energy Efficiency Perspective

The battery nonlinearity has never been considered for energy analysis in relay networks. In this letter, we adopt the realistic nonlinear battery model, apply the battery energy consumption results in to general relay networks, investigate the optimum and suboptimum energy allocation solutions for relaying transmission, and establish the relay selection criterion from the battery energy efficiency perspective. Our analyses and comparisons show that relaying does not always increase the system energy efficiency. We further establish closed-form conditions that can be easily checked to determine whether the relay transmission is preferable to the direct transmission. Numerical examples are also presented to verify these results.