On impact of relay placement for energy-efficient cooperative networks

This study considers communication from a source to a destination with the aid of a set of cooperative relaying nodes. Unlike previous studies in energy efficiency, the authors studied the effect of relay placements together with different relay-selection timing on the performance. The cooperative relaying schemes for a general relay placement and some specialised relay placements are characterised and analysed by a Markov chain model. They derive the expressions for the throughput and the expected energy consumption for both proactive and reactive relay selection for different relay placements and densities. By using the analytical expressions, the authors find the optimal relay locations for different relay-selection schemes to achieve higher energy efficiency with the consideration of system throughput. The performance improvements offered by the authors proposed relay placement are demonstrated by numerical results. Moreover, the two new cooperative relaying schemes with selection combining for a certain relay placement are discussed. Their throughput and energy consumption are also derived and compared with the existing techniques.