Comparison of the energy efficiency for decode-and-forward and amplify-and-forward two-way relaying

This paper considers the scenario where a given number of message bits is exchanged between two nodes with the assistance of a relay node using two-way decode-and-forward (DF) or amplify-and-forward (AF) relaying protocols. The minimum energy consumption for the two-way DF or AF relaying protocol is derived first. Then, the energy for both protocols is compared and the criterion is presented to indicate when the DF relaying is more energy efficient. It is shown that the DF relaying is more energy efficient when the channel power gain between the relay and a node is significantly different than that between the relay and the other node, or when a small number of message bits is exchanged between the two nodes. The theoretical analysis is corroborated by simulation results.