Joint subcarrier pairing and power allocation for achieving energy-efficient decode-and-forward relay networks

In this paper, subcarrier pairing and power allocation are jointly investigated to maximize the energy efficiency (EE) of a dual-hop multicarrier decode-and-forward (DF) relay network. The optimization problem is formulated as a ratio of the spectrum efficiency (SE) over the entire power consumption of the network subject to total power and subcarrier pairing constraints. A near-optimal iterative scheme is proposed to perform the subcarrier pairing and power allocation for achieving the maximum EE of the network. A two-step suboptimal resource allocation scheme is further proposed to reduce the complexity, in which the subcarrier pairing is first performed by considering the channel quality of the source-to-relay (SR) and relay-to-destination (RD) links, followed by an energy-efficient power allocation scheme to maximize the EE. Numerical results are presented to confirm the effectiveness of the proposed schemes and to demonstrate the tradeoff between EE and SE performances.