Optimal power control of parallel orthogonalfrequency-division-multiplexing relaying networks

This article studies the power allocation (PA) problem for dual-hop orthogonal-frequency-division-multiplexing (OFDM) relaying networks, in which a source communicates with a destination with the help of multiple amplify-and-forward relays that employ parallel transmission protocol. The objective is to maximise the system achievable rate, under which an aggregate power constraint is imposed on all relays, and an individual link rate constraint is imposed on each OFDM subchannel. Based on Zhao et al´s prior work, the simpler PA problem without considering those rate constraints is firstly solved by optimally allocating the total power across all OFDM subchannels. Then, for the original problem with both power and rate constraints, an order structure is proposed such that in the optimal PA scheme, those subchannels that attain respective maximum link rates are determined one by one, that is the complexity to determine those subchannels is considerably reduced from exponential to linear order.