Optimal power allocation over parallel relay channels with orthogonal regenerative decode-and-forward strategy

We consider the problem of optimal power allocation over a family of parallel Gaussian relay channels, each with a different set of channels´ power gains. The applied cooperative strategy is half-duplex regenerative decode-and-forward which is multiplexed orthogonally with a direct transmission link from the source node to the destination node. We assume the availability of channel-state-information of the three links in every channel realization. We obtain a characterization of the optimal solution which includes the power allocated for each channel realization as well as the power allocated to the source node and the relay node so that the long-term average total transmitted power constraint is maintained. The solution has a simple structure and can be applied practically in relay-assisted wireless systems.