  We consider a wireless relay network with one source, one relay and one
destination, where communications between nodes are preformed via N orthogonal
channels. This, for example, is the case when orthogonal frequency division
multiplexing is employed for data communications. Since the power available at
the source and relay is limited, we study optimal power allocation strategies
at the source and relay in order to maximize the overall source-destination
capacity under individual power constraints at the source and/or the relay.
Depending on the availability of the channel state information at the source
and rely, optimal power allocation strategies are performed at both the source
and relay or only at the relay. Considering different setups for the problem,
various optimization problems are formulated and solved. Some properties of the
optimal solution are also proved.
