  In this paper, we present a new power allocation scheme for a
decode-and-forward (DF) relaying-enhanced cooperative wireless system. While
both source and relay nodes may have limited traditional brown power supply or
fixed green energy storage, the hybrid source node can also draw power from the
surrounding radio frequency (RF) signals. In particular, we assume a
deterministic RF energy harvesting (EH) model under which the signals
transmitted by the relay serve as the renewable energy source for the source
node. The amount of harvested energy is known for a given transmission power of
the forwarding signal and channel condition between the source and relay nodes.
To maximize the overall throughput while meeting the constraints imposed by the
non-sustainable energy sources and the renewable energy source, an optimization
problem is formulated and solved. Based on different harvesting efficiency and
channel condition, closed form solutions are derived to obtain the optimal
source and relay power allocation jointly. It is shown that instead of
demanding high on-grid power supply or high green energy availability, the
system can achieve compatible or higher throughput by utilizing the harvested
energy.
