  A harvest-use-store power splitting (PS) relaying strategy with distributed
beamforming is proposed for wirelesspowered multi-relay cooperative networks in
this paper. Different from the conventional battery-free PS relaying strategy,
harvested energy is prioritized to power information relaying while the
remainder is accumulated and stored for future usage with the help of a battery
in the proposed strategy, which supports an efficient utilization of harvested
energy. However, PS affects throughput at subsequent time slots due to the
battery operations including the charging and discharging. To this end, PS and
battery operations are coupled with distributed beamforming. A throughput
optimization problem to incorporate these coupled operations is formulated
though it is intractable. To address the intractability of the optimization,a
layered optimization method is proposed to achieve the optimal joint PS and
battery operation design with non-causal channel state information (CSI), in
which the PS and the battery operation can be analyzed in a decomposed manner.
Then, a general case with causal CSI is considered, where the proposed layered
optimization method is extended by utilizing the statistical properties of CSI.
To reach a better tradeoff between performance and complexity, a greedy method
that requires no information about subsequent time slots is proposed.
Simulation results reveal the upper and lower bound on performance of the
proposed strategy, which are reached by the layered optimization method with
non-causal CSI and the greedy method, respectively. Moreover, the proposed
strategy outperforms the conventional PS-based relaying without energy
accumulation and time switching-based relaying strategy.
