A harvest-use-store power splitting (PS) relaying strategy with distributedbeamforming is proposed for wirelesspowered multi-relay cooperative networks inthis paper. Different from the conventional battery-free PS relaying strategy,harvested energy is prioritized to power information relaying while theremainder is accumulated and stored for future usage with the help of a batteryin the proposed strategy, which supports an efficient utilization of harvestedenergy. However, PS affects throughput at subsequent time slots due to thebattery operations including the charging and discharging. To this end, PS andbattery operations are coupled with distributed beamforming. A throughputoptimization problem to incorporate these coupled operations is formulatedthough it is intractable. To address the intractability of the optimization,alayered optimization method is proposed to achieve the optimal joint PS andbattery operation design with non-causal channel state information (CSI), inwhich 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 layeredoptimization method is extended by utilizing the statistical properties of CSI.To reach a better tradeoff between performance and complexity, a greedy methodthat requires no information about subsequent time slots is proposed.Simulation results reveal the upper and lower bound on performance of theproposed strategy, which are reached by the layered optimization method withnon-causal CSI and the greedy method, respectively. Moreover, the proposedstrategy outperforms the conventional PS-based relaying without energyaccumulation and time switching-based relaying strategy.
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