In this paper, we apply the power splitting-based energy-harvesting protocol to enhance the transmission between a wireless access point and a mobile user via a helping relay. The mobile user exploits the energy supplied by the access point and forwarded by the relay to transmit its own data back to the access point, again with the helping of the relay. Here, the effect of various system parameters, including power-splitting factor and the power-to-noise ratio on the system performance, is rigorously studied, with closed-form expressions for the outage probability and system throughput as the results. Furthermore, we figure out the optimal power-splitting ratio at which the information throughput from the user to the AP is maximized, subject to the constraint on the transmitting power at the access point. All above analytical results are also supported by Monte Carlo simulation.KEYWORDS amplify and forward, bidirectional relay, decode and forward, energy harvesting, power splitting