In this paper, we investigate the outage performance for simultaneous wireless information and power transfer (SWIPT) relaying systems in the presence of direct link between the source and the destination. For the SWIPT relaying system, we employ a power splitter (PS) at the relay, which splits the received signal into the information transmission and the energy harvesting parts. First, we provide an analysis of the outage probability as a closed-form based on a high signal-to-noise ratio approximation. From the analysis, it is recognized that the diversity order of the SWIPT relaying systems equals that of the non-SWIPT cases regardless of the energy harvesting efficiency. The closed-form outage expression also enables us to obtain a simple expression for the PS factor which minimizes the outage probability. Simulation results demonstrate the accuracy of the derived analysis and the efficiency of the proposed PS scheme.

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