User scheduling in wireless information and power transfer networks

Wireless power transfer has been recognized as a promising energy harvesting technique. The aim of this paper is to characterize the impact of this new energy harvesting concept on user scheduling. Particularly a multi-user cooperative network is considered in this paper, where M source-destination (SD) pairs communicate with each other via an energy harvesting relay. When m = 1, the addressed scheduling problem is mathematically equivalent to relay selection for the scenario with one SD pair and M relays. It is well known that the max-min selection criterion has the capability to achieve the optimal diversity gain, and one important conclusion made in this paper is that the max-min approach can only achieve a diversity gain of M+1/2 in wireless power transfer systems. To compensate for this diversity loss, two user scheduling approaches are proposed in this paper and it is shown that both schemes can achieve larger diversity gains than the max-min approach.