In this paper, we apply the notion of opportunistic scheduling in wireless-powered communication networks (WPCNs). The considered WPCN model consists of a base station (BS) and multiple energy harvesting users (EHUs), where the BS broadcasts radio frequency energy to the EHUs over the downlink and receives information from the EHUs over the uplink. We differentiate the WPCNs based upon the battery management policy at the EHUs, i.e., whether an EHU spends the total amount of energy harvested in its battery for each IT (WPCN type 1), or spends only a part of it for the current IT and saves the other part for future ITs (WPCN type 2). We propose two opportunistic scheduling policies, referred to as the harvest-then-select and harvest-or-select protocols, employed at the WPCN type 1 and WPCN type 2, respectively. These protocols have significant practical advantages over the state-of-the-art schemes proposed for maximizing the WPCN sum-rate, because they introduce fairness in the resource utilization by the EHUs, and require much lower amount of channel state information. Both protocols achieve these benefits at the expense of a minor rate degradation relative to the rates achieved by their counterpart protocols employing multiple access, denoted as the harvest-then-transmit and harvest-or-concurrently-transmit protocols.
- Energy harvesting
- fair resource allocation
- opportunistic scheduling
- wireless information and energy transfer