Spatial Throughput Maximization of Wireless Powered Communication Networks

TL;DR

This paper analyzes how to maximize spatial throughput in large-scale wireless powered communication networks by optimizing energy transfer and data transmission, considering battery-free and battery-equipped nodes using stochastic geometry.

Contribution

It introduces a joint optimization framework for frame partition and transmit power in WPCNs, considering both battery-free and finite-capacity battery nodes, with analytical bounds and numerical validation.

Findings

Optimal transmit power is lower for battery-free nodes to maximize transmission opportunities.

In infinite-capacity battery scenarios, the optimal charging design is not unique.

Finite-capacity batteries have performance bounds between battery-free and infinite-capacity cases.

Abstract

Wireless charging is a promising way to power wireless nodes' transmissions. This paper considers new dual-function access points (APs) which are able to support the energy/information transmission to/from wireless nodes. We focus on a large-scale wireless powered communication network (WPCN), and use stochastic geometry to analyze the wireless nodes' performance tradeoff between energy harvesting and information transmission. We study two cases with battery-free and battery-deployed wireless nodes. For both cases, we consider a harvest-then-transmit protocol by partitioning each time frame into a downlink (DL) phase for energy transfer, and an uplink (UL) phase for information transfer. By jointly optimizing frame partition between the two phases and the wireless nodes' transmit power, we maximize the wireless nodes' spatial throughput subject to a successful information transmission probability constraint. For the battery-free case, we show that the wireless nodes prefer to choose small transmit power to obtain large transmission opportunity. For the battery-deployed case, we first study an ideal infinite-capacity battery scenario for wireless nodes, and show that the optimal charging design is not unique, due to the sufficient energy stored in the battery. We then extend to the practical finite-capacity battery scenario. Although the exact performance is difficult to be obtained analytically, it is shown to be upper and lower bounded by those in the infinite-capacity battery scenario and the battery-free case, respectively. Finally, we provide numerical results to corroborate our study.