Wirelessly Powered Communication Networks with Short Packets

TL;DR

This paper analyzes the performance of wirelessly powered communication systems with short packets, deriving analytical expressions and design guidelines for optimizing energy transfer and data transmission under finite blocklength constraints.

Contribution

It provides a finite-length information theory framework for system performance analysis and derives the asymptotically optimal transmit power in wirelessly powered short packet communications.

Findings

Power control significantly improves achievable rates.

Optimal transmit power closely matches asymptotic solutions.

Trade-offs between energy harvesting and data transmission are characterized.

Abstract

Wirelessly powered communications will entail short packets due to naturally small payloads, low-latency requirements and/or insufficient energy resources to support longer transmissions. In this paper, a wirelessly powered communication system is investigated where an energy harvesting transmitter, charged by one or more power beacons via wireless energy transfer, attempts to communicate with a receiver over a noisy channel. Under a save-then-transmit protocol, the system performance is characterized using metrics such as the energy supply probability at the transmitter, and the achievable rate at the receiver for the case of short packets. Leveraging the framework of finite-length information theory, tractable analytical expressions are derived for the considered metrics in terms of system parameters such as the harvest blocklength, the transmit blocklength, the harvested power and the transmit power. The analysis provides several useful design guidelines. Though using a small transmit power or a small transmit blocklength helps avoid energy outages, the consequently smaller signal-to-noise ratio or the fewer coding opportunities may cause an information outage. Scaling laws are derived to capture this inherent trade-off between the harvest and transmit blocklengths. Moreover, the asymptotically optimal transmit power is derived in closed-form. Numerical results reveal that power control is essential for improving the achievable rate of the system in the finite blocklength regime. The asymptotically optimal transmit power yields nearly optimal performance in the finite blocklength regime.