On the Efficiency of Far-Field Wireless Power Transfer

TL;DR

This paper analyzes the efficiency of far-field wireless power transfer in future communication systems, demonstrating how opportunistic scheduling can significantly improve power transfer efficiency by exploiting channel diversity among users.

Contribution

It introduces analytical power scaling laws for different user scenarios and shows how opportunistic scheduling enhances efficiency compared to traditional methods.

Findings

Power transfer efficiency scales as ln(N) for symmetric users.

Efficiency scales linearly with N for asymmetric users.

Opportunistic scheduling significantly outperforms round-robin scheduling.

Abstract

Far-field wireless power transfer (WPT) is a promising technique to resolve the painstaking power-charging problem inherent in various wireless terminals. This paper investigates the power transfer efficiency of the WPT segment in future communication systems in support of simultaneous power and data transfer, by means of analytically computing the time-average output direct current (DC) power at user equipments (UEs). In order to investigate the effect of channel variety among UEs on the average output DC power, different policies for the scheduling of the power transfer among the users are implemented and compared in two scenarios: homogeneous, whereby users are symmetric and experience similar path loss, and heterogeneous, whereby users are asymmetric and exhibit different path losses. Specifically, if opportunistic scheduling is performed among $N$ symmetric/asymmetric UEs, the power scaling laws are attained by using extreme value theory, and reveal that the gain in power transfer efficiency is $\ln{N}$ if UEs are symmetric whereas the gain is $N$ if UEs are asymmetric, compared with that of conventional round-robin scheduling. Thus, the channel variety among UEs inherent to the wireless environment can be exploited by opportunistic scheduling to significantly improve the power transfer efficiency when designing future wireless communication systems in support of simultaneous power and data transfer.