Joint Energy Harvest and Information Transfer for Energy Beamforming in Backscatter Multiuser Networks

TL;DR

This paper proposes a novel energy beamforming design for wirelessly powered backscatter communication networks that balances energy harvesting and data transmission, significantly improving performance over existing methods.

Contribution

It introduces a max-min optimization framework considering energy and information transfer, deriving closed-form expressions and demonstrating near-optimal performance with estimated CSI.

Findings

Outperforms existing energy beamforming schemes.

Achieves over 90% of the rate with perfect CSI.

Provides closed-form expressions for energy harvesting and rate bounds.

Abstract

Wirelessly powered backscatter communication (WPBC) has been identified as a promising technology for low-power communication systems, which can reap the benefits of energy beamforming to improve energy transfer efficiency. However, existing studies on energy beamforming fail to simultaneously take energy supply and information transfer in WPBC into account. This paper takes the first step to fill this gap, by considering the restrictive relationship between the energy harvesting rate and achievable rate with estimated backscatter channel state information (BS-CSI). To ensure reliable communication and user fairness, we formulate the energy beamforming design as a max-min optimization problem by maximizing the minimum achievable rate for all backscatter tags subject to the energy constraint. We derive the closed-form expression of the energy harvesting rate, as well as the lower bound of the achievable rate for maximum-ratio combining (MRC) and zero-forcing (ZF) receivers. Our numerical results indicate that our scheme significantly outperforms state-of-the-art energy beamforming schemes. Additionally, the achievable rate of our scheme approaches more than $90\%$ of the rate limit achieved via beamforming with perfect CSI for both receivers.