# Energy Beamforming for Wireless Information and Power Transfer in Backscatter Multiuser Networks

## TL;DR

This paper introduces an energy beamforming scheme for wirelessly powered backscatter communication networks that balances energy harvesting and data rate, outperforming existing methods with estimated channel information.

## Contribution

It is the first to consider both energy supply and information transfer in energy beamforming for WPBC, formulating a max-min optimization for fairness and efficiency.

## Key findings

- The proposed scheme outperforms state-of-the-art beamforming methods.
- It achieves performance close to perfect CSI-based beamforming.
- Closed-form expressions for energy harvesting and achievable rate are derived.

## 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. 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 trade-off between the energy harvesting rate and achievable rate using 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 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 ergodic achievable rate. Our numerical results indicate that our scheme can significantly outperform state-of-the-art energy beamforming schemes. Additionally, the proposed scheme achieves performance comparable to that obtained via beamforming with perfect CSI.