# Max-min Fair Beamforming for SWIPT Systems with Non-linear EH Model

## TL;DR

This paper proposes a novel beamforming design for SWIPT systems using a non-linear energy harvesting model, optimizing for fairness and performance under imperfect CSI, with solutions derived via SDP relaxation.

## Contribution

It introduces a globally optimal beamforming approach for SWIPT with a non-linear EH model, considering imperfect CSI and SINR constraints, revealing that only one energy beam suffices.

## Key findings

- Significant performance gains over baseline schemes.
- Improved fairness among users.
- Optimality achieved with at most one energy beam.

## Abstract

We study the beamforming design for multiuser systems with simultaneous wireless information and power transfer (SWIPT). Employing a practical non-linear energy harvesting (EH) model, the design is formulated as a non-convex optimization problem for the maximization of the minimum harvested power across several energy harvesting receivers. The proposed problem formulation takes into account imperfect channel state information (CSI) and a minimum required signal-to-interference-plus-noise ratio (SINR). The globally optimal solution of the design problem is obtained via the semidefinite programming (SDP) relaxation approach. Interestingly, we can show that at most one dedicated energy beam is needed to achieve optimality. Numerical results demonstrate that with the proposed design a significant performance gain and improved fairness can be provided to the users compared to two baseline schemes.