Secrecy Wireless Information and Power Transfer with MISO Beamforming

TL;DR

This paper investigates secure simultaneous wireless information and power transfer in a MISO system, optimizing beamforming to maximize energy transfer while ensuring secrecy of the information to the IR.

Contribution

It introduces an optimal beamforming solution for secure SWIPT in MISO systems and proposes two low-complexity suboptimal schemes.

Findings

Optimal beamforming maximizes energy transfer under secrecy constraints.

Two suboptimal schemes offer trade-offs between complexity and performance.

The proposed methods improve secure energy transfer in SWIPT systems.

Abstract

The dual use of radio signals for simultaneous wireless information and power transfer (SWIPT) has recently drawn significant attention. To meet the practical requirement that energy receivers (ERs) operate with much higher received power than information receivers (IRs), ERs need to be deployed closer to the transmitter than IRs. However, due to the broadcast nature of wireless channels, one critical issue is that the messages sent to IRs cannot be eavesdropped by ERs, which possess better channels from the transmitter. In this paper, we address this new secrecy communication problem in a multiuser multiple-input single-output (MISO) SWIPT system where a multi-antenna transmitter sends information and energy simultaneously to one IR and multiple ERs, each with a single antenna. By optimizing transmit beamforming vectors and their power allocation, we maximize the weighted sum-energy transferred to ERs subject to a secrecy rate constraint for the information sent to the IR. We solve this non-convex problem optimally by reformulating it into a two-stage problem. First, we fix the signal-to-interference-plus-noise ratio (SINR) at the IR and obtain the optimal beamforming solution by applying the technique of semidefinite relaxation (SDR). Then the original problem is solved by a one-dimension search over the optimal SINR value for the IR. Furthermore, two suboptimal low-complexity beamforming schemes are proposed, and their achievable (secrecy) rate-energy (R-E) regions are compared against that by the optimal scheme.