Secure Communication Via a Wireless Energy Harvesting Untrusted Relay

TL;DR

This paper investigates secure wireless communication using an energy-harvesting untrusted relay, employing destination-assisted jamming and analyzing power splitting and time switching policies to optimize secrecy performance.

Contribution

It introduces a comprehensive analysis of secrecy performance in energy-harvesting untrusted relays with jamming, deriving new analytical expressions for secrecy outage and ergodic secrecy rate.

Findings

Power splitting policy outperforms time switching at high secrecy rates.

Optimal secrecy performance depends on system parameters like energy harvesting ratio and relay location.

Analytical expressions enable better system design for secure energy-harvesting relay networks.

Abstract

The broadcast nature of the wireless medium allows unintended users to eavesdrop the confidential information transmission. In this regard, we investigate the problem of secure communication between a source and a destination via a wireless energy harvesting untrusted node which acts as a helper to relay the information; however, the source and destination nodes wish to keep the information confidential from the relay node. To realize the positive secrecy rate, we use destination-assisted jamming. Being an energy-starved node, the untrusted relay harvests energy from the received radio frequency signals, which include the source's information signal and the destination's jamming signal. Thus, we utilize the jamming signal efficiently by leveraging it as a useful energy source. At the relay, to enable energy harvesting and information processing, we adopt power splitting (PS) and time switching (TS) policies. To evaluate the secrecy performance of this proposed scenario, we derive analytical expressions for two important metrics, viz., the secrecy outage probability and the ergodic secrecy rate. The numerical analysis reveals the design insights into the effects of different system parameters like power splitting ratio, energy harvesting time, target secrecy rate, transmit signal-to-noise ratio (SNR), relay location, and energy conversion efficiency factor, on the secrecy performance. Specifically, the PS policy achieves better optimal secrecy outage probability and optimal ergodic secrecy rate than that of the TS policy at higher target secrecy rate and transmit SNR, respectively.