Simultaneous harvest-and-transmit ambient backscatter communications under Rayleigh fading

Abstract

Ambient backscatter communications is an emerging paradigm and a key enabler for pervasive connectivity of low-powered wireless devices. It is primarily beneficial in the Internet of things (IoT) and the situations where computing and connectivity capabilities expand to sensors and miniature devices that exchange data on a low power budget. The premise of the ambient backscatter communication is to build a network of devices capable of operating in a battery-free manner by means of smart networking, radio frequency (RF) energy harvesting and power management at the granularity of individual bits and instructions. Due to this innovation in communication methods, it is essential to investigate the performance of these devices under practical constraints. To do so, this article formulates a model for wireless-powered ambient backscatter devices and derives a closed-form expression of outage probability under Rayleigh fading. Based on this expression, the article provides the power-splitting factor that balances the tradeoff between energy harvesting and achievable data rate. Our results also shed light on the complex interplay of a power-splitting factor, amount of harvested energy, and the achievable data rates. Index TermsAmbient backscatter communications, Energy harvesting, Internet of Things (IoT), Smart networking, Wireless-powered communication I. INTRODUCTIONThe grand vision of the Internet of things (IoT) is quickly turning into reality by bringing everything to the Internet [1], [2]. Latest devices ranging from smartphones to implantable sensors and wearables are claiming to be "IoT capable". Although significant improvements have been seen from the design perspective of wireless devices, the objective of connecting everything to the Internet is still a far cry [3]. It is because several important challenges arise when ensuring ubiquitous connectivity of devices. As indicated in [4], one of the first challenge is the limited life-cycle of miniature wireless devices. The energy constrained nature of devices becomes an obstacle as the massive amount of data is transferred across an IoT network and the devices are required to be operated in an untethered manner. Then, there is a requirement of communication reliability which is even more difficult to maintain in large-scale wireless systems [5]. The increased reliability most often comes at a cost of increased energy consumption which cannot be regulated by small energy reservoirs of miniature IoT devices. Above all, these devices would need to demonstrate services like ultra-reliable low-latency communications (URLLC), enhanced mobile broadband (eMBB), and massive machine type communications (mMTC)for beyond 5G networks. Resultantly, it has become evident that an ultra low-powered communication paradigm is essential for enabling short-range communication among devices, without compromising the reliability of communications [2], [6].Of late, backscatter communication has gathered the attention of the researchers as a key enabling technology for connecting IoT...

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