Backscatter communication is expected to help in revitalizing the domain of healthcare through its myriad applications. From on-body sensors to in-body implants and miniature embeddable devices, there are many potential use cases that can leverage the miniature and low-powered nature of backscatter devices. However, the existing literature lacks a comprehensive study that provides a distilled review of the latest studies on backscatter communications from the healthcare perspective. Thus, with the objective to promote the utility of backscatter communication in healthcare, this paper aims to identify specific applications of backscatter systems. A detailed taxonomy of recent studies and gap analysis for future research directions are provided in this work. Finally, we conduct measurements at 590 MHz in different propagation environments with the in-house designed backscatter device. The link budget results show the promise of backscatter devices to communicate over large distances for indoor environments which demonstrates its potential in the healthcare system. Index TermsBackscatter communication, Healthcare, In-body implants, Link budget, On-body sensors I. INTRODUCTIONThe medical industry today is seeking new solutions for in-body and on-body devices that transfer the data over a wireless channel [1], [2]. This includes pacemakers for generating electric pulses, micro-scale robots that operate in the bloodstream, and smart pills for identifying abnormalities in the gastrointestinal tract. However, the modern deep tissue systems consume a significant amount of energy by generating their own radio signals. For instance, wireless capsules for endoscopy consume up to 10 times more power than the sensors [1]. Due to these reasons, the large battery of the capsule consumes 40-50% of the total space of the capsule [2]. Reduction in this form-factor (i.e., the size, shape, and other physical specifications of electronic components) of these capsules can not only improve the likelihood of completion of endoscopy but also make them easy to swallow and excrete. Similar challenges are faced in the case of on-body sensors. The premise of on-body sensor networks is to build a network of devices capable of operating in a battery-free manner by means of smart networking, and power management at the granularity of individual bits and instructions. This is challenging to achieve through conventional networking approaches due to the need for active radio circuits, large form-factors, and their energy constraint nature. Thus, we expect that it is important to divorce the healthcare from conventional wireless solutions and move towards innovative systems for seamlessly connecting the in-body and on-body wireless devices.Backscatter communication is an emerging paradigm and a key enabler for pervasive connectivity of low-powered wireless devices [3]. It is primarily beneficial in situations where computing and connectivity capabilities expand to sensors and miniature devices that exchange data on a low power budget. Due to this in...

In Ambient Backscatter Communications (AmBC), a backscatter device communicates by modulating the ambient radio frequency (RF) signal impinging at its antenna. In many cases, the system setup is bi-static such that the receiver and the ambient signal source are separated in space. This configuration suffers from the direct path interference problem. The direct signal component can be several orders of magnitude stronger than the scattered one. This imposes a challenge for the receiver that needs to have high dynamic range in order not to lose the scattered signal component to the quantization noise. In this paper, we propose a novel AmBC system concept, in which a polarization conversion between the direct and scattered path is introduced at the backscatter device and exploited at the dual polarization based receiver antenna to mitigate the direct path interference. The proposed system is agnostic to the ambient signal source characteristics as long as it uses linearly polarized antennas. The backscatter device changes the polarization from linear to circular. The receiver antenna is a circularly polarized patch antenna with a 180°-hybrid to obtain the difference between the left-and right-hand polarized fields. Ideally, this receiver antenna and 180°-hybrid combination would completely remove linearly polarized direct path and reflected components. In this paper, we propose a robust design that can mitigate the direct path signal power more than 25 dB despite nonidealities in the antenna manufacturing. INDEX TERMS Polarization conversion, ambient backscatter communication.

Ambient backscatter communications system (ABCS) has recently been introduced as a cutting edge technology in which devices communicate in wireless mode by exploiting ambient radio frequency (RF) signals instead of actively generating them. ABCS is a promising technology for Internet of Things (IoT) use cases in which the power efficiency is a major challenge yet to be addressed. ABCS is in its early development stages from theoretical and practical perspectives. In this regard, it is highly important to understand the multi-aspects of the link budget of ABCS. Hence, in this paper we conducted a comprehensive study including measurements in different propagation environment and thorough simulation. The measurements are preformed in sub-1 GHz band and particularly in 590 MHz with the tags designed in the house. The results confirm the match between measurements and the simulations with trivial error.

No abstract