Page 21 - ITU Journal, Future and evolving technologies - Volume 1 (2020), Issue 1, Inaugural issue

ITU Journal on Future and Evolving Technologies, Volume 1 (2020), Issue 1

BACKSCATTER COMMUNICATIONS WITH PASSIVE RECEIVERS: FROM
FUNDAMENTALS TO APPLICATIONS

1
Milutin Stanaćević , Akshay Athalye , Zygmunt J. Haas 2,3 , Samir R. Das , Petar M. Djurić 1
1
4
2
1 Electrical and Computer Engineering, Stony Brook University, Stony Brook, NY 11794, Computer Science,
3
University of Texas at Dallas, Richardson, TX 75080, School of Electrical and Computer Engineering, Cornell
University, Ithaca, NY 14853, Computer Science, Stony Brook University, Stony Brook, NY 11794,
4
NOTE: Corresponding author: Milutin Stanaćević, milutin.stanacevic@stonybrook.edu
Abstract – The principle of backscattering has the potential to enable a full realization of the Internet of Things.
This paradigm subsumes massively deployed things that have the capability to communicate directly with each other.
Based on the types of excitation and receivers, we discriminate four types of backscattering systems: (i) Dedicated
Exciter Active Receiver systems, (ii) Ambient Exciter Active Receiver systems, (iii) Dedicated Exciter Passive Receiver
systems, and (iv) Ambient Exciter Passive Receiver systems. In this paper, we present an overview of bacskscattering
systems with passive receivers which form the foundation for Backscattering Tag-to-Tag Networks (BTTNs). This
is a technology that allows tiny batteryless RF tags attached to various objects to communicate directly with each
other and to perform RF-based sensing of the communication link. We present an overview of recent innovations in
hardware architectures for backscatter modulation, passive demodulation, and energy harvesting that overcome design
challenges for passive tag-to-tag communication. We further describe the challenges in scaling up the architecture
from a single link to a distributed network. We provide some examples of application scenarios enabled by BTTNs
involving object-to-object communication and inter-object or human-object dynamic interactions. Finally, we discuss
key challenges in present-day BTTN technology and future research directions.

Keywords – Backscatter-based communication, baterryless tags, Internet of Things, protocols, tag-to-tag networks

1. INTRODUCTION rise to different classes of systems and networks. In the
broad literature, backscatter systems are classified based
on the source of excitation into two types:
The promise of the Internet of Things (IoT) has fo-
mented research into a wide array of wireless technolo- 1. Dedicated exciter (DE) systems: a source of ex-
gies and devices capable of providing the required ubiq- citation is deployed specifically for the purpose of
uitous connectivity at a very large scale. In order to enabling backscatter transmissions, and
maximize the everywhereness and scalability of the IoT,
such devices should satisfy the following two key re- 2. Ambient exciter (AE) systems: backscatter trans-
quirements: (i) very low power consumption allowing missions leverage preexisting sources of excitation
for batteryless operation and (ii) direct communication in the environment such as TV towers, WiFi APs
with one another and networking without the need for and cell phone towers.
a central master controller. It is in this context that Independent of the excitation source, we posit that an
backscattering technology has seen a rapid emergence equally important classifying feature of backscatter sys-
in recent years, beyond its traditional uses in radar and tems is the type of receiver. Based on this, we identify
more recently in Radio Frequency Identification (RFID). the following two subclasses of backscatter systems:
Backscattering is a form of wireless transmission based
on modulated reflection of external RF signals. Since 1. Active receiver (AR) systems: the receiver is
the source of the RF signal is external, such transmis- a device with an on-board radio transceiver ca-
sion does not require an ‘active’ radio transceiver, al- pable of IQ demodulation and carrier cancella-
lowing devices to function in an extremely low power tion resulting, typically, in a very high sensitivity
regime (under 10 ). The power needed to operate (down to −110 dBm for data rate of 20 kb/s and
the transmitter can be harvested from the external RF 30 mW power consumption for commercially avail-
signal itself, and thus it is possible for such devices to able transceivers [1]), and
be batteryless.
2. Passive receiver (PR) systems: the receiver is a
While the backscattering transmitter is a necessary con- radio-less passive device using an envelope detec-
stituent of every backscatter system, the type of RF ex- tor for signal demodulation resulting in a much
citation source and the type of receiver can vary, giving lower sensitivity (−56 dBm for data rate of 8 kb/s

© International Telecommunication Union, 2020 1