Page 16 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 7 – Terahertz communications

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 7

Fig. 2 – THz‑enabled drone sensor networks: Applications, challenges, and solutions.

2.2 Terahertz for sensing An example of detecting a dangerous gas, such as carbon
monoxide is illustrated in Fig. 1. Here, a THz wave with
spectrum ranging from to is transmitted through a
1
3
Unlike infrared and microwaves, THz waves hold many
drone Tx, which is then received by the drone Rx. If the
unique transmission properties such as a quasi‑optical
dangerous gas pertaining an absorption at is available,
nature and molecular absorption, making the THz band 2
the received THz wave level at shall be lower as
an appropriate candidate for some sensing applications, 2
compared to the other frequencies. Thus, the gaseous
such as gas and material sensing, quality control, che-
presence is sensed/detected. For the gas sensing,
mical and biological sensing, bearing unique THz
THz band of 0.2‑1 THz has been considered in the
spectral signatures. Hence, THz‑enabled DSNs can be
literature [27]. After detecting the gas successfully,
deployed in a variety of practical sensing applications.
again, the THz band can be utilized for relaying
THz signals possess distinctive spectral signatures, i.e.,
(communicating) the sensed information via drone net‑
quasi‑optical nature having varying absorption loss
across the THz band, due to the molecular rotations/ works to a nearby monitoring station for rapid rescue
operations. Thus, an all‑in‑one operation (sensing and
vibrations, promising that THz waves can be highly
communication) can be conveniently achieved by
suitable for applications related to the rotational
deploying THz‑enabled DSNs and drone networks.
spectroscopy, such as gas detection [6, 22]. Consequently,
it becomes possible to utilize THz waves for the purposes
2.3 Localization
of detecting various poisonous/dangerous gases like
hydrogen cyanide, carbon monoxide, etc., possibly over Besides other requirements of the prospective 6G
disaster‑struck places, including ire eruption, massive systems, high precision localization is also expected.
earthquakes, volcanic eruptions, etc. THz‑enabled DSNs, It is predicted that the THz band will promise
here, can be employed to promptly detect/sense such localization accuracy in the order of centimeters [28],
poisonous gases with the aid of THz waves by rapid which is far better than the existing localization‑
detection and relaying such vital information, saving any based ser‑ vices, such as Global Positioning System
further victims and avoiding other secondary disasters. (GPS), and cell‑ multilateration. Localization methods at
Both active and passive sensing methods can be employed higher frequencies, such as across the THz band rely on
for poisonous gas detection using THz spectroscopy. the technique of Simultaneous Localization and Mapping

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