Page 63 - 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

SELF‑CONFIGURING ASYNCHRONOUS SLEEPING IN HETEROGENEOUS NETWORKS

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Ali Medlej , Eugen Dedu , Kamal Beydoun , Dominique Dhoutaut 1
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1 FEMTO‑ST Institute/CNRS, Univ. Bourgogne Franche‑Comté, Montbéliard, France, L’ARICoD Laboratory, Faculty of
Sciences I, Lebanese University Beirut, Lebanon
NOTE: Corresponding author: Ali Medlej, ali_ghasswan.medlej@univ‑fcomte.fr

Abstract – Nowadays, the heterogeneous wireless nano‑network topology becomes a need for diverse applications based
on heterogeneous networks composed of regions of different node densities. In Wireless Nano‑networks (WNNs), nodes are
of nano‑metric size and can be potentially dense in terms of neighbouring nodes. Nano‑nodes have limited resources in terms
of processing, energy and memory capabilities. In nano‑network(s), even in a communication range limited to tens of cen‑
timeters, thousands of neighbours can be found. We proposed a ine‑grained duty‑cycling method (sleeping mechanism),
appropriate to nanonodes, which aims to reduce the number of receptions seen by a node during data packet routing. The
present study reveals the usefulness of implementing the sleeping mechanism in heterogeneous networks, as well as con i-
guring a dynamic awaken duration for nodes based on a density estimation algorithm. We also proposed an algorithm
that helps in increasing the reliability of the packet received by the destination node.
Keywords – Density estimation, heterogeneous nano‑network, sleeping mechanism, routing

1. INTRODUCTION
T s time
Nano‑network(s) are made up of tiny nodes, called
T p
nanonodes, of a nanometric size. These nodes use electro‑
magnetic waves from the THz band (0.1–10 THz) [1] for
their communication. Nano‑nodes possess sensors, actu‑ 1 1 0 1
ators, a processor, and a memory. They can move and
communicate with each other [2]. These nodes are
Fig. 1 – TS‑OOK modulation.
limited in their computing capabilities, storage, and
energy. Therefore, they need to collaborate with other way must be used. For that, a spatial addressing routing
nodes to ful il their tasks [3]. protocol that forwards messages in the direction of a
destination could be used.
1.1 Modulation and routing techniques
Stateless Linear‑path Routing (SLR) [6] is a spatial ad‑
Given the very limited energy of nanonodes, a modula‑ dressing and routing protocol we use in our evaluation.
tion technique based on femtosecond pulses for It implements a coordinate‑based routing, in which data
terahertz communications called Time Spread On‑Off packets are routed in a linear routing path. The SLR pro‑
Keying (TS‑ OOK) was proposed by Jornet and Akyildiz tocol has two phases: (1) initial/addressing phase and (2)
[4]. TS‑OOK is based on femtosecond‑long pulses where routing phase.
communica‑ tion data is sent using a sequence of pulses
1.2 Applications and node limitations
interleaved by a randomly selected constant duration
(Fig. 1). TS‑OOK uses an electromagnetic pulse of
Nano‑network(s) can be potentially used in a wide range of
duration to transmit a bit “1”, and silence (no applications and ields such as: (1) health ield (e.g.
transmission) for bit “0”. The time between two
monitor human vital signs, drug delivery systems), (2)
consecutive bits is . Due to hardware and power military ield (e.g. border control to prevent any penetra‑

constraints, the spreading ratio = / can be very tion), (3) agricultural ield (e.g. monitoring the tempe-

large. Using = 100 femtosecond, the total available rature, humidity, and water level of plants), (4)

bandwidth in the network is very high, in the order of telecommunication sector [5]. In such applications the
terabit per second.
network topology is often heterogeneous. A heterogeneous
In very dense nano‑network(s), a nanonode cannot fre‑ nano‑network is a network composed of zones of different
quently update its neighbourhood list. Also, the commu‑ densities. Nowadays, many applications use this type of net‑
nication range is short and the desired destination node is works. For example, in agricultural applications, some areas
often beyond its communication range. Therefore, it is have high nodes’ density while others have a small
necessary to have a routing protocol that performs the density due to the varied geographical terrains. Also, the
tasks of data routing between nodes. A traditional ad‑ human body is considered as a natural heterogeneous
dressing scheme like IP is useless. An alternative addressing network because of its internal and external structure.

© International Telecommunication Union, 2021 51