Instrumentation & Measurement Magazine 26-4 - 20

measurement
andapplications continued
measurement systems. In some kinds of applications, mostly
related to wireless sensor networks, the communication technologies
can also be suitably exploited for nodes' indoor
localization [5].
After recalling the communication technologies typical
of distributed measurement system frameworks, the column
provides some examples of applications selected for involving
several kinds of communication solutions, which differ
for physical medium, communication standard, and coverage
areas.
Evolution of Wired and Wireless
Technologies
Communication technologies can be divided into two main
categories: wired and wireless. Both typologies are characterized
by some peculiarities that can be suitably exploited for
specific applications.
Generally, wired communication technologies are preferable
whenever great distances have to be covered, to keep a high
data rate, a good level of immunity to electromagnetic interferences,
and deterministic behavior. The past years have seen
a continuous development of standards and technologies for
different kinds of applications and satisfying different aspects.
As an example, in the case of the industrial fields, several communication
technologies have been proposed such as General
Purpose Interface Bus (GPIB) [6], DeviceNet [7], CanOpen [8],
Profibus [9], Foundation Fieldbus [10], to cite a few.
Beyond these technologies, specifically designed for industrial
networks, the standard de facto for local area networks,
i.e., Ethernet based on IEEE 802.11 [11], has received great attention
in the last decades since it allows performance at low
costs and automatic integration of the industrial networks
with the enterprise and company local area networks, thus significantly
increasing the opportunities offered by the related
connectivity and networking for the end users. As a consequence,
new versions of DeviceNet, Profibus, and Foundation
Fieldbus, respectively known as EtherNet/IP, Profibus on Ethernet,
and HSE (High-Speed Ethernet), were proposed for
promoting such an integration [12].
As is well known, Ethernet cannot assure determinism, isochrony,
and real-time operating, so it can be adopted only
in monitoring applications characterized by weak time constraints.
However, some evolutions of Ethernet, known as
Real Time Ethernet (RTE) have been proposed to satisfy these
kinds of requirements [13] and to follow the emerging trend
of time-sensitive networks [14]. On the other hand, wireless
communication technologies offer several advantages mainly
concerning the possibility of mobile measurements and easy
deployment, setup, scalability, and reconfigurability. Depending
on the distance covered between two nodes of the same
network which have to establish a connection, they can be further
divided into short-range and long-range [15].
20
Due to the increasing interest in Wireless Personal Area
Network (WPAN) and Wireless Body Area Network (WBAN)
applications, among short-range technologies, several
solutions have been presented in the last few years. In the Industrial
Scientific and Medical (ISM) 2.4 GHz band, which is
an unlicensed band, several technologies are available in several
releases such as WiFi [16], BlueTooth [17], and ZigBee [18],
to cite a few. In particular, ZigBee and recent versions of BlueTooth
(from BlueTooth Low Energy, also known as BLE up to
the release 5.2), have addressed the typical constraints of wireless
sensor networks and allowed low costs and low power.
Indeed, in such contexts, these figures of merit are of paramount
importance rather than coverage area and data rate.
Concerning the meaning of the term short-range, it refers
to the distance between two nodes of the same network which
have to establish a connection. Due to the low transmitted
power and the harsh electromagnetic environments (typically
crowded by other communication technologies on the same
unlicensed band), the coverage areas of short-range communications
vary from a few meters up to hundreds of meters in
favorable propagation scenarios (typically outdoors). However,
thanks to suitable access points or gateways able to
interconnect the measurement nodes with existing communications
infrastructures, the distance between a measurement
node and the remote user can also be practically unlimited.
Looking at long-range communication technologies, the
first solutions for measurement systems appeared several
years ago and were based on a key element called " radio modem "
which allowed links from hundreds of meters up to tens
of kilometers to be realized. This technology works in the Radio
Frequency band from 77.5 MHz up to 800 MHz, which is
an unlicensed band if the transmitting power is below 20 mW.
Depending on the kind of radio modem adopted, the data
rate varies from tens of kbps up to hundreds of kbps. The possibility
of introducing suitable repeaters and increasing the
transmitted power (while generally paying a license) allows for
reaching also a distance of tens of kilometers. Some of the most
interesting features of radio modems are the low latency and
robustness concerning the possibility of eavesdropper attacks.
Further long-range solutions currently available are mainly
based on cellular networks (GSM, UMTS, LTE, and so on) and
LoRa (LongRange) [19]. In particular, the cellular networks
work on licensed bands and allow covering very long-range
distances and high data rates thanks to the existing infrastructures,
which are based on the concept of cells (covering
small areas) that are all interconnected through several kinds
of backbones. As a consequence, once a measurement node
gains access to the most nearby cell, it can transmit data practically
worldwide thanks to the deep-rooted communication
infrastructure. The evolution from GSM (2G technology) to the
more recent LTE and LTE Advanced (often known as 4G and
4G+) allow covering data rates from tens of kbps up to 75 Mbps
IEEE Instrumentation & Measurement Magazine
June 2023
Instrumentation & Measurement Magazine 26-4

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