Wireless Sensor Networks
Evolution of Industrial Wireless Sensor Networks
By Mark Miller, Wireless Product Manager, L-com Global Connectivity
Industrial automation powered by
wireless sensor networks (WSN)
is heralding the Industrial Internet
of Things and Industry (IoT) 4.0. Key
enabling cloud and wireless mesh networking
technologies promise to bring
multi-year battery life, IP addressability
to machines and sensors, cloud-based
provisioning and management systems,
as well as fieldbus tunneling. Though
currently prevalent wireless standards,
such as WirelessHART and Wi-Fi will
likely account for the majority of the
industrial wireless network technologies,
upcoming low power wide area (LPWAN)
technologies are likely to grow in value
for current and future applications.
FROM HARDWIRED CONNECTIONS
TO SMART LINKS
Unlike datacenter communications and
interoffice interconnections with patch
cords and plenum Ethernet cables, the
backbone for industrial-based communication
require cables that are resistant
to a number of environmental aggressors
including chemicals, oils, moisture,
vibration, and abrasion. This has been
necessary for the fieldbus- and Ethernet
based hardwired industrial links
but industrial wireless sensor networks
(IWSN) are poised to replace much of
that costly infrastructure with hundreds
to thousands of modular sensor nodes.
There are a great variety of challenges
to making this technology ubiquitous,
for instance, the bit error rate (BER) of
an industrial sensor node can stand
between 10-2 to 10-6 1 while IEEE 802.3
Ethernet standards call for performance
between 10-10 and 10-12. For ultra-low
latency time sensitive networking (TSN)
applications such as factory automation
with high speed robotic arms time
synchronization protocols have to reliably
achieve sub-millisecond cycles and
sub-microsecond jitter for plant operations
(e.g., PROFINET IO). WSN technology
is limited by the amount of energy
available to small battery-powered sensors,
a limited bandwidth, and computational
power; complex schemes that
are traditionally used such as network
time protocol (NTP) are not viable due to
these restrictions 3. Furthermore, many
factory automation, process automation,
and building automation facilities
traditionally leverage the Purdue Enterprise
Figure 1: Illustration of a WSN with a number of sensors that perform a diverse
range of functions, a sink node that collects and sends data to the internet via
cabling, Nearly 8 of 10 WSN users leverage wireless mesh topologies 2.
Source: http://article.sapub.org/10.5923.j.jwnc.20150501.03.html.
Figure 2: Most important features to WSN adopters based on ISA/ON World
Survey done in 2012 and 2014 2.
Reference Architecture (PERA) for
integrating applications in manufacturing
operations and control as well as
business systems. Each layer of hierarchy
is highly custom and optimized
independently to meet the requirements
of specific tasks, this makes interoperability
with industrial IoT (IIoT) networks
challenging thereby slowing the proliferation
of this technology 4.
Still, the ability to add a level of
abstraction between the hardware and
software and the integration with internet
protocol (IP) allow for scalable architectures
to support a wide variety of
industrial applications, this can allow for
the economies of scale to arise much
more rapidly than custom, proprietary
systems. Additionally, the maintenance
that comes with cables for interconnect
is eliminated. In highly corrosive
environments, the specially designed
connector heads and cable jackets
have to be inspected and maintained
regularly to prevent network latencies
and failures.
AN EVOLUTION IN OPPORTUNITIES
AND CHALLENGES
As shown in Figure 1, WSNs involve
tiny wireless sensor nodes installed on
industrial equipment to monitor its per-
www.mwee.com November - December 2017 MW 11
