Image Processing Reference
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everyday, and they are changing deeply many aspects of human life, by enabling new perspectives
and opportunities that could hardly even be thought of only few years ago (e.g., personal mobility,
WiFi hotspots, Bluetooth-enabled devices, and so on). Likely, this is going to happen in industrial and
factory environments as well, where highly automated production systems can get significant benefits
from the introduction of most advanced wireless communication techniques. Indeed, several studies
have recently proved that some very popular wireless solutions are suitable for the employment in
industrial scenarios, too, including real-time communications at the shop-floor [].
Adopting wireless communications in industrial environments is particularly appealing as, in prin-
ciple, it avoids (or, at least, reduces) cabling, which turns out to be cumbersome and/or expensive in
many real cases. For instance, reliability problems could arise with cables used to connect moving
parts, as a consequence of mechanical stress and/or attrition. In the same way, wireless connections
between working cells may increase system flexibility, by reducing set up times and costs. How-
ever, while a number of standard solutions and components are already available for wired industrial
communications, wireless systems are far from being considered well settled for such kinds of appli-
cations. It is worth pointing out that, as a matter of fact, the straightforward introduction of highly
innovative solutions in industrial and manufacturing systems has neither been simple nor fast. his
is due to several reasons, such as for example reliability, efficiency, safety, cost, and security, just to
mention a few. As a consequence, the growth of wireless technologies in industrial applications is
not being as quick as in other areas, even though they are envisaged to play an essential role in many
next-generation automated production systems.
A point most experts agree on is that wireless communications are unlikely to be able to replace
completelythewiredsolutionscurrentlyadoptedinindustrialscenarios,atleastinthemid-term.
Indeed, it is worth noting that, in most practical applications, this is not considered a real require-
ment. What is often needed in real-world factory automation systems is the ability to connect a few
components to an already deployed wired communication system that cannot be reached (easily
and/or reliably) with a cable. he most common example is a sensor mounted on a moving/rotating
axis that has to exchange data with a controller attached to a wired segment.
This kind of problems may be easily solved by providing wireless extensions to the existing wired
systems. The resulting configurations are “hybrid” networks in which, typically, wireless segments
have limited geographic extension (some tens of meters) and connect only few stations (in the order
of ten). In such a kind of networks, controllers (e.g., programmable logic controllers [PLCs], com-
puter numeric controls [CNCs], or industrial personal computers [PCs]) are usually located on the
wired segment. This means that wireless networks will have to coexist with more traditional wired
communication systems for quite a long time. Consequently, the integration of wireless and wired
communications in industrial scenarios is becoming a crucial issue that has to be dealt with carefully
to achieve both reliability and performance.
This chapter focuses on some of the most relevant aspects concerning the aforementioned hybrid
networks. After a general analysis of hybrid wired/wireless configurations and the related issues, the
ways wireless extensions can be effectively implemented for both fieldbuses and real-time Ethernet
(RTE) networks are described. Some examples are then provided that are based on popular networks:
in particular, the well-known Profibus DP [] and DeviceNet (controller area network [CAN]) []
fieldbus networks are taken into account, as well as the EtherNet/IP [] and Profinet IO [] RTE
networks.Forthesakeoftruth,itisworthrememberingthatmanyotherinterestingsolutionsactually
exist that could be provided with a wireless extension. However, as it would have been practically
unfeasible to deal with all of them, it has been decided to focus on a reduced set of networks that are
nevertheless representative of a wider class of industrial solutions.
Both the IEEE . wireless local area network (WLAN) [] and the IEEE .. low-rate wire-
less personal area network (LR-WPAN) [] have been considered as candidate technologies to imple-
ment wireless extensions. WLANs have already been considered in many other studies, and tested
in practical applications that demonstrated their suitability for the use in industrial environments
