industrial wireless book special edition - Networking ...

60GHz Industrial Wireless:
perfect for point-to-point
Radio systems operating in the licence-free 60GHz band – yes there is one – have characteristics that make
them significantly different from the more familiar hardware operating at the traditional 2.4 and 5GHz ISM
frequencies. These altered qualities give 60GHz millimetric wavelength radios operational advantages not
found in other wireless systems. For instance it is possible to achieve orders of magnitude higher link
budgets than those possible with IEEE 802.11n and Ultra Wideband (UWB) systems – which translates into
reliable and affordable wireless connections. Frank Ogden reports
THERE ARE OCCASIONS when network cabling media characteristics: the necessary patch
antennas are both physically small and highly
directional while oxygen spectral absorption
restricts path length to about 1.6km. And of
course the signal path must be entirely line
of sight for the link to operate. Against this,
the highly directional antennas make the signal
– a beam – almost impossible to intercept and
virtually immune to interference, either from
all the usual industrial sources of EMI or from
other inhabitants of the crowded lower
frequency ISM bands. Other 60GHz operations
just can’t do the job and the practical alternative
is wireless Ethernet. Most industrial transmissions only ‘illuminate’ what they point
are unlikely to interfere since narrow beam
applications can be adequately served by at and, in any case, oxygen signal attenuation
IEEE802.11a/b/g/n WLAN hardware operating places a limit on interference from distant
at 2.4 or 5GHz, certainly where the link distance sources.
is no more than a couple of hundred metres. When it comes to possible data bandwidth,
Beyond this span, office-style wireless installation
gets a bit more problematic with both 100 times wider than the channel bandwidth
the RF baseband is 7GHz wide – getting on for
performance and security concerns. If the link available under 5GHz ISM band operation. There
requirement is fixed point-to-point, then 60GHz is already plug and play 60GHz COTS hardware
operation might be an alternative.
on the market which delivers true 100Mbps Fast
With its own licence-free operational Ethernet full duplex performance but the
frequency allocation just like existing ISM, it potential data bandwidth achievable is much
is possible to set up and operate 60G fixed links greater, limited only by the confines of
to implement a plug and play extension to a Shannon’s Law.
network without wires. Of course a millimetric Possible industrial applications include all
operational frequency brings with it specific those where one might presently use multimode
optical fibre media but are precluded because
a cable might get in the way, or otherwise be
difficult or expensive to install. For instance,
When you can’t dig up the road, this 60GHz wireless
bridge from Huber & Suhner implements a useful
Ethernet-based line-of-sight wireless solution…
sponsored by Advantech
PHOTO: HUBER & SUHNER PHOTO: HUBER & SUHNER
industrial ethernet book
Airbus explores 60GHz for wireless IFE, WAIC
a 60G fixed link would be perfect for connecting
up buildings separated by public roads, implementing
low installation effort temporary links
around tank farms and utilities and similar. Away
from industrial plant, 60G is receiving serious
interest for ‘last mile’ telecoms distribution,
cellular backhaul and data centre connections,
in fact anywhere which needs flexible, noninvasive
point-to-point network segments.
Friis’ Law is good!
The high antenna gain typical for 60GHz
systems comes in part from the Friis Equation
for Path Loss. This equation, also known as
Friis’ Law, holds that as the frequency of
operation changes, the effective area of any
particular antenna varies proportionately to the
square of the operational frequency. Put
another way, this means that the gain possible
from an antenna of any given size increases by
the operational frequency squared. An antenna
with an area of of just over 6cm 2 – a square an
inch on a side – will have a gain of approximately
25dBi at 60GHz versus a gain of
approximately 3dBi at 5GHz. This characteristic
provides the mechanism by which millimetre
wave systems deliver better link budget performance
than systems operating at lower
frequencies.
First published in the industrial ethernet book February
2011
The Fraunhofer-Heinrich Hertz Institute in Berlin has carried out several projects with Airbus in the use
of 60GHz technology for wireless in-flight entertainment as well as low rate WAIC (Wireless Avionics
Intra-Communications) at lower frequencies for sensor and crew communication applications.
The basic idea of wireless onboard communication is to replace wired infrastructure by wireless links.
The applications range from traditional in-cabin connections such as crew communication through new
passenger services, and individual in-flight entertainment to use in sensor networks with hundreds
of sensor nodes inside the whole aircraft structure. The motivation for these developments include the
saving of weight and wiring harness maintenance, the higher robustness of a self organised wireless
networks compared to wires and connectors, higher flexibility in cabin configurations, and the
implementation of new functions such as sensors at moving or non-accessible parts.
The 60GHz frequency band is a most promising candidate. It provides several gigahertz of bandwidth
for license-free worldwide use, and the high free space attenuation minimises interferences between
different aircrafts and allows a reuse of frequencies, even within the same cabin.
Similar work is presently being done at Boeing, mainly in the use of WiFi, but 60GHz is also under
investigation by the US plane maker.
Dr.-Ing. Wilhelm Keusgen
industrial wireless
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