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Geotechnical News •June 2015
GEOTECHNICAL INSTRUMENTATION NEWS
(NLOS) transmission which is often
the case for an underground or tunnel-
ing environment where line of sight
can be challenging. Another consider-
ation is power consumption and range.
All other things equal, a 900MHz
radio will provide up to 2.7 times the
range than the otherwise equivalent
2.4GHz product for the same given
transmit power. This means that for a
same given installation the transmit
power of the 900 MHz radio can be
reduced, further improving battery
life. A typical underground range for
our 900MHz mesh network (battery-
powered) is between 50-150m at
+14dBm transmit power and using a
+3dBi omnidirectional antenna , but
can sometimes throw as far as 350m
when tunnel size and conditions are
ideal. Surface range with a standard
omni-directional antenna is typically
300-1000m.
Data backhaul
Data backhaul options in mining are
unique in comparison to surface.
Often there are no backhaul options
at all, and in these cases a store-and-
forward type of system where the data
are collected and relayed to a central
gateway which can then be polled at a
later time is quite beneficial. How-
ever, this is not the ideal option as real
time data is sacrificed. In most North
American mines there is usually a
radio network for voice communica-
tion (called Leaky-Feeder), and also
fibre-optic cables for backhaul. Fibre
is always the preferred option, allow-
ing for much higher bandwidth than
leaky feeder, and in most cases this
is what is used in the top-tier mines
worldwide. In this way, the mesh is
deployed to the point where the sen-
sors are installed (sometimes upwards
of 50 nodes in a linear fashion) and
relayed back to the gateway for back-
haul over fibre to surface.
Network topology
The network topology should always
be designed with robustness in mind,
so ensuring that there are redundant
links is important. In the case of min-
ing, wireless node placement is critical
to ensure not only that the signal prop-
agation is the best available, but the
risk of damage to the node is minimal
from effects from blasting and damage
caused by vehicles. The consider-
ations for surface deployments are
often very different in nature. Things
like snow, rain, wind, extreme hot or
cold then become potential issues and
cause for concern. Snow and rain may
affect signal propagation, whereas
with extreme hot or cold one also has
to consider the effects on battery life
over time. If you deploy in the middle
of winter in a forested area, what will
be the effect of leaves growing on the
trees in the spring - will this affect
your signal (let me answer that for
you: yes). If careful consideration is
taken during the planning phase, there
is a very high probability of success
during deployment.
The future of wireless monitoring
is promising, and should never be
discounted just because someone has
‘tried wireless before’ without success.
Both businesses and consumers alike
are driving the research and develop-
ment of new wireless technologies and
applications every day, so what may
have been problematic before can now
be resolved. It’s always worth picking
up a copy of GIN to see what’s new
and improved!
Adam Dulmage and Matt Trenwith
Mine Design Technologies Inc.
6-1045 John Counter Blvd.
Kingston, ON Canada K7K 6C7
Tel: +1-613-549-5223,
email:
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