IEEE Spectrum - North American - March 2015 - 36
aaron ellison [below] puts
ants in chambers [right] heated
by hot air [bottom] to model the
effects of global warming .
ing above the treetops provide the main backbone for the network, communicating via 5.8-gigahertz radio links capable
of very high data rates. Because these high-frequency signals
are attenuated by foliage, a dozen 900-megahertz radios are
used to punch through leaves and branches. The third leg of
the hybrid consists of a handful of 2.4-GHz Wi-Fi access points
at ground level to provide Internet access for the laptops and
smartphones of researchers working nearby.
logged for much longer, that longevity came with risks.
"Murphy's Law says that when you only get out to these once
a month, if you have a problem it's going to be the day after
your last visit, and you'll lose a month's data," says Emery
Boose, who manages the forest's internet of trees.
In 2010, Harvard Forest researchers decided to move to a
wireless network. But tall trees and steep hills created dead
zones that a traditional Wi-Fi network could handle only with
scores of access points. A high-powered cellular system, on
the other hand, would cost a lot of money and need regulatory approval.
In the end, the project's engineers concocted an ingenious
hybrid of three kinds of wireless technology. Five towers pok36
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SPECTRUM.IEEE.ORG
aside From signal-sapping Foliage, nature has other
devilry. Animals chew on cables, ice builds up on metal equipment, and storms knock down trees and cables. But the main
enemy is lightning. Every summer, dozens of bolts surge into
the towers. The towers are well grounded, of course, so many
strikes are not even noticed. However, says Boose, "last summer
we had three or four episodes of significant damage. Our insurance company realized that this was no longer a good business
model for them, so we aren't able to insure any longer." To keep
replacement costs down, the forest now uses hand-me-down
switches and access points from the main university campus.
Each experimental site in the forest has many devices and
sensors associated with it. Some are gathering information
for a particular project; others are collecting background data
that could help scientists years from now. A weather station,
for example, collects a full set of meteorological data every
second, including air and soil temperatures, humidity, precipitation, and solar radiation. Meanwhile, the level and flow
of every stream is monitored by ingenious pressure meters
whose trick is to force water through a carefully shaped trough
http://SPECTRUM.IEEE.ORG
Table of Contents for the Digital Edition of IEEE Spectrum - North American - March 2015
Contents
IEEE Spectrum - North American - March 2015 - Cover1
IEEE Spectrum - North American - March 2015 - Cover2
IEEE Spectrum - North American - March 2015 - 1
IEEE Spectrum - North American - March 2015 - 2
IEEE Spectrum - North American - March 2015 - Contents
IEEE Spectrum - North American - March 2015 - 4
IEEE Spectrum - North American - March 2015 - 5
IEEE Spectrum - North American - March 2015 - 6
IEEE Spectrum - North American - March 2015 - 7
IEEE Spectrum - North American - March 2015 - 8
IEEE Spectrum - North American - March 2015 - 9
IEEE Spectrum - North American - March 2015 - 10
IEEE Spectrum - North American - March 2015 - 11
IEEE Spectrum - North American - March 2015 - 12
IEEE Spectrum - North American - March 2015 - 13
IEEE Spectrum - North American - March 2015 - 14
IEEE Spectrum - North American - March 2015 - 15
IEEE Spectrum - North American - March 2015 - 16
IEEE Spectrum - North American - March 2015 - 17
IEEE Spectrum - North American - March 2015 - 18
IEEE Spectrum - North American - March 2015 - 19
IEEE Spectrum - North American - March 2015 - 20
IEEE Spectrum - North American - March 2015 - 21
IEEE Spectrum - North American - March 2015 - 22
IEEE Spectrum - North American - March 2015 - 23
IEEE Spectrum - North American - March 2015 - 24
IEEE Spectrum - North American - March 2015 - 25
IEEE Spectrum - North American - March 2015 - 26
IEEE Spectrum - North American - March 2015 - 27
IEEE Spectrum - North American - March 2015 - 28
IEEE Spectrum - North American - March 2015 - 29
IEEE Spectrum - North American - March 2015 - 30
IEEE Spectrum - North American - March 2015 - 31
IEEE Spectrum - North American - March 2015 - 32
IEEE Spectrum - North American - March 2015 - 33
IEEE Spectrum - North American - March 2015 - 34
IEEE Spectrum - North American - March 2015 - 35
IEEE Spectrum - North American - March 2015 - 36
IEEE Spectrum - North American - March 2015 - 37
IEEE Spectrum - North American - March 2015 - 38
IEEE Spectrum - North American - March 2015 - 39
IEEE Spectrum - North American - March 2015 - 40
IEEE Spectrum - North American - March 2015 - 41
IEEE Spectrum - North American - March 2015 - 42
IEEE Spectrum - North American - March 2015 - 43
IEEE Spectrum - North American - March 2015 - 44
IEEE Spectrum - North American - March 2015 - 45
IEEE Spectrum - North American - March 2015 - 46
IEEE Spectrum - North American - March 2015 - 47
IEEE Spectrum - North American - March 2015 - 48
IEEE Spectrum - North American - March 2015 - 49
IEEE Spectrum - North American - March 2015 - 50
IEEE Spectrum - North American - March 2015 - 51
IEEE Spectrum - North American - March 2015 - 52
IEEE Spectrum - North American - March 2015 - 53
IEEE Spectrum - North American - March 2015 - 54
IEEE Spectrum - North American - March 2015 - 55
IEEE Spectrum - North American - March 2015 - 56
IEEE Spectrum - North American - March 2015 - 57
IEEE Spectrum - North American - March 2015 - 58
IEEE Spectrum - North American - March 2015 - 59
IEEE Spectrum - North American - March 2015 - 60
IEEE Spectrum - North American - March 2015 - 61
IEEE Spectrum - North American - March 2015 - 62
IEEE Spectrum - North American - March 2015 - 63
IEEE Spectrum - North American - March 2015 - 64
IEEE Spectrum - North American - March 2015 - 65
IEEE Spectrum - North American - March 2015 - 66
IEEE Spectrum - North American - March 2015 - 67
IEEE Spectrum - North American - March 2015 - 68
IEEE Spectrum - North American - March 2015 - 69
IEEE Spectrum - North American - March 2015 - 70
IEEE Spectrum - North American - March 2015 - 71
IEEE Spectrum - North American - March 2015 - 72
IEEE Spectrum - North American - March 2015 - 73
IEEE Spectrum - North American - March 2015 - 74
IEEE Spectrum - North American - March 2015 - 75
IEEE Spectrum - North American - March 2015 - 76
IEEE Spectrum - North American - March 2015 - Cover3
IEEE Spectrum - North American - March 2015 - Cover4
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