provided by: 
In an effort to make a better wireless network, the Cambridge MA-based company BBN Technologies
announced last week that it has built a mesh network that uses
significantly less power than traditional wireless networks, such as
cellular and Wi-Fi, while achieving comparable data-transfer rates.
The technology, which is being funded by the Defense Advanced Research Projects Agency
(DARPA), was developed to create ad hoc communication and surveillance
networks on battlefields. But aspects of it are applicable to emergency
or remote cell-phone networks, and could potentially even help to
extend the battery life of consumer wireless devices, says Jason Redi,
a scientist at BBN.
Mesh
networks -- collections of wireless transmitters and receivers that
send data hopping from one node to another, without the need of a
centralized base station or tower -- are most often found in research
applications, in which scientists deploy hordes of sensors to monitor
environments from volcanoes to rainforests. In this setting, mesh
networks are ideal because they can be deployed without a large
infrastructure. Because they lack the need for costly infrastructure,
mesh networks can also be used for bringing communication to remote
areas where there isn't a reliable form of electricity. In addition,
they can be established quickly, which is useful for building networks
of phones or radios during a public emergency.
While
mesh networks have quite a bit of flexibility in where they can be
deployed and how quickly, so far they've been less than ideal for a
number of applications due to their power requirements and relatively
slow data-transfer rates. All radios in a mesh network need to carry an
onboard battery, and in order to conserve battery power, most low-power
mesh networks send and receive data slowly -- at about tens of kilobits
per second. "You get the low power," says Redi, "but you also get poor
performance."
Especially
in military surveillance, the data rates need to be much faster. If a
soldier has set up a network of cameras, for example, he or she needs
to react to the video as quickly as possible. So, to keep the power
consumption to a minimum and increase data-transfer rates, the BBN team
modified both the hardware and software of their prototype network. The
result is a mesh network that can send megabits of data per second
across a network (typical rates for Wi-Fi networks, and good enough to
stream video), using one-hundredth the power of traditional networks.
To
make the mesh network more efficient, the BBN team looked at three
areas that could be improved. First, they modified the hardware in each
node by building more energy-efficient radios. They split the radios
into two parts: one uses little power and sends data short distances
and slowly, the other uses more power but is able to blast data over
kilometers and at a high rate. Most of the time, says Redi, the nodes
communicate using the low-power radio, while the high-power radio
sleeps. The high-power radio comes to life only when needed to send a
lot of information or a powerful signal over a longer distance.
Second,
the team looked at the algorithms used to synchronize communication
between nodes. These algorithms are needed because, most of the time,
radios in nodes aren't sending or receiving data, just listening for
it, an activity that "burns up power," Redi says. The BBN researchers
designed a protocol so that each node transmits data about its
presence, and listens for other nodes, at particular times. In effect,
the protocols synchronize the nodes' watches.
By Kate Greene
Read article at techreview.com