radios make intranet
Technology Research News
There are times when being able to log
onto the Internet to send a quick message or find key information would
be useful but impractical, like when a firefighter is trapped in a burning
building and needs to let someone know exactly where he is, or during
war games, which regularly coordinate large, mobile groups of people over
Researchers from ITT Industries are working on a scheme to bring Internet-like
communications to groups of field radios. The researchers' scheme would
allow radios to form a self-contained wireless
could pass along voice and data signals, boosting the distances they could
cover. The scheme would also allow for radio access to data on networks
like the Internet.
Internet radio islands could eventually be useful in military applications,
firefighting and in the trucking and construction industries, said Joe
Visvadoer, a senior scientist for technical communications at ITT industries.
A firefighter connected to an Internet radio island could, for instance
"report back where he is, what his situation is, what the field situation
is, and be able to communicate anything he needs to [even eventually]
including video images. And if a man goes down people know where he is
and they could help," he said.
Mobile networks could also prove useful in keeping track of equipment,
said Visvadoer. "You'd be surprised how often a truck is lost for... days...
because it's parked on one construction site and somebody forgot it was
there," he said.
There are several challenges to corralling radios into a coherent network,
said Visvadoer. The central problem is the nature of the radios -- battery-powered
and mobile. "As people move around the quality of the communications is
going to vary [and] we're talking about very low-power pieces of equipment,"
A network whose nodes vary both in location and power needs a lot of adjusting,
said Visvadoer. "Most networks measure changes in minutes, hours, or days.
We're measuring [them] in hundreds of milliseconds."
The Internet radio islands use the same networking software -- Internet
Protocol (IP) -- that links computers to each other over the Internet.
The software theoretically allows any radio in an Internet radio island
to communicate with any host computer in the world.
The radio frequency network is considerably different even from other
networks that include wireless communications equipment because the entire
radio network is mobile. In a cell phone network, for example, the wireless
phones transmit data packets directly to immobile base stations, said
Visvadoer. "A cellphone [network] communicates with one hop directly to
the handheld platforms. We have to communicate across multiple hops,"
he said. For long-range communications cellphone data packets go to a
base station and then across telephone wires. In contrast, the handheld
radios in the field form a self-contained network.
The key to making the scheme work is two underlying layers of software
-- a link layer and a radio network layer -- that manage and hide from
the Internet Protocol the many adjustments needed to make mobile radios
into a seemingly stable network.
"The link layer finds what radios are in range, measures the quality of
the connectivity with those radios, and it adapts communications as those
links change," said Visvadoer. The link layer automatically adjusts three
variables: power levels, in order to use battery power efficiently and
avoid detection; the route that packets of voice data are traveling as
radios move in and out of range or are turned on or off; and the speed
data travels through the network.
There could be as many as 12,000 adjustments in a five-minute conversation
between two people who are far enough apart that the signals must hop
from the originating radio through two intervening radios before reaching
their target, said Visvadoer. "We're going to send about one voice packet
every 90 milliseconds, so that's about 10 a second and about 600 a minute.
[In] five minutes, that's about 3,000 packets," he said. Each of the four
radios can change the power, data rate or path of every packet, adding
up to the 12,000 potential adjustments. In a typical five-minute conversation,
there are likely to be about 2,000 adjustments, said Visvadoer.
Most of those adjustments are to adapt power; a smaller number are to
change the path the packets take to get from one radio to another. Changing
the data rate -- usually slowing down to boost power when more power is
available and there's no alternative path -- is done least often, said
The radio layer manages the radio frequency environment as a whole, said
Visvadoer. "Who can I see, what radios can I communicate with and how
well can I communicate with them? The radio software provides that information
to the [Internet Protocol] networking software and makes it appear to
the networking software like it's a more stable environment than it really
is. The radio environment forms subnetworks and then connects those subnets
up together based on information that the radio provides them," he said.
The software also manages the transmission frequencies the radios use
in order to avoid congestion, prevent eavesdropping, and maximize power
efficiency. The radios can transmit information over waves ranging from
30 megahertz to 2.5 gigahertz. That range is typically divided up into
local, medium haul and long haul tiers, said Visvadoer. The shortest radio
waves -- 900 megahertz to 2.5 gigahertz -- provide very high data rate
connections between radios less than two kilometers apart. The midrange
300 to 500 megahertz waves allow for larger hops of 9 or 10 kilometers
at lower data rates. The 30 to 50 megahertz range is reserved for long
haul connections of up to 15 kilometers at the lowest data rates.
The researchers are working with two types of military radios and can
make Internet radio islands of either or both types. The smaller model
can support two simultaneous conversations and act as a conduit for four
more. The larger model allows for four conversations and eight additional
In theory, the Internet radio network could link up to 2,000 radios, said
Visvadoer. The difficulty of linking more radios is the network becomes
less efficient as it gets larger. "There's more overhead -- it takes more
resources to keep track of 2,000 radios than it does to keep track of
50. But if you have 2,000 radios they're going to be spread out over a
fairly large area. So the capacity of the network increases dramatically
at the same time," he said.
The researchers have also looked at ways to eventually extend the network
to 10,000 radios, said Visvadoer. "We believe there are ways of building
upon this basic software to get to 10,000 radios," he said.
The concept is interesting, and the researchers have some interesting
ideas for implementation "but the level of wishful thinking is high,"
said Charles Bostian, a professor of electrical and computer engineering
at the Virginia Institute of Technology.
The way the researchers are making radios aware of their neighbors at
the network link level, and the algorithms they're using to form islands
of radios are interesting concepts, he said. It may be difficult to extrapolate
the scheme to 10,000 users, however, he said. If they are able to make
it work, "it would be useful for ad hoc tactical networks," he added.
The researchers are currently testing prototype hardware, and they have
networking software running, said Visvadoer. "We've built the first set
of islands -- it's working," he said. There are preliminary military tests
scheduled for this fall and operational tests scheduled for the end of
the year, said Visvadoer. The radio network scheme could be practical
in two or three years, he said.
Visvadoer's research colleague is Larry Williams of ITT. Williams published
the research in the April, 2001 issue of International Electronic and
Electrical Engineers (IEEE) Spectrum. The research was funded by the Defense
Advanced Research Projects Agency (DARPA) and ITT Industries.
Timeline: 2-3 years
TRN Categories: Internet; Wireless Communications
Story Type: News
Related Elements: Technical paper, "Technology Advances
from Small Unit Operation Simulation Awareness System Development," April,
2001, International Electronic and Electrical Engineers (IEEE) Spectrum.
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