Subject: [NEXTEL-1] Beyond Wi-Fi: A New Wireless Age

From: [email-masked]
Date: Sun, 14 Dec 2003 23:05:48 -0500

Beyond Wi-Fi:  A New Wireless Age
By Catherine Yang in Washington
December 15, 2003

Three technologies will boost the capacity of our airwaves -- and innovation,
too

On the clear morning of June 10, Mark McHenry climbed onto the rooftop of a
seven-floor office building near Washington's busy Dupont Circle. Lugging an
unwieldy 10-foot antenna and a gray metal box, he and another engineer set
up an experiment to measure the actual usage of airwaves above the Nation's
Capital during peak business hours.

They were out to debunk a popular myth: With the explosion of wireless
devices, the air is nearly saturated with zinging TV, radio, cell-phone, and
BlackBerry signals, right? Not to mention satellite and air-traffic-control
signals, police dispatches, and mushrooming Wi-Fi networks. And yet, the duo
found that even in a heavily trafficked part of the airwaves above the
District of Columbia, only 19% to 40% of the spectrum was occupied at any
moment during an eight-hour period.

The experiment highlights a paradox that vexes the wireless industry.
Although nearly all of America's best ready-to-use spectrum is rented out to
tenants ranging from broadcasters to the U.S. military, most of the time,
it's unused -- just vacant space. "It's as though every operator had his own
personal road to go to work instead of sharing the road,'' says McHenry,
president of tech startup Shared Spectrum Co. (See
http://www.sharedspectrum.com/) in McLean, Va. The upshot: Wireless
inventors with a new idea may not get access to the airwaves.

As any of these inventors might tell you, however, momentous changes are in
the air. Digital technologies have already allowed cellular operators to
pack more signals into each band than they could under the old analog
regime. Now, a wave of intelligent network technologies is sweeping from
university and military labs into the marketplace. The innovations are known
by various names, including smart antennas, mesh networks, and agile
radios -- all of them sharing the same basic breakthroughs in digital signal
processing. Together, they appear poised to knock down the lane dividers on
the spectrum highway, which were devised about 75 years ago when federal
regulators concluded that the airwaves were a scarce resource.

Regulators are applauding the liberation of the spectrum -- especially after
witnessing the meteoric rise of Wi-Fi. This wireless networking standard,
and the ubiquitous Internet  "hot spots'' it has spawned, took off in the
U.S. only because there was a swath of airwaves that regulators left open
for unlicensed gadgets such as microwave ovens and garage-door openers.
That's why the FCC is dismantling more fences. In mid-November, it offered
up a new slice of lightly regulated frequency in the 5-gigahertz range. "The
more people who can play in the sandbox, the higher the probability of
technological innovation,'' says Federal Communications Commission Chief
Engineer Edmond Thomas.

DUG-IN RESISTANCE

Broadcasters, cell-phone carriers, and other longtime licensees of spectrum
rights won't give up their exclusive hold without a fight. ``If we have to
pay for spectrum and others can gain access to those very bands for free, it
becomes a parity issue,'' says Brian F. Fontes, vice-president for federal
relations at Cingular Wireless. Still, engineers, inventors, and their
financial backers are sure to keep up pressure on the FCC to use the
airwaves with greater efficiency and imagination. Together, new ideas about
intelligent devices and novel network architectures will open up a wireless
frontier. Here's what the engineers have in mind:

Smart Antennas: When the first AM radio tower went up in 1920 at KDKA in
Pittsburgh, the proud antenna on top beamed out signals 360 degrees around
it. Like a pebble thrown into a pond, it sent energy indiscriminately in
concentric ripples through the air.

What a waste, say many engineers today. If you could throw all that energy
in just the direction of the users you want to reach, the signal could
travel much farther and avoid unnecessarily jamming airwaves in other
directions. With a "smart antenna,'' a narrow beam shoots a greater distance
in the same way that a water hose sprays farther when the gardener puts a
thumb over the nozzle. But that doesn't capture the intelligence of these
systems. Wireless consultant Nitin Shah prefers the analogy of a spotlight
following individual actors on a stage, as opposed to a room light that
illuminates everyone.

There are many approaches to such antennas under study at universities and
corporate labs -- including a commercial product from San Francisco startup
Vivato Inc. (See http://www.vivato.net/) By clustering 128 pencil-size
antennas, Vivato can project signals as far as 2.5 miles. They achieve this
by squishing a tiny bit of energy -- roughly 100 milliwatts, or half the
power of a cell phone -- into narrow seven-to-eight-degree beams. Each
antenna, starting at a different moment, sends out its own signals on
regular radio waves. When the waves of one start waning, those of another
might be cresting. Taken together, these waves can form rays specially
shaped to reach a particular target. With the help of software, the antennas
can change the shape and direction of these rays at a moment's notice when
targets move. In this way, Vivato expects to extend the range of Wi-Fi,
currently limited to about 300 feet. "Smart antennas are the future of
spectrum sharing for wireless,'' says Greg Raleigh, CEO of Airgo Networks
Inc.(See http://www.airgonetworks.com/)
in Palo Alto, Calif., which makes a more complex extension of this
technology. ``Ten years from now, they'll be in every wireless device.''

Mesh Networks: Just as smart antennas free up more airwaves than traditional
towers, a new routing technology makes even today's most efficient digital
networks look like spectrum hogs. With cell-phone systems today, for
example, users must be within the range of a cell tower, also known as a
base station, to get a link. The cell tower is the central hub connecting
the phones around it.

With so-called mesh networks, one transmitter can get a connection from the
antenna next to it, even if neither is in the range of the hub. All that's
required is a connection between users, circuitous or not, that leads to a
hub -- which may be an Internet access point or a cell tower. To explain
this idea, engineers often invoke the analogy of a crowded cocktail party.
Instead of shouting across the room to tell your spouse it's time to go
home, thus drowning everyone else out, the guests transmit the message
person by person in whispers across the room.

In the case of mesh networks, each device -- whether it's a laptop computer,
as in most prototypes today, or a futuristic cell phone -- becomes the
equivalent of a base station or network hub. As soon as one of the devices
is switched on, it puts out a signal announcing its presence and searches
for signals from others. Once the newcomer finds a group of networked
devices, it knocks on the door, and the others welcome it to the group.
True, wired Internet switches achieve the same effect. But the challenges
multiply in the wireless world, where changing topography is ever a threat.
If a building goes up across your street, a mesh network would spot the
obstruction and route itself around it.

Various companies have experimented with ad hoc networks like these -- so
far, without much commercial success. For one thing, the demands of a mesh
network can drain everyone's batteries. Even if your laptop doesn't want to
communicate across the network at the moment, it ends up being used as a
hopping station for other people's messages. Despite that, Nokia, Microsoft,
Intel, and others hope to use the technology to extend the range of Wi-Fi.
And it's not just commercial ventures that are interested. In San Mateo,
Calif., the Police Dept. is testing a system from a local startup, Tropos
Networks (See http://www.troposnetworks.com/), to connect laptops in police
cars across the downtown area.

Agile Radios: On the blue waters of San Diego Bay, engineers have implemente
d the first phase of an experiment that could lead to the biggest radio
breakthrough of all. Twelve sailors on the USS Coronado, a Navy flagship,
are testing a radio from General Dynamics Corp. that can communicate in 10
different frequency bands. That matters because the military has access to
many swaths of spectrum, but different branches of the Armed Forces use
different radios, which often can't talk to one another. The gizmo on the
Coronado uses software to transmit and receive in multiple frequences, thus
breaking down the barriers. "Think of these radios as a computer with an
antenna,'' says John D. Bard, CEO of Space Coast Communication Systems Inc.
(See http://www.spacecoastcomm.com/ in Melbourne, Fla., which is writing new
radio software.

AN ULTRASMART MACHINE

The military's work in software-defined radio is the prelude to what many
consider the ultimate solution for the wireless future: the agile radio.
This device can hop in and out of empty spaces in the spectrum, operating in
a variety of different bands, in spaces nobody else is using. The Defense
Advanced Research Projects Agency (DARPA) (See http://www.darpa.mil/) is
funding the development of this ultrasmart machine, which would be able to
scan the airwaves and determine the vacant spaces on its own. As other users
pile into these frequencies, the agile radio would see the traffic and
instantly seek out "white space'' in other bands.

It will take at least 10 years to create a workable agile radio, according
to Vanu Bose, CEO of Vanu Inc (See http://www.vanu.com/), which is
developing software-defined radios. For one thing, it must be smart enough
to ensure that the vacant bands are indeed available, and not cause
interference with existing users. "We have to prove we can coexist,'' says
Preston Marshall, DARPA's program manager for the agile radio. But if such a
sensitive radio can be made, researchers say users can harvest up to 10
times more out of the airwaves.

The lure of such bountiful yields has turned federal regulators into
evangelists for these potentially disruptive technologies. At first, the FCC
is likely to move slowly, releasing small blocks of spectrum that are under
lease to the military and others. But once the dam is compromised, there is
no stopping the deluge. On the flood plain, wireless innovators may realize
their wildest dreams -- and citizens will gain access to a new frontier in
the sky.

http://businessweek.com/magazine/content/03_50/b3862098.htm

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