Beyond Wi-Fi: A New Wireless Age

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 US 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. 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 US
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. 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. in Palo Alto, California, 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.

Mesh Networks: A Polite Whisper

Cell phone calls today hog bandwidth–like two people shouting across a crowd. Mesh networks, in contrast, resemble a group of people carefully passing a message, person by person, across a room. Each user’s device–laptop or handset– serves as a base station, passing signals on to other users, who pass them to others. All that’s required is that a few of the users have a connection to a network gateway.

Agile Radios: On the blue waters of San Diego Bay, engineers have
implemented 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 frequencies, 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. in Melbourne, Fla.,
which is writing new radio software.

An Ultra-smart 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) is funding the development of this ultra-smart
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, 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.

By Catherine Yang in Washington
in BusinessWeek. Copyright 2004 by The McGraw-Hill Companies, Inc