Subject: [NEXTEL-1] How the radio changed its spots

From: [email-masked]
Date: Sat, 13 Dec 2003 13:11:43 -0500

How the radio changed its spots
Dec 4th 2003
From The Economist print edition

Smart radios: Radios capable of switching from one wireless standard to another,
with nothing more than
a dose of new software, are at last emerging from the laboratory

WHEN is a radio not a radio? When it's a computer program. Whether in a mobile
phone, a fireman's walkie-talkie or
a laptop's Wi-Fi card, a radio plucks a raw signal from the air and translates
it into a useful stream of information
(and vice versa). This translation involves several steps, most of which are
normally done by dedicated
signal-processing chips. But given enough processing power, the same job can
also be done using software, rather
than hardware. The result is a “software-defined radio” (SDR), also known as a
“reconfigurable” or “smart” radio.
As these names suggest, such a device can switch from being one kind of radio to
another simply by loading some
new software.

This chameleon-like ability is useful for a number of reasons. A mobile phone
based on smart-radio technology
might, for example, be able to switch between cellular standards used in
different parts of the world. Mobile-phone
base stations could be quickly and easily reconfigured to support new wireless
standards. Smart radios could also
ensure compatibility between the various radio standards used by different
emergency services in a
disaster-recovery situation, or link up soldiers in a multinational force whose
radios might otherwise be
incompatible.

Such flexibility comes at a cost, however. Dedicated signal-processing chips are
designed to do one thing well, and
use much less power than a general-purpose microprocessor. But as
general-purpose chips continue to become
smaller, cheaper and more powerful, the smart-radio approach will become
increasingly practical, even in mobile
devices where power consumption is constrained.

Smart radios will also make more sense as new wireless technologies proliferate,
increasing the number of radio
standards that a single device is expected to support, which in turn increases
the number of dedicated radio chips
required. A wireless-data card for a laptop might have to support various
cellular standards, the Wi-Fi wireless
local-area network standard, and Bluetooth, a short-range technology used to
link computers with mobile phones.
With exotic new standards such as 3.5G, 4G, WiMax and 802.20 on the horizon,
smart radios could provide
flexibility and compatibility. Now, after years in the laboratory, they are
starting to emerge into the market.

Alphabet soup with chips

Next year, for example, Sandbridge Technologies of White Plains, New York, plans
to launch a new smart-radio chip
called Sandblaster. Once the appropriate software has been loaded, this chip can
support a range of wireless
standards, including GSM and CDMA cellular standards, their respective
“third-generation” (3G) standards, W-CDMA
and CDMA2000, plus Wi-Fi, Bluetooth and global-positioning system (GPS)
standards. Sandblaster can even support
more than one of these standards at the same time, such as W-CDMA and Bluetooth,
for example. A single smart
chip can thus replace several dedicated ones.

The trick to doing all this while maintaining low power consumption, says
Guenter Weinberger, the company's boss,
is that Sandblaster is both optimised for signal processing and based on a very
efficient “multi-threaded” design
which allows it to run several interleaving programs, or threads, at once.
Supporting one of the 3G protocols, he
says, requires the chip to run multiple threads. Simpler standards such as GSM
and Bluetooth require just one
thread. The chip throttles back its power consumption when performing less
arduous tasks. The goal, says Mr
Weinberger, is for the chip's power consumption to be comparable to that of
dedicated signal-processing chips.

These are bold claims, but they are being taken seriously. Sandbridge has
heavyweight backers including Siemens
and Infineon Technologies. It demonstrated a prototype chip, acting as a Wi-Fi
radio, at the 3GSM wireless
conference in Cannes earlier this year. Sandblaster chips could be used to make
mobile phones capable of working
on both the CDMA standard, popular in America, South Korea and Japan, and the
GSM standard that is dominant
elsewhere. Mr Weinberger says he can also imagine smartphones for corporate
users that include Wi-Fi capabilities
too.

But smart-radio chips, from Sandbridge and other firms, will initially be used
to build 3G handsets. The 3G standard
being adopted in Europe, W-CDMA, is completely different from existing GSM
technology. So 3G handsets must be
able to switch between two radio standards in order to ensure coverage outside
3G areas. This is currently done
using multiple radio chips. But, notes Mr Weinberger, this “dual mode” design
lends itself to the smart-radio
approach.

Another motivation is that 3G standards are still evolving. “W-CDMA is changing
every year, but it takes two years
to implement on a chip,” says Mr Weinberger. A handset based on a smart radio,
however, just needs a software
upgrade, which can be devised quickly and then delivered to the handset over the
air. This approach appeals to
network operators, because it is far cheaper than recalling hundreds of
thousands of handsets when an upgrade is
needed.

Another school of thought, however, claims that the greatest opportunity for
smart
radios lies in cellular base stations, rather than in handsets. Al Margulies of
the SDR
Forum, an industry body that is dedicated to the development and deployment of
software-based radio technology, says that size and power constraints mean that
the
technology will appear in radio infrastructure first, and handsets later. But
the benefit is
the same: flexibility. As wireless standards evolve, “you don't want to do
fork-lift
upgrades every two years,” he says.

PicoChip, based in Bath, England, is one of several companies building wireless
base
stations using smart-radio technology. It has built a 3G/W-CDMA base station
based on
its specially designed smart-radio chip, the PC102, and appropriate software.
The
high-speed upgrade to W-CDMA, called HSDPA, can be added as a software upgrade,
and the company is working
on new software to support additional protocols such as CDMA2000, 802.16 (a
fixed-wireless protocol) and
TD-SCDMA (yet another 3G technology expected to be adopted in China).

Building base stations on a flexible, software-based foundation means there is
no need to send engineers out to
install upgrades when new protocols emerge or existing ones are updated.
“Operators are worried about
interoperability, bug fixes, obsolescence, new features, so they want software
upgrades in the base station so
that their investment will live as long as possible,” says Rupert Baines of
picoChip. In future, he suggests,
operators might even choose to reconfigure base stations dynamically in response
to usage patterns so that, for
example, they offer more data capacity at some times of day, and more voice
capacity at others.

“The wonderful thing about the software approach is that it frees you from the
tyranny of the standards cycle,”
says Vanu Bose of Vanu, a smart-radio spin-out from the Massachusetts Institute
of Technology. His firm's
software-based GSM base station runs on industry standard Hewlett-Packard
servers. The software-based
approach has particular appeal in America, he suggests, where multiple wireless
standards co-exist and overlap.
Several operators use three different standards—AMPS, TDMA and GSM—within their
networks. With a software
base station, they could reallocate channels between these standards
automatically depending on demand, says Dr
Bose.

Software-defined base stations might also be more reliable, suggests Joseph
Mitola, a pioneering smart-radio
researcher at the Mitre Corporation, a non-profit research organisation, who is
currently working with America's
Defence Department. Conventional base stations, he points out, have hundreds of
coaxial cables connecting the
bits of various signal-processing circuitry. Replacing all this circuitry with a
powerful computer, and doing the
processing in software instead, means there are fewer things to go wrong as the
circuitry heats up and cools
down, and fewer cables for rats to chew.

Smart radio on the march

As with many technologies, however, smart radio will make its first widespread
appearance in the military arena,
says Mr Margulies. Military users are less sensitive to price, weight and power
constraints. In America, the first
radios based on smart-radio technology are about to be delivered as part of the
Joint Tactical Radio System
(JTRS). A software-based approach, says Mr Margulies, will enable new radios to
communicate with existing radios,
but will also allow future upgrades, both to improve security and ensure
interoperability between emergency
services and the various branches of the armed forces. “These new radios will
allow the army, navy and air force
to talk,” he says. In addition, JTRS is expected to reduce maintenance costs by
replacing multiple incompatible
radios, all of which require different spare parts, with a single radio. Work is
under way to make JTRS compatible
with the military radios used by Britain and other countries, for use in
multinational operations.

Interoperability is also a cause of concern in the field of public safety. “In
the United States it is not uncommon for
city police to be unable to communicate with the fire department, the county
police, or federal organisations,”
says Mr Margulies. At the moment, the usual approach is to standardise on a
single radio channel. But this limits
capacity and interferes with the chain of command. In the wake of the terrorist
attacks of 2001, radio
interoperability has been identified as a key priority by the Department of
Homeland Security. But issuing new
radios would be prohibitively expensive. A smart radio, however, can switch from
one network to another.

Vanu has developed just such a radio, based on an iPaq handheld computer.
Clicking on different icons on its
screen reconfigures the radio's software, so that it can switch between
different emergency bands. Cleverer still,
however, is the radio-bridging technology the company is developing under a
military contract. A cluster of smart
radios is configured to transmit and receive on different emergency bands, and
an icon-based control system
allows a controller to decide who can communicate with whom. If the police need
to talk to the National Guard, for
example, says Dr Bose, “the system listens to traffic on both networks, and
patches them together.”

Taking this several steps further, the ultimate smart radio, says Dr Mitola,
would be aware of its surroundings, be
able to adapt itself in response and learn from experience—a concept he has
dubbed “cognitive radio”. Such a
radio might take into account its location, the local spectrum policy, the
weather and the amount of battery power
left, and then agree a suitable protocol with the local network infrastructure.
“The handset talks to the
infrastructure and says ‘I want to do a video call, and I have this much battery
left',” says Dr Bose. “And the
infrastructure says ‘This is the spectrum available, use this standard, here is
the software'. The standard is
dynamic.”

This is a far cry from the current state of affairs, where standards take years
to hammer out. Ultimately, smart
radios could do away with the standards wars that bedevil the wireless industry
and so irritate users. The
technology would promote innovation by allowing all kinds of new standards to
flourish, while concealing the
underlying complexity from users who are currently mired in an alphabet soup of
incompatible standards. Now that
really would be smart.
http://www.economist.com/science/tq/displayStory.cfm?story_id=2246155

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