IT CAN create undetectable, unjammable communications systems; cheap, portable radar that can see though walls; it could even help park your car. And, fingers crossed, it will create a lightning-quick wireless superhighway powerful enough to beam music, video and even high-definition television pictures around your home.
This might sound like the prospectus of an over-eager tech start-up. But for Gerald Ross, a 73-year-old engineer living in semi-retirement in rural Massachusetts, the applications are old and familiar friends. Most emerged from the seminal paper he wrote in 1978, and all derive from a simple yet novel idea: why squeeze radio signals into narrow bands when smearing them across the spectrum can give them incredible properties. Back then, the concept was called time-domain electromagnetics. Nowadays it is known as ultra-wideband (UWB).
More than 25 years after his paper was published, the first commercial UWB devices are about to appear in the home. So why the wait? “Lawyers and politicians,” Ross sighs. “That’s what slows it all down.”
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This technology has indeed stirred up a hornet’s nest of controversy. Just as its potential for high-speed home networks and radar for all has excited consumers and electronics manufacturers alike, UWB has left many others angry and deeply worried, particularly among the military, telecommunications regulators, the airline industry and mobile phone companies. UWB advocates say they are right to be concerned: a UWB revolution could render their investments in technology and radio spectrum redundant. Others are more concerned with the violence of the revolution. Without careful checks, they say, Ross’s radio of the future could break the radio of the present, long before it is able to replace it. The result could be anarchy on the airwaves.
Ross grew up in the golden age of radio. At 15, and as one of the youngest radio amateurs in the US, he got a job as a radio operator at the broadcaster CBS. In his twenties, he worked for Sperry Gyroscope, one of the companies at the heart of the US military-industrial complex, where he soon got a reputation as an all-purpose fixer.
When Sperry had a problem with hairdryers made by its subsidiary, Remington, it was Ross they turned to. He came up with a simple solution, and the hairdryers were back in production within six weeks. “They didn’t always understand what I was doing,” he says, in a Brooklyn accent undiminished after 40 years of living in Massachusetts, “they just knew that what I did worked.” And when, in 1964, Ross convinced his managers that he had a new approach to radio transmission – one ripe with possibilities – they gave him a team of 16 engineers and set him to work.
Ross’s idea came from his experiences with radar. The signals beamed out by early radar transmitters were sine waves modulated at specific frequencies and emitted in short bursts. What, Ross wondered, would happen if they sent out an extremely short pulse, a simple on-off lasting less than a nanosecond.
Normally a short blip would be drowned out in the buzz of the airwaves. But Ross’s radar receiver would know when the pulse was sent and roughly when it would return. Rather than filter by frequency, he filtered the radar return by time, eliminating other irrelevant signals. Any small variation in the time the pulse took to return would give the distance to the target.
With this new approach, which was less concerned with frequency and more with timing, he and his team found they could design better radars. This was a topic of some interest to the US military, Sperry’s biggest customer, and for 15 years Ross’s pioneering work was hushed up.
By 1978 the secret was out. Over the next decade, others caught up with, and overtook, the military’s research, developing all kinds of new detectors based on Ross’s idea. But now attention was starting to shift towards an entirely different use for the technology.
Short radio pulses have one very important characteristic. Fourier analysis reveals that a short pulse of radio waves is equivalent to a thin smear of electromagnetic energy across a large band of frequencies. The narrower the pulse, the wider the smear: for example, a pulse a nanosecond long has a bandwidth of 1 gigahertz while a pulse half a nanosecond long has twice the bandwidth: about 2 gigahertz. And the greater the bandwidth of a signal, the higher its information-carrying capacity.
In theory, a UWB signal could carry gigabits of data per second, over 50 times faster than Wi-Fi, today’s wireless technology. This makes it perfect for beaming high-quality video or music from set-top boxes or DVD players. Since the signals are weak – just a few watts – UWB wouldn’t work over a distance of more than 50 metres or so, but it would be just the thing for creating high-speed personal area networks. No wonder Ross and his team were one group among many eager to take UWB out of the realm of the spooks and into the wider market.
Right, as it turned out, into a regulatory brick wall. In 1992 Ross went to meet with the US radio-frequency regulators, the Federal Communications Commission. The idea he described, and the opportunities it offered, he felt, were unprecedented. “But they took one look, and told me I was operating a spark-gap generator,” recalls Ross.
Ross’s technology was not unprecedented. In fact it had the worst precedent of all. Banning spark-gap generators had been one of the first acts of the FCC’s predecessor, the Federal Radio Commission, in 1928. Spark-gaps were the devil the FCC was created to beat.
Spark-gap radios were common early in the 20th century and easy to construct. No tuning of the receivers was necessary: the spark from a transmitter generated a radio signal right across the spectrum. That was fine, until two stations needed to broadcast at the same time. The only solution was regulation. International committees agreed to standardise on continuous-wave transceivers which could be restricted to one part of the frequency spectrum. That meant banning spark-gap.
Certainly any interference would be bad news. But by 1995, Ross and the US military had been testing UWB for communications and radar for over a decade, yet the tests had passed unnoticed, even during experiments close to sensitive receivers. “I’d been working at Logan International airport in Boston using UWB for surface-traffic control for months. ‘If we hear you, we’ll make you stop,’ they said,” Ross recalls. “They never heard a thing.”
Ross’s radio transmissions were low power, and that power was smeared across a broad swathe of the spectrum. A traditional receiver would only pick up a fraction of this signal – so little that it would be drowned out by the natural radio background. In other words, Ross says, the signal was no noisier than one of Remington’s hairdryers.
In 1998, after pressure from the UWB proto-industry, as well as more established companies such as Intel and IBM, the FCC finally relented. In preparation for licensing the technology, it tentatively put out a call for comments.
All hell broke loose. Over 900 claims and counter-claims by dozens of companies and individuals were submitted for and against UWB. Prominent objectors included mobile telephone providers who had spent millions to purchase their segment of the spectrum. Others, such as manufacturers of GPS satellite navigation systems, feared that an explosion in the UWB market risked swamping the signals their devices rely on. “We’ve got nothing against UWB,” says Michael Swiek, executive director of the US GPS Industry Council, “but the hairdryer line is a red herring. Hairdryers are not connected to an antenna. Hairdryers are not networked.”
Military tests were one thing – but having millions of these devices running could be another case entirely. What if all the noise added up, raising the background levels? Satellite signals like GPS can barely make themselves heard above natural interference as it is. Airline navigation instruments and radio astronomers could similarly suffer.
Under the microscope
Over the next five years UWB underwent an assault course of tests, with results that pleased neither side. Researchers at Stanford University’s GPS lab in California showed that prototype UWB devices could interfere with GPS signals, causing receivers to lose their lock on satellites. Other tests by the FCC, and by NASA and United Airlines on Boeing aircraft, showed that UWB devices jammed collision-avoidance systems and impaired instrument landing systems. Yet UWB manufacturers, working with GPS companies, claimed to be unable to show any interference when using their particular transmission systems. No one could agree conditions under which UWB could operate without creating interference.
Finally, in February 2002 the FCC compromised. It approved UWB transmissions, but rejected designs based on Ross’s original concept of a short pulse covering the whole spectrum. UWB was restricted to a broad, but finite, set of frequency bands between 3.1 and 10.6 gigahertz, with tough power restrictions for transmission in regions used by GPS and other sensitive applications (see Diagram).
These strict limits cost the UWB industry the simplicity of their designs. “It’s not as straightforward anymore,” says Robert Aiello, CEO of Staccato Communications, based in San Diego. His previous UWB company ran out of money waiting for the FCC to reach a decision.
Dewayne Hendricks, member of the FCC’s Technological Advisory Council and long-time advocate of change at the FCC, is more brutal. “UWB is essentially crippled. With the current rules, you can’t do more than a personal area network.” We must return to the original UWB approach, he says, which is what the military were using all along. Unfortunately this would entail a complete rethink of the way the FCC defines radio interference, and that would require a unprecedented degree of cooperation between radio spectrum users. After years of acrimony between incumbent radio users and UWB upstarts, a sudden show of teamwork would seem unlikely. What happened next seems to confirm this. Having finally agreed a ceasefire with their critics, UWB supporters began to brawl among themselves.
High-speed wireless networks, the hottest commercial application of UWB, are currently trapped in a battle between two different industry standards: one is promoted by Motorola, the other by a consortium of companies, including Staccato Communications, and Intel. Both systems are complex hybrids of Ross’s original design mixed with modern frequency-domain technology. They are also incompatible, and amid angry scenes at meetings of the US Institute of Electrical and Electronics Engineers (IEEE) personal area network committee late last year, neither group mustered enough votes to proclaim victory. Each side accused the other’s technology of creating interference, and of being too expensive. Now the two groups are in a race to market in order to establish dominance.
Arguments and instability look set to continue for some years yet. And that’s just personal area network technology. What about all the other applications that Ross originally proposed, like personal radar and intrusion detectors? Mostly restricted to the security, mining and emergency services, wider commercial exploitation is still strictly limited due to worries over interference.
Yet Hendricks and Aiello say that UWB, in its original, revolutionary form, still stands a chance. “Perhaps the best thing to do would be to develop it in another country,” says Aiello, “to show that UWB can be used without interference.”
It’s an intriguing idea. But while the FCC seems to have moved at a glacial pace, its counterparts in other countries have been even more cautious. No decision has been made in the European Union or Japan, and it is unlikely that devices permitted in the US will be legal in those countries when they reach the market later this year.
Going oversees
So could someone else steal a march, and attract UWB development from its home in the US? Last month Singapore announced it was establishing experimental “UWB-friendly zones” in its science parks. And two academic lawyers, Christopher Guzelian and John C. Miller from Stanford University in California, recently suggested that the Native American tribal homelands could exercise their sovereign independence from the FCC and take the provocative step of implementing their own wireless infrastructure using UWB.
Even Ross, in semi-retirement, can’t escape the controversy. He is still involved in UWB, and has designed and implemented a pulse-based intrusion-detection system called QUPID for use around sites vulnerable to terrorist attack, such as air bases and power stations. The FCC is still in the process of considering whether to license it. QUPID is already employed by the US air force, yet among those appealing against the licence are some in the US military, Ross’s original customer. Also in the fight is the GPS industry – whose band is covered by QUPID’s signal, and the IEEE’s own radio-regulation group, who describe the licensing requirements of QUPID as “grossly excessive”.
But Ross is, at last, happy to wait. Despite the controversies, he won the IEEE Pioneer award this year. He is also spending a lot of time at the golf course. He designed a solar-powered signalling system for his local green that warns golfers when people are on the next tee. It has now been adopted at courses across the US. This is one signalling system lawyers and politicians seem happy to use.
Why wideband?
Just as with conventional radar, ultra-wideband radar works by detecting radio pulses reflected from objects. The delay between the emitted and reflected pulse gives the distance. However, since the pulse from UWB radar lasts about one-thousandth of the time of a pulse from conventional radar, it is far more accurate, and works well even when the target is at close range.
UWB has other advantages too. A UWB pulse is approximately 30 centimetres long, rather than tens or hundreds of metres for conventional radar. Since this is far less than the size of a typical target – an aircraft or tank, for example – it is possible to extract information about the shape of the target from the shape of the reflected pulse. And, thanks to digital circuits, it is much simpler to create short pulses for UWB radar than the complex, modulated signals of conventional radar.
The future of ultra-wideband
Ultra-wideband’s first mission in the home will be to destroy all cabling. A group of companies, headed by Intel, is intent on developing a wireless alternative to the USB connection built into virtually all modern computers and aim to commercialise it later this year. Wireless USB will move data at up to 480 megabits per second but since the signals are weak, it will only cover distances of a few metres. It will replace the cables that connect cameras, memory cards, hard drives and printers to a PC, and should be easy to install.
More ambitiously, Intel says it is also working on linking computers, monitors and TVs so that the computer itself can be removed from a crowded desktop and hidden away in a cupboard instead. In future, Intel promises, we will send high-definition TV signals around the house on UWB and every television will have a UWB chip built in. And portable MP3 players could stream high-quality audio to surround-sound speakers anywhere in a room. Right now however, there is more hype than prototype: maintaining data-transmission speeds, extending transmission distance, and keeping to FCC regulations are all proving tricky.
The short pulses that make UWB radar so accurate can also create a positioning system accurate to centimetres – perhaps why the GPS industry is so worried. The technology is throwing up a few more exotic applications too. UWB has been touted as a replacement for X-rays for breast cancer scans, a warning system for sudden infant death syndrome that detects the movement of air in babies’ lungs, and even as a system for turning on the fan in a toilet cubicle. Not surprisingly, the FCC has denied permission for this last idea.
