IP: UWB once held so much promise, but now seers are predicting a slide downward

[David Farber <dave () farber net>]

> From: Dewayne Hendricks <dewayne () warpspeed com>
> To: "Dewayne-Net Technology List" <dewayne-net () warpspeed com>
>
> [Note:  This comes from a reader who doesn't wish attribution.  My thanks 
> to my reader for sending this along.  I know the reporter who wrote this 
> article and I haven't spoken to him in over six months. The remarks that 
> he attributes to me are not accurate.  Also, what he's said about our 
> operations in Tonga is not true.  That being said, I continue to be 
> disturbed by how the media persists in giving UWB seemingly 'magic' 
> properties.  Spread spectrum technology has always been mishandled by the 
> media, but they really have gone overboard with their coverage of UWB 
> technology.  I just spent a week in Washington and I did some snooping 
> around to find out where the UWB rulemaking stands.  Chairman Powell has 
> told Congress that he was going to get a R&O out this year on UWB.  At the 
> moment, I'm inclined to doubt that this will happen.  The opposition to 
> UWB continues in earnest.  I think that the Commission is going to punt 
> this one into next year.  DLH]
>
> > To: Dewayne Hendricks <dewayne () warpspeed com>
> > Subject: UWB
> > Date: Mon, 12 Nov 2001 19:03:05 -0800
> > MIME-Version: 1.0
> >
> > Dewyane:
> > You're quoted.  I might have missed this.  No
> > attributes, please.
> >
> > ~~~~~~~~~~~~~
> > UWB once held so much promise, but now seers are predicting a slide downward
> >
> > November 1, 2001  By: Dan Sweeney  America's Network
> >
> > <http://www.americasnetwork.com/americasnetwork/article/articleDetail.jsp?id=812>
> >
> > The prophets of ultrawideband wireless always felt that they commanded a 
> > truly disruptive technology, to use the currently fashionable Silicon 
> > Valley jive. As an unlicensed alternative to conventional wireless 
> > technologies, UWB held out the promise of high throughput, low cost and 
> > immunity to interference - and initial proselytizing a year or two ago 
> > elevated UWB to the status of technology of the moment.
> >
> > Events in the technology world in the intervening months have lent an 
> > ironic cast to the disruptive accolade, however. For rather than 
> > presaging disruptions of an invigorating and ultimately benign sort, UWB 
> > now appears just as likely to fulfill the negative implications of the 
> > term. Particularly damning are the results of a recent series of tests 
> > sponsored by the FCC. The tests, which were conducted by the National 
> > Telecommunications and Information Administration, suggest that UWB 
> > transmissions at the power levels required in public metropolitan area 
> > networks have the potential for generating serious interference in the 
> > bands used by vital safety services such as navigational radar and GPS.
> >
> > Adversaries charge (and even some proponents admit) that UWB also has the 
> > potential of interfering with all manner of existing radio services 
> > including mobile telephone service, broadcast radio and television, GPS 
> > military and civilian aviation transmissions, to name just a few.
> >
> > UWB, so full of promise in the last year of the old millennium, is now 
> > fast approaching a crisis that will determine if it remains confined to 
> > the laboratory, or, at best to a few clandestine military applications, 
> > or whether it enters the mainstream of commercial and consumer 
> > communications. According to Chairman Powell, the FCC may complete the 
> > rules governing the use of UWB before the end of current calendar year.
> >
> > The FCC's preliminary remarks suggest that UWB might be restricted to 
> > operating above 3 GHz, which is beyond the bands where most radios 
> > operate. Such a solution, coupled with probable power restrictions, could 
> > preclude UWB's use in public networks.
> >
> > The NTIA testing will play a key role in the FCC's decision, and not 
> > surprisingly, the interpretation of the test results is currently subject 
> > to fierce controversy.
> >
> > Tried and found wanting?
> >
> > "We don't see a problem," says Eileen Heaton, a spokeswoman for UWB 
> > developer Time Domain, Inc. "We're very happy with the test results. They 
> > confirm what we've always maintained."
> >
> > "The tests only show problems at less than three meters, and that's true 
> > of any white noise source," adds Michal Freedhoff, director of regulatory 
> > policy for the same firm. We feel that we've been vindicated."
> >
> > The Joint Spectrum Center for the Department of Defense indicates in its 
> > analysis of the tests that a pulsed UWB signal is probably less 
> > troublesome than Gaussian white noise. Bob Fontana, president of rival 
> > Multispectral Solutions, takes issue with Time Domain's sanguine 
> > interpretation, however. "What do you expect Time Domain to say?" he 
> > says. "They've got to tell their investors something cheerful. I would 
> > say the findings are very adverse for them, but I don't believe that's 
> > true for everyone making ultrawideband equipment. What I think is that 
> > the tests pretty much rule out anyone making equipment operating below 3 
> > GHz. I also think that they will result in rules that are unfavorable to 
> > outdoor systems in general."
> >
> > John Santhoff, chief technical officer of Pulse-LINK, another key 
> > developer, rejects either position. "We believe that an ultrawideband 
> > system can be operated below 3 GHz if the appropriate modulation scheme 
> > is used. If it's not, the interference problems cited in the tests might 
> > well occur. We think ultrawideband technology is actually very well 
> > suited to metropolitan wireless public networks, but I don't see it 
> > happening in the US in the near term. We're concentrating on sales 
> > abroad, and we already have a number of carriers trialing our equipment."
> >
> > Andy Schneck, vice president of finance, administration, and strategic 
> > planning for UWB developer XtremeSpectrum, generally concurs. "We've shot 
> > holes in the NTIA analysis, but we're concentrating on local area 
> > networks, anyway. We think that companies attempting to sell wide area 
> > equipment will need an FCC exemption, and that will be very difficult to 
> > obtain."
> >
> > The real world
> >
> > Actual ultrawideband implementations are almost nonexistent so far. 
> > "We've never been presented with a single radio for evaluation," says one 
> > FCC source.
> >
> > DeWayne Hendricks, founder of the Dandin Group, a system integrator and 
> > r.f. research firm with a specialization in the areas of UWB and 
> > software-defined radio, was involved in an ambitious project to design an 
> > entire communications infrastructure based upon UWB in the Kingdom of 
> > Tonga in the South Pacific. But for undisclosed reasons the construction 
> > of that network has been abandoned, at least for the time being.
> >
> > Hendricks feels that UWB has been done in by ideologues - and his remarks 
> > on the subject come close to suggesting a conspiracy theory. He argues 
> > that large and powerful segments of the communications industry have 
> > never been disposed to give the technology a fair hearing, and that their 
> > lobbying efforts have dissuaded the FCC from permitting the technology to 
> > be deployed.
> >
> > Certainly those who have paid for spectrum are unlikely to welcome a 
> > technology that would enable other players to deploy competitive networks 
> > without the expense of obtaining licenses. "If you paid for spectrum, 
> > would you want it made available to someone who didn't?" asks Craig 
> > Matthias a principal in the FarPoint Group.
> >
> > But others tell a different story. "I think the FCC has bent over 
> > backwards to give ultrawideband a chance," says Fontana.
> >
> > An unnamed source at the FCC agreed, and predicted that the agency would 
> > eventually rule in favor of limited use of the technology in broadband 
> > communications, most likely within local or personal area networks.
> >
> > Such a resolution would fall considerably short of the place envisioned 
> > for the new technology by the firms that pioneered it, and might 
> > discourage fresh investments in the further development of UWB, 
> > investments that are crucially needed if the technique is ever to go 
> > beyond proof of concept.
> >
> > "What I see is ultrawideband being restricted to very short ranges, and 
> > when you consider the prior acceptance of wireless technology for 
> > personal area networking, that's not encouraging," says Matthias, one of 
> > the few industry analysts who tracks UWB. "Look at IR data and Bluetooth. 
> > I just don't see the need for an additional indoor wireless standard 
> > beyond 802.11."
> >
> > Considering that the 802.11 standard has hundreds of corporate users and 
> > is beginning to achieve economies of scale, UWB would face a tremendous 
> > uphill struggle if it were to try to compete against it.
> >
> > While Matthias does not appear to share Hendricks' belief that the dark 
> > forces of entrenched economic interests are solidly arrayed against a 
> > handful of beneficent entrepreneurs, he does see regulatory constraints 
> > forcing UWB into a role where it cannot realize its potential. "I see 
> > ultrawideband as a replacement technology, one that obsolesces most 
> > conventional radio transmissions. If the world went over to 
> > ultrawideband, I think we'd see tremendous increases in spectral 
> > efficiency." But he adds, "It's not in the offing."
> >
> > =
> >
> > Interference issues
> >
> > "Ultrawideband" can be defined as a type of transmission consisting of 
> > sequential, very short duration noise bursts lacking a carrier frequency 
> > and occupying a band of spectrum that may exceed 1 GHz.
> >
> > Various terms have been coined for this type of transmission - 
> > carrierless, baseband, non-sinusoidal, impulsive. But all such terms 
> > refer to the same core propagation technique - one which, as it happens, 
> > really is as revolutionary as its champions maintain.
> >
> > Ultrawideband is unlike virtually every other form of radio 
> > communications that exists today in that it does not use a carrier or 
> > pilot signal.
> >
> > Typically, with carrier-based transmissions, the actual message, whether 
> > it be audio, video or raw bits, is impressed upon a carrier signal that 
> > is much higher in frequency and takes the form of a repetitive sine wave. 
> > Transmissions over carriers offer far greater range and efficiency than 
> > ones where only a message signal is conveyed. They also permit several 
> > messages to be transmitted simultaneously because the carriers themselves 
> > reside in different parts of the spectrum.
> >
> > Ultrawideband turns this whole technology on its head. Instead of using a 
> > carrier, the signal consists of intermittent pulses which themselves 
> > constitute a continuous sequence of frequencies, in some cases, extending 
> > from a few Hertz up to several gigaHertz. Each pulse has the 
> > characteristics of electrical noise, and no information at all is 
> > contained within the envelope of the individual pulse.
> >
> > Instead, information is coded in the timing of the pulses. Typically 
> > pulses are offset slightly from a standard clock rate, and the deviations 
> > establish a code which serves both to identify the source of the 
> > transmission and the message it contains. In this sense UWB is a pure 
> > digital radio technique.
> >
> > Because the UWB pulses are actually noise, they emit energy that 
> > interferes with every channelized radio service in the region of the 
> > spectrum occupied by the pulse, which may be several gigaHertz.
> >
> > The interference may be benign, that is, the energy levels at the 
> > frequencies to which any given "victim receiver" is sensitive may be too 
> > low to cause a loss of information. Such benign interference may look 
> > like nothing more than a slight rise in the level of background 
> > electrical noise.
> >
> > One of the more discouraging aspects of UWB, however, is that the faster 
> > the data rate of the UWB transmission, the greater the potential for 
> > interference. The way to send data faster via a pulse train is obvious:
> > send more pulses within a given time span. But to do that one must reduce 
> > the duration of the pulses themselves, and therein lies the rub.
> >
> > By shortening a pulse, one increases its bandwidth. The explanation of 
> > how this occurs is beyond the scope of this article. The important result 
> > to note, though, is that, as frequency range increases, so does the 
> > potential for interference as the pulsed signal overlaps more and more 
> > licensed bands. A high pulse repetition rate also results in a high 
> > peak-to-average power ratio.
> >
> > Here, an FCC informant provides a rather disturbing analysis. "We're 
> > thinking that average powers of billionths of a watt are all that are 
> > going to be permitted for these services [UWB]. We just don't think 
> > they're safe to operate at higher levels."
> >
> > No one in the UWB community disputes that UWB transmissions must be low 
> > in average radiated power, though many would take issue with the 
> > billionths of a watt figure.
> >
> > But most argue that power level within a given licensed band is really 
> > what matters, and that UWB is no worse than existing unlicensed radio 
> > transmissions in that regard. Many cite a published analysis of test 
> > results by John Hopkins commissioned by Time Domain in support of that theory.
> >
> > Unfortunately, another problem presents itself, one cited in an FCC 
> > notice of proposed rule making, and that has to do with the interaction 
> > of the pulse repetition frequency with the front end of a victim 
> > receiver, which can result in massive interference.
> >
> > "This rules out a lot of systems," says John Santhoff, chief technical 
> > officer of UWB developer Pulse-LINK.
> >
> > A final caveat and an ironic one is provided by Multispectral Solutions. 
> > A white paper published on that company's Web site states that UWB 
> > receivers themselves might be the most vulnerable to interference simply 
> > because they are sensitive to such a broad range of frequencies.


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