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Vinge wrote about localizers in the very good A Deepness in the Sky after talking to the people at Ather Wire and Location.

I went to a presentation by the principals of Aether Wire about eight years ago, at that point they had working localizers that were about the size of a stack of two or three quarters. These devices use Ultra-Wide-Band signalling for extremely low-power low-probability-of-intercept communication. The UWB pulse-trains they were using were remarkably able to penetrate thin metal walls (e.g. a refrigerator.)

UWB technology has a long and sordid history of patent fights, and fights with the FCC over how much interference it would cause. For the conspiracy theorists out there, some suspect that the gov't would like to squash UWB because it's so easy to build almost undetectable (not just undecipherable) radios.

thad

Another group that's doing research in this space is Aether Wire & Location. They're building localizer frobs with the objective of getting down to coin size, and doing lots of work on Ultrawideband networking technology, which is good at very-low-power connectivity.

The firm has applied for an array of patents to cover its wired UWB technology and apparently is the only company to use this approach

I've noticed a disturbing feeding frenzy for UWB patent applications similar to the internet business models. Somehow I can't believe that feeding the UWB signal down a cable TV transmission line instead of an antenna is a non-obvious patentable idea.

Here's a current list of some of the patents around UWB. Notice that only a few groups hold almost all of the cards:
http://www.aetherwire.com/CDROM/General/titles.htm l

There's a few papers and other interesting bits on UWB and localizer technology at the AEther Wire & Location, Inc. Homepage

Two companies that have been pioneers in UWB are Pulson and Aetherwire.

Pulson (and its predecessor company, Time Domain) has been desparately trying to commercialize this technology for radio communication for years. More than five years ago they demonstrated a few-milliwatt UWB radio with 100-mile range. They have mostly been held back by patents taken out by Lawrence Livermore. Livermore claims to have invented all of this stuff, and has been rediculously rough on licensing. Also, the FCC has been unclear until very recently on how it would license UWB.

Aetherwire has attempting to use UWB technology to build localizers, basically extremely short range, extremely low-power peer-to-peer short-range version of GPS. The localizers would all cooperate at keeping track of where the other ones were within a few hundred meter radius. If you've read A Deepness in the Sky by Vernor Vinge, it's all about localizers.

Now that the FCC has cleared the way, I expect to see tremendous progress in UWB. It's going to revolutionize many fields, from radio to positioning to radar.

thad

Through Google I found the UWBWG, and there's lots of detailed papers at Aetherwire. Interesting reading.

If you wanna check out a sizable collection of .PDF's on the subject of Ultra Wide Band, uwb.org has some links here.

Aether Wire on the other hand was the exact opposite in my experience. Not only was I able to talk to someone, but that someone was one of the head engineers. At the time they were planning on having prototype kits available for testing this summer, but I don't know if that date has changed. Aether Wire is focusing on positioning and tracking applications of UWB, and these products could have many important uses for warehouses, hospitals, emergency services, and the military. That is, if the products ever exist and live up to everyone's claims.

Ultrawideband is not exactly new, I worked on a UWB radar almost 10 years ago. It has promise, but it also has problems that you don't see with traditional carrier based methods- since you are talking about picosecond resolution, communication with a reciever that is moving with respect to your transmitter is hard- in a picosecond, light travels about .3 mm. Virtually any motion can cause your reciever to start looking at the wrong part of the data- since the data is all time-coded.

Many have said that you can't detect UWB, but usually, they are looking at it with a traditional carrier based spectrum analyzer- you can't see it, but it is there. It just looks like additional noise. which looks very similar to spread spectum- which is exactly what UWB is, but you're spreading the spectrum very, very wide- an impulse in the time domain is uniform (all frequencies, equal amplitude) in the frequency domain.

Time domain has been around, and pretty big in the UWB arena for a long time, but most of what they have is vapor- big promises, but they fail to deliver. There are other players in the field, Aetherwire is one of the other biggies of UWB. There has been a huge amount of money poured into UWB, but dreadfully little usable technology.

http://www.aetherwire.com/

It's too bad, too, because I'd like to believe in them! The idea of an undectable, unjammable, milliwatt radio that works over a hundred miles is enticing. Ultra-wideband radars that detect anything is exciting. These things should be possible, but are hard to realize.

There's a company called Aetherwire that was mentioned in /. a few months ago. They've actually got some reasonable working pulse-radio hardware.

Ultrawideband is a form of spread spectrum. The major difference between it and traditional forms of spread spectrum is that it is spread over a band which is wide relative to the center frequency (>25% of center frequency)

For example, Qualcomm's CDMA is spread over 1.25MHz around a center frequency in the 800MHz band while a typical UWB system covers over 1GHz starting at around 500MHz.

Conventional spread spectrum systems use frequency hopping or direct sequence to spread the signal. UWB uses a simple and often forgotten form of spread spectrum called time hopping where short pulses are transmitted at pseudo-random intervals. The reason this modulation is used is simply because FH and DS cannot be practically implemented over such a wide bandwidth.

It's not new. It has been used in jamming resistant radars for at least two decades. What's new is an implementation on a single chip which is potentially cheaper than even conventional carrier-based RF technology at large quantities.

The primary advantage of ultrawideband is its insensitivity to fading. Narrowband transmissions can experience significant attenuation of the signal due to signals travelling through different reflection paths canceling out each other. A wideband signal is virtually immune to this and therefore requires about 20db less power usually taken as a safety margin against fading.

Ultrawideband systems can communicate over significant distances using a lower power spectral density than the electromagnetic noise generated by a typical computer.

The primary limitation to using ultrawideband systems is the wording of part 15 of FCC rules - apparently while your computer is allowed to pollute the spectrum for no good reason it is not allowed to transmit the same power INTENTIONALLY.

The FCC has issued a NOI (Notice Of Inquiry) seeking comments on possible change to these rules. Opposing comments come from the usual suspects: mostly users of the restricted bands such as government agencies.

Links:

Ultrawideband working group
Aetherwire - makers of an ultrawideband gizmo called the locator which is both exciting and very frightening.