Talk:Ultra-wideband

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Call for papers[edit]

Do not post them here. --Adoniscik (talk) 02:44, 5 March 2008 (UTC)

Impulse Radio and UWB[edit]

I notice that there is a redirect from "Impulse radio" to the UWB page. Is there any difference in what the two terms refer to? I do find one mention of "impulse radio" in the article, but it doesn't seem to be explained very well. Mas2265 21:06, 6 July 2006 (UTC)

As I understand it, UWB is usually implemented by impulse radio. --Apoc2400 06:48, 28 July 2006 (UTC)
There are two separate implementations of UWB today: multiband OFDM and impulse radio. The section about advantages is not very NPOV: one example is that the GPS system uses narrowband signalling, but is still used for positioning.Mossig 09:35, 29 October 2006 (UTC)
Good point. I'll try to put some qualifiers in there.Qz27 09:28, 31 October 2006 (UTC)

Ultra-wide band refers to the spectrum used, independent of signalling, modulation, codeing, etc. "Impulse Radio" refers to a signalling technique where symbols are constructed with pulses of very short duration with occupied bandwidth inversly proportional to pulse duration (shorter=more bandwidth : under 2ns for a 500MHz bandwidth) There have been quite a few implementations of UWB systems in the last 10 years. Early work was focused on pulse based systems.

The FCC Report and Final Order on UWB issued in 2002 gave a more general definition for UWB, leading to alternatives exploiting multiple bands and more modulation techniques. Ultimately a multi-band OFDM technique became the basis for the WiMedia (ECMA-368) high data rate (480Mbps) standard. An impulse based high-rate standard (DS-UWB)had been championed but has ultimately fallen dormant.

The IEEE P802.15.4a amendment defines an UWB PHY which is an impulse radio. The purpose of P802.15.4 is low data rate, low power, low cost systems. The Task Group 4a was created to add precision ranging capability. Impulse UWB is advantageous for accurate time-of-flight measurment. The 4a ammendment is now in final stages of IEEE publication. The standard defines a UWB PHY with modulation using pulse position and polarity, approx. 500MHz chip rate, multiple data rates (different chips/symbol), with forward error correction, multiple operating bands and bandwidths, and a number of optional features. The nominal data rate for 4a is 1Mbps with optional rates up to 25Mbps.

BTW the FCC rules allow multiple UWB bands, with different masks, throughout the spectrum, not just 3.1-10GHz. The FCC has approved numerous systems that operate below 1GHz, for example. —The preceding unsigned comment was added by 64.74.213.146 (talk) 15:17, 25 April 2007 (UTC).

UWB Radar?[edit]

Why isn't there more information on ultra-wideband radar? At least there should be a disambiguation page, since UWB radar is probably considered a more mature technology (being applied commercially in ground-penetrating radar and militarily in foliage-penetrating radar). Granted, UWB radar isn't as sexy as UWB communications, but how come the whole concept of UWB in wikipedia is focused just on the communications aspects? —Preceding unsigned comment added by Robotbeat (talkcontribs) 03:12, 10 March 2008 (UTC)

forward error correction[edit]

This article currently claims

Current forward error correction technology, as demonstrated recently in some very high data rate UWB pulsed systems (like Low density parity check code) can--perhaps in combination with Reed–Solomon error correction--provide channel performance very closely approaching the Shannon limit (See Shannon–Hartley theorem).

I agree that "Current forward error correction technology, ... can ... provide channel performance very closely approaching the Shannon limit". But that is true for just about any communication system; it has little to do with UWB in particular.

Has someone actually demonstrated a UWB system that used Low density parity check code or Reed–Solomon error correction or both? Or is this merely theoretically true, as implied by the "perhaps"?

And I am mystified at "forward error correction technology ... perhaps in combination with Reed–Solomon error correction". Since Reed–Solomon error correction is a kind of forward error correction, that's like saying "electric light technology ... perhaps in combination with electric light bulbs".

Could someone clarify this article, adjusting sentences like this to make them easier to understand? --68.0.124.33 (talk) 02:28, 4 August 2008 (UTC)

Yes, you could.- (User) WolfKeeper (Talk) 02:42, 4 August 2008 (UTC)
Yes, someone has actually demonstrated a UWB system that uses Reed-Solomon error correction.
Someone else demonstrated a OFDM system that uses LDPC in combination with Reed-Solomon.
I agree that paragraph is confusing.
I suspect that paragraph is an attempt to summarize page 3 of the reference at the end of that paragraph.
I tried to clarify and added more references that say the same thing -- with a few more details on the above two systems. --DavidCary (talk) 19:47, 16 January 2013 (UTC)

Latest Band Group Usage[edit]

Hi,

Does anyone have information on the latest usage of the various Band Groups around the world? I'm specifically interested in BG6 adoption. Thanks.

Tomkost (talk) 17:03, 26 January 2010 (UTC)

Proposed Updates, Jan 2011[edit]

My company is working on high data-rate communications with UWB. There are many challenges, but I agree that some of the info on this Wiki UWB page seems out of date. I'd like to propose several changes, see if anyone has any issues with them over the next month, then I'll update the page.

  1. I see lots of application for communications, therefore include that in summary paragraph at top. Second summary paragraph mentions possible conflicts with existing systems, but I thought that was determined not to be the case before the FCC opened the spectrum in 2002, stating that the rise in noise seen by traditional transmitters would not be significant.
  2. I've done a search of FCC filings and found >120 devices that have received certification.
  3. Will update regulatory status to include China, Korea, Japan, EU. Australia currently in flux. Since WiMedia Alliance is disbanded, I'll directly upload their last regulatory status picture from Jan 2009 when China finished regulations.
  4. I'm going to create a new "List of UWB Channels" page similar to "List of WLAN Channels" to make all of the channel/band/TFC linkage clearer since this is something we've struggled to understand.

spazvt (talk) 12:34, 23 January 2011 (UTC)

Difference from spread spectrum[edit]

This sounds like the old (and still relevant) ideas from Spread spectrum. Is there a key difference? Can ultra-wideband be considered a type or a subset of spread spectrum? I think this would be good material to add to the main page. Lavaka (talk) 01:17, 2 March 2011 (UTC)

Totally different from Spread Spectrum signals. UWB is not a type or a subset of classical spread spectrum modulation techniques. It is an entirely different modulation scheme. (Classical Spread Spectrum signals can be either frequency hop (FH) or PN sequence type signals.) Close to these spread spectrum transmitters, both FH and PN SS (Spread Spectrum) can be easily detected by even a narrowband receiver. UWB signals, on the other hand, are extremely difficult to detect even in close proximity to the UWB transmitter unless rather esoteric correlation techniques are employed. UWB signals can be thought of as being orthogonal in all ways to classical modulation types. Technically, UWB signals are spread spectrum signals only in terms of the power spectral density sense, but without any really significant peaks in amplitude over frequency, even at close distances to the UWB transmitter, unlike seen with both FH and PN SS transmitters. Miguel Escopeta (talk) 23:36, 1 December 2016 (UTC)

Antenna design?[edit]

Given that most antenna designs (eg normal dipole) are narrow band, should there be some comments about ultra wideband antennas eg spiral designs - http://www.antenna-theory.com/antennas/travelling/spiral.php or other small element planer designs( http://www.researchgate.net/profile/Hans_Schantz/publication/4056610_Introduction_to_ultra-wideband_antennas/links/00b7d52a8a5d128046000000.pdf , http://www.piers.org/piersonline/pdf/Vol2No6Page544to549.pdf )

115.64.210.168 (talk) 10:05, 11 January 2015 (UTC) Aart Bluestoke

Spiral antennas are very wide band, but not suitable for or relevant to UWB. UWB antennas must preserve the temporal relationship between the different frequency bands, i.e. they must be non-dispersive. Most types of frequency-independent antennas like spirals, log-periodic antennasTypical UWB antennas in fact are fat conical dipoles, with various tricks to make them work reasonably well over a very wide band. Thomasonline (talk) 06:37, 28 November 2016 (UTC)
The phase linearity of antennas for UWB transmissions is super critical. Although fat conical dipoles do work, typical UWB antennas most commonly used for actual applications are not usually conical fat dipoles, but, rather, are planar antennas designed based upon time dispersal mitigation techniques. These techniques are specifically known in the industry as complementary antennas. This way, the antennas can be manufactured using standard planar PC printed antenna types of construction. See for example, Frequency Independent Antennas by Victor H. Rumsey (Academic Press, 1966, starting on p. 25.) It is probably the best introduction to designing such antennas. Miguel Escopeta (talk) 23:26, 1 December 2016 (UTC)

Does not interfere[edit]

I removed the line about UWB not interfering with conventional narrowband users. This is false from first principles, as any energy in the band used by another radio will interfere with it to some extent. Of course it interferes less, and probably less than commonly used spread-spectrum techniques, but it's wrong to have a headline saying "it's special because it does not interfere".

For a practical example, consider that regulations dramatically limit the UWB radiated power in the 0.96 - 1.61 GHz band, precisely because of the potential for interference with GPS signals [1].

In practice this limits UWB to starting at 1.61 GHz, no great hardship for the currently envisaged small devices and short-range transmissions.

Thomasonline (talk) 06:51, 28 November 2016 (UTC)

Actually, when the UWB total radiated power is kept under the FCC established limits, with regards to both power and spectral density vs. frequency, UWB does not interfere with narrowband systems. Also, the interference with GPS is also widely discounted by those who have actually tested for any effects of such interference. The FCC regulations for UWB transmissions were also written to preclude interference against spread spectrum (SS) signals, too. For FCC compliant UWB transmissions, no interference occurs to either narrowband or GPS spread spectrum signals or to spread spectrum signals in general. "First principles" regarding interference apply only to modulations based on amplitude, phase, frequency, and older modulation formats. Time-modulated pulses of sufficiently low total integrated power levels do not interfere with any of the classical modulation techniques, nor with other time-modulated pulses, as the gating with respect to time windowing precludes interference. Have restored the factually correct claim. Miguel Escopeta (talk) 23:15, 1 December 2016 (UTC)
do you have a source for "Time-modulated pulses of sufficiently low total integrated power levels do not interfere with any of the classical modulation techniques..."?
It seems to me that relying on the fcc limit for unlicensed UWB is a bit like saying "radio waves cannot harm humans" when you mean "wifi cannot harm humans".
This article is more general than that, and talks about UWB radar, which would certainly interfere with other systems.
Doing some sums, forgetting about the modulation woo. The 290K thermal noise power of a quiet receiver on earth is -113 dBm/MHz, a long way below the FCC limit of -41.3 dBm/MHz radiated. Depending on the antennas and distance between them, this receiver will hear a full-legal-power UWB emitter many dB above its noise floor.
The fact is that it can interfere. The FCC limits keep this interference reasonable for most users.
Thomasonline (talk) 21:10, 11 December 2016 (UTC)
Further - recent papers discuss the interference potential of FCC-limited UWB transmissions on other users of the same frequency spectrum, including 802.11.[2][3]
One says "For example, FCC has approved a large frequency band (3.1 - 10.6 GHz) with maximum effective isotropic radiated power (EIRP) of -41.3 dBm/MHz. As a result, UWB degrades the perforamnce of the systems which operate in the same or nearby frequency bands. A typical example of NB system is 802.11a down-link receiver. Close proximity of UWB transmitter and 803.11a down-link receiver degrades the performance of 802.11a down-link receiver"
Here is a complete thesis about the interference between the systems: [4]
The FCC itself has detailed studies of the sensitivity of GPS to UWB[5]
It's false to imply that UWB does not interfere with other users of the spectrum because the different types of modulation cannot see each other. It's still possible for it to coexist, by careful management of frequency bands and power limits, as per normal planning practice.
Thomasonline (talk) 14:12, 12 December 2016 (UTC)