Long distance readable( and writable) RFID reader+tags for robot localization

Hi Everyone,
In these days, many vehicles are installed with RFID tags (E-Tags) for highway/freeway tool collections. The tool collection RFID readers are able to read the tags from a
distance about 4-6meters. These readers can be focused to a particular lane, so that vehicles on the next lane will not be read (ie. readers can have narrow sensing beam)
Is there such thing as "low-cost" (for amateurs/hobbyists) long range (4-10meters), small (so that an indoor mobile robot can carry) RFID readers?
I want to investigate if we can use them for localization (assuming that RFID reader can have narrow reading/writing beam) of the mobile robot in indoor environments.
If you have RFID experience (particularly for localization) in robotics would you share your experience with us?
Regards,
Albert
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Nothing to add here, but will add that I am interested in RFID for robot localization as well. But, in my case, indoor, read only ability is all I want.
Joe Dunfee
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This article may be relevant for you:
2006/05/08: How to Build a Low-Cost, Extended-Range RFID Skimmer by Ilan Kirschenbaum, Avishai Wool <http://www.eng.tau.ac.il/~yash/kw-usenix06/index.html
<regards> -het
-- "Progress in software has not followed Moore's law." -John Holland
How's yer crap detector? http://www.autobahn.mb.ca/~het/detector.html H.E. Taylor http://www.autobahn.mb.ca/~het /
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Albert Goodwill wrote:

If you're willing to place beacons, do time-of-flight, not beam angle.
                John Nagle
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Hello John,
Can you elaborate a bit more ? What types of beacons and how to measure time-of-flight in low-cost fashion? Is there such units as off the shelf product?
Albert,
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Doing time-of-flight with electromagnetic waves is not a trivial thing. Light travels too fast to make it easy or cheap to measure time-of-flight.... well, at least it has been. II just Googled "Laser Distance" and found a product by Stanley tools, which does it and costs only $100!
http://www.stanleytools.com/default.asp?TYPE=PRODUCT&CATEGORY=LASER+MEASURING&PARTNUMBERw-910
However, none of their instruments have an interface.
Are you suggesting Time-of-flight can be used with RFID chips? Does the RFID chip respond with enough timing reliability to work with this concept?
Joe Dunfee
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A third, but somewhat more complex, approach is to measure signal strength. Of course, you need to have control over the transmitter output power and be able to measure the strength of the received signal, and it's far from precise, but in some cases (e.g. "locating" a wireless router within a building) it may be "good enough".
Frank McKenney, McKenney Associates Richmond, Virginia / (804) 320-4887 Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all) -- Do not follow where the path may lead. Go instead where there is no path and leave a trail. -- Ralph Waldo Emerson --
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Joe wrote:

Counting at a few gigahertz just isn't a big deal any more. And if the other end is an active device, not a passive one, it's even easier. See
http://www.rfid-radar.com /
And that works with really dumb tags.
It ought to be possible to do this with WiFi technology. It might take some additional timing hardware to time exactly when packets go in and out, down to a nanosecond or so, but it should work.
                    John Nagle
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I looked at their web site, and they have a lot of white papers and general information about the technology for those interested. I wrote them and inquired about its viability for a robot hobbiest. He didn't give me a price, but said it is too expensive for this sort of use.
Joe Dunfee
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Was googling for RFID, and came across this interesting product called an "RFID Radar". It can do distances up to 35 meters. I have no idea of cost.
http://www.transpondernews.com/radaracc.html
Joe Dunfee
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