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Wireless Networking Privacy Hardware Your Rights Online

Office Surveillance: Locating And Tracking 802.11b 120

Posted by timothy from the oh-really-mister-anderton dept.
securitas writes "The NY Times recently ran an article about locating and tracking users of 802.11b WiFi networks in three dimensions using triangulation (Google) with multiple base stations. The goal is to create context-aware networks that can allocate bandwidth and provide location-based services such as uploading relevant information to a PDA. The article can be seen in a new light when coupled with the growth in workplace surveillance of employees by corporate executives (Google / short version at IHT) and the associated practical, ethical and legal problems. Interlink Networks 802.11 wireless detection and tracking white paper (PDF)." (This seems as good a place as any to mention Kensington's handheld 802.11 detector; they claim it to be the only such device on the market today. This is the cheapest detector I've seen; have the others all disappeared?)
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Office Surveillance: Locating And Tracking 802.11b More

Office Surveillance: Locating And Tracking 802.11b

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  • I thought that was obvious??

    -

  • Hmmm... (Score:2, Interesting)

    by Kai_MH ( 632216 )
    I think Radio Detectors work fairly well, too, but they don't tell you whether it's 802.11x or not, so I guess that is pretty good.

  • Kensington WiFi detector (Score:5, Insightful)

    by Rosco P. Coltrane ( 209368 ) on Wednesday July 16, 2003 @06:51AM (#6451453)
    Features and Benefits

    The only WiFi detector on the market today

    Completely hassle free -- no more booting up your notebook to find a WiFi signal

    Instantly detects WiFi networks with the press of a button

    Three lights indicate signal strength

    Messrs Kensington, could you make a version that

    1) doesn't require me to push a button to detect WiFi networks (i.e. works continuously)
    2) has a connector for an external antenna and an optional car lighter plug to power it
    3) has a 4th led to indicate if the network uses encryption or not ?

    I believe such a device would sell very much better. Thank you.

  • Heh (Score:3, Funny)

    by bazik ( 672335 ) <bazikNO@SPAMgentoo.org> on Wednesday July 16, 2003 @06:52AM (#6451456) Homepage Journal
    Do I see Google [slashdot.org] links in that article? ;)

  • How well does this work in indoor environments? (Score:5, Interesting)

    by pv2b ( 231846 ) on Wednesday July 16, 2003 @06:54AM (#6451464)
    The signal gets weaker as it passes through walls. Therefore, the signal strength can not be easilly be correlated to a distance from the base station for purposes of triangulation.

    Triangulation traditionally relies on measuring distance through signal strengths and so is limited to an outdoor environment, where the signal loss per kilometer can be predicted with much greater accuracy than in an indoor environment.

    The article is short on technical details -- did they somehow also enter a 3D-model of how the building weakens radio signals, and use that in order to create three 3D-shapes at the point of intersection the transmitter can be located? Just like traditional triangulation, but with weirder shapes than simple spheres...

    Perhaps a better way would be to use "ping" to check the travel times, rather than the signal strength, compensating for any delays imposed by TCP/IP-stacks and hardware etc. Is this even possible, or is the Signal/Noise ratio just too low?

    • Re:How well does this work in indoor environments? (Score:5, Informative)

      by Rosco P. Coltrane ( 209368 ) on Wednesday July 16, 2003 @06:59AM (#6451483)
      Triangulation traditionally relies on measuring distance through signal strengths and so is limited to an outdoor environment, where the signal loss per kilometer can be predicted with much greater accuracy than in an indoor environment.

      Where did you get that ?

      Triangulation works by being in 2 or 3 different locations, determining what direction the signal comes from with a directional antenna at each location, then drawing the lines on a map and see where they intersect. It'a called triangulation because it draws a triangle on the map. It has nothing to do with signal stength.

      • Then the slashdot article is also wrong.

        There is no way for the base station to know what direction the signal is coming from, since the antenna is omnidirectional, so I assumed it was using SNR's.

        I was under impression that the word triangulation could be used for both techniques, both using directional antennas, and by determining the distance to the receiver from several points and checking where circles intersect.
        • There is no way for the base station to know what direction the signal is coming from, since the antenna is omnidirectional, so I assumed it was using SNR's.

          It would be possible to create a directional antenna using a tetrahedron of omnidirectionals and measuring the signal delay between them, I don't know if thats what they did though

        • Re:How well does this work in indoor environments? (Score:1, Funny)

          by Anonymous Coward
          Then the slashdot article is also wrong

          Translation: Since everything I know comes from Slashdot, I accept everything in Slashdot articles as gospel. Ergo, if a Slashdot article says it, it is fact. Ergo, if I'm completely talking out of my ass, it's not my fault.

      • Re:How well does this work in indoor environments? (Score:5, Informative)

        by Anonymous Coward on Wednesday July 16, 2003 @07:19AM (#6451558)
        Almost.

        TRIangulation works exactly as you say (except the tri means 3 measurements only). Multiangulation uses >3 measurements in the same way.

        When you have ranges (i.e. distances as derived from signal attenuation), it's called lateration. Trilateration == 3 ranges. Multilateration == >3 ranges.

        However, triangulation is commonly used when lateration is meant, just because people are more familiar with the term.
      • Not always. It can work on direction or signal strength or combination of the two (especially in terms of radio aerials). For instance, lets say we are in open land with omnidirectional aerials. Direction cannot be known so we plot strength (equating approximate distance) on a graph. Where the circles overlap gives us an approximate position. This can be done with other aerial shapes and in three dimensions by working out the signal in every aera on the map. Imagine it as three circles with a gradien
        • The requirements for this are:

          1) knowing the strength of the transmitter. While 802.11b transmitters are allowed to be up to 100 mW in power. Not all work at the highest levels, and they can be set less than this to limit propagation of the signal (and a very good way to limit exposure of warchalking).

          2) knowing the propagation characteristics of the signal wavelength. Different wavelengths are absorbed or bounced by different materials. The short wavelengths used by 802.11 don't penetrate or bounce m
          • I'm wondering if custom hardware would provide some benefit here. An access point pings the client (the client will only be connected to one AP at a time anyway). A number of 2.4 Ghz receivers then look for the return signal from the client when it acknowledges. As you say calibrated receivers must be used and we would likely have to be outdoors

            This brings an interesting point. It is far easier for a client to locate itself if it knows where access points are by connecting to each in turn and using dir
            • I can't see the original article (requires subscription), so I can't comment on the details. However, this was my thought also -- that what is being worked on is a new type of access point that uses it's diversity antenna (2 or more) to get a direction on the signal. You would also need to tell the access points their location, at least in relation to each other, to be able to interpret the location on an actual floor plan.

              While only one access point "works" the card at a time, I think multiple can "see"

      • Re:How well does this work in indoor environments? (Score:4, Interesting)

        by forged ( 206127 ) on Wednesday July 16, 2003 @09:09AM (#6452178) Homepage Journal
        It has nothing to do with signal stength.

        Actually, it has everything to do with signal strength. I believe that the poster of the comment to which you responded to, meant that indoors you can't just assume that the signal strength will diminish on a more or less linear scale (or whatever) with distance.

        Take into account the thickness and materials of the floors and walls, the office furniture, the people inside packed lecture rooms, and you will understand what he meant. You cannot just assume that because signal from base station A is twice as strong as signal from base station B, that user is closer to B. It may be that there is some obstacle on the path to A weakening the signal, making it look loke user is several meters apart the triangulated position assumed from the signal strength alone.

        Ideally the calculations should be done based on knowlege of how well Wifi signals transmits through various indoors obstacles, and with a detailed map of the premices. But I can't think of anyone in their right mind who would want to do that unless they had considerable resources.

        • You're wrong - or maybe missing the point.

          The original poster answered his own question... there wouldn't in general be any way of knowing how the signal would attenuate in various directions, so measuring the signal strength wouldn't be a viable way of determining the DISTANCE to the transmitter. It's not just a matter of permanent structures affecting the signal... atmospherics, movable office furniture, etc, would all change the signal attenuation in unpredictable ways.

          However, as someone else in the t
    • and let's not forget the effect of multi-path in the equation. In some cases, multipath will improve the SNR, in others, it will reduce SNR. Simply using signal strenth is inadaquate. Using a set of directional antennas will work better, but then you have to have helpers or some very expensive phase detection equipment that will work for azimuth and elevation.
    • All the triangulation schemes I've seen are based on time, not power. Of course they were all in college design labs. The premise was that each tower would send out a "packet" and the object would send a "packet" back with the time delay of the internal circuitry accounted for. The tower would recieve this signal and the time difference between the send/recieve minus the internal circuitry delay would be the travel time. Divide that by 2 to get the one way time delay. This coupled with the speed of pr
    • The signal gets weaker as it passes through walls. Therefore, the signal strength can not be easilly be correlated to a distance [...]

      Perhaps a better way would be to use "ping" to check the travel times, rather than the signal strength, compensating for any delays imposed by TCP/IP-stacks and hardware etc. Is this even possible?

      It's possible. But IMHO indoors the variability of the response time of the processor to the message will probably introduce far too much jitter for the result to be useful. Fi

    • did they somehow also enter a 3D-model of how the building weakens radio signals, and use that in order to create three 3D-shapes at the point of intersection the transmitter can be located?

      This is just off the top of my head, but if you're referring to the Carnegie Mellon project, CMU has been working for several years to get 100% wi-fi coverage across the entire campus. This work includes a complete analysis of each room of each buildings' wireless signal strengths to all visible routers, to assure tha

  • I hope these companies that are building a network like this also deploy a security system that will prevent outsiders. Unfortunately "Most computers are pretty" so someone has to execute a good solution.

  • Simpler solution (Score:5, Insightful)

    by stefanvt ( 75684 ) on Wednesday July 16, 2003 @06:55AM (#6451470)
    In the article they mention the use of this in a hospital to push patient information to a handheld the doctor is carrying when doing rounds.

    Instead of triangulating (requiring more power) wouldn't it be simpler and possibly quicker to outfit each bed with e.g. a rfid tag?

    This seems an overly complex solution to a, relatively, simple problem.

    The rfid would also be a plus when the patient is being transfered in his bed (from his room to the or)

    • Re:Simpler solution (Score:2, Interesting)

      by mashx ( 106208 )
      Yup, agreed, then the doctor/surgeon/nurse just needs to read the patient code, and retrieve the info from the server. Wherever they are.

      But rather than the bed, why not just put it in the wrist tag that most patients wear now? Then you wouldn't get any mix ups in the nursery, or any problems when patients go walkabout.

      • Actually, I think you could do both.

        I think the added security (beds switched between chambers) in a hospital setting is absolutely necessary.

        When in doubt the tag on the patients wrist has precedence.
    • Wouldn't it be simpler and possibly easier to outfit each patient with an RFID tag? I mean - that way there would be no confusion if a patient switched beds. The hospital could track all patient information in a database keyed on this tag. Then when nurses/doctors/security walk up they can easily scan and get all the relevant personal information.

      Even better is that the hospital could then sell this information to preferred buisness partners (such as Wal Mart). This will allow the hopsital an alternative

    • There is a whole market niche in medicine for location tracking, which includes beds, patients, and equipment. If seen products based on RF, and the RFID things are just starting to influence these products.

      I've also seen products based on IR, where there are sensors along the ceilings and the IR transmitters are on the tops of devices to be tracked.

      FDA Guidlines [fda.gov]

      A Vendor group here [aami.org]

      One vendor's explanation here [radianse.com]

  • Pretty stupid approach (Score:5, Interesting)

    by dg1kjd ( 159535 ) on Wednesday July 16, 2003 @07:06AM (#6451505) Homepage
    This is a pretty stupid approach from the communications theory point of view. 802.11b frames contain a pretty long preamble in front of the packet header and data payload. This preamble (basically 11-bit barker sequences convolved with a prn-sequence) have excellent autocorrelation characteristics since they must be used for time and frequency syncronization at the RX station.
    By cross correlating the received signal with the (known) barker sequence at all three base stations precision would be increased drastically as it would be possible to measure the actual time lag (->way) the signal took to the receiver.

    • Re:Pretty stupid approach (Score:5, Interesting)

      by pv2b ( 231846 ) on Wednesday July 16, 2003 @07:23AM (#6451576)
      Moderate parent up.

      At risk of being moderated as redundant here, I'll just attempt to clarify this.

      Finding positions through time measurements is much more practical in a wireless solution than using directional antennas, mostly since you don't want to get the packet loss incurred by using a rotating directional antenna, although it might look cool. :-)

      Signal/Noise ratio measurements, that the people mentioned in the article is doing, is problematic becuase the unpredictable nature of radio wave signal weakening (I don't know the technical term), although they seem to have tackled that problem to some degree of accuracy.

      However, the speed of light is constant never mind how weakened the signal is, making it an excellent way to determine distance from the base station. This is in essence what GPS does, and also why it needs to carry along precise atomic clocks.
      • However, the speed of light is constant

        Well, the speed of light is constant in a uniform medium, but that doesn't mean that the speed of light is the same in all media. So a signal passing through air will have a different speed than one traveling through concrete.

      • --However, the speed of light is constant never mind how weakened the signal is, making it an excellent way to determine distance from the base station. This is in essence what GPS does, and also why it needs to carry along precise atomic clocks.--

        I guess with the price of atomic clocks spirialing downward, these 802.11_ detectors should be common place in a couple of years.
    • "By cross correlating the received signal with the (known) barker sequence at all three base stations"

      Try doing that within the tolerances required to measure distance based on the propagation of radio waves.

      The only systems that can do triangulation worth a shit are phased array / smart antenna technology, which can determine direction without using a moving highly directional antenna.

  • Slightly OT, but here's a nice OSS tool... (Score:5, Informative)

    by pen ( 7191 ) on Wednesday July 16, 2003 @07:08AM (#6451512)
    AirTraf [sourceforge.net]is a 100% passive packet sniffing tool for the wireless 802.11b networks. It captures and tracks all wireless activity in the coverage area, decodes packets, and maintains acquired information associated by access points, as well as detected individual wireless nodes. It dynamically detects any access points in the area, finds association between wireless clients and access points, and builds information table for each packet that is transmitted via the air. AirTraf is able to maintain packet count, byte information, related bandwidth, as well as signal strength of nodes.

  • Not that new... (Score:5, Interesting)

    by Anonymous Coward on Wednesday July 16, 2003 @07:15AM (#6451538)
    Positioning in office environments using WLAN really isn't that new. Microsoft did it in 2000 with the RADAR system (http://citeseer.nj.nec.com/bahl00radar.html), and loads of people have tried since.

    There are two approaches to it:

    1. Use signal strength to estimate range and then multilaterate. This usually does a poor job because you can't match distance reliably to signal strength because of wall attenuation etc. Also, most WLAN systems quantize the signal strength into a few bins. :-(

    2. Pattern recognition. Have a calibration phase where you put the device in lots of positions around the office, measuring the signal strengths to various stations. Record all this. Then try to match what you're seeing to this database of strengths to localise yourself. Problem is, the radio environment changes VERY easily, so you need lots of points in calibration. Plus, if the environment changes, so do the signal strengths!

    The best I've seen for a WLAN system achieved accuracy to about 2 metres. That used quite a few WLAN dase stations, too. And they had a fair error on that too - enough that you wouldn't be able to guarantee which office you're in...

    Location indoors is a tricky business. It's an active research area. The best so far is based on ultrasonics (the Bat system at (www.uk.research.att.com/bat). UWB looks good too (www.ubisense.net).

  • This has been around for a while (Score:5, Informative)

    by Jarit99 ( 689901 ) on Wednesday July 16, 2003 @07:15AM (#6451541)
    The same discussion seems to be popping up every 6 months or so. Check out what companies such as Ekahau [ekahau.com] and BlueSoft [bluesoft-inc.com] are offering.

  • other wifi finder dissapeared... (Score:2, Interesting)

    by Anonymous Coward
    there used to be idetect, from www.idetect.co.sg.
    based in singapore, i mailed them for prices, but they only had a product samples available, no real production was going on. now their site is down, have they dissapeared? their wifi finder was featured in wired magazine a few months back.

  • Real life example (Score:5, Informative)

    by alanjstr ( 131045 ) * on Wednesday July 16, 2003 @07:27AM (#6451596) Homepage
    This article [computerworld.com] on Computerworld talks about tracking down unauthorized access points.

  • The other detectors (Score:5, Funny)

    by AndroidCat ( 229562 ) on Wednesday July 16, 2003 @07:31AM (#6451616) Homepage
    This is the cheapest detector I've seen; have the others all disappeared?

    They were tracked and located.

  • Erricsson does the same with GSM (Score:3, Interesting)

    by Peer ( 137534 ) on Wednesday July 16, 2003 @07:49AM (#6451700) Homepage
    Erricsson MPS allows for location aware services on GSM phones. I've seen a demo from a WAP (hehehe) site that showed your location on a map, but that was a few years ago. I haven't seen anything after that.

    ERRICSSON'S MOBILE POSITIONING SYSTEM (MPS) [mobilecomm...nology.com]

    The Ericsson mobile positioning system (MPS) (to be delivered to the Taiwanese company) is a server based solution that allows positioning services to be introduced into any GSM network that has Ericsson switching systems. The system will work with any GSM standard radio network and all existing GSM phones. At the heart of the Ericsson MPS is the mobile location centre (MLC), a system that allows user applications to access position information for GSM phones. An application programming interface (API) will be available to allow the development of custom applications. The MLC also handles access security and protects subscriber privacy by allowing GSM users to choose whether or not their phones and other devices are tracked.
    • Yes this works fairly well, but i imagine it being rather heavy on the server side(at least in massive scale). And it's potential legal mess. Doesnt need anything from the gsm phone, iirc works by measuring round time from few gsmpoints,wouldnt work for 3d

  • Could this stop war-driving? (Score:4, Interesting)

    by KrunZ ( 247479 ) on Wednesday July 16, 2003 @07:55AM (#6451733)
    Could this be used to stop war-driving, by not letting anybody in that hadn't the right 2d/3d position (eg: inside the company)?
    It would probably not stop sniffing, but possibly it could prevent a break-in?

  • = a new security method? (Score:4, Interesting)

    by huntz0r ( 580511 ) on Wednesday July 16, 2003 @08:00AM (#6451761)
    It occurs to me that this system could seal a major hole in the concept of wireless security. As we all know, the biggest problem with trying to lock down a wireless network is that it's basically just a radio broadcast and anyone within range can easily tap into the signal (whether they can get anywhere from there is another matter, but theoretically it's always possible to crack through software guards). But if the triangulation worked well enough, then a system could be set up to, say, detect if a client is sitting on the ground in the alley next to the building, and if so shut off the connection to that client. Or it could be used to limit wireless access to only clients in certain offices or floors - no access for random people in the lobby, for instance.
    • I was thinking the same thing, but with a public twist...

      It is my opinion, which I know many share, that public hotspots are cheap enough that many businesses will soon provide free access as a loss leader. A potential problem is, however, that without a fee based subscription, there is substantial risk that free-loaders will use the internet access without using the services of the business.

      As an example, I live withing 500 feet of a Starbucks. I have clear line-of-sight from my roof. With an approp

  • This is awesome! (Score:3, Funny)

    by capt.Hij ( 318203 ) on Wednesday July 16, 2003 @08:11AM (#6451809) Homepage Journal
    With this in place I just have to set up my laptop so that the network card turns on and off at the right times, and my boss can just sit in his office with that smug look thinking that I'm working my tail off while I'm sitting in the star bucks with my laptop working away.... Oh kr4p. Does Kensington sell an 802.11b emitter?

  • Great... (Score:3, Funny)

    by deman1985 ( 684265 ) <dedwards AT kappastone DOT com> on Wednesday July 16, 2003 @08:17AM (#6451841) Homepage
    Now my boss can track me down to the bathroom if I keep my PDA with me

  • Not that novel (Score:1, Interesting)

    by Anonymous Coward
    About 3 years ago, researchers at MSR created a system called RADAR, that tracks users based on RF signal strength. At around the same time, researchers at MIT created Cricket, which does the same thing, but with auxilliary hardware.

    The novelty here is simply *tracking* users instead of letting users locate themselves, and then optionally telling everyone else where they are. That's what makes this story sexy (oooh, they can see where I am!) But, users are much more likely to adopt one of the above appr

  • Prices and usefulness (Score:5, Interesting)

    by v1 ( 525388 ) on Wednesday July 16, 2003 @08:35AM (#6451951) Homepage Journal
    Following the links, Kensington doesn't list an MSRP or sell it directly, but the other links indicated the "going rate" for the toy is $22.00, and I think that's well within budget for a computer toy.

    It could really use an external antenna though. If it had this, (or if the unit itself exhibited some amount of directional reception?) then it would be much more useful to find the actual location (down to say, which building on the storefront) the hotspot was at. The closer bench gets the better connectivity!

    Maybe someone will post a hack shortly that shows how to jurry-rig an antenna port on the little bugger. I'd also like to "me too" a previous post that suggested an external power connection. Just keep the puppy sitting on your dash whilst driving around town until the green lights start climbing up.

    Was anyone able to spot where these could be bought at? (this really looks like something ThinkGeek would carry)
    • Best Buy carries them, but it seems like they may be selling quickly. They should be back in the computer department with all of the cheesy laptop accessories (ie. USB fans, lights, etc.). My local store had several but I've heard complaints that other stores sell out quickly.
    • Google for 33063 Kensington to find some retailers.

      There also is a "where to buy" link on the Kensington site, but I don't know if that is for any product or a specific one.

      • Nope (Score:2)

        by kikta ( 200092 )
        Google only returns one site selling it, which list three retailers. All of them have 0 in stock. The link on the Kensington site is for all Kensington products & so far I haven't one that carries it.

        Has anyone found a place that carries it? Someone mentioned Best Buy, but it's not on their website.
        • I own one purchased from a retail location of Best Buy.
          • Yeah, I guess I'll drive down there & have a look. Calling them is pointless. Our Best Buy seems hopelessly inept over the phone. :-)
            • Not to cut on Best Buy employees.. well, I guess I am lol, but most employees that work at Best Buy can't really tell the difference between an Athlon and an Intel processor, much less an 802.11(alphabet soup) detector.

  • i hope the concept of office surveillance... (Score:1, Interesting)

    by Anonymous Coward
    does not surprise anyone.

    whereas before WiFi, a boss had to actually get up and ask around "have you seen Joe?" now he asks a computer by clicking on Joe's computer icon.

    having worked in low-tech high surveillance offices before, I can tell you that this approach to managing people creates a really nasty environment. I can only imagine how much a high-tech high surveillance office would breed employee paranoia.
    • Works both ways, of course. Think of a handheld detector from the Alien movies, displaying approaching coworkers instead of goo-spewing double-jawed monsters.

      Ideally, you'd want to implant each coworker with their own RFID tag so that you could get identity as well as proximity information. How best to accomplish this is an exercise I leave to your own imagination.
  • When searching for a suitable localization system for my robotics project [mrinal.net], I found a few research papers which detail the methods used to determine the location of a wireless node to an accuracy of 1 meter. Here are the [rice.edu] papers [rice.edu], and here [rice.edu] is the site that contains both the papers.
  • What I need is a cellphone detector and short range directional jammer so I can keep people from getting calls during movies, lectures and exams.

  • Cisco Wireless LAN Solution Engine (Score:1, Interesting)

    by Anonymous Coward
    I don't believe this is covered by an NDA, because it was presented to the "general public" at Cisco Networkers 2003 and certain questions could not be answered in this general session because the speaker said he didn't know who had an NDA or not (implying anything he presented was not covered). So...

    The 2.5 version of the Cisco WLSE due out in the Fall timeframe is supposed to have rouge AP detection. You would import the floor plans of your building into the system and place the APs where they are inst

  • I haven't seen this referenced... (Score:5, Interesting)

    by Bagheera ( 71311 ) on Wednesday July 16, 2003 @11:09AM (#6453253) Homepage Journal
    One pertinant thing I noted in the article was the following:

    As part of that work, Dr. Junglas modified a Wi-Fi network that operated in the business school's two buildings so that each of its many base stations had a radius of about 15 feet.

    Emphasis mine. This is an insanely dense network of AP's! At over $100 a pop for a cheap one, it seems wildly impractical to simply use stock access points with software corelation to figure out where people are - assuming such density is required.

    In a commercial deployment, AP's are going to be deployed in such a way as to give good coverage without costing too damn much. ie: as few AP's as will give adequate coverage for the site.

    There are other solutions, of course. Using a phased array antenna (sorry, no cool rotating dish) to get a direction and using signal strength to approximate range (random attenuation in the site will have a large affect on accuracy) or using multiple antennas in fixed locations to triangulate a source location (the more vectors you can get, the more accurate your fix will be) Using signal timing between different AP's (time difference between arriving signals) is plausible, but would add considerably to the cost (current AP's aren't equipped with ultra accurate clocks and transmission times over the network aren't accurate enough for the purpose.)

    Phased arrays for direction finding use precise measurements between antenna elements to get their accuracy. They effectively use a harmonic tone to determing the shift angle between antennas, and thus the relative direction to the source. Accurately placing and orienting the AP's would be vital.

    Locating wireless source points isn't exceptionally hard, and could be rather useful. But accuracy costs. Existing AP's would give limited accuracy, so this study used lots of them. More acurate location capability on an AP would cost more.

    Take your pick.

    • I built a real-time mapping system that dynamically displays user-locations (if they are connected to the wireless lan). Unfortunately, the resolution is fairly low (b/w 30 and 100+ feet depending). It essentially takes various parameters such as signal strength and AP name into account to discern location. Check out the map at: http://www.cmusky.org/map_usercentric.html
      • Interesting site you have there. Especially interesting since one of my former cohorts was a CMU grad and one of our interns is about to head there for his Masters.

        This seems veryt similar to the system described in the original thread. What are you using to get relative directions to the hosts?

  • from the oh-really-mister-anderton dept.

    I think that should be Mr. Anderson.

    I'm sorry, it just bugged me.

  • Just pick up a prism-based pcmcia card and download airfart [sourceforge.net].
  • I'm just as whiney as the next guy about Big Brother, but businesses monitoring their facilities for 802.11 traffic is not about Big Brother, it is about network security. What use is hardening your wired network if someone can put a $99.00 wireless access point on your network and open a gaping hole in your security. For this reason it seems prudent network security to monitor for these "rogue" wireless access points. We use a product called AirMagnet, which is an iPaq based, packet sniffer developed by
  • Fluke Networks, makers of industrial test instruments, has two extremely powerful handheld wireless network analysis tools [flukenetworks.com] that make the Kensington ping detector look like a Fisher-Price telephone.

    -mazor

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