determining your location using ONLY wifi signals?

Question

i will be working on a project that tries to determine your position using the wifi signal strength from a few access points. i was wondering if anyone knew of any similiar projects or any articles on that topic

if anyone cares: its a research project in at my university. the app is written is used as a playing ground to develop new wifi antenna that are better suited for this type of usage. i only work on the coding part of the project though. oh and its written using c# which is not optional

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clarification: its ONLY wifi. no GPS goodnes for us becaus its supposed to work indoors the software is supposed to determine your location by using the known locations of the access points and their signal strenghts to tell you where you are. its currently at around 4-5 meters of accuracy aside from that i already have a working prototype and was just wondering if anything similiar has been done before or if anyone has any tips or ideas for/about the project

Answer 1

I wouldn't have thought that signal strength would work well: too many things interfere with it (like walls). But you might try measuring ping times, especially if you threw a hundred pings at the AP and took the average. Most of the time will be the AP digesting the ping and generating the pong, but there will also be a time-of-flight component for the signals. If the AP response time is consistent then you should be able to subtract it and hence compute the distance to the AP. By well-known hyperbolic maths you can then find your position from 3 or 4 APs.

Paul.