James Fator

Wi-Fi Trilateration

27 June 2013

I wanted to experiment with some old routers I had sitting around. I put them in the 4 corners of my house and used my Android device to get the signal strength of each router. I can take that strength value, convert it to a measurement of distance and use trilateration algorithms to essentially give me a rough estimate of where I am in the house.

It ended up working! Well, for the most part. The experiment was to determine if the Wi-Fi strength was constant enough to actually become a method of accurately determining location. Unfortunately in the testing that I did, with the old routers that I have... it was not.

The picture above is how the app worked; the rectangles on the edges are the routers and the rectangle in the middle of the top is where the app detected my location. I had to calibrate for the different models of routers, the interference, the different distances, etc., but it was still jumping around every now and then.

Maybe this is not the easiest way of going about determining where you're located, but the overall idea of location in the house is one that I think should be expanded upon. With all this home automation arising, imagine if you could just say "lights on" and the lights for only the room your in would turn on. The original thought that gave me this idea was to have speakers in every room and as you leave one room, the speakers would fade out and the speakers in the next room would fade in giving you a dynamic sound system that you would never need to pause.

A man can always dream. For more information on trilateration, check out this pdf written by a professor at my university.