Fingerprinting using Wi-Fi strength signal

Question

I'm working on how to determine distance with the Wi-Fi signal strength, from this article: Indoor Position Detection Using Wi-Fi and Trilateration Technique.

How can I do this method? What is the meaning of offline and online phase in this context?

Answer 1

Well after some research I found a solution to my question, in case someone else needs it. Concerning FingerPrinting:

Starting Point - Mapping out Your Location

1. We need to divide the location into grid points.
2. Collect the signal strength from each grid in relation to all the access points. For example, if you are in position X and you have 4 AP, you are going to collect 4 measurements.
3. Put your collected data in a database.

Locating Your Position

1. Determine the signal strength that you receive from different AP.
2. The algorithm will determine the correspondence between the Signal Strength in a database and the current Signal Strength, the most position (from DB) that matches with your Signal Strength, will be your position.

The disadvantage of this method is that it requires extra time at the beginning.

For more information : http://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XXXVIII-4-C26/1/2012/isprsarchives-XXXVIII-4-C26-1-2012.pdf

http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1007&context=cpesp