in Wireless

Testing RTLS in a non RTLS environment

RTLS (Real Time Location Services)  incorporates identification, location, and timing—what, where, and when. The term RTLS generally encapsulates systems providing proximity-based data or actual coordinates

In essence, RTLS shows the what, where, and when within a defined locale, quantifying these factors in a way decision-makers can understand.

For instance, RTLS could be used to show which laptop (what) sitting in a given room (where) at a specific time (when). Another example: RTLS can visualize which person (what) was in a building  (where) at a given point during the workday (when)

1) For RTLS to work good we need AP’s at the edge so they can do more accurate location services.
2) And for accurate triangulation to happen we need at least -62dBm or better from 3 APs.

Now let’s see what it looks like when we go sit at this spot, that happens to have these first requirements in place.

Keep in mind that when you look at the maps these APs are not around the perimeters of the building but rather in the middle of the rooms for General voice and High-speed connectivity and we don’t put APs at the perimeter of the building because then a lot of signals will go out the target building and we wasting the signal. So we tend to put them more inside the building and in the middle of the rooms.

We can see 3 AP’s with at least -62dBm of signal strength

The red star on the screen shot is ‘where’ the RTLS system plotted my MacBook pro. It’s 1.2 Meter from the actual location where I was.

   The real position 


 Triangulation calculation, the green Pokeball is the AP to which I was connected, and the other whited out are the two APs I can see within the -62dBm received signal strength.

Triangulation is a technique borrowed from the Mobile Realm and already exist for more than 20 years. The police often use it to track bad people.

Cell Tower Triangulation - Windows® Phone 8 Unleashed [Book]

I also tested a location where I could only see 2 APs above -62dBm and one AP above 72dBm.
The measurement was off by 3 meters and plotted near the AP where I was close, but it could not calculate where I was sitting accurately.. so 3 AP’s we need to have the location fairly right!

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