Hey everyone, thanks for coming back to Wi Fi fundamentals with location and analytics. This course will help you to muster the air. In this course we have gone through Wi Fi fundamentals, free space path loss, RF waves ranging rssi. And now it's time to understand location. The hard part was getting an accurate distance from our station to the access point. Our society is the only information we have.
To turn this into a distance. We use a measurement based on known signal strength, free space path loss, or we use a radio map based on our society finger print. Calculating distances to three or more access point allows us to estimate this stations location using trilateration given the known location of our access point, let's see how it works. So before we start with a radio map based on our society fingerprint, it is still true access points in different positions in the area and record their placement. Divide the space into grid points. collect our society data in different reference points based on the readings of your access point, or your smartphone.
Keep moving around the area starting from access point one. collect data set from each reference point. For each grid point, repeat the measurements several times and gather our society values plus noise. They represent a union Unique fingerprint. Now we will calculate the relative distance between the access point and the station based on the signal strength, the placement of the access point, free space path loss and other calculations. We have a dedicated video chapter on our sight distance measurement.
For more signals reading we can see that station one is positioned at minus 45 minus 48 and minus 51 dBm. doing the math using distance equation, the results are one meter, two meter and four meter from the access point respectively. Now bear in mind that the station doesn't have to be associated to the access point. The access point can monitor stations Based on the probe request, now comes the nicest part. Imagine that each distance is a circle radius. Now knowing that the radius is half a diameter, we can plot a circle for each access point towards the station, which is in its middle.
The place where the circle lines interact, it is the position of the station. More on that magic in our next part trilateration See you soon