Hey everyone, thanks for coming back to Wi Fi fundamentals wood location and analytics. This course will help you to muster the air. There are two ways to measure distances using rssi. The more accurate way rssi fingerprint, or is using a radio map and it will be discussed in our next video. The second method the less accurate uses a distance equations that are based on the free space path loss and received power. rssi distance can be calculated for short ranges using the following equation taken from this white paper.

D equals to distance the measure power in the brackets is the transmitted power for one meter away. Is the signal propagation constant in free space it is equal to two. In more challenging environments, it is raised up to four. And the received our society is the received rssi at the other side. Let's work it out together, we have an access point with a measure power one meter away of minus 45 dBm. On the other side, we have our tablet with the received power received rssi of minus 60 db.

Now let's look at the equation and see what is the result. What is the measured distance between our access point and our tablet. Using our equation, it seems that the distance between our access point and tablet is equal to five dot 62 meters. Let's see how it is calculated. I'm using my Android phone calculator. So the equation says 10 to the power minus 45, which is the received power one meter away minus minus 60, which is the received power at the other side divided by 10 times and which is our constant.

And that gets us to five dot six meters. All right, well, it was too good to be true. Right rssi measurement is good for short ranges, but it has its own weaknesses due to multipath obstacles interferences. If we want to make the most out of our sight distance measurement, we need to use another method, which is the rssi fingerprint. And that is coming in our next video. See you soon