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Indoor Positioning System

Photo by Natalya Letunova on Unsplash
Indoor Position System (IPS) are the systems used to locate people and goods in indoor environments, where the satellite signal of GPS cannot help.
Here at Allinit srl mostly we experienced in hardware and firmware for Wi-Fi tag which use RSSI to guess a position.
The use of a Received Signal Strength Indicator (RSSI) is a conventional technique, it is also currently the most used in i-Beacon or other beaconing solution.
It has the advantage of being easy to implement because almost all hardware radio receivers have a way to measure it, but it has the big disadvantage that its measures are affected by many environmental factors so that the result cannot be as desired.
Based on the fact that the Radio signal strength decrease from the source until reaching the receiver, according to a well known logarithmic function, known the source power and measuring the received signal strength, it is possible to calculate the distance from source and receiver. Now if we have at least 3 sources and 3 lengths of the receiver from them, then with trilateration (a geometric solution) you can find the position of receiver related to the sources.
Unfortunately, when on the field, many factors affect a correct measurement of the radio signal received and instead than a point you can find an area in which locate, with most probability, the receiver.
Photo by Jad Limcaco on Unsplash


That's why, with a simple solution you can achieve a precision of 16 meters which means that with a certain probability the real position is far from the point you found, up to 16 mt. With more work and particular infrastructure you can, reasonably, reach a precision of 3 mt. but rarely more precise than this. The significant advantage of using the Wi-Fi signal is that you can realize a simple real-time locating system, just using the Wi-Fi Access point as the source of the signal to analyze, so leveraging the current WLAN infrastructure, but you cannot get high precision in location.
If you need more precise indoor locations, there are others solutions, some still using Wi-Fi transmission or Bluetooth but we prefer to change the physic wave and transmission and target a solution with UWB, but this is another story...


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