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G. Retscher:
"Differential Wi-Fi - A New Approach for Wi-Fi Positioning Using Lateration";
Talk: IUGG 2015 General Assembly, Prag (invited); 2015-06-22 - 2015-07-02.

For positioning using Wi-Fi either location fingerprinting or lateration is commonly employed. Fingerprinting is very labour consuming as a database with RSSI (received signal strength indicator) scans from all visible access points (APs) measured on a large number of known reference points has to be established. Lateration requires the use of theoretical path loss models to convert the RSSI measurements into ranges to all visible APs. The idea of the novel approach is based on the well-known DGNSS operation principle. For differential Wi-Fi (DWi-Fi) positioning corrections can be deduced if reference stations are deployed at certain AP locations. They measure the RSSI to all other visible APs similar as it is done on the mobile userīs side. The RSSI and the deduced range or coordinate corrections are obtained from a comparison with the known ranges between the AP reference stations. In addition, in a reference AP network area correction parameters can be calculated similar as it is done in RTK-GNSS positioning in a CORS network. They are then applied to the current RSSI scans from the mobile user. The major advantage of DWi-Fi is that the RSSI to range conversion is based on the area correction parameters and not only on standard theoretical path loss models. Thus the positioning performance is significantly improved compared to conventional approaches. In this contribution the concept is discussed in detail and analyzed using simulations and field experiments. It is shown that the positioning accuracy is increased by a factor up to 3 to 4 using this new DWi-Fi approach.

Wi-Fi, differential positioning, lateration