Tight Hybridisation fos Positioning whit GPS and WLAN

Projecte realitzat en col·laboració amb l’empresa CTAEIn the last few years there has been an incrementing interest on LBS (Location Based Services) and ITS (Intelligent Transport Systems), and therefore location systems able to calculate user’s position have become crucial. GNSS (Global Navigation Satellite Systems), especially GPS (Global Positioning System), has been offering this kind of services for 20 years, but it doesn’t work properly in all environments. Despite the latest advances in GNSS high-sensitivity receivers for harsh environments, signal blocking caused by buildings makes it unfeasible to consider GNSS as an overall positioning solution to cover outdoor urban areas entirely. Since this can limit the deployment of LBS and ITS in urban zones, numerous proposals exist for augmenting GNSS availability with terrestrial signals. Most of them employ public cellular networks like GSM (Global System for Mobile Communications)/GPRS (General Packet Radio Service), UMTS (Universal Mobile Telecommunications System), etc. and are therefore constrained in terms of flexibility, due to operator dependency, and accuracy. Another alternative considered is the use of pseudolites, but they are not suitable for widespread use due to legislation and cost reasons.In the last years local authorities are deploying WLAN (Wireless Local Area Network) access points (WiFi, IEEE 802.11) on the streets of many cities in order to provide municipal services or wireless internet access, while the integration of GNSS and WLAN in a single device is now very common. The main objective of this project is to take advantage of these existing WLAN infrastructures to increase urban positioning coverage (i.e. availability) of GNSS by means of a flexible and cost-effective solution, thus achieving a practical positioning system able to combine WLAN and GNSS signals, keeping the location accuracy as close as possible to that provided by GNSS alone