Wifi localization as a network service

Abstract

In last years, many efforts have been made to build indoor positioning systems using different types of signals and different types of position algorithms. Experiences with sound, light, infra-red, Bluetooth and popular IEEE 802.11 network signals have been carried out both by commercial and academic entities. The major goal is to fulfill the lack of GPS coverage inside buildings with a more precise and/or cheaper alternative. WiFi based Localization systems gain special attention in this context due to its huge usage inside all modern facilities. Many algorithms have been proposed to estimate the device position within the WiFi network using the signal strengths (RSS) obtained by 802.11 device drivers. RSS values can be registered by each packet received, either by the the user’s device or by the network’s Access Points. Values can then be compared with a pre-configured map of signal strengths obtained in a calibration (offline) phase. This paper presents a localization system, where the location is determined exclusively by the network infrastructure. The location computation is based on the signal strength measured at Access Points and sent to a localization server. The localization server determines the location, stores it in a database and accepts requests from authenticated clients. Results obtained in experimental tests are discussed and compared with those published by other authors, allowing us to conclude that the system combines a good accuracy, with the advantage of not requiring any intervention from clients in the localization process. The entire system is designed in order to make locations available as a network service.