Trials of commercial Wi-Fi positioning systems for indoor and urban canyons

It is now widely accepted that GPS meets, under ideal operational conditions, all attributes of a ubiquitous positioning system, i.e. accuracy, reliability and availability. However, its performance quickly deteriorates in certain environments, such as indoors or in urban canyons. In such environments, the demand for location based services (LBS) is growing exponentially, mainly because of the rapid expansion of the smart-phone market. In this context, 802.11-based positioning systems can be used as they are accurate enough for most current LBS and most importantly because they do not require any specialised hardware or additional infrastructure. In this growing market, two main companies, Skyhook and Ekahau, have emerged, proposing two different Wi-Fi positioning solutions, both relying on the fingerprinting technique. The purpose of this paper is to test these two different 802.11 positioning systems in environments where one cannot rely on GPS alone to obtain a position, i.e. indoors and in urban canyon environments. First, the results obtained indoors are detailed, and then those obtained in urban canyons. An attempt was also made to link the positioning error with observable parameters of the wireless network such as the number of access points scanned. Static and mobile tests were conducted, both indoors and outdoors, and with different types of hardware. The results show that the Ekahau system performs well indoors with position errors less than 10 metres most of the time, and that Skyhook has accuracies up to 10 metres outdoors, but is very dependent on the environment.