Automatic RF Interference Maps and their relationship with Wi-Fi Positioning Errors

The interference in Wi-Fi networks severely degrades the quality of service. In contrast to cellular networks that operate in regulated radio frequencies, and where the use of the radio spectrum is controlled and planned, the deployment of Wireless LAN networks infrastructures is unregulated and often uncontrolled, leading to high levels of interference. The interference analysis process normally requires a manual site survey, similar to the site survey required by indoor positioning Fingerprinting, which in large buildings is unpractical.In this paper we argue that the recently introduced FastGraph solution [1], [2], in addition to provide unsupervised positioning, can also be used to automatically map the level of interference in Wi-Fi environments. The proposed solution can automatically provide interference maps based on two distinct strategies: AP-Based Interference Mapping or Sample-Based Interference Mapping, each one with its own characteristics and advantages.The experimental results presented in this paper suggest that FastGraph can be used to easily create interference maps. In addition, a good correlation between the level of interference and the positioning error was observed - to the best of our knowledge, a relationship never reported before. This finding is very interesting, and can be explored for example to improve the positioning performance, as well as to provide a confidence indicator for the estimated positions, which it is currently not possible to obtain in Wi-Fi Fingerprinting-based systems.