Proximity Motion Detection Using 802.11 for Mobile Devices

The market for 802.11 based wireless LAN technology has matured greatly in recent years and it is now being used in homes, offices, cafes, airports, and even in hot spots in urban areas. Each 802.11 frame transmitted from 802.11 equipped devices contains information on signal strength and noise. By measuring the signal strength information included in frames sent from a fixed node to a mobile node, it is possible to approximate the distance between the fixed and mobile node. However, as many research papers pointed out, positioning based on received signal strength is difficult, since 802.11 is very susceptible to the effects of various factors, such as reflection or attenuation of the signals. In this paper, we take into account these behavioral characteristics of 802.11 and propose a different approach, where instead of trying to estimate the exact location of a mobile node, we only try to detect incoming movement or access within a given proximity range. Since most recent mobile devices available in the market incorporate or have the capability to add-on 802.11 technologies, mobile users can utilize motion sensing applications without relying on other technologies such as RF-tags or infrared.