In recent years, smart devices have become ubiquitous. Many of these devices are equipped with global positioning system (GPS), Wi-Fi, and other sensors. With their high mobility, the idea of mobile devices as probes has been attracting more and more attention. Mobility and flexibility offered by smart mobile devices are what traditional fixed sensors lack. However, mobile devices' power supplies are quite limited. Although GPS is accurate, its high power consumption somewhat limits its accessibility and sustainability. In contrast, Wi-Fi is less power hungry, but at the same time, less accurate. For the sake of sustainability, by adopting Wi-Fi as an alternative to GPS, longer operation is attainable at the cost of losing some degree of accuracy. In this paper, a Wi-Fi-based algorithm based on log-normal probability distribution of distances with respect to received signal strength is proposed. It is suitable for an outdoor environment, where Wi-Fi access points (APs) are abundant. Simulations are conducted over known AP locations, and results show that the proposed algorithm can save, on average, as much as 35% more battery power than GPS does. The average localization error is similar to 18 m, and the average velocity estimation error is similar to 25%.
- Mobile phone sensing; Wi-Fi-based localization; received signal strength indicator; log-normal distribution; positioning algorithm