FLASH: fine-grained localization in wireless sensor networks using acoustic sound transmissions and high precision clock synchronization

Sensor localization in wireless sensor networks is an important component of many applications. Previous work has demonstrated how localization can be achieved using various methods. In this paper we focus on achieving fine-grained localization that does not require external infras-tructure, specialized hardware support, or excessive sen-sor resources. We use a real sensor network and provide measurements on the actual system. We adopt a localiza-tion approach that relies on acoustic sounds and clock synchronization. The contribution of our work is achieving consistent sound pulse detection at each sensor and precise range estimation using a high-precision clock synchroniza-tion implementation. We first describe our technique and then we evaluate our approach using a real setup. Our results show that our approach achieves an average clock synchronization accuracy of 5µs. We verify this accuracy using an external global clock via an interrupt mechanism. Our sound detection technique is able to consistently identify sound pulses up to 10m distances in indoor environments. Combining the two techniques, we find that our localization method results in accurate range estimation with an average error of 11cm in distances up to 7m and in consistent range estimation up to 10m in various indoor environments. 1