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 infrastructure, specialized hardware support, or excessive sensor resources. We use a real sensor network and provide measurements on the actual system. We adopt a localization 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 synchronization 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 5 mus. 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 10 m distances in indoor environments. Combining the two techniques, we find that our localization method results in accurate range estimation with an average error of 11 cm in distances up to 7 m and in consistent range estimation up to 10 m in various indoor environments.