We introduce a new technique for determining a mobile phone’s indoor location even when Wi-Fi infrastructure is unavailable or sparse. Our technique is based on a new ambient sound fingerprint called the Acoustic Background Spectrum (ABS). An ABS serves well as a room fingerprint because it is compact, easily computed, robust to transient sounds, and surprisingly distinctive. As with other fingerprint-based localization techniques, location is determined by measuring the current fingerprint and then choosing the“closest”fingerprint from a database. An experiment involving 33 rooms yielded 69% correct fingerprint matches meaning that, in the majority of observations, the fingerprint was closer to a previous visit’s fingerprint than to any fingerprints from the other 32 rooms. An implementation of ABS-localization called Batphone is publicly available for Apple iPhones. We used Batphone to show the benefit of using ABS-localization together with a commercial WiFi-based...
Stephen P. Tarzia, Peter A. Dinda, Robert P. Dick,