Indoor localization using controlled ambient sounds


Audio-based receiver localization in indoor environ-ments has multiple
applications including indoor navigation, loca-tion tagging, and
tracking. Public places like shopping malls and consumer stores often
have loudspeakers installed to play music for public
entertainment. Similarly, office spaces may have sound conditioning
speakers installed to soften other environmental noises. We discuss an
approach to leverage this infrastructure to perform audio-based
localization of devices requesting local-ization in such environments,
by playing barely audible controlled sounds from multiple speakers at
known positions. Our approach can be used to localize devices such as
smart-phones, tablets and laptops to sub-meter accuracy. The user does
not need to carry any specialized hardware. Unlike acoustic approaches
which use high-energy ultrasound waves, the use of barely audible (low
energy) signals in our approach poses very different challenges. We
discuss these challenges, how we addressed those, and experimental
results on two prototypical implementations: a request-play-record
localizer, and a continuous tracker. We evaluated our approach in a
real world meeting room and report promising initial results with
localization accuracy within half a meter 94% of the time. The system
has been deployed in multiple zones of our office building and is now
part of a location service in constant operation in our lab.