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Voice assistants such as Amazon Echo (Alexa) and Google Home use microphone arrays
to estimate the angle of arrival (AoA) of the human voice. This paper focuses on adding
user localization as a new capability to voice assistants. For any voice command,
we desire Alexa to be able to localize the user inside the home. The core challenge
is two-fold: (1) accurately estimating the AoAs of multipath echoes without the knowledge
of the source signal, and (2) tracing back these AoAs to reverse triangulate the user's
location.We develop VoLoc, a system that proposes an iterative align-and-cancel algorithm
for improved multipath AoA estimation, followed by an error-minimization technique
to estimate the geometry of a nearby wall reflection. The AoAs and geometric parameters
of the nearby wall are then fused to reveal the user's location. Under modest assumptions,
we report localization accuracy of 0.44 m across different rooms, clutter, and user/microphone locations. VoLoc runs in near real-time but needs to hear around 15 voice commands before becoming operational.
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