  Acoustic ranging based indoor positioning solutions have the advantage of
higher ranging accuracy and better compatibility with commercial-off-the-self
consumer devices. However, similar to other time-domain based approaches using
Time-of-Arrival and Time-Difference-of-Arrival, they suffer from performance
degradation in presence of multi-path propagation and low received
signal-to-noise ratio (SNR) in indoor environments. In this paper, we improve
upon our previous work on asynchronous acoustic indoor positioning and develop
ARABIS, a robust and low-cost acoustic positioning system (IPS) for mobile
devices. We develop a low-cost acoustic board custom-designed to support large
operational ranges and extensibility. To mitigate the effects of low SNR and
multi-path propagation, we devise a robust algorithm that iteratively removes
possible outliers by taking advantage of redundant TDoA estimates. Experiments
have been carried in two testbeds of sizes 10.67m*7.76m and 15m*15m, one in an
academic building and one in a convention center. The proposed system achieves
average and 95% quantile localization errors of 7.4cm and 16.0cm in the first
testbed with 8 anchor nodes and average and 95% quantile localization errors of
20.4cm and 40.0cm in the second testbed with 4 anchor nodes only.
