Wireless location system

Abstract

A system and methods for estimating the location of a mobile device are disclosed. In accordance with one embodiment, a mobile device receives, at a first time t1, a wireless electromagnetic signal, where the wireless electromagnetic signal comprises a first identifier that identifies a first beacon that transmitted the wireless electromagnetic signal. The mobile device receives, at a second time t2, t2>t1, an ultrasound signal lacking an identification of the source of the ultrasound signal. A time difference of arrival (TODA) t2−t1 is compared to a maximum TDOA. A location of the mobile device is estimated based on the TDOA only when the TDOA is less than or equal to the maximum TDOA.

Dependencies are inferred from the claim text.