In March Apple acquired indoor-GPS company WifiSLAM, a sign that the war over indoor mobile location services is heating up. The company stated that their product "Allows your smartphone to pinpoint its location (and the location of your friends) in real-time to 2.5m accuracy using only ambient WiFi signals that are already present in buildings." Now a new Microsoft patent application published by the US Patent and Trademark Office titled "Sound-based Positioning" has surfaced describing one of their solutions regarding indoor mobile location services based on ultrasonic signals. Microsoft provides an extensive scenario of a shopper using the new technology in a store. Yes, the war over indoor mobile location services is heating up and Microsoft has a new solution in the works.
Microsoft's Patent Background
Accurately determining the position of a user or mobile device within an indoor setting presents various challenges. For example, global positioning systems (GPS) technologies do not work well within an enclosed building, where the mobile device's communications with the GPS satellites can be impeded by the surrounding structure. Further, available consumer devices are limited in their communication capabilities, sensing capabilities (e.g., mobile device microphones), the accuracy of their internal clocks, available power, etc. Accordingly, obtaining highly accurate, real-time location information on a mobile user within enclosed buildings (or where GPS positioning is otherwise unavailable) is difficult without nontrivial modifications to the hardware of available mobile devices.
Microsoft's Indoor Location System Solution
Implementations described and claimed in Microsoft's invention address the foregoing problems by using a receiving device to capture sounds signals (e.g., ultrasonic) from multiple sound signal sources, selecting the sound signals satisfying a reliability condition for use in determining an initial position of the receiving device relative to the corresponding sound signal sources, determining the initial position of the receiving device using multilateration of the selected sound signals, and updating the current position of the receiving device as the reliability of individual sound signals varies in the presence of dynamically changing environmental interference, multipathing, and movement between the receiving device and the sound signal sources.
Microsoft's patent FIG. 3 shown above illustrates an example data flow diagram for sound-based positioning. A receiving device, such as a mobile phone, executes an operating system to manage its resources and provide a platform upon which a sound-based positioning application can be run.
Microsoft's patent FIG. 1 illustrates an example in-store scenario employing sound-based positioning.
Microsoft's patent FIG. 4 illustrates example operations for sound-based positioning.
For full technical details and Microsoft's shopper scenario, see Microsoft Patent Application 20130083631
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