ELEC 432

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Background

For outdoor applications which require determining position to an accuracy of a few meters, GPS is the only reasonable choice. Differential GPS can improve the accuracy to a few centimeters, although at considerable additional expense. Indoors, or in dense urban environments, GPS suffers significantly reduced performance, or fails altogether. Indoor applications and those requiring economical sub-meter resolution are better served by a different system.

Finding position to centemeter resolution requires accurate timing and a wide bandwidth (hence high frequency) signal. In an indoor system, such a signal can suffer severe multipath distortion, requiring a complex system for successful operation. In an indoor (or limited area outdoor) environment, the use of acoustic signals becomes feasable. Their much lower propagation velocity significantly eases timing requirements, and the ability to combine them with essentially instantanious RF signals can significantly simplify system design. Multipath can still be a problem indoors, but the reduced bandwidth and availability of a parallel RF channel make handling it more tractable.

Description.

The system will consist of a number of fixed nodes and one or more mobile nodes whose location is to be determined with respect to the fixed nodes. The system should be self calibrating. I.e. it should not be necessary to measure the positions of the fixed nodes. Instead, they can be placed in any suitable locations and the system calibrated by placing the mobile node at a number of known locations.

Target Applications

Your project prototype must successfully realize one of these applications:

• Lego Mindstorms Location Sensor
• Virtual Tour Guide
• Crash-Proof Model Helicopter