Graduation Year

2005

Document Type

Thesis

Degree

M.S.Cp.E.

Degree Granting Department

Computer Engineering

Major Professor

Srinivas Katkoori, Ph.D.

Committee Member

Nagarajan Ranganathan, Ph.D.

Committee Member

Soontae Kim, Ph.D.

Keywords

GPS, Power dissipation, Codec, Dynamic power management, System modeling

Abstract

We present an energy conscious location-aware computing system that provides relevant information about the users current location. The location-aware computing system is initialized with a map (in the form of a graph) as well as audio files associated with several locations in the map. The system consists of: GPS receiver module, Serial port, Compact flash module, Stereo codec, Power manager module implementing three sub modules namely, GPS-to-real-world position conversion module (implements algorithm to convert GPS co-ordinates to graph nodes), Nearest-location-search module (implements modified Dijkstras algorithm), and User speed estimation module. The location-aware computing system receives the GPS co-ordinates for the current location from GPS receiver through the serial port. The system converts the GPS co-ordinates to map co-ordinates stored in the Compact Flash card. If the current location matches the landmarks of interest in the site, then the relevant audio details of the current location is played out to the user.

The power manager sets the GPS co-ordinates update frequency to avoid keeping the system component on throughout the entire course of travel. The power manager implements an algorithm that works as follows: at any given location, the algorithm predicts the user speed by exponential average approach. The attenuation factor of this approach can be varied to account for the user speed history. The estimated speed is used to predict the time (say T) required to reach the next nearest location determined by Nearest-location-search module implementing modified Dijkstras algorithm. The subsystems are shut-down or switched to low-power mode for time T. After time T, the system will wake up and re-execute the algorithm.

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