System Level Energy Optimization for Location Aware Computing

We present a system-level energy optimization technique for a location-aware computing system that provides relevant information about the user´s current location. The 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 Dijkstra´s algorithm), user speed estimation module. 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 Dijkstra´s algorithm. The subsystems are shutdown or switched to low-power mode for time T. After time T, the system wakes up and re-executes the algorithm. Based on a system-level model (VHDL and C), compared to simple time-out and constant update policies, the proposed algorithm results in energy savings in the range 55-99%. Work is ongoing to implement the entire system as a single chip solution