Optimum Location Provider for Devices with Multiple Location Sensors

Wayne Ballantyne, Jeff Markwell, Hancheng Geng

Abstract:	Manymobile devices, especially smartphones,now offer several choices of location sensors, such as A-GPS, 802.11-based location, and Cell ID. Each sensor can be characterized in terms of at least three performance metrics: Location Accuracy, Time to First Fix (TTFF), and Energy per Fix or Average Tracking Power. We propose a scalar performance metric for a location session incorporating application weights and the sensor parameters of Accuracy, TTFF, and Energy per Fix, and a Location API that allows a Location-based Services (LBS)application to indicate the relative importance of each via weighting factors. We present a simple procedure for optimizing the location sensor performance metric, assuming the location application provides the LBS weighting factors described above. Unfortunately, with a mobile device, many of these location sensor parameters are highly dependent on the local environment, e.g., whether the mobile subscriber (MS) is indoors or outdoors. It is therefore desirable to apply more adaptive and aware algorithms to determine or infer the current location sensor performance. In our work, we will show a procedure to optimize Accuracy and Energy per Fix while still providing acceptable Location accuracies using the sensors available. This is especially helpful when there is a loose TTFF requirement such that a fix can be delayed until better conditions arise. We further propose a procedure based on use of readings from environmental sensors that monitor inputs such as ambient light, ambient temperature, or modem RSSI, which incur a low Energy per Reading (EPR), but can indicate when an accurate location fix will be possible. The final summary of our work is that an optimized approach is given which provides for selection of the most appropriate location sensor for the current environment. The LBS application can provide weights to indicate which sensor performance metrics should be emphasized. Incorporation of environment sensors provides additional guidance as to how a location sensor will perform. The net result is that the end user’s LBS applications will obtain a sufficiently accurate result while not expending excess energy from the MS.These results can apply to smartphones as well as other location monitoring devices such as personnel or pet trackers.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	3263 - 3273
Cite this article:	Ballantyne, Wayne, Markwell, Jeff, Geng, Hancheng, "Optimum Location Provider for Devices with Multiple Location Sensors," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 3263-3273.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In