Abstract
Indoor localization systems typically locate users on their own local coordinates, while outdoor localization systems use global coordinates. To achieve seamless localization from outdoors to indoors, a handover technique that accurately provides a starting position to the indoor localization system is needed. However, existing schemes assume that a starting position is known a priori or uses a naïve approach to consider the last location obtained from GPS as the handover point. In this paper, we propose an accurate handover scheme that monitors the signal-to-noise ratio (SNR) of the effective GPS satellites that are selected according to their altitude. We also propose an energy-efficient handover mechanism that reduces the GPS sampling interval gradually. Accuracy and energy efficiency are experimentally validated with the GPS logs obtained in real life.
Highlights
The widespread use of smartphones has fostered diverse location-based services, such as life logging [1], geotagging [2], tour guide service [3], and Social Network Services (SNS) [4,5]
Memorial Hall is surrounded by other buildings, so the signal-to-noise ratio (SNR) fluctuated near the building
We compared the proposed technique (Selected SNR) with two other approaches: the All SNR method, which monitors the SNRs of all visible satellites, and the Signal cutoff method, which uses as the handover point the location where GPS becomes unavailable
Summary
The widespread use of smartphones has fostered diverse location-based services, such as life logging [1], geotagging [2], tour guide service [3], and Social Network Services (SNS) [4,5]. Because the PDR system locates the user on its own local coordinates system, the scheme is commonly integrated with GPS In this scenario, a handover process is necessary to trigger the PDR system whenever a smartphone user enters a building. There have been several seamless localization systems that used additional anchors or devices to perform accurate handover [15,16,17,18,19] Those approaches are not practical for smartphone users. The proposed method achieves high accuracy, but large energy consumption is inevitable due to the continuous GPS sampling We overcome this problem by gradual increment of the GPS sampling rate over several visits to the Point of Interest (POI). – We propose an accurate outdoor-to-indoor handover technique that works by monitoring the SNRs of GPS satellites without additional infrastructures.
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