Wi-Fi based radio map for location sensing by hypothesizing existence of barriers

ABSTRACT

Location-aware services using mobile devices have become popular and many WiFi-based location systems have been developed. Position estimation algorithms in radio waves often use radio maps in order to achieve accurate positioning. Widespread use of WiFi-based location systems requires radio maps precisely representing the actual radio conditions at low cost. We propose an algorithm for making precise radio maps by hypothesizing the existence of barriers. The algorithm we propose can adopt training data collected by many common training methods. This algorithm combines training data and location information of access points in order to infer accurate radio conditions. We explain how the algorithm works when used with training data obtained from an Autonomous Acquision Mechanism. We evaluated and confirmed the utility of our radio map using a particle filter method.

REFERENCES

• 1: P. Bahl and V. N. Padmanabhan. Radar: An in-building rf-based user location and tracking system. IEEE INFOCOM 2000, pages 775--784, March 2000.
• 2: B. Ferris, D. Haehnel, and D. Fox. Gaussian processes for signal strength-based location estimation. Robotics: Science and Systems II(RSS 2006), August 2006.
• 3: T. Ishihara, M. Kuwabara, and N. Nishio. Implementation and evaluation of an outdoor positioning system using an autonomous training data acquisition mechanism (in japanese). IPSJ UBI, 15:63--68, July 2007.
• 4: N. Kawaguchi and S. Ito. Evaluation of pre-acquisition methods for position estimation system using wireless Ian. MM-10, June 2007.
• 5: T. Kitasuka, T. Nakanishi, and A. Fukuda. Design of wips: Wlan-based indoor positioning system. Korea Multimedia Society, 7(4):15--29, Dec 2003.
• 6: J. Rekimoto, T. Miyaki, and T. Ishizawa. Lifetag: Wifi-based continuous location logging for life pattern analysis. 3rd International Symposium on Location-and Context-Awareness(LOCA2007), pages 35--49, 2007.
• 7: H. Satoh, S. Ito, and N. Kawaguchi. Position estimation of wireless access point using directional antenna. International Workshop on Location and Context-Awareness (LoCA 2005) in cooperation with Pervasive 2005 (Pervasive 2005), Lecture Notes in Computer Science (LNCS3479):144--156, May 2005.

INDEX TERMS

Keywords:
location-aware system, radio map, wireless LAN