Page 325 - Mechatronics for Safety, Security and Dependability in a New Era

Ch63-I044963.fm Page 309 Thursday, July 27, 2006 12:08 PM
Page 309
Thursday, July 27, 2006
Ch63-I044963.fm
12:08 PM
309
309
DEVELOPMENT OF LOCAL POSITIONING SYSTEM USING
BLUETOOTH

1
1
1
1
1
1
T. Hirota , S. Tanaka , T. Iwasaki , H. Hosaka , K. Sasaki , M. Enomoto and H. Ando 1
1
Graduate School of Frontier Sciences, the University of Tokyo,
Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-8656, JAPAN
ABSTRACT

A local positioning system utilizing propagation loss of Bluetooth wireless technology is presented.
The distance between a stationary station and a mobile station (both located indoor) carried by a person
is derived from the propagation loss. The position of the person is calculated from distance
measurements on three different fixed stations. The positioning accuracy was 1.2m at average fixed
station installation density of one station in every 8.3m2. The system is intended for tracking worker's
position in a work environment.

KEYWORDS
Indoor positioning, Bluetooth, Propagation loss, Compensation, Attenuation by human body

INTRODUCTION

Location-based services, such as car navigation systems, restaurant and hotel guides for mobile phones
are becoming popular. Most of these systems obtain location information from GPS(Global Positioning
System), which is limited to outdoor use. But needs for indoor navigation systems in museums,
department stores, and for work assistant system in hospitals or factories exist, and an indoor
positioning system combined with GPS will provide user's position data seamlessly from outdoor to
indoor and broaden the application fields of location-based services. Although several methods for
indoor positioning have been proposed, they have some shortcomings.
Typical requirements for tracking worker's position are: a) Accuracy of 1m in order to track worker's
position and action in indoor work environment b) Low power consumption to enable operation of 24
hours with batteries c) Bi-directional communication capability for exchanging location-based
information between the mobile unit and the system. Current GPS technology is limited to outdoor use.
Positioning systems using infrared or ultrasound are sensitive to physical interferences, because the
line of sight between the transmitter and the receiver must be kept clear (for example, see Priyantha et
al.(2000) or Want et. al. (1992)). This will be a severe limitation for tracking people's positions and