| Summary: | 碩士 === 銘傳大學 === 資訊傳播工程學系碩士班 === 94 === Global Positioning System (GPS) is a well-known Location-based Service (LBS). GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user''s location. Essentially, the GPS receiver calculates the time of the signal was transmitted by a satellite and the time who receives. The location of GPS is accurate about 5 meters to 40 meters. But it must keep line of sight (LOS) between receivers and satellites, it is ineffective indoors. As regards indoor environment based on Wireless LANs, P. Bahl and V. N. Padmanabhan proposed the RADAR (Radio Detection and Ranging) mechanism in 2000 IEEE INFOCOM, a radio-frequency (RF) based system for locating and tracking users inside buildings. RADAR operates by recording and processing signal strength information at multiple base stations to triangulate the user’s location. Triangulation is done using both empirical-determined and theoretical computed signal strength information. This thesis exhausts an indoor locating mechanism and implements a location-aware system based on WiFi environments. During the on-line phase we gather received signal strength indicator (RSSI) as the substitution from multiple Access Points (AP) with the prediction model to estimate the mobile user’s location. As the experimental results of our research which indicated that the mean of error distance within 4 meters. According to the proposed radio prediction model, we can reduce the number of training points during the off-line phase, and improve the computing load of mobile devices efficiently.
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