| In recent years, wireless network has covered many public places. Especially, mobile operators, such as China Mobile, China Unicom and China Telecom, have supplied large scale of network coverage in airport, hotel, and business building, and so on, where therefore, value added service is arising. Therefore, to meet the demand of practical application, the research based on estimated radio map of indoor WLAN location system is attracting more and more attention.In order to meet the demand of engineering application, this thesis does research on key points of calculating user's location by making use of existing hardware in various kinds of open indoor office environments. First, RSSI (Received Signal Strength Indicator) from AP (Access Point) is used as the basement of location system. The work is to build RSSI database by estimating RSSI. Second, according to indoor signal propagation characteristics and existing model, suitable estimated model is proposed.The proposed location system works in two phases:the radio map building phase and real-time location phase. In the first phase, the classic logarithmic model is modified by the principal attenuation factors, to process penetration, reflection and diffraction. When being applied, parameters of propagation model are determined according to type of environment and APs' position. After parameters are finished determining, accurate radio map can be calculated. In the second real-time location phase, match the estimated radio map with ones collected in real time phase to output the location result by some location algorithm, like k-NNSS.At the end of the thesis, tests on location system are implemented in several different kinds of office environments. These environments include 3 types, small, medium and large and size is 350m2,800 m2,1500 m2 respectively. Experimental results show that the 75th percentile values of the location distance error is within 5m, and it meets the engineering requirement. |
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