Design And Implementation Of The Portable Indoor Positioning System By WIFI

With the development of science and technology and the wide spread of smart mobile devices, the demand for indoor location information is increasing.Benefiting from the low cost, widely deployment,the WLAN based indoor positioning has attracted a lot of research attentions recently.The fingerprint location method has high location accuracy since it can combat the multipath effect. Therefore, we focused on the fingerprint location technique in this paper. Firstly,WIFI fingerprint location technique was analyzed and studied from the aspects of signal propagation models and fingerprint location algorithm performance, etc. The WIFI fingerprint location system was illustrated and the classical fingerprint location algorithms were described.Today, there are a lot of different kinds of smart mobile devices, which use different kinds of WIFI modules. The RSS properties of different WIFI modules are different either. Therefore, the RSS information used in the on-line phase and those used in the off-line phase perhaps must come from the same kind of smart mobile devices. This decreases the universality of the location system. In order to overcome this shortcoming, the signal strengths of different smart mobile devices at the same point were analyzed. It was verified that the signal strength trends of APs measured by different mobile devices are similar, although their values are very different. The cosine similarity algorithm was used to cancel the effect of different mobile devices on the location performance. Moreover, a weighted cosine similarity algorithm was proposed to improve the positioning accuracy. The experiments evaluated the efficiency of the proposed algorithm.Finally, a fingerprint-based WLAN indoor positioning system was designed and implemented in Android platform of smart mobile phone. The system employs the proposed weighted cosine similarity algorithm. The system consists of a mobile positioning terminal, a mobile monitoring terminal and a server. The mobile positioning terminal together with the server completes the precise positioning. The location and coordinates of mobile positioning terminal can be displayed on the map of the three terminals(mobile positioning terminal, portable mobile monitoring terminal and server). The system can provide the position information of the mobile positioning terminal in real-time through the mobile monitoring terminal. The field test verified that the system can obtain a satisfied performance. The implemented portable location system has practical application value for its low lost.