Implementation and Evaluation of Indoor Localization System using WiFi Channel State Information
Date Issued
2014
Date
2014
Author(s)
Tsai, Chang-Ning
Abstract
Demand for indoor positioning systems has increased in recent years. In outdoor environments, the Global Positioning System (GPS) can be used to obtain information on a person’s current position. However, GPS does not work very well in indoor environment because the GPS signals are affected by buildings. Therefore, we use other methods to implement indoor positioning. In this thesis, we measure the Wi-Fi signal strength to determine the indoor position. Most buildings contain numerous Wi-Fi access points, meaning that no additional deployment cost is required. Therefore, we implemented the indoor positioning system in this study by analyzing Wi-Fi channels.
Indoor positioning comprises two steps: sensing, and using a local positioning algorithm to estimate the user’s location. In previous studies, Wi-Fi received signal strength indicator (RSSI) has typically been used in the sensing step. However, an RSSI measurement does not provide sufficient channel information. Therefore, in this study, we measured the channel state information of the 802.11n physical layer to improve the accuracy. Fingerprinting and propagation models were used in the local positioning step. Fingerprinting provides superior accuracy, but the deployment cost is high. The path loss model method provides inferior accuracy, but costs less to deploy compared with fingerprinting. We hoped to create a propagation model that was both accurate and economical. Thus, we referred to the propagation model to design a positioning algorithm, and determined that this algorithm can increase the position accuracy by approximately 11.6%.
Subjects
頻道狀態資訊
室內定位
Type
thesis
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