Biography
Enrollment Date: 2013
Graduation Date：2016
Degree：M.S.
Defense Date：2016.05.30
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design of Indoor Positioning Prototype Based on Wi-Fi
Abstract:
With the continuous emergence of demand for indoor positioning application and the large-scale popularization of Wi-Fi technology, the Wi-Fi Based indoor positioning system has become an attractive field at present. This paper presents the design scheme based on Wi-Fi and TDOA, and launches researches on related technologies.
This paper employs TDOA positioning algorithms to Wi-Fi Based indoor positioning system. By comparion of the GPS positioning principle, the IEEE 802.11b DSSS PHY is chosen for developing and verification. And this paper presents the design scheme by employing 2 USRP to get 4 channels synchronous receiving and calculate the time difference.
This paper introduces the overall structural design of the transmitter and the transmission flow. The transmitter includes CRC32 verification module, bit joint module in MAC layer and CRC16 verification module, scrambling module, DBPSK modulation module, symbol joint module, spreading by Barker code module and pulse shaping by root raised cosine filter module. Then the transmitter is implemented on FPGA in the USRP and the transmission front panel of Wi-Fi protocol is developed on LabVIEW in the Host PC. In the end, the testing of Beacon frame transmission is conducted for instance, and test results show that the transmitter could work normally.
The whole structure of the receiver and the processing flow of receiving is proposed in this paper, which consisted of frame detection module in USRP FPGA, and matched filtering, timing synchronization, RSSI measurement, frequency offset estimation and correction, channel estimation, despreading, DBPSK demodulation, descrambling, SFD searching, CRC-32 verification, SSID and MAC address display in the Host PC. The receiving front panel of Wi-Fi protocol is implemented in LabVIEW development environment. In the end, the testing of Beacon frame receiving is conducted for instance, and test results show that the receiver could work normally.
TDOA time difference calculation algorithm of indoor positioning system is completed in this paper, including the frequency offset estimation, initial phase estimation, frequency offset and initial phase compensation, positive and negative correlation judgment and three points quadratic interpolation. And the construction of the indoor positioning system prototype and the calculation of position in 2D plane are also completed. The static points, 1D linear movement and 2D movement are tested, and the results show that the indoor positiong system could reach 0.3 m accuracy and precsion, and the refresh rate for each point is 1 s, which could meet the requirement of indoor positioning system.