Biography
Enrollment Date: 2010
Graduation Date：2013
Degree：M.S.
Defense Date：2013.05.27
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Research and Design on the TDOA Location System
Abstract:
With the booming and development of the digital mobile communication technology, location services in the wireless network are on the increasing demand nowadays. Wireless positioning technology first appeared in the military field, for the purpose to provide navigation services. However, with potentially huge commercial and academic value, this technology has become a hot topic in the commercial, medical, transportation and public safety as well as other fields.
The time difference of arrival (TDOA) is the most potential method among the wireless positioning systems, though the worldwide research on it is still in the exploratory stage at present. As a fact, the accuracy of the TDOA positioning system has not yet fully met the needs of people, and previous research works also have proposed more and more urgent problems that need to address.
This paper first introduces the basic principle and constitution of the time difference positioning system, and discusses its engineering implementation method deeply afterwards. Then we research and analysis the synchronization technology of the base stations in theory, in order to provide a viable solution to the practical application in the future. Subsequently, the paper details the realization steps of the time difference location method and the key technologies on time difference measurement and positioning algorithm. Aiming to improve the accuracy of the positioning systems, we analysis the error sources and properties in accordance with the TDOA positioning mechanism, and put forward some methods to overcome the system error in order to further improve the positioning accuracy.
In the main part of this thesis, we focus on the research and design of the high-precision time difference measurement technology. On the basis of the correlation method, we have designed two different methods: interpolating sampling and curve fitting. The principles and hardware implementation for both of them are given respectly, and some key design ideas are analyzed in detail. The simulation results show that both methods can achieve a time difference measuring precision within 1 ns under the current device performance. Based on the design, one application scheme is proposed to synchronize the base stations.
Finally, we realized a time difference measurement system in TDOA localization method by the use of NI virtual instrument platform. This system not only can realize the demodulation of the RF signal, but also obtain the high-precision TDOA measurement without increasing the hardware resources. Therefore it can provide data information as well as the time of arrival of the information.
System test results show that the design can provide excellent demodulation performance and less than half of the sampling period in regard of the time difference measurement accuracy. Thus, it can meet the needs of most applications. The fusion of time difference measurement and data demodulation makes it possible that the system can provide data along with location services for the user, which without doubt will bring more widely used applications to the TDOA location systems.