Use of a Vector-based Tracking Loop Receiver for Solving the Near-Far Problem in a Pseudolite Navigation System

H. So, T. Lee, S. Jeon, C. Kim, C. Kee, M-B. Heo

Abstract:	This paper deals with the implementation and performance analysis of vector-based signal tracking algorithm designed for pseudolite navigation system. It includes field test results that were performed in an indoor pseudolite navigation system. There have been many researches about the vector-based GNSS signal tracking loops, such as weak signal tracking, noise performance analysis, GNSS/INS deep coupling and so on. In this paper, as a countermeasure to the near-far problem, the vector-based tracking algorithm is applied to the pseudolite navigation system. The vector-based tracking loop, also known as vector delay lock loop (VDLL) and vector frequency lock loop (VFLL), uses a single vectorprocessing loop that combines signal tracking and navigation. Advantages of vector-based tracking loop are very suitable for improving the performance of pseudolite navigation system. A near-far problem is one of the most severe problems in use of pseudolites that are, in general, installed closely each other. When a receiver is too close to a certain pseudolite, its signal comes to saturate an automatic gain controller (AGC) of the receiver and makes the other signals be buried under the noise level. It restricts the operation coverage of the pseudolite navigation system. The goal of this paper is to implement the vector-based tracking algorithm applicable to the pseudolite navigation system in order to cope with the near-far problem. We implemented VFLL and VDLL designed for an asynchronous pseudolite navigation system on a software receiver. The field test was performed in an indoor asynchronous pseudolite navigation system constructed in GNSS laboratory in Seoul National University. The test results show that VDFLL can keep tracking both a weak signal in far zone and several weak signals in near zone. As a result, the operation coverage of pseudolite navigation system came to be widened. And it also could be useful to mitigate GNSS-pseudolite interference for the combined use of GNSS and pseudolite outdoor.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	243 - 251
Cite this article:	So, H., Lee, T., Jeon, S., Kim, C., Kee, C., Heo, M-B., "Use of a Vector-based Tracking Loop Receiver for Solving the Near-Far Problem in a Pseudolite Navigation System," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 243-251.
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