Outdoor Navigation System Using Pseudolites

Taikjin Lee, Haeyoung Jun, Doohee Yun and Changdon Kee

Abstract:	In recent days, navigation technology becomes more important as location based services (LBS) in many fields. Commercial LBS requires that navigation system should be inexpensive and available anytime and anywhere. If we consider these requirements, it is out of question that GPS is the most favorite system in the world. However, GPS has several serious problems. The Problems are that GPS does not operate indoors and downtown very well and GPS has big errors in vertical direction with respect to horizontal. This is because GPS satellites are about 20,000km above the ground so that indoor signals are too weak to be used in signal processing and constellation of satellites is bad in vertical. To solve these problems, many research activities have been done around the world since 1990s. This paper is also one of them and we will introduce one possible solution, which uses pseudolite. We already developed synchronized pseudolite system (indoor navigation system) a few years ago. At that time, we installed reference station which calculated difference of pseudolites’ clock and sent the information of difference of psudolites’ clock to pseudolites. This synchronization process was a kind of control loop and we designed it by use of a 3rd order phase locked loop (PLL) assisted with 2nd order frequency locked loop(FLL). Now, we install the system outdoors and develop pseudolite navigation system mixed with GPS. It is classified asynchronous pseudolite system and synchronous pseudolite system. At this paper, we show experimental results for outdoor asynchronous pseudolite navigation system mixed with GPS. And then, show the possibility for pseudolite synchronization with respect to GPS. The basic concept of synchronization is similar to indoor system but the resultant system is different from indoor system in practical operation. Due to this system, the vertical accuracy of GPS is improved extremely and redundancy of the system is also improved with respect to GPS only. Our research goal is to integrate Pseudolite with GPS so that the system can be used indoor easily, vertical accuracy of the system is improved. This system will be able to support GPS. And now, we designed it, tested it, and proved it. After several years, we may see the synchronized pseudolite system instead of instrument landing system (ILS) as automatic landing system in airport. Figure 2 Use GPS service using PLs
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1948 - 1958
Cite this article:	Lee, Taikjin, Jun, Haeyoung, Yun, Doohee, Kee, Changdon, "Outdoor Navigation System Using Pseudolites," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1948-1958.
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