An Indoor Positioning System Using Time-Delayed GPS Repeater

S-H. Im, G-I. Jee, Y.B. Cho

Abstract:	A new method to deal with GPS indoor positioning by means of time synchronized switching GPS repeater has been developed by authors[3]. But the developed indoor positioning system has problems such as limitation of a number of retransmission antenna, difficulty of navigation data demodulation resulted from switching, and increasing of pseudorange error by increasing tracking bandwidth in order to track the instantaneous code bias. Therefore, we proposed the new method for indoor positioning using repeating of time delayed GNSS signal by time-delay component such as SAW(surface acoustic wave) filter, delay line, and optical fiber. The basic idea of proposed algorithm is use of orthogonal property of DSSS(direct sequence spread spectrum) signal with delayed one over one chip. For example, if two different retransmission antennas with difference delay over 2 chip lengths is placed in different spatial position and continuously retransmit the common signal but delayed, two different signals from two different retransmission antennas aren’t interfered by each other because of orthogonal property of DSSS signal. Each signal with different delay can be tracked without changing of receiver tracking bandwidth and each pseudorange can be measured in two different GNSS receiver channels. Each measured pseudorange is result that sums up the initial delay time by delay line and spatial delay by geometry of receiver to retransmission antenna. Therefore the difference of two measured pseudoranges is TDOA(time difference of arrival) measurement. Using above idea, if four retransmission antennas with difference delay are used, the 3-D position of receiver can be easily calculated with specific receiver for indoor positioning. In this paper, we showed the performance of the proposed indoor positioning system in terms of accuracy and efficiency of development using simulation and experiments. When the proposed indoor positioning system was used in environment without multipath, positioning accuracy was below 2 meter.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	2478 - 2483
Cite this article:	Im, S-H., Jee, G-I., Cho, Y.B., "An Indoor Positioning System Using Time-Delayed GPS Repeater," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 2478-2483.
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