An OFDM Based Indoor GPS Retransmission System

Y. Guo, R. Horton, P. Coiner

Abstract:	Although the GPS signal is not designed to work in indoor environment, for some applications it is necessary to receive the GPS signal indoors. Some indoor GPS application examples are timing, metrology, GPS product development, system maintenance and indoor navigation. To that end, retransmitting GPS signals from an outside antenna to indoor antenna is a quick solution. However, the GPS signal band is not open to public to be retransmitted freely. Retransmission requires finely controlled transmitted power level and an experimental license that has to be renewed every two years. Only the unlicensed bands, ISM or U-INI, are open to public. Therefore, utilizing the unlicensed band for GPS signal retransmission is an obvious solution. In this paper, we propose an indoor GPS retransmission system based on Orthogonal Frequency Division Multiplexing (OFDM) digital modulation technology. Compared to analog techniques, a digital technique for transferring the signals is a better choice in terms of bandwidth and channel optimization. The GPS L1 C/A signal has at least a 1MHz bandwidth. To transfer the GPS signal without much degradation, a high speed channel is required. The success of OFDM multicarrier modulation in wireless communications illuminates a path towards a high speed channel for the GPS signal retransmission system. While what we proposed is not a direct indoor navigation system, it could benefit the navigation community in current and future indoor GPS applications.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2236 - 2240
Cite this article:	Guo, Y., Horton, R., Coiner, P., "An OFDM Based Indoor GPS Retransmission System," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 2236-2240.
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