Analysis and Simulation of a Candidate Deployment Geometry and Characteristics of Pseudolites Within a Tunnel

Randal C. Galijan

Abstract:	Results of analyses and simulations are presented concerning the geometry and characteristics of a candidate deployment networks of pseudolites within a tunnel. The objective of deploying pseudolites within a tunnel is to provide data for lateral and longitudinal control of vehicles operating on an Automated Highway System (AHS). Vehicles operating on an AHS are expected to require horizontal location accuracies of I-50 cm, velocity accuracies of l-5 cm/s, and update rates of 25-100 Hz. Under ideal conditions, GPS data are sufficient for attaining these accuracies, but blockage of GPS satellite signals by natural and manmade features--such as hills, trees, buildings, and tunnels--limits the accuracy and availability of GPS measurements in the AHS environment. Inertial-aided GPS receivers are not sufficient under all conditions, most notably when the use of inexpensive equipment is desired and periods of signal loss are greater than 30 seconds in duration. A software simulation tool was used to predict accuracies available from a configuration of six pseudolites within a tunnel. The concept of user equivalent carrier measurement error (UECME), as opposed to user equivalent ranging error (UERE), is discussed. Simulation results including dilution of precision (DOP) calculations are analyzed to arrive at expected accuracies. Results indicate that horizontal location accuracies of l-5 cm are feasible. GPS receiver characteristics such as reacquisition time and measurement accuracies are discussed. Techniques available for mitigating near-far problems in a tunnel environment are discussed, including code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA).
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	527 - 533
Cite this article:	Galijan, Randal C., "Analysis and Simulation of a Candidate Deployment Geometry and Characteristics of Pseudolites Within a Tunnel," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 527-533.
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