Enhanced Sensitivity for Acquisition in Weak Signal Environments Through the Use of Extended Dwell Times

John L. Shewfelt, Robert Nishikawa, Chuck Norman and Geoffrey F. Cox

Abstract:	The assimilation of GPS technology into a variety of low power, small form-factor consumer devices and the need to operate in obstructed, attenuated, and fluctuating signal environments has resulted in unique challenges for commercial GPS receivers. Due to antenna and other implementation losses typical of handheld receivers, the ergonomic considerations of handheld devices, and the anticipated use model scenarios for many consumer applications, the signal levels at which the GPS receiver is expected to perform are significantly lower that typical open sky conditions. As a result, the GPS receiver must acquire and track signals at increasingly lower signal levels. The SiRFstarIIe chipset provides a flexible hardware and software architecture for implementing signal acquisition and tracking of low level signals using a combination of coherent and non-coherent (I/Q) hardware and software integration techniques. In the standard Satellite State Tracking Engine (SSTE), a hardware tracker is implemented to perform signal search, acquisition, detection, code lock, and carrier lock. Internal detection thresholds and hardware integration registers are programmed to provide a theoretical 95% Probability of Detection (POD) with a False Alarm Rate (FAR) or false detection rate of 3.0 x 10-2 per second.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	155 - 203
Cite this article:	Shewfelt, John L., Nishikawa, Robert, Norman, Chuck, Cox, Geoffrey F., "Enhanced Sensitivity for Acquisition in Weak Signal Environments Through the Use of Extended Dwell Times," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 155-203.
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