Wireless Assisted GPS-SiRF Architecture and Field Test Results

L.J. Garin, M. Chansarkar, S. Miocinovic, C. Norman, D. Hilgenberg

Abstract:	Wireless E911 service has recently attracted much interest. Knowledge of a cell phone caller’s location can greatly improve emergency dispatch time. The FCC has now mandated that all cellular, personal communications service (PCS) and other wireless operators implement an E911 location capability by October 2001. The currently mandated accuracy for wireless E911 is 125 meters (RMS) horizontal at least 67% of the time. Several types of network-based locations services have been tested, but all require considerable network cost and only achieve marginal accuracy and availability results. GPS positioning promises significant advantages in terms of availability and location accuracy over network-based solutions. However, the E911 environment is quite different from traditional GPS applications. Much of the data required for satellite acquisition, signal tracking, time synchronization and location determination can be obtained from the wireless network much faster than it can be gotten directly from GPS satellites. Thus, time-to-first- fix, even from a cold start situation, signal sensitivity, and position accuracy are all improved with respect to a stand-alone GPS receiver. The SiRFLoc™ architecture for wireless phone positioning services including E911 seamlessly supports any level of network assistance from standalone to network centric. It exhibits greatly improved signal sensitivity. Contrary to several other E911 implementations, SiRFLoc can be operated in a handset-centric mode that adds a very limited burden to the wireless network, and achieves overall performance at least as good as the network-centric methods. SiRFLoc can also, if required, support a network-centric type of architecture. Finally, SiRFLoc can be used as a standalone GPS receiver, when network assistance is not available (out of range, or network assistance not implemented or failing), or when the assisted mode performance is not desired or too costly. SiRFLoc is very effective in terms of cost, volume, and power consumption and is easily and seamlessly integrated into any current generation cellular handset. Field testing of SiRFLoc demonstrates significant performance improvements in terms of time-to-first-fix, weak signal acquisition, tracking (indoor capabilities), and position accuracy.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	489 - 498
Cite this article:	Garin, L.J., Chansarkar, M., Miocinovic, S., Norman, C., Hilgenberg, D., "Wireless Assisted GPS-SiRF Architecture and Field Test Results," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 489-498.
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