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Cooperative Networked GPS signal acquisition

Description:

OBJECTIVE: Develop GPS signal acquisition methods by cooperative networked techniques, describe trade-offs, develop concepts of operations for alternatives, and demonstrate operation. DESCRIPTION: With GPS chipsets such as the CGM (common GPS module) mounted in communication devices such as cell phones or JTRS (joint tactical radio system) radios, the acquisition of GPS signals should be able to be shared among the devices that are in communication with each other. The purpose of this research is to develop methods to accomplish cooperative networked GPS signal acquisition, describe the trade-offs, develop concepts of operations for different alternatives, and demonstrate operation. Goals are to reduce the acquisition time (<1 min) and enable direct acquisition of P(Y) signals. The basic idea is to first synchronize all the participants to the time of one GPS/comm. device. This time is not perfectly known. The code (time) space to be searched is now divided among all the participants. Each participant searches his time space. Once one of the participants acquires the signal, he communicates the results to all the others that participated in the acquisition. The concept can be extended to including ephemeris in addition to GPS time. Those participants that do not need GPS signal can now shut off their devices to save battery power. Those participants who want the GPS signal can continue with the timing information supplied by the participant who acquired the signal. With this information on timing and on which satellite was acquired, all of the other participants can now quickly acquire the GPS signal since the code search space now is very small, saving battery power; the time to acquire can also be significantly shortened. An additional benefit of cooperative networked GPS signal acquisition is signal acquisition at higher interference levels. The fact that the acquisition is distributed over many devices means that, if the total acquisition time is fixed, then each participant can dwell longer and thereby search over his code space segment to overcome higher interference levels. In addition to exchanging time information over communication links, each participant can exchange any additional navigation aid information such as approximate location, almanac, ephemeris, etc. (see Ref. 5). Cooperative networked GPS signal acquisition has interference, fast time to fix, and battery power benefits for all applications: military, commercial and civil. Demonstrate using a prototype system that civil applications, particularly cooperative team efforts such as search-and-rescue missions where participants are both inside and outside buildings, are well suited for this technique. PHASE I: Develop methods to accomplish cooperative networked GPS signal acquisition, describe the trade-offs, and develop concepts of operations for different alternatives. Prepare a report on the findings and develop a plan to demonstrate a cooperative networked GPS signal acquisition system. PHASE II: Based on the recommendations, research outcomes and the plan developed in Phase I, develop a prototype system to demonstrate the benefits of cooperative networked GPS signal acquisition. Determine the battery power saved and the improved performance in high interference situations. PHASE III: Cooperative networked GPS signal acquisition has interference, fast time to fix, and battery power benefits for all applications: military, commercial and civil. Demonstrate using a prototype system that civil applications are well suited for this technique. REFERENCES: 1. http://www.globalsecurity.org/military/systems/ground/jtrs.htm (JRTS reference). 2. http://www.gpsworld.com/gnss-system/gps-aep-55c-rest-story-we-went-source-9599 [mention of CGM (common GPS module)]. 3. Kaplan, E.D. and Hegarty, C., ed,"Understanding GPS: Principles and Applications", 2nd edition, Nov. 30, 2005. ISBN Number: 1-58053-894-0. 4. Misra, P, and Enge, P.,"Global Positioning System: Signals, Measurements, and Performance", 2nd edition, 2006, ISBN 0-9709544-1-7. 5. A-GPS: Assisted GPS, GNSS, and SBAS by Frank van Diggelen, 2009, Artech House, ISBN 13: 978-1-59693-374-3.
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