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Heterogenous Power Exploitation in GPS Receivers

Description:

TECHNOLOGY AREA(S): Sensors 

OBJECTIVE: Identify, evaluate, and demonstrate techniques for receivers to use one or a small number of higher power M-code signals to substantially improve jamming tolerance, relative to that without the higher power signals. 

DESCRIPTION: Heterogeneous Power Exploitation (HPE) allows GPS receivers to more fully benefit from a small number, as few as one, of higher power signals when the others are lower power. HPE involves a combination of signal use logic (smartly selecting higher power signals for acquisition and tracking) as well as advanced signal processing techniques that use the more robust higher power signals to aid tracking of less robust, lower power signals. For the foreseeable future, the GPS constellation will provide a range of received M-code power levels. Even the mix of Block II satellites and early GPS III satellites will provide received M-code power levels varying by more than 12 dB, not accounting for variations in receive antenna gain. With regional military protection (RMP) or higher power hosted quasi M (QM)-signals, the variation in received signal power levels could approach 25 dB. Current receivers are not specified or tested to fully benefit from the higher power signals. Research and development is needed to identify and demonstrate practical and effective techniques for HPE. The objective should be receiver processing techniques and approaches that use one or a small number of higher power signals to substantially improve jamming tolerance, relative to that without the higher power signals. 

PHASE I: The first phase will focus on the identification of receiver-based techniques to exploit the HPE and initial performance evaluation. Candidate techniques can be identified via literature review and/or invented by the performers. Once identified these techniques will be initially evaluated (e.g. via software simulation) to quantify their relative performance improvident. Recommendations will be made as to which techniques should be implemented in hardware as part of Phase II. Approaches and techniques should provide trade-off analyses including performance gain versus implementation complexity (e.g. power, SLOC, etc.) 

PHASE II: The second phase will focus on selective implementation of the best techniques identified in Phase I. These should be implemented in a real-time GPS receiver to allow for hardware-in-the-loop (HITL) testing. Once implemented the performance of these techniques will be evaluated over a range of situations (GPS constellation power levels, user state, user dynamics, etc.) 

PHASE III: The third phase will transition the capability to contractors for potential implementation in military GPS User Equipment. In addition, this phase could explore the techniques for applicability to civilian signals (e.g. L1C/A, L1C, L2C, and L5) to improve signal performance in jamming conditions since 5-10 dB variation in gain of these signals can be expected from fixed-radiation pattern antenna receive antennas. 

REFERENCES: 

1. Spilker, J. J. Jr., “Vector Delay Lock Loop Tracking—Position Estimation,” Paper presented at the IEEE Communication Theory Workshop, FL, April 1993.; 2. US Patent Number US5398034A, “Vector delay lock loop processing of radiolocation transmitter signals” 1993-03-29; 3. Barker, B.C., Betz, J.W., Clark, J.E., et al, “Overview of the GPS M Code Signal” The MITRE Corporation accessed 11/2018 from https://www.mitre.org/publications/technical-papers/overview-of-the-gps-m-code-signal; 4. Jones, Michael, “The promises of M-Code and quantum,” GPS World 13 December 2017, accessed 11/2018 from https://www.gpsworld.com/the-promises-of-m-code-and-quantum/

KEYWORDS: Global Positioning System, M-Code, MGUE, Vector Delay Lock Loop 

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