GPS Receiver Code Phase Search Narrowing via RPS Time
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Solution Overview
Problem
Conventional GPS receivers face challenges in reducing the time required to acquire signal power, which contributes significantly to the overall time to first fix (TTFF), due to the need for extensive correlations between the incoming GPS signal and local replica code phases.
Innovation Solution
A radio positioning system (RPS) is used to determine radio signal times-of-arrival (TOAs) to compute an RPS-based position and time, which are then employed to preset a local GPS PRN replica code phase close to the incoming GPS signal, thereby narrowing the search range for the correct code phase and reducing the number of correlations needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional search algorithms are used to acquire GPS signal power by testing all possible code phases, then the GPS receiver can ensure finding the correct code phase, but the time to first fix increases significantly
Solution Approach 1:
The patent applies preliminary action by using a radio positioning system to pre-determine the approximate code phase before the GPS signal acquisition process begins. The RPS provides preliminary position and time information that allows the GPS receiver to narrow down the search range to a small window around the expected code phase, rather than searching all possible phases from scratch.
Solution Approach 2:
The patent applies local quality by focusing the code phase search within a localized narrow range rather than searching the entire code phase space. The RPS-based position and time information creates a localized search window that concentrates computational resources on the most likely code phase region, improving efficiency while maintaining reliability.
2Measurement precision
If the local frequency is set to trial frequencies and correlations are performed with all possible code phases, then the correct code phase can be found, but the number of correlations required increases the acquisition time
Solution Approach 1:
The RPS performs preliminary determination of the code phase using radio signal TOAs and position calculations before the GPS correlation process begins. This preliminary action establishes a narrowed search range that reduces the number of correlations needed while maintaining sufficient precision to identify the correct code phase.
Solution Approach 2:
The patent applies partial action by performing correlations only within a partial (narrowed) range of code phases rather than all possible phases. The RPS-based estimation provides enough accuracy to define a small search window, making the partial search both feasible and sufficient for reliable code phase acquisition.
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AI summary
A mobile GPS location system. The location system includes a mobile radio transceiver for transmitting a radio positioning signal and receiving a responsive radio system signal having a radio positioning system (RPS)-based time and position derived from the radio positioning signal; a mobile global positioning system (GPS) receiver; and a code range selector using the RPS-based time and position for selecting a code search range. The mobile GPS receiver uses the code search range for focusing a code phase search to a narrow range for rapidly acquiring a GPS signal. The RPS-based time and position are derived from a plurality of radio signal times-of-arrival (TOA)s determined by a plurality of system units from the radio positioning signal.