GPS Receiver Fast Time-to-First-Fix via Data Bit Correlation
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Solution Overview
Problem
Conventional GPS receivers require significant time to determine the GPS clock time, which prolongs the time to first fix and increases hardware cost or power consumption when attempting to achieve ten millisecond or better time accuracy.
Innovation Solution
A GPS receiver that stores expected data bits for a GPS signal and uses a coarse time estimate to identify a search range, comparing chunks of received data bits to determine the GPS clock time without waiting for Zcounts, thereby reducing latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the GPS receiver monitors GPS data bits to determine clock time using conventional methods, then the GPS clock time can be determined accurately, but the time to first fix is significantly prolonged
Solution Approach 1:
The patent performs preliminary actions by maintaining a running correlation of the incoming data bits with expected data bits before needing to determine GPS clock time. This allows the receiver to have the correlation information already prepared and stored, eliminating the need to monitor and process data bits from scratch when time determination is needed, thus significantly reducing the time to first fix while maintaining accurate time determination
2Measurement precision
If the GPS receiver uses a very stable internal clock to maintain ten millisecond or better time accuracy, then time accuracy is improved, but hardware cost and power consumption increase
Solution Approach 1:
The patent uses the GPS signal itself to provide time synchronization information through the correlation method. Instead of relying on a separate stable internal clock system that consumes power, the receiver derives time accuracy information from the GPS data bits correlation, allowing the system to self-synchronize using the incoming signal rather than requiring expensive and power-hungry standalone timekeeping hardware
3Measurement precision
If the GPS receiver uses a very stable internal clock to maintain ten millisecond or better time accuracy, then time accuracy is improved, but hardware cost increases
Solution Approach 1:
The patent uses the GPS signal itself to provide time synchronization information through the correlation method. Instead of relying on a separate stable internal clock system that consumes power, the receiver derives time accuracy information from the GPS data bits correlation, allowing the system to self-synchronize using the incoming signal rather than requiring expensive and power-hungry standalone timekeeping hardware
4Reliability
If the GPS receiver monitors GPS data bits for extended periods to verify TLM words, then time determination reliability is improved, but the time to first fix is significantly prolonged
Solution Approach 1:
The patent performs preliminary correlation processing continuously or periodically, so that when time determination is needed, the correlation information is already prepared and stored. This preliminary action ensures reliability because the data has been pre-processed and verified, while avoiding the need for extended monitoring at the moment of time determination, thus reducing time to first fix without sacrificing reliability
Data Source
AI summary
A GPS receiver having a fast method for determining GPS clock time. The GPS receiver includes a signal processor for receiving GPS signals from GPS satellites and detecting current GPS data bits carried by the respective GPS signals, a chapter memory for storing a block of expected GPS data bits for the respective GPS satellites, and a GPS time detector for detecting a successful match when a chunk of the expected data bits within a selected search range within the block matches a chunk of the current data bits, and using the successful match for determining the GPS clock time. In an anytime embodiment the GPS receiver enters an operation mode at any time in order to minimize user request latency. In a focused embodiment the GPS receiver enters the operation mode at a prescribed time-of-entry in order to minimize power consumption for cycles of standby and operation modes.