Navigation Receiver Cold Start TTFF Reduction via Geolocation
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Solution Overview
Problem
Navigation receivers face a long Time-To-First-Fix (TTFF) during the 'cold start' mode due to the need to search all possible satellite signals and Doppler frequencies, which is undesirable and often unavoidable when no prior information is available.
Innovation Solution
The system reduces TTFF by using approximate geographical location information from the user, such as a city or state, to narrow down the search range for satellite signals and Doppler frequencies, allowing for faster signal acquisition and position estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the receiver performs a complete search of all satellite signals and Doppler frequencies during cold start, then the position fix can be obtained with full accuracy, but the Time-To-First-Fix (TTFF) increases to 80-100 seconds
Solution Approach 1:
The system performs preliminary actions by obtaining approximate position information from external sources (GPS, cellular networks, or user input) before initiating the satellite signal search. This preliminary position data allows the receiver to pre-calculate which satellites are likely visible and what their Doppler frequencies might be, thereby narrowing the search space before the actual cold start acquisition begins.
Solution Approach 2:
The search space is segmented into manageable portions based on the approximate position. Instead of searching all possible satellites and frequencies uniformly, the system divides the search into targeted segments corresponding to visible satellites from the approximate location, reducing the overall search complexity and time while maintaining acquisition accuracy.
2Loss of time
If the receiver reduces the search range using approximate location information, then the TTFF decreases to 10-20 seconds, but the complexity of the system increases due to additional location acquisition mechanisms
Solution Approach 1:
The system introduces intermediary components such as auxiliary positioning systems (GPS, cellular networks) and a database of geographic information that mediate between the user and the main satellite signal acquisition process. These intermediaries provide the approximate position data needed to optimize the search without requiring the receiver to perform a complete blind search.
Solution Approach 2:
The receiver is designed with multi-functionality, capable of obtaining position information through multiple channels (GPS, cellular networks, user input) and adapting its signal acquisition strategy based on the available information. This universal approach allows the system to reduce TTFF across various scenarios while maintaining a manageable level of complexity through standardized processing methods.
Data Source
AI summary
The present invention provides systems and methods for reducing the ‘cold start’ TTFF of navigation receivers. The systems and methods receive geographical information from a user, such as the nearest city, state or country, and use this geographical information to approximate the position of the receiver. The systems and methods then make use of the approximate position to reduce the ‘cold start’ TTFF. In an embodiment, the approximate position of the receiver is determined from a co-ordinate database in the receiver based on the geographical information provided by the user. In another embodiment, a user provides geographical information to the receiver through a displayed map with several stages of zooming capability.