V2X-Assisted GNSS Hot Start via Ephemeris Relay
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Solution Overview
Problem
Global navigation satellite systems (GNSS) receivers face prolonged time-to-first-fix (TTFF) during cold starts due to the need to acquire both almanac and ephemeris data, which can take up to an hour, hindering efficient navigation applications.
Innovation Solution
A method and apparatus that utilize Vehicle-to-Everything (V2X) communication to provide satellite navigation data, including ephemeris and almanac data, to a GNSS receiver, allowing for a hot start by using the time and position data from a V2X message, thereby reducing the time required to obtain a position fix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GNSS receiver performs a cold start and acquires almanac and ephemeris data from satellites, then the receiver obtains complete navigation data, but the time to first fix (TTFF) is prolonged to 15 minutes to an hour
Solution Approach 1:
The V2X transmitter performs preliminary acquisition of almanac and ephemeris data from satellites and stores this navigation data in memory before it is needed by the GNSS receiver. When the GNSS receiver requires navigation data, it can immediately retrieve pre-acquired data from the V2X transmitter's memory, eliminating the need for the receiver to perform the time-consuming acquisition process itself.
Solution Approach 2:
The V2X transmitter acts as an intermediary between the satellite navigation system and the GNSS receiver. It receives navigation data from satellites, processes and stores it in its memory, and then provides this data to the GNSS receiver upon request. This intermediary role allows the receiver to obtain navigation data without directly acquiring it from satellites, significantly reducing TTFF.
2Measurement precision
If a GNSS receiver waits to acquire satellite signals and process almanac/ephemeris data, then positioning accuracy is achieved, but navigation applications cannot start efficiently
Solution Approach 1:
The system performs preliminary acquisition and validation of navigation data (almanac and ephemeris) by the V2X transmitter before the GNSS receiver needs it. The transmitter continuously monitors satellite signals, acquires navigation data, and stores validated information in its memory, so that when the receiver needs positioning, the data is already prepared and available.
Solution Approach 2:
The V2X transmitter autonomously acquires, validates, and stores navigation data from satellites without requiring the GNSS receiver to perform these functions. The transmitter serves itself by maintaining an up-to-date navigation data cache in its memory, which it can then provide to receivers on demand, enabling rapid positioning initialization.
Data Source
AI summary
A method and system are provided. A first request for satellite navigation data is provided to a vehicle to everything V2X receiver. Satellite navigation data recovered from a V2X message is received from the V2X receiver. The satellite navigation data is provided to a satellite navigation system receiver. The satellite navigation data comprises the data required by the satellite navigation system receiver to perform a hot start.