Distributed Orbit Propagation for Mobile GPS Positioning
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Solution Overview
Problem
Current GPS systems in mobile devices face challenges in maintaining accurate satellite orbit predictions due to limited computational power and harsh signal environments, leading to increased data transmission demands and latency in satellite position calculations.
Innovation Solution
A distributed orbit propagation method that uses a predicted GPS server to provide seed data to mobile devices, allowing them to locally propagate satellite orbits and generate synthetic ephemeris, reducing the need for continuous network connectivity and data transmission, and enabling accurate position calculations with minimal accuracy degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous ephemeris data transmission is used to maintain accurate satellite position predictions, then position accuracy is improved, but data transmission requirements and network loading increase significantly
Solution Approach 1:
The system pre-computes and transmits orbit predictions for future time periods before they are needed. The server calculates satellite positions for multiple future epochs and transmits this predictive data to mobile devices in advance, allowing the devices to have accurate ephemeris data without requiring continuous real-time updates from the network.
Solution Approach 2:
The continuous ephemeris data stream is segmented into discrete prediction blocks covering specific future time periods. Instead of transmitting continuous data, the system transmits discrete orbit prediction datasets that can be stored and queried by the mobile device at specific future times, reducing overall data transmission volume while maintaining accuracy.
2Measurement precision
If real-time ephemeris updates are transmitted continuously, then position prediction accuracy is maintained, but network latency and transmission time increase
Solution Approach 1:
The system performs orbit calculations and ephemeris generation in advance before the actual positioning is needed. By pre-computing satellite positions for future time periods and caching this data on mobile devices, the system eliminates the need for real-time network queries during critical positioning operations, significantly reducing latency.
3Measurement precision
If complex orbit propagation calculations are performed continuously, then position accuracy is improved, but computational power requirements increase
Solution Approach 1:
The computationally intensive orbit propagation is segmented into two parts: (1) centralized pre-computation by the server using powerful processing resources to calculate future orbits in advance, and (2) simple data retrieval and interpolation by the mobile device. This division moves the heavy computational workload from the device to the server.
Solution Approach 2:
Instead of continuously calculating and receiving updated ephemeris data from the server, the mobile device receives a copy of pre-computed orbit predictions and stores this data locally. The device then uses this copied data for positioning without requiring continuous computational updates, significantly reducing its processing requirements.
4Measurement precision
If frequent ephemeris data requests are made from the network, then position accuracy is maintained, but network connectivity requirements increase
Solution Approach 1:
The system establishes network connectivity and retrieves ephemeris data in advance before the device needs positioning services. By caching the pre-fetched orbit prediction data on the mobile device, the system can maintain position accuracy even when network connectivity is interrupted or unavailable, reducing reliance on continuous network reliability.
Data Source
AI summary
A mobile device includes a processor for generating a predicted orbital state vector using an initial satellite position and velocity and force model parameters received from a server, the predicted orbital state vector being used to generate satellite navigation data; and a GNSS receiver in communication with the processor for receiving the satellite navigation data; wherein the satellite navigation data is valid for a time period.