NTN Ephemeris Encoding for Accurate Sync With Lower Bit Overhead
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Solution Overview
Problem
In non-terrestrial network (NTN) based wireless communications, large timing and frequency offsets due to the distance and movement of base stations or radio repeaters like satellites or UAVs cause challenges in accurate timing and frequency compensation, which are exacerbated by the signaling overhead and power consumption associated with precise ephemeris formats.
Innovation Solution
The method involves optimizing ephemeris information formats by using association indices and relative positions to divide the space into reference regions, reducing the bit size required for accurate prediction of base station or repeater positions and velocities, and employing polar coordinate systems and truncated octahedrons to map parameters efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a format with larger bit size is used for ephemeris information, then prediction accuracy is improved, but signaling overhead and power consumption increase
Solution Approach 1:
The ephemeris information is segmented into multiple fields with different bit allocations. The position information is divided into latitude, longitude, and altitude components, each with configurable bit sizes. Velocity information is similarly segmented. This allows selective precision allocation to different parameters based on their importance and variability, achieving overall accurate prediction while minimizing total bit size.
Solution Approach 2:
Different bit precision levels are applied to different components of the ephemeris data based on their local requirements. For example, latitude and longitude may use higher precision bits when the satellite is in regions requiring fine positioning, while altitude may use fewer bits when vertical variation is minimal. This local quality approach optimizes the balance between accuracy and bit size for each parameter.
2Reliability
If ephemeris information is broadcast periodically, then UE can perform pre-compensation for timing and frequency offsets, but signaling overhead increases
Solution Approach 1:
The ephemeris broadcast mechanism is made dynamic through configurable parameters. The network can adjust the broadcast period, the number of ephemeris parameters included, and the precision level based on current system conditions, satellite motion characteristics, and UE requirements. This dynamic adaptation allows the system to maintain synchronization reliability while minimizing signaling overhead when conditions permit.
Solution Approach 2:
The patent employs parameter changes to optimize ephemeris transmission. By varying the bit allocation for different ephemeris parameters based on their rate of change and importance, the system transmits only the necessary precision level. For example, when a satellite's position changes slowly, fewer bits are allocated to position parameters, reducing overhead while maintaining adequate prediction accuracy for pre-compensation.
Data Source
AI summary
A wireless communication method for use in a wireless terminal is disclosed. The method comprises receiving, from a wireless network node, ephemeris information comprising a node position and a velocity of a wireless network node, wherein the ephemeris information comprises an association index and a relative position.