Satellite Network Entry via Sky Coverage Maps
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Solution Overview
Problem
The challenge in communication systems using satellite constellations is the lengthy time required for user terminals to establish communication due to the dynamic nature of non-geosynchronous satellites, which complicates initial network entry and is exacerbated by factors like beacon beamwidth and receive beamwidth, leading to inefficient searches across the sky.
Innovation Solution
The implementation of sky coverage maps that define discrete covered areas based on beacon and receive beamwidths, allowing user terminals to steer their antennas towards predetermined areas rather than scanning the entire sky, combined with the use of stored and updated ephemeris data to predict satellite locations and reduce search space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If user terminals scan the entire sky to find satellites, then they can ensure complete coverage, but the time required to establish communication becomes excessively long
Solution Approach 1:
The sky is segmented into multiple discrete sky coverage areas, each associated with specific satellites. Instead of scanning the entire sky uniformly, the terminal divides the search space into manageable segments based on geographic location and satellite orbital positions, allowing focused searching in relevant areas only.
Solution Approach 2:
Sky coverage maps are pre-calculated and stored in the user terminal before actual satellite acquisition. These maps contain predetermined information about which sky areas correspond to which satellites based on ephemeris data, allowing the terminal to directly jump to relevant search areas without exhaustive scanning.
2Productivity
If user terminals use dynamic non-geosynchronous satellite constellations, then they can achieve better coverage and lower latency, but the complexity of tracking and acquiring satellites increases significantly
Solution Approach 1:
The system pre-calculates sky coverage maps using stored ephemeris data before the terminal needs to acquire a satellite. This preliminary computation of satellite positions and coverage areas transforms a complex real-time tracking problem into a simpler lookup and verification process, reducing the computational burden during actual satellite acquisition.
Solution Approach 2:
The sky coverage map acts as an intermediary data structure that mediates between the terminal and the dynamic satellite constellation. It translates complex orbital mechanics and satellite positions into simplified directional guidance for the terminal antenna, reducing the complexity of direct satellite tracking.
3Measurement precision
If user terminals store detailed ephemeris data for all satellites, then they can accurately predict satellite locations, but the memory requirements and data management complexity increase
Solution Approach 1:
The terminal stores and processes ephemeris data selectively for satellites that are relevant to its geographic location and current time, rather than maintaining complete ephemeris data for all satellites in the constellation. The sky coverage map only includes entries for satellites that may be visible from the terminal's location.
Solution Approach 2:
The ephemeris data is segmented and organized by satellite identifier and time period, allowing the terminal to load only the necessary portions of ephemeris data relevant to current operations. The sky coverage map divides the sky into discrete areas, each associated with specific satellites, allowing selective data retention.
Data Source
AI summary
A satellite provides communication between user terminals (UTs) and ground stations that connect to other networks, such as the Internet. To establish initial contact with a satellite, a UT searches for a satellite's beacon using a phased array or other steerable antenna with a directional receive pattern. The UT retrieves a sky coverage map and stored satellite ephemeris data. The sky coverage map defines discrete areas of the entire sky, with each area based on satellite beacon coverage areas, receive beamwidth of the UT receive antenna, and receive antenna horizon limits. Based on a geolocation of the UT, time, and the ephemeris data, a predicted area in the sky of the satellite is determined. Candidate areas of the sky coverage map are determined that overlap the predicted area, and the receive antenna is directed to search the candidate areas for the satellite beacon.