Satellite Handoff Timing Coordination for LEO Link Continuity
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Solution Overview
Problem
Non-geosynchronous satellite communication systems, such as LEO satellite-based systems, face challenges in maintaining high-quality user experience and minimizing call drops or delays during satellite-to-satellite handoffs due to the need to minimize disconnection of data links during these procedures.
Innovation Solution
A handoff procedure is coordinated between the gateway and user terminal to schedule and execute a satellite-to-satellite handoff with reduced messaging round-trip delays, ensuring no outage on the return link and forward link by aligning the timing of packet transmissions between the source and target satellites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If satellite-to-satellite handoff is performed in non-geosynchronous satellite systems, then communication coverage and system flexibility are improved, but disconnection of data links and communication outages occur during handoff procedures
Solution Approach 1:
The gateway pre-calculates and transmits handoff parameters to the user terminal before the handoff event occurs. This includes timing information, frequency allocation, and other necessary parameters that enable the user terminal to execute the handoff procedure without interruption, thus maintaining communication continuity while enabling satellite-to-satellite handoff capability
2Productivity
If conventional handoff procedures are used in non-geosynchronous satellite systems, then satellite mobility and coverage are improved, but messaging round-trip delays and handoff delays increase
Solution Approach 1:
The gateway performs preliminary calculation of handoff parameters including timing and frequency information before the handoff is needed. This advance preparation eliminates the need for real-time round-trip messaging during the actual handoff execution, significantly reducing handoff delay while maintaining efficient satellite coverage
Solution Approach 2:
The gateway acts as an intermediary that pre-processes and prepares handoff parameters, transmitting them to the user terminal in advance. This intermediary role allows the system to avoid direct real-time coordination between satellites during handoff, thereby reducing messaging round-trip delays while maintaining effective satellite mobility and coverage
3Adaptability or versatility
If satellite-to-satellite handoff is implemented, then system adaptability is improved, but call drops and communication disruptions occur
Solution Approach 1:
By pre-calculating and transmitting complete handoff parameters before the handoff event, the gateway enables the user terminal to execute the handoff autonomously and seamlessly. This preliminary preparation ensures that the handoff capability is fully implemented while preventing call drops, as the user terminal has all necessary information to maintain continuous communication during the satellite transition
Data Source
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AI summary
Aspects of the disclosure provide a handoff procedure for a satellite communication system such as a broadband low-Earth orbit (LEO) satellite communication system. A gateway and a user terminal (UT) coordinate and schedule a satellite-to-satellite handoff in such a way that there are no messaging round-trip delays between the last return service link (RSL) packet transmitted from the user terminal to the source satellite and the first RSL packet transmitted from the user terminal to the target satellite. Therefore, an outage on the return link (from the user terminal to the gateway) can be limited to the actual time for moving the antenna feed from the source satellite to the target satellite. Furthermore, an outage on the forward link (from the gateway to the user terminal) can be limited to a single round-trip delay in addition to the time for moving the antenna feed.