LEO Satellite Handover via Preliminary Timing Synchronization
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Solution Overview
Problem
Mobile satellite communications systems, particularly those using Low Earth Orbit (LEO) satellites, face challenges with frequent handovers due to beam movement, requiring efficient and dynamic handover processes that can manage random access procedures and channels to maintain continuous communication.
Innovation Solution
A method for user terminal handover in a satellite communications network involves receiving an initial handover message with a target frequency and timing correction, reconfiguring the receiver, decoding data transmissions to determine physical random access channel allocations, and transmitting reply messages to complete channel configuration, ensuring seamless data flow across satellites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If LEO satellite beam movement is used to provide coverage, then area coverage is improved, but handover frequency increases
Solution Approach 1:
The patent performs preliminary actions by pre-synchronizing uplink transmissions from multiple user terminals to arrive simultaneously at the moving satellite beam. Timing correction values are calculated in advance based on predicted satellite positions and terminal locations, allowing terminals to adjust their transmission timing before handover occurs. This preliminary synchronization reduces the complexity and frequency of handover operations by maintaining continuous uplink synchronization as the satellite moves across the beam footprint.
2Reliability
If timing synchronization is maintained for moving satellites, then communication reliability is improved, but system complexity increases
Solution Approach 1:
The patent implements self-service by having each user terminal autonomously calculate and apply its own timing correction value based on received synchronization information from the satellite. Each terminal independently determines its timing offset relative to the moving satellite beam and adjusts its uplink transmissions accordingly, without requiring complex centralized control or coordination with other terminals. This self-service approach maintains synchronization reliability while reducing overall system complexity.
Data Source
AI summary
Approaches for efficient, dynamic and continuous handover processes, which encompass selection of an optimal path (consisting of a satellite, a satellite beam and carrier frequency set) over which a mobile user terminal (UT) communicates with the radio access network in a mobile satellite communications system, are provided. A set of path factors are determined regarding each of a plurality of communications paths for the UT. A path selection metric (PSM) for each communications path is determined, wherein the PSM for each communications path is determined via a weighted calculation based on the respective set of path factors for the communications path. A decision is made as to whether to perform a handover of the UT from a first of the communications paths to a second of the communications paths, wherein the determination is based on an evaluation performed based at least in part on the PSM.