Objective: Design and demonstration of link protection and restoration protocols that can be deployed to provide optical feeder link diversity in mega-constellations with inter-satellite links. Targeted Improvements: >30% increased optical network throughput witha reduced number of ground stations and reduced CAPEX. Description: Optical feeder links for LEO satellite systems suffer from frequent disruptions due to cloud blockages that render them inadequate for telecommunications services that require high availability. GW site diversity is a promising solution to achieve the necessary optical feeder link availability. For LEO satellites, optical feeder links close at about minimum 20 degrees elevation angles. In order to mitigate cloud blockage, site diversity solutions need minimum 300 km distance between GWs. Therefore, GWs that are sufficiently apart from each other to exploit site diversity as a mitigation to cloud blockage are unlikely to be within the footprint of a single LEO satellite. Moreover, due to satellite mobility, it is not easy to maintain long-lasting mappings between redundant GW groups and corresponding LEO satellites. Thus, we cannot use GW site diversity protocols that are designed for GEO satellite systems. Instead, one must consider feeder path diversity between ground GWsand multiple LEO satellites in the constellation, in contrast to feeder link diversity between multiple ground GWs and a specific GEO satellite. The solution uses multiple paths between a network of ground GWs and the LEO satellite constellation. Each path is between a satellite and a GW. The paths are link-disjoint, meaning that they do not share any common links. There are different strategies that can use these paths in 1:1, 1+1, and simultaneous fashions, and that route the traffic along these paths. Link protection and restoration mechanisms in terrestrial network protocols such as OTN/SONET/SDH, MPLS, Ethernet, and IP are defined in various standards. The proposed activity shall investigate, design and demonstrate similar link protection and restoration mechanisms for satellite constellation network with optical feeder links. In addition to these solutions, those solutions that simultaneously use multiple paths shall be investigated for minimum disruption durations. The solutions shall be evaluated at high transmission rates under realistic cloud blockage statistics. The key performance indicators are delay, jitter, disruption durations, required buffering space for delay compensation, and additional capacity needed in redundant paths.

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