Quantum Communication in 6G Satellite Networks: Entanglement Distribution Across Changing Topologies

Abstract: As LEO/VLEO satellites offer many attractive features, such as low transmission delay, they are expected to be an integral part of 6G. Global entanglement distribution over LEO and VLEO satellites network must reckon with satellite movement over time. Current studies do not fully capture the dynamic nature of satellite constellations. We model a dynamic LEO/VLEO satellite network as a time-varying graph and construct a sequence of static graphs to represent a dynamic network. We study the entanglement distribution problem between a set of source-destination node pairs in this dynamic network utilizing Multi-commodity Flow (MCF). Solving MCF over a sequence of graphs independently for each graph may produce a completely different set of paths. Changing the set of paths every time the graph topology changes may involve a significant amount of overhead, as an established set of paths must be taken down and a new set of paths established. We propose a technique that will avoid this overhead by computing only one set of paths P to be used over all the graphs in the sequence. The degraded performance offered by P may be viewed as the cost of using P. The benefit of using P is the overhead cost of path switching that can be avoided. We provide a cost-benefit analysis in a LEO/VLEO constellation for entanglement distribution between multiple source-destination pairs. Our extensive experimentation shows that a significant amount of savings in overhead can be achieved if one is willing to accept a slightly degraded performance.