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Inter-satellite links (ISLs) are adopted in global navigation satellitesystems (GNSSs) for high-precision orbit determination and space-basedend-to-end telemetry telecommand control and communications. Due to limitedonboard ISL terminals, the polling time division duplex (PTDD) mechanism isusually proposed for space link layer networking. By extending the pollingmechanism to ground-satellite links (GSLs), a unified management system of thespace segment and the ground segment can be realized. However, under thepolling system how to jointly design the topology of ISLs and GSLs during everyslot to improve data interaction has not been studied. In this paper, weformulate the topology design problem as an integer linear programming, aimingat minimizing the average delay of data delivery from satellites to groundstations while satisfying the ranging requirement for the orbit determination.To tackle the computational complexity problem, we first present a novelmodeling method of delay to reduce the number of decision variables. Further,we propose a more efficient heuristic based on maximum weight matchingalgorithms. Simulation results demonstrate the feasibility of the proposedmethods for practical operation in GNSSs. Comparing the two methods, theheuristic can achieve similar performance with respect to average delay butwith significantly less complexity.

Topology Design for GNSSs Considering Both Inter-satellite Links and Ground-satellite Links