Large-scale low earth orbit (LEO) satellite constellation projects are increasingly adopting inter-satellite links (ISLs) to enable their autonomous and collaborative operation. Due to the large number of satellite constellation network nodes and their continuous movement in orbit, the network nodes may not remain visible to each other at all times, so the ISL-building choices among satellites are diverse and vary with time. As a result, maintaining a network topology requires onboard planning and management. In this paper, we creatively propose an onboard centralized ISL-building planning scheme with the goal of autonomous topology management. A multi-antenna visibility calculation method that takes the antenna installation angle and the turntable rotation threshold into account is provided for the visibility calculation procedure. Additionally, the link-building planning process is modeled using integer linear programming (ILP); however, to tackle the computational complexity problem of ILP, a link-building planning method based on topology stability optimization is presented. The simulation results show that the proposed onboard centralized ISL-building planning scheme can operate among satellites to successfully realize network status collection, visibility calculation, link-building planning, and planning result distribution, as conducted by the dynamic primary satellite. Moreover, the inter-plane link-building planning method based on topology stability optimization improves the network topology stability on the basis of reducing the network delay.

The low earth orbit (LEO) satellite networks are characterized by their significant dynamics of topology and traffic load which pose huge challenge to the development of routing algorithm. In this paper, a novel routing scheme based on link state routing, Satellite networks Link State Routing (SLSR), is proposed for LEO satellite networks. In order to relief the problem of high overhead and slow convergence time when applying link state routing to satellite networks, some measures are taken. Firstly, the link propagation delays which can be predicted are calculated in advance rather than collected in real-time. Secondly, only the uncertain link queuing delays, link and node failures are collected in real-time. Thirdly, the network information is flooded using enhanced flooding algorithm which has much less overhead than original flooding algorithm.

By introducing inter-satellite links (ISLs), global navigation satellite system (GNSS) can achieve inter-satellite ranging, which can enable autonomous navigation, and inter-satellite communication, which can enable the GNSS to form a global network. Due to the resource constraints of satellite platforms, only limited number of ISLs (e.g. only one ISL) can be equipped on one navigation satellite, which makes the navigation satellite network a delay/disruption tolerant network (DTN). Generally, the number of ISLs is less than the number of visible satellites; thus, only those visible satellites which can together meet an overall goal shall be selected. Therefore, contact plan, which comprises all future contacts among satellites, needs to be carefully designed to accommodate the constraints of both inter-satellite ranging and inter-satellite communication. In this paper, a topology handling scheme based on finite state automaton is first presented as the orbiting of GNSS is periodic. Secondly, the contact plan design problem is formulated as a constraint optimization problem with the inter-satellite ranging as a constraint and inter-satellite communication delay as the optimization object. Thirdly, a heuristic algorithm based on simulated annealing is proposed to compute the contact plan. Simulation results show that the delay performance of optimized contact plan is improved and the delay of contact graph routing under optimized contact plan is also improved.