Using Inter-Mesh Links to Reduce End-to-End Delay in Walker Delta Constellations
Xiaoxin Qi, Bing Zhang, Zhiliang Qiu, Ling Zheng
Abstract
In Walker delta constellations, satellites moving in different directions form two meshes. Inter-mesh links that connect satellites in different meshes are typically not used due to high relative speed. However, this hurts the end-to-end delay performance. In this letter, we aim to find a tradeoff between the system complexity of establishing such links and the delay performance. An inter-mesh link scheduling method is proposed by considering multiple constraints, including link distance, angular velocity, link setup time, and link switching frequency. First, for a given set of satellites, a set of candidate inter-mesh links are identified which fulfill link distance and angular velocity constraints and maximize topology duration. The inter-mesh links are selected based on maximum matching in general graphs. Then, a set of satellite positions are identified which prolong the topology duration. Based on these positions, satellites in an orbit alternately establish inter-mesh links to fulfill the link setup time constraint. Simulation reveals the benefits of the proposed method: the average end-to-end delay is reduced significantly with acceptable system overhead.