Fine-Over-Coarse Spectrum Sharing With Shaped Virtual Cells for Hybrid Satellite-UAV-Terrestrial Maritime Networks

Spectrum sharing among the satellite, unmanned aerial vehicle (UAV), and terrestrial components is crucial to alleviate spectrum scarcity in a hybrid maritime communication network (MCN). Fine-grained spectrum sharing based on ms-level time-domain slices is widely envisioned. However, ms-level time synchronization is challenging in the hybrid MCN due to the large diversity in the link delay. To tackle this challenge, we propose a fine-over-coarse spectrum sharing framework based on coordinated link scheduling, which is realized by joint subcarrier and time slice allocation. Specially, by link-cluster-based scheduling with grouped time slice allocation for the satellite links, time-slice-oriented spectrum sharing is realized with coarse time synchronization at time scales much larger than a single time slice duration. In the framework, only large-scale channel state information (CSI) is utilized for saving cost. A worst-case model is introduced to depict interference caused by satellite link clusters, and an NP-hard mixed integer programming (MIP) problem is formulated. Based on analysis on the characteristics of the optimal solution, a novel link clustering algorithm is proposed to form a group of shaped virtual cells within the coverage area of the MCN. A suboptimal spectrum sharing scheme with only a small performance gap to the optimal one is then proposed. Simulations show that a significant improvement in both energy efficiency and spectrum efficiency can be achieved by the proposed framework.