Fig. 1. Formation network model of UAV

Fig. 2. Flexible and rigid frameworks. (a) Flexible graph; (b) rigid graph

Fig. 3. UV ALOS communication link model

Fig. 4. Flowchart of UVORF algorithm

Fig. 5. Hemispherical communication node structure

Fig. 6. Local topology composed of node A and its neighbors. (a) Initial topology; (b) optimal rigid topology

Fig. 7. Curves of neighbor discovery success probability.

Fig. 8. Formation topologies derived by different algorithms. (a) Maximum power topology; (b) UVORF; (c) GG^3D; (d) RNG^3D

Fig. 9. Comparison of average node degree

Fig. 10. Comparison of node degree. (a) Maximum node degree; (b) minimum node degree

Fig. 11. Comparison of average communication radius