Space-Based Unidirectional Networks and Resiliency

The bidirectionality of networks makes them resilient, but also vulnerable to propagating failures from cyberattacks. Unidirectional systems are mostly immune to cyberattack. The radio navigation component of the Global Positioning System (GPS) is unidirectional. However, it may be assessed as a bidirectional network when it is used to provide equivalent information in place of terrestrial networks that have failed. GPS thus serves as a case study for a novel mathematical formulation of the contribution of space-based unidirectional systems to the resilience of strategic cyber networks. The technical basis for this formulation is a parametric model of the exceedance probability for N GPS satellites in view of a receiver. The exceedance probabilities form an N+1 node network whose spectral radius can be computed. Three resiliency attributes for space-based unidirectional networks that use the resulting spectral radii are examined: connectedness as a function of failure, unidirectionality, and directness.