Space-based Unidirectional Networks and Resiliency

The bidirectionality of networks makes them resilient, but also vulnerable to propagating failures from cyber-attacks. Unidirectional systems are mostly immune to cyber-attack. 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.