Rate of degradation of centralized optimization solutions and its application to high performance domain formation in ad hoc networks

Future military systems such a FCS and WIN-T require a robust and flexible network that supports thousands of ad hoc nodes; therefore, we must ensure the scalability of networking protocols (e.g., routing, security and QoS). The use of hierarchy is a powerful solution to the scaling problem, since it allows networking protocols to operate on a limited number of nodes, as opposed to the entire network. We have proposed an automated solution to dynamically create and maintain such hierarchy based on a combination of global optimization algorithms (K. Manousakis et al., 2004) and local distributed maintenance protocols (R. Morera et al., October 2003). Global optimization clearly improves performance in a static network but it is unclear how effective it is in a dynamic ad hoc environment. In this paper, we analyze how the hierarchy created deteriorates from the optimal as network conditions change. We show that the fragility of the optimization depends on the particular cost function and the number of metrics that change. More important, we show, for the first time, that global optimization can remain effective for long periods with good cost functions, even in large dynamic ad hoc networks (where metrics may change rapidly due to node mobility and links making and breaking). This result shows that, with fast optimization algorithms such as modified simulated annealing (K. Manousakis et al., 2004), future military systems can use global optimization to autoconfigure domains to significantly improve performance. We also show that local maintenance protocols support the global optimization mechanisms by extending the time the hierarchy remains feasible.