Active Maintenance of Hierarchical Structures in Future Army Networks

The application of appropriate hierarchical structures is an efficient mechanism for improving the survivability and scalability of mobile ad hoc networks (MANETs). Due to network dynamics and infrastructureless character of MANET, however, the imposed hierarchy may harm the performance as the network environment evolves. This degradation can be prevented by adapting the hierarchy to the new network characteristics, so that the resulting hierarchy continues to be beneficial. This hierarchy maintenance is traditionally localized and driven by the constraint violations (feasibility) due to network dynamics. The traditional class of hierarchy maintenance is called passive, since it is triggered only by infeasibility. In this paper we present a new class of hierarchy maintenance algorithms, called active hierarchy maintenance. Unlike the Passive approach, Active Maintenance continuously operate for both preserving the feasibility and improving the evolving hierarchical structures. Our active maintenance algorithms operate locally using the same basic objective functions used in hierarchy creation. For a specific class of objective functions, we prove that the localized reconfigurations applied by the active maintenance result in global hierarchy quality improvement. Using an example of creating balanced size domains, our simulation results show that Active Local Maintenance preserves good hierarchy quality (cost increase is less than 50% of the global optimal), independently of the network dynamics. To the contrary, Passive Local maintenance shows rapid quality degradation (cost increase up to 400%)