Virtual backbone generation and maintenance in ad hoc network mobility management

In this paper, we present the implementation issues of a virtual backbone that supports the operations of the uniform quorum system (UQS) and the randomized database group (RDG) mobility management schemes in an ad hoc network. The virtual backbone comprises nodes that are dynamically selected to contain databases that store the location information of the network nodes. Together with the UQS and RDG schemes, the virtual backbone allows both dynamic database residence and dynamic database access, which provide high degree of location data availability and reliability. We introduce a distributed database coverage heuristic (DDCH), which is equivalent to the centralized greedy algorithm for virtual backbone generation, but only requires local information exchange and local computation. We show how DDCH can be employed to dynamically maintain the structure of the virtual backbone, along with database merging, as the network topology changes. We also provide a means to maintain connectivity among the virtual backbone nodes. We discuss optimization issues of DDCH through simulations. Simulation results suggest that the cost of ad hoc mobility management with a virtual backbone can be far below that of the conventional link-state routing.