Efficient virtual-backbone routing in mobile ad hoc networks

Since the physical topology of mobile ad hoc networks (MANETs) is generally unstable, an appealing approach is the construction of a stable and robust virtual topology or backbone. A virtual backbone can play important roles related to routing and connectivity management. In this paper, the problem of providing such a virtual backbone with low overhead is investigated. In particular, we propose an approach, called virtual grid architecture (VGA), that can be applied to both homogeneous and heterogeneous MANETs. We study the performance tradeoffs between the VGA clustering approach and an optimal clustering based on an integer linear program (ILP) formulation. Many properties of the VGA clustering approach, e.g., VGA size, route length over VGA, and clustering overhead are also studied and quantified. Analytical as well as simulation results show that average route length over VGA and VGA cardinality tend to be close to optimal. The results also show that the overhead of creating and maintaining VGA is greatly reduced, and thus the routing performance is improved significantly. To illustrate, two hierarchical routing techniques that operate on top of VGA are presented and evaluated. Performance evaluation shows that VGA clustering approach, albeit simple, is able to provide more stable (long lifetime) routes, deliver more packets, and accept more calls.