Beacon assisted discovery protocol (BEAD) for self-organizing hierarchical ad-hoc networks

This paper describes a beacon assisted discovery mechanism for self-organizing hierarchical ad-hoc networks. The discovery protocol, which operates between the medium access control (MAC) and network layers, is responsible for topology formation in the ad-hoc network taking into account performance objectives such as throughput, delay, energy consumption and robustness. The proposed discovery protocol operates by listening to augmented MAC-layer beacons from neighboring radio nodes and then selects a subset of these for routing associations based on specified criteria. A distributed heuristic algorithm for topology formation is considered and compared with upper-bound centralized algorithms with optimization objectives such as maximum throughput, minimum delay or minimum energy. Simulation results (based on ns-2 models) are given for the performance of the proposed discovery methods, demonstrating significant improvements in routing overhead when compared to an ad hoc network without discovery. A proof-of-concept prototype implementation for an IEEE 802.11b-based three-tier hierarchical ad hoc network is briefly described in conclusion.