Telephony over Metropolitan Area Ad Hoc Networks: From Concept to Field Test

Self-organizing multi-radio mesh networks can be used to establish metropolitan ad hoc telephony networks in disaster recovery situations and public safety settings such as after a flood or a terrorist attack. These networks can be employed to enable forces to extend the remaining circuit- switched communication infrastructure. This paper introduces a system architecture, a self-organized topology construction and channel allocation algorithm and its implementation in a distributed protocol. The architecture relies on commercially available IEEE 802.16-2004 (WiMAX) equipment that can be employed to build routers and gateways to a wired network. The topology construction and maintenance are based on a modified Dijkstra shortest path algorithm that maximizes a combined metric of path qualities and gateway load. Path qualities are derived from link qualities determined by SINR measurements. The channel allocation greedily allocates the locally least-interfered channel. The protocol includes four sub- protocols: a join protocol, a hello protocol, a leave protocol, and a conflict resolution protocol to resolve inconsistencies in topology data across the network. The proposed architecture, algorithms, and protocol have been assessed via extensive simulations and implemented on hardware. Both, simulation results and field tests confirm their applicability/usability.