Topology discovery and maintenance for heterogeneous wireless back-haul networks supporting unidirectional technologies

Wireless operators, in developed or emerging regions, must support the triple-play service offerings demanded by the market or by regulatory bodies through so-called Universal Service Obligations (USOs). The same USO often also requires the coverage of a large percentage of the population, which especially in emerging regions lives in vast rural areas outside the larger cities. Since individual operators might have different requirements such as available spectrum licenses or technologies, we have developed a carrier-grade heterogeneous multi-radio back-haul architecture which may be deployed to extend, complement or even replace traditional operator equipment. This Wireless Back-Haul (WiBACK) architecture integrates broadcast technologies to off-load the distribution of live content, such as TV or radio, to longer range, e.g. DVB-T, overlay cells. Therefore, the WiBACK architecture provides a cost-effective low-power alternative to extend the wireless back-haul coverage in urban, but especially in rural and previously unconnected areas. In order to manage the physical and logical resources of such a network, a centralized coordinator approach has been chosen, where no routing state is kept at plain WiBACK Nodes (WNs) which merely store QoS-aware MPLS forwarding state. In this paper we present our design of the centralized Topology Management Function (TMF) and its ring-based approach, validate its functionality and evaluate the performance for dense and sparse topologies.