Achieving Fault-Tolerant Network Topology in Wireless Mesh Networks

Abstract

Additional information is available at the end of the chapter http://dx.doi.org/10.5772/50173 IntroductionWireless Mesh Network (WMN) is an ad-hoc network with a fixed network infrastructure (see an example in figure 1). The physical structure of a WMN includes base stations, a backbone and mobile stations. The base stations (also known as mesh routers or mesh points) are static wireless nodes, forming the network infrastructure and providing wireless network access to the mobile stations. The backbone is a wireless ad-hoc network among the base stations. The fixed network infrastructure provides wireless network access to the mobile stations in a service area. Service area is a finite three-dimensional space. The mobile stations are wireless We consider a wireless mesh network which supports a business process and is under the administration of an organization. This is not a MANET (Mobile Ad-hoc Network) consisting of self-dependent mobile nodes, like it is often in the literature. The organization has control over the network infrastructure and aims at providing radio coverage and connectivity in a clearly defined service area. The management appliance is a central instance for basic configuration and diagnosis of the WMN, including topology monitoring, protocol settings, traffic management, etc.Radio coverage and connectivity are basic services of a wireless mesh network which are required for communication. Radio coverage ensures that the mobile stations can access the network infrastructure (backbone) while they are located or moving in the service area. Connectivity ensures that the topology of the backbone is connected. Radio coverageThe service radio coverage is correct, if the service area is covered by the base stations. The service area is covered, if the unification of radio cells of all base stations contains the whole service area. The radio cell of a base station is a part of the space around it, in which a mobile station observes the base station with a radio signal strength sufficient for communication.The sufficient radio signal strength in the service area is a basic requirement for the mobile stations to be able to access the WMN. The radio coverage service ensures this sufficient signal strength in the service area. Service location is a point of the service area, specified by its coordinates. A service location is covered, if the unification of radio cells of all base stations contains the service location. ConnectivityThe service connectivity is correct, if the backbone graph is connected. The backbone graph is a graph with the base stations as vertices and the routing layer links among them as edges. A link exists if two wireless devices can communicate through the wireless medium obeying some qualitative parameters (see section 4.3 for more information). The backbone graph represents the network topology at the routing layer. This graph is connected, if a path (a sequence of edges) exists between every two vertices. A connected backbone graph means a connected routing layer topology whic...