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Application Scenarios

In general, novel technology needs promising applications. Indeed, they already exist for WMNs. To become commercially successful and widely accepted WMNs must offer added value to a large audience. The support of only special or military applications, as in case of MANETs, seldom leads to mass-market deployment. In contrast, WMNs have a wide range of civil applications and various scenarios are conceivable. In this section, four use cases of WMN deployment will be presented. The first three are exemplary for WMNs and they take ample advantage of their characteristics. These scenarios were chosen because they do not only differ in size but also in the traffic pattern they generate within the network. Therefore, they illustrate common but distinct applications. The last scenario represents widespread examples of MANETs and clarifies that in these cases WMN are applicable as well. However, this list is not exhaustive and further examples can be found in [AkyWanWan05] and [BruConGre05].

Broadband Home Networks

In recent years, WLANs became popular in providing easy-to-deploy broadband Internet access at home, e.g., via DSL or cable modem. Their drawback is that a single wireless AP cannot cover a wide area like a whole house. Especially indoor placement can reduce the communication range due to walls, ceilings, and other interfering ob jects such as electronic devices. Thus, cabling is still needed for the interconnection of APs. Here, a WMN can be built up by mesh routers instead of conventional APs. They form the backbone that provides Internet access without any additional wiring. Conventional wireless clients are still able to connect to the WMN. The use of routing mesh clients is not mandatory but beneficial.

Nonetheless, broadband home networks are not limited to Internet access. High capacity hard discs and efficient video codecs of today make fully digital video recorders feasible. Out of this, the desire grows for watching TV or recorded programs anywhere, anytime in your house. Apart from the needlessness of additional cabling, the backbone of WMNs helps to establish a high-speed network connecting all the video devices. Remote control of those devices is easily enabled by the bidirectional nature of the network. Multimedia applications are time-critical and bandwidth-consuming, thus, a reliable and fast network is mandatory. WMNs will shortly be capable of fulfilling such requirements.

Another emerging application, IP telephony, has similar requirements. While it does not consume as much bandwidth as video streams do, it is also time-critical but certainly demands for higher mobility. Again, WMNs provide extensive network coverage with low installation effort and costs.

Enterprise Networks

In enterprise networks, the need for multiple APs is evident. Enterprise buildings often consist of several floors and many offices that have to be interconnected. Modern buildings may be prepared for wired computer networks, but as enterprises grow and network technology evolves existing cabling sooner or later becomes insufficient. Thus, networks are not only a one-time investment, but they have to be renewed regularly. Nonetheless, WMNs can be easily extended by adding mesh routers and upgraded by simply replacing them. In contrast, the renewal of wired networks often results in an all new, costly cabling.

When it comes to bridge several buildings, cabling gets really expensive. For legal and/or cost reasons leased lines are often inevitable. In an enterprise WMN, the costly, inflexible, and time-consuming cabling is replaced by wireless connections between mesh gateways, routers, and clients. Multiple mesh gateways and routers can provide redundant links to improve the robustness of the network.

Enterprises regularly maintain their own servers, e.g., for an intranet. Thus, as in broadband home networks, there is a huge amount of internal traffic. While Internet access speed is expected to be comparably low, one is accustomed to high-speed internal network access. Low reliability or high latency to access vital business applications is unacceptable. Thus, providing fast and reliable intranet service wirelessly is a challenging task. The wireless backbone of WMNs can greatly improve reliability utilizing multiple radios and multiple links.

Community and Metropolitan Area Networks

Community networks and wireless metropolitan area networkss (WMAN) aim at offering an alternative to wired broadband network access. On the one hand, communities as the “Freifunker” [freifunker] envision the spread of free networks, democratization of communication systems, and promotion of local social structures. By networking whole districts, villages, and regions they want to counteract the digital divide, while providing low cost Internet access is not their main aim. On the other hand, WMANs—like the one of Cisco Systems mentioned above—have the more pragmatic goal to offer wireless Internet access instead of bridging the last mile by wire.

Generally speaking, community networks fall into the category “Semi-managed WMN” and WMANs into “Fully managed WMN”. The ma jor difference is whether the mesh clients participate in the routing process or not, while their intended network coverage is comparable. Nonetheless, these networks share the traffic pattern of the first and the size of the second application scenario, if not even more. This combination of factors clearly demands the hierarchical approach that is provided by WMNs.

Emergency and P2P Networks

In addition to the application scenarios mentioned above, WMNs also support typical MANET applications. For example, control centers and accommodations are established even in emergency or disaster situations. As they provide the infrastructure for the relief units, they can also provide a backbone and elevate the spontaneous network to a WMN. Furthermore, peer-to-peer (P2P) communication is supported and enhanced by WMNs. Their backbone offers reliable, long-term connections by reducing the amount of mobile intermediate hops between two peers.