LaNWiFi.NeTWorld's Wireless Technology Center // Wireless For Freedom.

• Multihop wireless network: One incentive to develop WMNs is to extend the coverage range of current wireless networks without sacrificing the channel capacity. Another major objective of WMNs is to provide nonline-of-sight (NLOS) connectivity among users without direct line-of-sight (LOS) links. To meet these requirements, mesh-style multihopping is indispensable , which facilitates higher throughput without sacrificing effective radio range via shorter link distances, less interference between nodes, and more efficient frequency reuse. • Support for ad hoc networking, and capability of self-forming, self-healing, and self-organization:Ad hoc networking enhances network performance, such as flexible network architecture, easy deployment and configuration, fault tolerance, and mesh connectivity, i.e., multipoint-to-multipoint communications. Due to these features, WMNs have low upfront investment requirement, and the network can grow gradually as needed.

• Mobility dependence on the type of mesh nodes: Mesh routers usually have minimal mobility, while mesh clients can be stationary or mobile nodes. Thus, the mobility in WMNs varies from node to node, which is different from adhoc networks.

• Multiple types of network access: InWMNs, both backhaul access to the Internet and peer-to-peer (P2P) communications within WMNs are supported . In addition, integration ofWMNs with other wireless networks and providing services to end-users of these networks can be accomplished through WMNs. However, an ad hoc network does not require these capabilities.

• Dependence of power-consumption constraints on the type of mesh nodes: Mesh routers in WMNs usually do not have strict constraints on power consumption. However, mesh clients may require power efficient protocols. As an example, a meshcapable sensor requires its communication protocols to be power efficient. Thus, the MAC or routing protocols optimized for mesh routers may not be appropriate for mesh clients, because power efficiency is the primary concern for wireless sensor networks.

• Compatibility and interoperability with existing wireless networks: For example, WMNs built based on IEEE 802.11 technologies  must be compatible with IEEE 802.11 standards in the sense of supporting both mesh-capable and conventional Wi-Fi clients. Such WMNs also need to be interoperable with other wireless networks such as WiMAX, ZigBee , and cellular systems.

• Wireless infrastructure/backbone: As discussed before, WMNs consist of a wireless backbone with mesh routers. The wireless backbone provides wide coverage, connectivity, and robustness in the wireless domain. However, the connectivity of ad hoc networks depends on the individual contributions of end users which may not be reliable.

• Integration: WMNs support conventional clients that use the same radio technologies as a mesh router. This is accomplished through a host-routing function available in mesh routers. WMNs also enable integration of various existing networks such as Wi-Fi, the Internet, cellular and sensor networks through gateway/bridge functionalities in the mesh routers. Consequently, users in one network are provided with services in other networks, through the use of the wireless infrastructure. The integrated wireless networks through WMNs resemble the Internet backbone, since the physical location of network nodes becomes less important than the capacity and network topology.

• Dedicated routing and configuration: In ad hoc networks, end-user devices also perform routing and configuration functionalities for all other nodes in the networks. However, WMNs contain mesh routers for these functionalities. Hence, the load on end-user devices is significantly decreased, which provides a lower energy consumption and high-end application capabilities to possibly mobile and energy-constrained end-users. Moreover, the end-user requirements are limited which decreases the cost of devices that can be used in WMNs.
• Multiple radios: As discussed before, mesh routers can be equipped with multiple radios to perform routing and access functionalities. This enables separation of two main types of traffic in the wireless domain. While routing and configuration traffic is performed between mesh routers, access to the network from end users can be carried on a different radio. This significantly improves the capacity of the network. On the other hand, these functionalities are performed in the same channel in ad hoc networks constraining the performance.
• Mobility: Since ad hoc networks provide routing using the end-user devices, the network topology and connectivity depend on the movement of users. This imposes additional challenges to routing protocols as well as network configuration and deployment. Since mesh routers provide the infrastructure in WMNs, the coverage of the WMN can be engineered easily. While providing continuous connectivity throughout the network, the mobility of end users is still supported, without compromising the performance of the network.
• Compatibility: WMNs contain many differences when compared to ad hoc networks. However, as discussed above, ad hoc networks can be considered as a subset of WMNs. More specifically, the existing techniques developed for ad hoc networks are already applicable to WMNs. As an example, through the use of mesh routers and routingcapable end users, multiple ad hoc networks can be supported in WMNs, but with further integration of these networks.