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Top1. Introduction
A new development in the wireless communication is introduced with the name of wireless mesh networks that promises enhanced flexibility, great performance and high reliability as compared to conventional WLANs (Zhang, Luo, & Hu, 2006). WMN supports load balancing and fault tolerance, so WMNs more robust against failures. Source node has more than one routing path to the destination when one path is down source node efficiently will use backup route without needing to establish a new routing path. The end users in a WMN consumes notable less energy as well as capable of running high-end applications comparing to the end users in an Ad-Hoc network. The WMN contains some Mesh Nodes. There are two types of mesh nodes, namely routers and access points. So that, Routers can perform data packet forwarding while APs are capable of both forwarding and helping the end users. Gateways form a subset of Mesh nodes which can communicate either to the wired backbone network or a neighboring mesh network. (Alotaibi & Mukherjee, 2012). The architecture of WMNs can be classified into three main groups based on nodes functionality. These groups are Infrastructure WMNs, Client WMNs and Hybrid WMNs (Akyildiz, Wang, & Wang, 2005).
Infrastructure WMNs: In this kind of architecture, mesh routers form an infrastructure for all clients to allow them connected with each other. In Figure 1, where sporadic and fixed links point to wireless and wired connections respectively. The mesh routers enhance a mesh self-configuring, self-healing links within themselves for linking to the internet by the functionality of gateway. This approach is also known as infrastructure meshing (Pradhan, Khan, Nijim, & Challoo, 2017) which acts as a backbone for conventional clients as well as WMNs can be integrated with the existing wireless networks through the available gateway/bridge functionality in the router mesh.
Client WMNs (client meshing): This network consists of mesh clients that have the capability to obtain routing and configuration functionalities and also providing end-device applications to users. In Figure 2, client nodes communicate directly with each other with the absence of mesh routers. In general, Client WMNs architecture using one type of radios technology on devices. In Client WMNs, a packet addressed to a node in the network hops through multiple nodes to reach its destination. A wireless mobile ad hoc (MANET) network can be an example of client mesh networks.
Hybrid WMNs: Hybrid WMNs architecture is a combination of both infrastructure and Client meshing. Also, it takes advantage of both types. Mesh Clients can access the network via mesh routers or immediately meshing with another mesh clients whereas the infrastructure meshing provides connectivity to another network such as the Internet, WiFi, WiMAX, sensor networks, etc. Figure 3 shows the Hybrid WMNs architecture.
Routing is a challenging issue for dynamic and mobile wireless networks (Alotaibi & Mukherjee, 2012), Among the destination and source nodes, the selection of path is key routing protocols’ task. Routing protocols should ensure the efficient and effective communication over a complete mesh network, In addition, the routing protocol may be in charge of producing different grades of Quality of Service (QoS) to handle various application requirements (Zhang et al., 2006). Many researchers employed various applications with different simulation tools in WMN fields such as FTP, VoIP, and video conferencing (Al-Ghadanfary & Al-Somaidai, 2013; Alshamrani et al., 2013; Benni, Manvi, & Anup, 2015; Chhabra & Singh, 2015; Meeran, Annus, & Le Moullec, 2017). The key challenges must be fixed in order to provide an effective real-time of voice and video communication during wireless mesh networks field because of the wireless channels instability. therefore, a lot of researchers are interested and consternated with the method of handling the design of wireless routing protocols design (Zhang et al., 2006).