By an increasing expansion of multimedia services and group communication applications, the need for multicast routing to respond to multicast requests in wireless mesh networks is felt more than before. One of the main challenges in multi-channel multi-radio wireless mesh networks is the efficient use of the capacity of channels as well as load balance in network. In this paper, we proposed an algorithm for building a multicast tree, namely, Load balanced Multicast routing with Genetic Algorithm (LM-GA). The purpose of this algorithm is to construct a multicast tree for requested sessions in Multi-Radio Multi-Channel Wireless Mesh Networks (MCMR WMNs) regarding load balance in channels through minimizing the maximum amount of channels utilization. The results show the efficiency of LM-GA in distribution of load in the channels of the network with finding near-optimal solutions, and also an increase in the network performance while avoiding creation of bottlenecks.
During the evolution of various wireless networks in the next generation for providing better service, a key technology has emerged which is known as wireless mesh networks (WMNs). These networks are popular for their low cost, convenient maintenance, robustness and reliability .
In WMNs packets are sent from the source node to the destination node in a multi-hop manner. Nodes consist of mesh routers and mesh clients. Mesh clients are called end user devices and at the same time routers play the role of transit access point for exchanging information either between clients or clients- internet. Some mesh routers have direct access to wired networks and they serve as gateway for other nodes for access to internet.
In wireless networks unlike the wired ones, owing to their broadcast nature, capacity reduction caused by interference is a basic challenge. A good way to overcome this challenge is to equip the mesh routers with several radios and to assign nonoverlapping channels to their radios. Using multi-radios causes a parallel transmission in different channels; however, it will complicate the routing process. Also, ignoring the channels usage may lead to congestion in specific channels; as a result, a bottleneck may be created or an early overload of a channel may occur. All these will lead to a decrease in the network throughput.
Multicast routing has been considered as a way for communication between several receivers; it means that data will be transmitted / sent from one source to a group of destinations. The aim of multicast routing is to find a multicast tree whose root is the source node and that it covers all the receivers.
Since the problem of constructing a Minimum Cost Multicast Tree (MCMT) is a NP-hard problem , an algorithm named Load balanced Multicast routing with Genetic Algorithm (LM-GA) was used to find the near optimal solution. This algorithm explores the space of solutions and leaves the local optimum in order to get to the best solution.
This paper is organized as follows. Section 2 provides a summary of related works; Section 3 presents the system model and defines the problem; our proposed algorithm is presented in Section 4; Section 5 evaluates the algorithm operation; finally, the discussion and the conclusion are provided in Section 6.
II. RELATED WORKS
The load balance may be studied at two general levels: the node and the channel. Many studies have been carried out on load balance at node level, namely, on the mesh router and gateway. Here the focus is on load balance in channels. Now some research carried out on the construction of the multicast tree and the load balancing on channels are briefly reviewed. For the rest of this paper, the terms mesh routers and nodes are used interchangeably.
In , Liu and Liao studied the problem of building a multicast tree by considering the interference between trees in dynamic traffic model in Multi-Radio Multi-Channel Wireless Mesh Networks (MCMR WMN). Moreover, in their research they proved that the problem of building multicast tree with the minimum cost is a NP-hard problem. Besides, in order to build a multicast tree, first they presented an optimal model and then proposed a near optimal algorithm called Wireless Closest Terminal Branching (WCTB) algorithm. In each stage of this algorithm, a branch from source to destination is added to the tree and this node is the closest uncovered destination to the source.
Avokh and Mirjalili  proposed an innovative algorithm for building a load-balanced multicast tree in MCMR WMN. They used a load-aware cost function to weight the links. In this function, two factors of Wireless Broadcast Advantage (WBA) and node load balance were considered, which resulted in building a multicast tree with the minimum transmission and fair distribution of load in the network and decreasing the interference.