مسیریابی کنترل تراکم با استفاده از مکانیزم اختصاص کانال بهینه به شبکه مش بی سیم Congestion Control Routing Using Optimal Channel Assignment Mechanism in Wireless Mesh Network

IEEE 802.11s standard is for Wireless Mesh Network (WMN) which is made up of mesh routers and mesh clients [1]. The mesh routers are the stationary access points which propagate the traffic from various routes to the gateway node that is connected to the internet, in a multi-hop fashion [2]. The multihop communication scenarios do not need a centralized control system. The out of range nodes transmits the packets using intermediate nodes. Therefore, the transmission power and thus interference effect can be reduced. IEEE 802.11s standard utilizes almost all the properties of IEEE 802.11 protocols. There are 12 non-overlapping channels in IEEE 802.11a protocols. An interference is produced if the nearby radios are operating on the same channel which results in congestion in the logical links. The nature of the congestion in MR-MC WMN is different to that in a wired network. The capacity of a wireless node highly depends on the transmission between its neighbors. The frequency channels are limited; therefore, the nearby radios may communicate on the same channel that causes the interference. This interference from a nearby node highly affects the network capacity; hence, results in network congestion. Efficient Channel Assignment (CA) scheme is needed to optimize the network performance [3] [4] [5]. During CA procedure, network undergoes a channel switching phenomenon. The switching from one channel to another produces switching overheads, needs tight time synchronization and produces a considerable amount of switching delay. IEEE 802.11 protocol states the physical channel switching time as 224µs [6]. The real delay is the addition of physical channel switching time, hardware registers reconfiguration time and MAC layer packets processing time. In this paper, the concept of Dijkstra’s algorithm has been used to avoid the congested links and reduce channel switching delay. We introduced a routing technique which is based on a congested link weighted score. In this regard, when the link becomes congested the node undergoes a channel switching procedure. The proposed algorithm saves the congestion information in the form of a table. Then, this congestion information is used using Dijkstra’s algorithm to assign a nonnegative weighted score and generate link ranks. The traffic is routed based on the link ranks. WMN has gained much popularity because it can increase network coverage area with less cost and complexity. CA is an active research area to increase the network capacity and performance by utilizing the frequency spectrum efficiently. IEEE 802.11 protocol provides a limited number of orthogonal frequency channels, therefore, some nearby radios may operate on the same frequency band. In MR-MC system, assigning the channels to the radios by keeping an interference and congestion to the minimum level is very challenging. However, during CA; network faces a channel switching delay and overheads which affect the overall network performance. Assigning multiple channels to the number of nodes without increasing delay caused by channel switching is a key challenge in WMN. This motivates us to highlight the importance of CA approach for enhancing the network performance by avoiding the congested links and employing efficient routing technique. In this paper, we present an effective solution using the channel selection technique which is based on congestion table information. Also, special emphasis is placed on provisioning appropriate algorithm for alleviating overhead and performance degradation resulting from continuous switching and computational complexity. In particular, the concept of Dijkstra’s algorithm to utilize the multi-path function by avoiding the weak links has been used. Moreover, the simulation setup to conduct the analysis is delineated. MC-MR WMN. The system model and problem statement are given in Section III. Section IV explains the overview of channel assignment in WMN and explains the proposed protocol. Section V describes performance evaluation and simulation results followed by the last section VI that concludes the paper.