Abstract —Wireless mesh networks (WMN) is one of the attractive wireless technologies which is expected to be the best alternative for the current wired broadband Internet access. WMNs use a completely wireless distribution system which can provide a good level of coverage, reliability and scalability. Multi- channel Multi-radio nodes can be used in the WMNs to enhance the capacity of the network. However, due to the limited number of orthogonal channels, interference and contention are still major factors. In this paper we propose an Integer linear optimization model, which minimizes the contention and the interference by reducing the number of the contending and the interference links along the active routes in the network. Numerical results are provided to show the effectiveness and potential of our proposed solution. Keywords— 802.11, channel assignment, global optimization, multi-hop, orthogonal channel, WMN. I. INTRODUCTION Wireless mesh network (WMN) is a promising technology which is expected to replace the current Internet last mile access [1]. WMN is a set of static wireless routers which forms a wireless backbone and provides services to the wireless clients within the vicinity of this backbone. Among these static routers, there are routers with gateway capabilities which can be connected to the Internet or other types of networks like cellular, sensor and ad-hoc networks. WMNs are easy to deploy and they can provide a wide coverage area. Also, WMNs considered an inexpensive solution since they use the 802.11 radio technology. Because the 802.11 standard was designed for single-hop wireless networks, WMNs performance degrades significantly due to the high level of interference and contention. It has been shown in [12, 13] that the capacity of the WMNs can be increased, if multi-radio multi-channel routers are used in the network. Using Multi-radio multi-channel nodes can increase the capacity of the network by increasing the number of the concurrent transmission throughout the network. The problem of assigning a channel to each communication link in the network in order to decrease the interference and contention level and consequently increase the capacity of the network is called the channel assignment problem. To obtain the maximum capacity of the network a channel assignment strategy is needed which can produce an optimal solution for the assignment problem. However the channel assignment problem is NP-complete problem and the optimal solution is difficult to obtain. The rest of the paper is organized as follows. In the next section we review related works to the channel assignment problem in WMNs. In Sections III-VII, we explain in detail the problem formulation and the system models. Numerical results are given in Section VIII. Finally, conclusions and the future work are given in Section IX. II. RELATED WORKS There are many proposed models and algorithm for the channel assignment problem in WMNs and in multi-hop networks in general. For example, in [11] a simple approach is considered, which assigns the same static set of channels to every node in the network. In this solution there is no need for coordination between the nodes since all the nodes use the same channels. This approach is simple but its far from optimal solution because it does not exploit the full benefit of spectrum. Utilizing all the orthogonal channels through the network by assigning different sets of channels to each node will break the collision domains into smaller ones. As a result the interference will be decreased and the network performance will be enhanced. However, a coordination technique is needed to guarantee the connectivity. Approaches like [2, 3] considered the different loads on the communication links as factor in the assignment. In [2] they assigned the channels to links in a descending order according to their traffic loads so that links with higher loads are assigned to the channels with the less contention level. This solution can increase the capacity but still it is not optimal. In [3], a channel assignment approach, which is based on a network architecture called Hyacinth is proposed. This approach divides the channel assignment problem into two phases: the first is neighbor-to-interface bending and the second is channel-to-interface bending. Each node is responsible to join a spanning tree which has a gateway router as its root. Thus, each node is connected to its parent through a single interface called the up-link. The other interfaces for the Integer Linear Optimization Model for Channel Assignment Problem in Wireless Mesh Network Nidal Nasser and Mosab Abu Zeid Department of Computing & Information Science University of Guelph, Guelph, Ontario, N1G 2W1 Canada {nasser, mosab}@cis.uoguelph.ca 978-1-4244-2202-9/08/$25.00 © 2008 IEEE