## 1 Introduction  
Wireless mesh networks (WMNs) have been a popular research topic as wireless devices have become more affordable, which was followed by the mass adoption of wireless technology. Because of its robust, reliable and cost-efficient features, many companies have developed different WMN protocols and products for different application purposes [1, 2, 3]. However, no industrial standard existed for WMNs, and thus, these devices were incompatible with each other. Therefore, the Institute of Electrical and Electronics Engineering (IEEE) started the 802.11s Task Group (TG) in July 2004 to unify the research and establish a draft standard for WMNs [4]. The main advantages of the proposed IEEE 802.11s standard are the robustness and the automated generation of the routing table that is used to choose the best path, _i.e._, whether it is through the proactive or reactive mode. These features of IEEE 802.11s allow the existing nodes to update the new path every time a node is added or deleted from the network, which means node failure will not affect the reliability of the network as much as it did with the previous WMN products. The widely deployed 802.11 infrastructure can also be used for wireless sensor networks (WSN) to save on the investment cost of deploying a new network and utilize the advantages of 802.11 technologies [5]. The power consumption concern of 802.11 was also eliminated with the power efficient 802.11, where the sensor device is able to run for 5 to 10 years with only 1 AA battery [5]. This device can then be used as a gateway for the WSN. The data rate of the 802.11 technology is also very high compared to the common technologies used in WSN, such as ZigBee, Bluetooth or 802.15.4 [6]. IEEE 802.11s can then be used to form the mesh topology for the WSN. However, the frequencies used by all of the nodes in the network will interfere with one other if they happen to be in the same or nearby frequency bands. Therefore, minimizing the interference in a WMN or WSN is very important to maximize the performance of the network. In the Wireless Local Area Network (WLAN) standard, IEEE 802.11 uses the unlicensed frequency bands range from 2.4 GHz to 2.4835 GHz (802.11b and 802.11g) and 5 GHz (802.11a) [7]. To maximize the usage of these limited resources or frequencies, non-overlapping operating channels are used simultaneously. The communication between these channels is less likely to interfere with each other's operation. For the IEEE 802.11b/g, the operating channels that are separated by at least five channels (or six for Europe) are the non-overlapping operating channels [7]. For example, channels 1, 6 and 11 are the non-overlapping channels. By utilizing 2 or even 3 non-overlapping channels at the same time, simultaneous data transmissions on their respective channels can occurs without causing interference to each other. The WMN has been applied in commercial products, such as the Open Mesh products, which offer plug-and-play WMN solutions to consumers [1]. However, the proprietary or non standard protocols used in these products make them incompatible with the products from another vendor. According to their official website, even with the existence of incompatibility issues, there are still millions of users around the world [1]. Thus, it is evident that not only is there a vast market for such a product but also research value in building a device that is in accordance with the IEEE 802.11 draft standard. The open source community then developed a few projects that include a wireless mesh networking ability that adheres to the IEEE 802.11s draft standard in their OS. The Linux community has developed the open80211s project [8], while the FreeBSD has its own implementation [9] that also adheres to the IEEE 802.11s draft standard. Currently, researchers that are working on test beds or prototypes of WMN based on the Linux open802.11s project, such as the CedtMesh project [10] and the framework implementation by the University of Pisa, Italy [11].