Single-radio Wireless Mesh Networks Research Articles

Channel Assignment Techniques for Multi-Radio Wireless Mesh Networks: A Survey

With the advent of multiple radio interfaces on a single device, wireless mesh networks start to achieve significant improvement in network capacity, latency, and fault tolerance. The improvement is achieved through concurrent transmissions over different channels utilizing the multiple radio interfaces. However, the introduction of different channels over multiple radios on single mesh node compels to retrospect different issues such as interference, channel diversity, and channel switching from novel perspectives. Due to these novel perspectives, conventional channel assignment techniques proposed for single-radio wireless mesh networks are not generally applicable to the multi-radio cases. Consequently, we have to reconsider the different issues while making a tradeoff among all the available channel assignment options to extract the best performance from a multi-radio wireless mesh network. There are a number of research studies that propose various channel assignment techniques to extract the best performance. In this paper, we present a comprehensive survey on these studies. First, we point out various design issues pertinent to the techniques presented in the studies, and adopt the issues as the basis of our further discussion. Second, we briefly describe several important already-proposed channel assignment techniques. Third, we present a number of channel assignment metrics that are exploited by the already-proposed techniques. Then, depending on the considerations in these techniques, we categorize the techniques and present an exhaustive comparison among them. Nevertheless, we point out a number of real deployments and applications of these techniques in real scenarios. Finally, we identify several open issues for future research with their current status in the literature.

Distributed joint flow-radio and channel assignment using partially overlapping channels in multi-radio wireless mesh networks

Equipping mesh nodes with multiple radios that support multiple wireless channels is considered a promising solution to overcome the capacity limitation of single-radio wireless mesh networks. However, careful and intelligent radio resource management is needed to take full advantage of the extra radios on the mesh nodes. Flow-radio assignment and channel assignment procedures should obey the physical constraints imposed by the radios as well as the topological constraints imposed by routing. Varying numbers of wireless channels are available for the channel assignment procedure for different wireless communication standards. To further complicate the problem, the wireless communication standard implemented by the radios of the wireless mesh network may define overlapping as well as orthogonal channels, as in the case of the IEEE 802.11b/g family of standards. This paper presents Distributed Flow-Radio Channel Assignment, a distributed joint flow-radio and channel assignment scheme and the accompanying distributed protocol in the context of multi-channel multi-radio wireless mesh networks. The scheme’s performance is evaluated on small networks for which the optimal flow-radio and channel configuration can be computed, as well as on large random topologies.

JORCA: joint opportunistic routing and channel assignment

Opportunistic routing (OR) can improve the throughput of wireless mesh networks (WMNs). Most existing studies on OR focus on single-radio WMNs, where the severe interference may largely decrease the performance. Only a few works have studied OR in multi-radio multi-channel WMNs, while they either select opportunistic route with given channel assignment, or assign channel based on selected opportunistic routing, which separate the interdependency of opportunistic routing and channel assignment, and can hardly achieve good performance. This paper formulates the joint problem of opportunistic routing and channel assignment as a mixed integer programming (MIP) problem and proves it to be NP-hard. To solve it, we propose a heuristic iterative algorithm named joint opportunistic routing and channel assignment (JORCA) which exploits multi-user diversity and channel resource. The simulation results demonstrate that, comparing with the two existing solutions, JORCA improves 44% and 15.5% in total throughput.

Characterization of the impact of network topology on the performance of single-radio wireless mesh networks

Stub Wireless Mesh Networks (WMNs) are used to extend Internet access. The use of multiple channels improves the capacity of WMN but significant challenges arise when nodes are limited to a single-radio interface to form the WMN. In particular, the assignment of mesh nodes to channels results on the creation of multiple sub-networks, one per channel, where individual capacity may depend on the sub-network topologies This paper identifies the relevant topological characteristics of the sub-networks resultant from the channel assignment process and studies, through simulation, the impact and relative importance of those characteristics on the maximal throughput enabled by the stub WMN. The number of nodes in the gateways neighborhood and the hidden node problem in the gateways neighborhood were identified as the characteristics having the highest impact on the WMN throughput.

Implementing and evaluating three routing protocols in dual-radio-dual-mode IEEE 802.11(b) wireless mesh networks

In a dual-radio-dual-mode IEEE 802.11(b) wireless mesh network (WMN), each mesh access point has two IEEE 802.11(b) interfaces. One interface operates in infrastructure mode to serve IEEE 802.11(b) client devices so that they can readily use the mesh network without any software modification or installation. The other interface operates in ad hoc mode to forward packets among mesh access points until they reach an Internet gateway or the access point with which the destination client device is associated. Compared with a single-radio WMN, such a WMN offers ease of use and higher network throughputs for client devices. In this paper, we implement and evaluate the performance of three routing protocols (OSPF, AODV, and STP) operating in dual-radio-dual-mode IEEE 802.11(b) WMNs. Our simulation results show that among the tested protocols, OSPF provides the highest system total througput and results in the largest number of stable connections in such a WMN.