Minimizing Interference through Channel Assignment in Multiradio Wireless Mesh Networks

Multi-radio wireless mesh networks (MR-WMN) with a smart channel assignment scheme can be used as a viable cost-effective alternative for a last mile broadband access. The channel assignment algorithm should be such that it reduces the overall interference and increases the aggregate capacity of the network. In this paper, we have concisely presented the key results of our work in progress, which pertain to the evaluation of self-organization algorithm for multi-radio mesh networks. Specifically, the study focuses on the impact of initialization process on the self-organization algorithm performance as it involves mesh node selection for channel assignment. The initialization process results in a topology control of MR-WMN by way of spatial distribution of connectivity between the mesh nodes. The process for initiating the topology of self-organized mesh networks is also described. In order to conclusively show the merits of our initialization process, we have carried out this study for realistic densities of the mesh nodes and their topologies varying from completely random to being ordered in a grid.

Opportunistic routing (OR) involves multiple forwarding candidates to relay packets by taking advantage of the broadcast nature and multi-user diversity of the wireless medium. Compared with Traditional Routing (TR), OR can evidently improve the end to end throughput of Wireless Mesh Networks (WMNs). At present, there are many achievements concerning OR in the single radio wireless network. However, the study of OR in multi-radio wireless network stays the beginning stage. In this paper, we focus on OR in multi-radio multi-channel WMNs. Directly using the existing channel assignment leads to decreasing the number of candidate forwarder and the performance of OR. According to OR with one-to-more transmission mode, the Candidate Forwarder Set based Channel Assignment (CFSCA) for OR is proposed. Firstly, according to the candidate forwarder selected by routing, we bound the sender node and its candidate forwarders as a Candidate Forwarder Set(CFS). Then we calculate the interference among all the CFSs. Then the channel assignment for OR is described as a minimum CFS interference optimization problem, which must obey the constraints of the channel number of CFS and the number of radio interfaces. The evaluation results show that CFSCA improves 25.2%, 10%, 19% of the aggregative throughput than random, uniform and tradition channel assignment, respectively.Keywordswireless mesh networksmulti-radio and multi-channelopportunistic routingchannel assignment

Multi-channel communication in a Wireless Mesh Network with routers having multiple radio interfaces significantly enhances the network capacity. Efficient channel assignment is critical for realization of optimal throughput in such networks. In this paper, we investigate the problem of finding the largest number of links that can be connected with the overall network interference is minimized. Since the number of radios on any node can be less than the number of available channels, the channel assignment must obey the constraint that the number of different channels assigned to the links incident on any node is at most the number of radio interfaces on that node. The above optimization problem is known to be NP-hard. By presenting the theoretical model, the above task is formulated as a multi-objective problem, and then a novel channel assignment based on improved NSGA-II is proposed. Extensive empirical evaluations represent that the novel algorithm proposed in this paper can implement network connectivity with little interference rapidly and efficiently. To meet the actual demand in wireless mesh network, ns-2 simulations are used to demonstrate the performance potential of our channel assignment algorithms in 802.11-based multi-radio mesh networks.

Seamless handoff support is an essential issue to ensure continuous communications in wireless mesh networks (WMNs). Due to the existence of multi-hop wireless links, traditional handoff schemes designed for single-hop wireless access networks can hardly guarantee the low handoff latency requirement in WMNs. Existing solutions on reducing the handoff delay in WMNs ignore one important factor for the long handoff delay: the channel access delay of handoff signaling packets over the multi-hop wireless mesh backbone network. Various WMN channel assignment algorithms are designed to optimize the performance of data packets, but they do not address how to resolve the contentions between data packets and handoff signaling packets. In this paper, we propose a novel channel assignment algorithm in WMNs to reduce the channel access delay of handoff signaling packets over multihop wireless links. In addition, handoff solutions under the new channel assignment scheme are proposed. OPNET simulation results show that handoff performance can be improved by our proposed handoff schemes, as compared to existing solutions.

Channel assignment problems in multi-radio wireless mesh networks (WMNs) have been shown to be NP-hard in various scenarios in the literature. By far, most of research efforts have focused on developing efficient approximation algorithms that run reasonably fast and provide good quality channel assignment rather than the optimal one. However, from the practical network design and deployment standpoint, engineers care more about whether it is feasible to optimally assign channels in the simplest way (i.e., exhaustive search), as most of existing commercial WMNs are of small/medium scale. In this paper, we attempt to answer this practical question. We study the complexity of general channel assignment problems with certain basic and common properties. The results show that the complexity in terms of the number of different possible assignments is exponential in the number of wireless links. Furthermore, we estimate the theoretical runtime of determining the optimal channel assignment by exhaustive search and validate it through experiments. We show that, given certain computing power (e.g., an off-the-shelf notebook PC), it is feasible to optimally solve channel assignment problems in small-scale and medium-scale commercial multi-radio WMNs. In other words, approximation algorithms are not needed for most of current commercial WMNs.

A multi-radio Wireless Mesh Network (WMN) is a multi-hop network that consists of mesh routers and mesh clients, where mesh routers are equipped with multiple radio interfaces and form the backbone of the mesh network. To provide backbone support, it is necessary to reduce interference and balance load in Wireless Mesh Networks (WMNs). We propose load-aware routing metric (LARM), which captures the difference in transmission rates, packet loss ratio, intra/inter-flow interference and traffic load in multi-radio mesh networks. The LARM metric helps finding paths that are better in terms of balancing load and reducing the inter-flow and intra-flow interference in multi-radio networks. Simulation results show that LARM metric significantly outperforms several existing routing metrics in multi-radio wireless mesh networks.

In this paper, a model for the static channel assignment in multi-radio multi-channel wireless mesh networks is proposed. We describe an interference model in wireless communication environment. The degree of detail in the model determines the accuracy of channel assignment. In many wireless mesh networks studies, the simplistic protocol interference model is adopted, but the model is usually not realistic and practical. Therefore, we construct a physical interference model and put forward a pure integer quadratic programming (PIQP) model to solve the channel assignment problem and maximize the capacity of wireless mesh networks. The feasibility and effectivity of the channel assignment solution are suggested by the results of simulation.

Multi-channel communication in a Wireless Mesh Network with routers having multiple radio interfaces significantly enhances the network capacity. Efficient channel assignment is critical for realization of optimal throughput in such networks. This paper addresses the channel assignment problem for multi-channel multi-interface (radio) wireless mesh networks. We focus on static wireless mesh networks where multiple non-overlapping channels are available for each wireless interface. In this network environment, our objective is to find a fixed channel assignment which maximizes the number of bidirectional links that can be activated simultaneously, subject to interference constraints. We present a mixed integer linear programming models for solving the fixed channel assignment problem with multiple radios. Detailed computational results are presented and discussed to validate the algorithm.

Wireless mesh networks are a special kind of ad hoc networks in which most nodes are static. The application purpose of wireless mesh networks is also different than that of ad hoc networks and is focused on broadband access services to the Internet. Recent studies have shown that nodes in a wireless mesh network have to be equipped with several radio interfaces for high performance. However, one of the challenges that still faces high performance wireless mesh networks is the capacity reduction due to interference of wireless links. In this paper, we address the problem of assigning channels to nodes in wireless mesh networks. For this, we propose and study the Cluster Channel Assignment (CCA) approach with the goal of reducing the network interference to increase the overall network performance.

Wireless mesh networks (WMNs) are gaining significant momentum as a promising technology for the next-coming state-of-the-art wireless networking. Among many factors, the performance of WMNs would be largely affected by the properness of the deployed routing protocols and the efficient usage of wireless resources. Routing protocols are required to well capture WMNs' features while wireless channels should be used efficiently in order to accommodate high amount of traffics over the mesh backbone. Recently, a Tree-based Routing (TBR) protocol become a popular state-of-the-art proactive routing protocol and its tree-based broadcasting become an often used technique. Though TBR protocol is well-suited for WMNs' architecture and the skewed nature of traffic toward the root, the protocol in its current form faces issues which has to be addressed. Specifically, when some or all nodes are equipped with multiple radios, to reduce collision and co-channel interference, not only the parent-child relationship but also the sibling relationship need to be constructed by the TBR protocol in the multi-channel WMNs. In this paper, we propose a hybrid tree-based protocol for concurrent routing and channel assignment over WMNs. The protocol makes use of sibling links to mitigate the aforementioned shortcomings of TBR protocol. Moreover, in order to address high backbone traffic, the protocol integrates a receiver-based channel assignment scheme. The protocol efficiently deploys the parent-child topological relationships of nodes to enhance efficiency of broadcast transmissions over receiver-based multi-channel WMNs. Simulation results over NS-2 network simulator reveal that our proposed hybrid tree-based protocol achieves much higher performance than the utilization of the original receiver-based CA and TBR protocol.

The performance of Multi-Channel Multi-Radio (MC-MR) Wireless Mesh Networks (WMNs) can be improved significantly with the increase in number of channels and radios. Despite the availability of multiple channels in several of the current wireless standards, only a few of them are non-overlapping and many channels are partially overlapped. In this paper, we formulate the joint channel assignment and flow allocation problem for MC-MR WMNs as a Mixed Integer Linear Program (MILP). Unlike most of the previous studies, we consider the case of using both non-overlapped and partially overlapped channels. We consider an objective of maximizing aggregate end-to-end throughput and minimizing queueing delay in the network, instead of the sum of link capacities, since the traffic characteristics of a multihop WMN are quite different from a single hop wireless network. Our formulation takes into consideration several important network parameters such as the transmission power of each node, path loss information, signal to interference plus noise ratio at a node, and frequency response of the filters used in the transmitter and receiver. We show by simulations that our MILP formulation makes efficient use of the spectrum, by providing superior channel assignments and flow allocations with the addition of partially overlapped channels, without the use of any additional spectrum.

In this paper, we propose a distributed algorithm for channel assignment in multi-radio, multi-channel mesh networks. Channel assignment in multi-radio mesh networks is complicated because, in addition to affecting the interference between spatially closely located links, binding interfaces to channels affects the topology of the network. If the channel assignment is done without taking the topology into consideration, distance between any two nodes may increase arbitrarily. We propose a novel distributed channel assignment algorithm that reduces interference and at the same time provides bounds on the distance between any two nodes in the topology resulting from channel assignment. Our algorithm is based on the concept of spanners. We also develop and implement a modification of AODV, which uses the cumulative metric WCETT [4] as the routing metric. We use this routing algorithm to analyze the performance of our channel assignment algorithm. Through extensive simulations in NS-2, we show that the proposed channel assignment algorithm provides nearly 30% improvement in throughput over a simple, minimal-connectivity preserving channel assignment algorithm.

Wireless mesh networks with multi-channel multi- radio availability are attracting more and more attention from the research community because of its performance improvement and relative low complexity. In this paper, we address the channel assignment problem for multi-channel multi-radio wireless mesh networks. We focus on heterogeneous static wireless mesh networks where multiple non-overlapping channels are available for each wireless radio. Our objective is to find the optimal channel assignment which maximizes the number of bidirectional links that can be activated simultaneously, subject to the interference constraints. We present an applied integer linear programming model for solving the fixed channel assignment problem with multiple radios. We then use this model to study the impact of channel and radio constrains.

Wireless mesh networks (WMNs) have emerged as a scalable, reliable, and agile wireless network that supports many types of innovative technologies such as the Internet of Things (IoT), Wireless Sensor Networks (WSN), and Internet of Vehicles (IoV). Due to the limited number of orthogonal channels, interference between channels adversely affects the fair distribution of bandwidth among mesh clients, causing node starvation in terms of insufficient bandwidth distribution, which impedes the adoption of WMN as an efficient access technology. Therefore, a fair channel assignment is crucial for the mesh clients to utilize the available resources. However, the node starvation problem due to unfair channel distribution has been vastly overlooked during channel assignment by the extant research. Instead, existing channel assignment algorithms equally distribute the interference reduction on the links to achieve fairness which neither guarantees a fair distribution of the network bandwidth nor eliminates node starvation. In addition, the metaheuristic-based solutions such as genetic algorithm, which is commonly used for WMN, use randomness in creating initial population and selecting the new generation usually leading the search to local minima. To this end, this study proposes a Fairness-Oriented Semichaotic Genetic Algorithm-Based Channel Assignment Technique (FA-SCGA-CAA) to solve node starvation problem in wireless mesh networks. FA-SCGA-CAA maximizes link fairness while minimizing link interference using a genetic algorithm (GA) with a novel nonlinear fairness-oriented fitness function. The primary chromosome with powerful genes is created based on multicriterion links ranking channel assignment algorithm. Such a chromosome was used with a proposed semichaotic technique to create a strong population that directs the search towards the global minima effectively and efficiently. The proposed semichaotic technique was also used during the mutation and parent selection of the new genes. Extensive experiments were conducted to evaluate the proposed algorithm. A comparison with related work shows that the proposed FA-SCGA-CAA reduced the potential node starvation by 22% and improved network capacity utilization by 23%. It can be concluded that the proposed FA-SCGA-CAA is reliable to maintain high node-level fairness while maximizing the utilization of the network resources, which is the ultimate goal of many wireless networks.

Realistic interference-free channel assignment for dynamic wireless mesh networks using beamforming