Spanner Based Distributed Channel Assignment in Wireless Mesh Networks

In this paper we present the DES-Chan framework for experimentally-driven research on distributed channel assignment algorithms in wireless mesh networks. The implementation process of channel assignment algorithms is a difficult task for the researcher since common operating systems do not support channel assignment algorithms out of the box. DES-Chan provides a set of common services required by distributed channel assignment algorithms. The modular architecture of DES-Chan allows the extensions with further modules or the modifications of existing ones. As a proof of concept, we present a reference implementation of a distributed greedy channel assignment algorithm. We evaluate its performance in the DES-Testbed, a multi-transceiver wireless mesh network (WMN) with 100 nodes at the Freie Universitat Berlin.

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.

Single-radio mesh routers operating on a single channel suffer from low throughput due to collisions. Equipping mesh routers with multiple radios operating on non-overlapping channels can significantly improve the throughput. However, the assignment of channels to radios in a multi-radio mesh network is a challenging task. In this paper, we propose a channel assignment algorithm, TICA (Topology-controlled Interference-aware Channel-assignment Algorithm), which significantly improves network throughput by minimizing interference within the mesh network using a novel approach of controlling the network topology based on power control before intelligently assigning the channels to the multi-radio mesh routers, as well as guaranteeing network connectivity.

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.

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.

Optimising channel assignment to prevent flow starvation and improve fairness for planning single radio WMNs in built environments

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.

This paper addresses channel assignment and random medium access design for single-radio multi-channel mesh networks. Two prior approaches include: (i) designing MAC protocols that dynamically select channels based on local information and (ii) partitioning the mesh into subnetworks with different channels and using 802.11 as the medium access protocol. Both of these approaches suffer from limited throughput improvement; the first approach due to wrong or incomplete channel state information that inherently arises in a multi-hop wireless environment, while the second approach due to high interference within each subnetwork. In this paper, we first introduce D1C-CA, Distance-1 Constrained Channel Assignment. D1C-CA statically assigns channels to a set of links as a function of physical connectivity, contention, and the unique gateway functionality of mesh networks, i.e, all Internet (non-local) traffic has a gateway node as its source or destination. To design D1C-CA, we model the channel assignment problem as a new form of graph edge coloring in which edges at distance one are constrained. We prove that the problem is NP-complete and design an efficient heuristic solution for mesh networks. Second, we design an asynchronous control-channel-based MAC protocol that solves multi-channel coordination problems and employs the proposed channel assignment algorithm. Finally, we investigate the performance of our approach through extensive simulations and show considerable performance improvements compared to alternate schemes.

Impact of multiple channels and radios on the performance of a TDMA based wireless mesh network

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.

Wireless mesh networks are being deployed all around the world both to provide ubiquitous connection to the Internet and to carry data generated by several services (video surveillance, smart grids, earthquake early warning systems, etc.). In those cases where fixed power connections are not available, mesh nodes operate by harvesting ambient energy (e.g., solar or wind power) and hence they can count on a limited and time-varying amount of power to accomplish their functions. Since we consider mesh nodes equipped with multiple radios, power savings and network performance can be maximized by properly routing flows, assigning channels to radios and identifying nodes/radios that can be turned off . Thus, the problem we address is a joint channel assignment and routing problem with additional constraints on the node power consumption, which is NP-complete. In this paper, we propose a heuristic, named minimum power channel assignment and routing algorithm (MP-CARA), which is guaranteed to return a local optimum for this problem. Based on a theoretical analysis that we present in the paper, which gives an upper bound on the outage probability as a function of the constraint on power consumption, we can guarantee that the probability that a node runs out of power with MP-CARA falls below a desired threshold. The performance of MP-CARA is assessed by means of an extensive simulation study aiming to compare the solutions returned by MP-CARA to those found by other heuristics proposed in the literature.

Nowadays, multi-channel multi-radio wireless mesh networks are gaining more popularity as they have enormous applications like last mile broadband Internet connectivity, home networking, commercial and civilian applications. The performance of wireless mesh networks can be improved by the proper assignment of channels to multiple radios of a mesh node. Thus, channel assignment problem has significant importance. This paper presents the literature survey of various algorithms of channel assignment along with the advantages and limitations of each algorithm. Also, the paper gives the directions for future research work of channel assignment algorithms of wireless mesh networks.

Realizing good system performance in IEEE 802.11 deployments requires thorough network planning, a sophisticated task, which, more often than not, requires expert knowledge. In cases where IEEE 802.11 networks operating under different administrations reside in the same geographical area (as defined by the bounds of radio signal transmission and reception), the problem of efficient radio resource allocation arises. Particularly for IEEE 802.11a/b/g systems, efficient radio resource allocation in a dense urban environment can be quite a challenge, due to the finite number of interference-free channels available. To address this shortcoming, we study the mechanisms provided by the IEEE 802.11k standard upon the performance of radio resource management strategies in WLAN type systems under a dense deployment. To this end, we present a Learning With Communication (LWC) Distributed Channel Assignment (DCA) algorithm that exploits local communication among access points to realize a rapidly converging self-organizing channel assignment scheme. We evaluate the performance of LWC DCA algorithm through simulation scenarios.

Recently, importance of wireless networks increased significantly. Wireless Mesh Networks (WMNs) are receiving growing attention and offer many advantages in terms of connectivity and reliability. Multicast communication is an important technology for wireless networks in which the same content of data should be delivered to a group of receiver nodes simultaneously. So multicast routing provides efficient data distribution among a group of nodes rather than other traditional unicast routing strategies. Here we focus on the Channel Allocation (CA) scheme which efficiently utilizes multiple wireless interfaces to achieve better throughput and improving the radio interference. This kind of problem has been proved to be NP-hard. Hence, solving the multicast channel assignment problem in MCMR WMNs will be more complicated than that of traditional networks. The research in this paper is aimed at improving the network performance for efficient joint channel assignment and multicast routing problem in MCMR WMNs by using the Q-learning scheme. We also implement our proposed channel assignment algorithm, and evaluate and compare its performance with LAMR. Simulations and experimental results demonstrate that QLMR outperforms the previous works in terms of achieved average throughput, average end-to-end delay, average packet delivery ratio and so on. We will evaluate the performance of the proposed scheme.

The wireless mesh network is an emerging technology that provides high quality service to end users as the "last milerdquo of the Internet. Furthermore, multicast communication is a key technology for wireless mesh networks. Multicast provides efficient data distribution among a group of nodes. However, unlike other wireless networks, such as sensor networks and MANETs, where multicast algorithms are designed to be energy efficient and to achieve optimal route discovery among mobile nodes, wireless mesh networks need to maximize throughput. This paper proposes two multicast algorithms: the level channel assignment (LCA) algorithm and the multichannel multicast (MCM) to improve the throughput for multichannel and multi-interface mesh networks. The algorithms build efficient multicast trees by minimizing the number of relay nodes and total hop count distances of the trees. The algorithms use dedicated channel assignment strategies to reduce the interference to improve the network capacity. We also demonstrate that using partially overlapping channels can further diminish the interference. Furthermore, additional interfaces help to increase the bandwidth, and multiple gateways can further shorten the total hop count distance. Simulations show that those algorithms greatly outperform the single-channel multicast algorithm. We also observe that MCM achieves better throughput and shorter delay while LCA can be realized in distributed manner.