Multi-radio Wireless Mesh Networks Research Articles

Channel Aware Opportunistic Routing in Multi-Radio Multi-Channel Wireless Mesh Networks

Opportunistic routing (OR) involves multiple candidate forwarders to relay packets by taking advantage of the broadcast nature and multi-user diversity of the wireless medium. Compared with traditional routing (TR), OR is more suitable for the unreliable wireless link, and can evidently improve the end to end throughput. 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. To demonstrate the benefit of OR in multi-radio multi-channel network, we propose a new route metric — multi-channel expected anypath transmission time (MEATT), which exploits the channel diversity and resource of multiple candidate forwarders for OR. Based on the new metric, a distributed algorithm named Channel Aware Opportunistic Routing (CAOR) is proposed. The simulation results demonstrate that MEATT improves 1.14 and 1.53 times of the average throughput than existing expected anypath transmission time (EATT)and metric of interference and channel switching cost (MIC) respectively. The average delay of MEATT is 17% and 40% lower than those of EATT, MIC, respectively.

An Efficient Interference Aware Partially Overlapping Channel Assignment and Routing in Wireless Mesh Networks

In recent years, multi-channel multi-radio wireless mesh networks are considered a reliable and cost effective way for internet access in wide area. A major research challenge in this network is, selecting a least interference channel from the available channels, efficiently assigning a radio to the selected channel, and routing packets through the least interference path. Many algorithms and methods have been developed for channel assignment to maximize the network throughput using orthogonal channels. Recent research and test-bed experiments have proved that POC (Partially Overlapped Channels) based channel assignment allows significantly more flexibility in wireless spectrum sharing. In this paper, first we represent the channel assignment as a graph edge coloring problem using POC. The signal-to-noise plus interference ratio is measured to avoid interference from neighbouring transmissions, when a channel is assigned to the link. Second we propose a new routing metric called signal-to-noise plus interference ratio (SINR) value which measures interference in each link and routing algorithm works based on the interference information. The simulation results show that the channel assignment and interference aware routing algorithm, proposed in this paper, improves the network throughput and performance.

Interference-aware QoS routing and dynamic channel assignment for multi-radio multi-channel wireless mesh network

QoS routing in multi-channel wireless mesh networks protocols is a very challenging problem. In this paper, we propose an on-demand bandwidth-constrained routing protocol combined with dynamic channel assignment for multi-radio multi-channel wireless mesh networks with the IEEE 802.11 DCF MAC protocol. A multi-channel available bandwidth estimation method is proposed which is based on the exchange of the bandwidth information for neighbour nodes at first, then a new jointing channel assignment and routing algorithm is designed which dynamically assigns the channel through the available bandwidth in the routing process according to the requirement of bandwidth, distributed call admission control is integrated to prevent network overload and the optimal path metric is advised to establish interference-aware QoS routing. Simulation results show that the routing algorithm can reduce co-channel interference and improve network performance and acceptance rate through assigning channels dynamically.

Price-based congestion control and local channel-link assignment for multi-radio wireless mesh networks

In multi-radio multi-channel wireless mesh networks, engineering the network capacity requires a complex cross-layer design. In this paper, in order to make the complex problem implementable in a distributed manner, we make a decoupling approach that breaks down the entire design space into routing and initial channel assignment, and distributed congestion control and local channel reassignment. We propose a unified priced-based framework for distributed congestion control and localized channel-link assignment algorithms. We demonstrate the convergence of the proposed algorithms with respect to different fairness objectives (i.e., proportional fairness and max–min fairness) via simulation on both grid and random topologies. The proposed algorithms achieve faster convergence with less overhead in the control and forwarding plane than previous multi-path based algorithms.

Interference Nomenclature in Wireless Mesh Networks

The Quality of Service of Multi-Channel Multi-Radio Wireless Mesh Networks is adversely affected by the complex behavior of interference patterns present between the sender and receiver of a link. This behavior is usually captured using wireless channel interference models. The accuracy of the interference model is highly dependent on the interaction of the Carrier Sense Multiple Access with Collision Avoidance Medium Access Control (CSMA/CA MAC) protocol based on the geometric location of the sender and receiver of the link. Therefore, this paper presents a nomenclature of interference modeling schemes available in Wireless Mesh Network (WMN) literature with respect to the geometric location of the sender and receiver of a link. The behavior and limitations of each model are analyzed with the help of empirical examples. The results indicate that Garetto’s model of interfering links is the best choice to model wireless channel interference in WMNs. In addition, this study provides an interference analysis of Garetto’s model for the two link case by computing the conditional packet loss probability of each class of interfering link. The probability analysis concluded that the links with disconnected senders are highly interfering compared to sender connected links. Further, the analysis will assist researchers and engineers in relay node placement, capacity analysis, channel assignment, and topology control schemes in the WMN.

An Efficient and Fair Strategy for Radio Resources Allocation in Multi-radio Wireless Mesh Networks

A Load and Interference aware Resource Allocation strategy (LIRA) is proposed for multi-radio Wireless Mesh Networks (WMNs), combining multiple mechanisms that efficiently optimise radio resources (rate, power and channel) to guarantee max---min fair capacity to every aggregating Mesh Access Point (MAP). LIRA is composed of a rate adaptation and power control mechanism, sensitive to the fat-tree traffic specificities of WMNs, using the highest bit rates at MAP gateways and using, for the ramified links, the minimum ones that satisfy their capacity needs. This enables to efficiently reduce the transmitted power and interference, advantageous for channel reutilisation. LIRA also integrates a load and interference aware channel assignment mechanism, allowing the simultaneous operation of all links without interference. When this is not achievable, two auxiliary mechanisms of channel sharing and interference-free channel reuse can be sub-sequentially used, reducing the capacity of certain MAPs to guarantee fairness to all nodes. LIRA's gateway flow-control mechanism guarantees that all MAPs respect the allocated capacity, guaranteeing that every MAP is able to operate at its max---min fair capacity. The performance of LIRA is evaluated through simulation, considering IEEE 802.11a. For a classical hexagonal deployment of 19 MAPs with an Internet gateway, it is shown how with only 5 channels LIRA guarantees to every MAP a max---min fair capacity of 3.2 Mbit/s, without packet loss, and delay below 6 ms. It guarantees a max---min fair throughput to every MAP, having a capacity usage efficiency of 66.7 %, an energy efficiency of 26.5 Mbit/J and spectrum efficiency of 0.58 bit/s/Hz. For a more challenging scenario with 27 MAPs and 4 gateways, it is shown how LIRA uses its mechanisms in heterogeneous conditions to also guarantee max---min fair throughput to every MAP, between 5 and 11 Mbit/s, without packet loss, and a delay below 12 ms. Any system improvement will enable to reach higher WMN performance levels using the proposed strategy.

Multi-rate multicast routing in multi-gateway multi-channel multi-radio wireless mesh networks

With increasing popularity of group communication applications, it is necessary to design efficient multicast routing algorithms. One important challenge in respect to multicasting is the bandwidth heterogeneity of the receivers, which limits the rate of data delivery to the receivers by the slowest one. In this paper, we study this problem in the context of Multi-gateway Multi-Channel Multi-Radio Wireless Mesh Networks (M3 WMNs). We design an efficient algorithm, which employs the well-established multi-rate technique for handling the bandwidth heterogeneity of the receivers. The proposed algorithm, namely Multi-Gateway Multi-Rate multicast routing (MGMR), aims at maximizing the total of the achieved data rates by the receivers while preserving fairness between them. We also formulate the optimal model of the problem to compare the outcomes of MGMR with the optimum. The simulation results demonstrate that MGMR yields high throughput results in a reasonable time.

An experimental study of the channel switching cost in multi-radio wireless mesh networks

A large body of research has recently addressed the channel assignment problem in multi-radio wireless mesh networks. In order to reduce interference, many proposals require radio interfaces to (more or less frequently) switch channels to exploit the availability of multiple orthogonal channels. However, such proposals have been almost exclusively evaluated by means of simulations and the impact of switching channels on the network performance has not been experimentally evaluated so far. In this article, we aim to fill such a gap and present the results of a thorough experimental campaign we conducted on the ORBIT wireless testbed to study the effects of switching channels in a multiradio wireless mesh network. Our experiments show that in common scenarios a channel switch causes a non-negligible interruption in the connectivity among nodes, which is on the order of 10 seconds. Also, our tests reveal that a rapid recovery from link failures caused by channel switches is prevented by a rather slow update of the advertised link quality. Inspired by the analysis of the experiments we conducted, we also propose and evaluate a preliminary technique to reduce the interruption in the delivery of packets caused by a channel switch.

A New MPLS-Based Forwarding Paradigm for Multi-Radio Wireless Mesh Networks

Routing in multi-radio wireless mesh networks is a very challenging problem. In this paper, we propose a forwarding paradigm based on MPLS (Multi Protocol Label Switching) which makes use of a novel mechanism, denoted as MPLS splitting policy. Such mechanism allows to configure multiple next hops at an intermediate node, so that the incoming traffic is partitioned among the next hops according to predefined coefficients named split ratios. The MPLS splitting policy has been designed to allow for load balancing and fast local restoration. With such a mechanism, it is crucial to properly determine the set of split ratios, as they determine how the traffic is routed across the network. We present an approach to compute a set of split ratios that guarantee high performance under different traffic loads. To this end, we adopt the hose traffic model, according to which we only have knowledge of the maximum amount of traffic entering or leaving the network at each edge node. A thorough simulation study is conducted to show that our approach outperforms other routing protocols in terms of throughput and robustness against traffic load variations and single node failures.

Improving Performance of Wireless Mesh Networks

Inspite of many advancements in multihop multiradio Wireless Mesh Network, it experiences frequent link failures because of increasing bandwidth demand, channel interference, etc. The Autonomous Reconfiguration System (ARS) presented in this paper helps Wireless Mesh Network to overcome such failures, thereby improving the performance of Wireless Mesh Network. ARS passively monitors the network and checks link quality, in case of failures it generates reconfiguration plan and forwards it to neighboring nodes. General Terms Wireless Mesh Network, Routing.

A Traffic-Aware Channel and Rate Reassignment Algorithm for Wireless Mesh Networks

Channel assignment is among the most challenging issues for multiradio wireless mesh networks, given the variety of objectives that can be pursued and the computational complexity of the resulting problems. The channel assignment problem has been also shown to be interdependent with the routing problem, i.e., the problem to determine the amount of traffic flow to be routed on every link. Such a relationship raises the need to recompute the channel assignment every time the traffic pattern changes. However, channel assignment algorithms designed to assign channels from scratch will likely return a completely different configuration of radios, which would disrupt the network operation for the time required to switch to using the links established on the new channels. As shown by the experiments that we conducted, such a time may not be negligible, due to the resistance of routing protocols designed for wireless ad hoc and mesh networks to rapidly flagging a link as established/lost. Such a consideration, along with the observation that channel assignment algorithms may be suboptimal, led us to the design of a channel reassignment algorithm that takes the current channel assignment into account and attempts to cope with the new traffic pattern in the best manner possible while modifying the channel on a limited number of radios. In this paper, we illustrate such a channel reassignment algorithm and evaluate its performance by means of both simulations and experiments with real hardware.

Implementation of ARS-STR in STR for Effective Energy Transmission

Wireless mesh networks (WMNs) have emerged as a key technology for next generation wireless networking. Because of their advantages over other wireless networks, WMNs are undergoing rapid progress and inspiring numerous applications. In multi-hop wireless mesh networks (WMNs) experience frequent link failures caused by channel interference, dynamic obstacles and/or applications bandwidth demands. These failures cause severe performance degradation in WMNs or require expensive, manual network management for their real-time recovery. This paper presents an Autonomous network Reconfiguration System (ARS-STR) that enables a multi-radio WMN to autonomously recover from local link failures to preserve network performance. ARS-STR also improves channel efficiency.

Channel assignment in multi-radio wireless mesh networks using an improved gravitational search algorithm

Wireless mesh networks have emerged recently to improve networking performance and other networking services. The combination of multi-radio nodes with multi-hop mesh architectures leads researcher to overcome some constraints of single-radio networks such as incapability of effective scale to exploit the increasing available system bandwidth. Therefore, a good channel assignment (CA) in multi-radio mesh networks can reduce the number of interference co-channels and improve the network throughput. In this paper, an improved version of gravitational search algorithm (IGSA) is proposed to solve CA problems; a local operator is combined with the gravitational search algorithm to find the best solution. In this study, the main goal is to minimize the overall interference and to increase the network throughput with ensuring network connectivity. The obtained results confirm the high performance of our algorithm in comparison with other related works.

A cross‐layer optimization for maximum‐revenue‐based multicast in multichannel multiradio wireless mesh networks

SUMMARYGiven a video/audio streaming system installed on a multichannel multiradio wireless mesh network, we are interested in a problem concerning about how to construct a delay‐constrained multicast tree to support concurrent interference‐free transmissions so that the number of serviced mesh clients is maximized. In this paper, we propose a heuristic approach called cross‐layer and load‐oriented (CLLO) algorithm for the problem. On the basis of the cross‐layer design paradigm, our CLLO algorithm can consider application demands, multicast routing, and channel assignment jointly during the formation of a channel‐allocated multicast tree. The experimental results show that the proposed CLLO outperforms the layered approaches in terms of the number of serviced mesh clients and throughputs. This superiority is due to information from higher layers can be used to guide routing selection and channel allocation at the same time. As a result, the CLLO algorithm can explore more solution spaces than the traditional layered approaches. In addition to that, we also propose a channel adjusting procedure to enhance the quality of channel‐allocated multicast trees. According to our simulations, it is proved to be an effective method for improving the performance of the proposed CLLO algorithm. Copyright © 2013 John Wiley & Sons, Ltd.

Channel Allocation and Routing in Hybrid Multichannel Multiradio Wireless Mesh Networks

Many efforts have been devoted to maximizing network throughput in a multichannel multiradio wireless mesh network. Most current solutions are based on either purely static or purely dynamic channel allocation approaches. In this paper, we propose a hybrid multichannel multiradio wireless mesh networking architecture, where each mesh node has both static and dynamic interfaces. We first present an Adaptive Dynamic Channel Allocation protocol (ADCA), which considers optimization for both throughput and delay in the channel assignment. In addition, we also propose an Interference and Congestion Aware Routing protocol (ICAR) in the hybrid network with both static and dynamic links, which balances the channel usage in the network. Our simulation results show that compared to previous works, ADCA reduces the packet delay considerably without degrading the network throughput. The hybrid architecture shows much better adaptivity to changing traffic than purely static architecture without dramatic increase in overhead, and achieves lower delay than existing approaches for hybrid networks.

Network Coding-based Directional Scheduling for Fairness Provisioning in Wireless Mesh Networks

This paper addresses the problem of fairness portioning in multi-channel, multi-radio wireless mesh networks by applying the integration of network coding and directional antennas techniques. It is the fact that Network coding can increase transmission efficiency in wireless networks. Moreover, directional antennas, concentrating the beam energy at a specified direction, can also improve the network performance. However, the interacting of the two techniques is scarcely studied. In this paper, we propose an analytical model to figure out the incorporation of directional antennas and network coding schemes to improve fairness provisioning. To address the problem, we first present integer linear programming formulation optimizations, which maximize the throughput while satisfying the fairness requirements. Based on solving the linear programming, we propose a link scheduling and channel assignment with a heuristic method. The evaluations show that the algorithm we propose can effectively take advantages of the number of channels and radios. In addition, it shows that our algorithm outperforms other algorithms which either coding-oblivious or directional antenna-oblivious.

Channel Assignment Algorithms and Strategies for Wireless Mesh Networks

This research report is about providing a solution to the problem of channel assignment in the multi radio wireless mesh networks that have an ad hoc based infrastructure. The aim was to minimize the fractional interference so that throughput can be maximized. The algorithms to solve this problem were classified and explained how they work. A description of channel assignment techniques is given along with a brief comparison in the literature. Main focus was towards the use on genetic algorithm. It also gives a detailed explanation of how genetic algorithm could be implemented in order to solve this problem along with conflict graphs being made by running functions in MATLAB.

A Classification Framework for Scheduling Algorithms in Wireless Mesh Networks

Scheduling MAC-layer transmissions in multi-hop wireless networks is an active and stimulating area of research. There are several interesting algorithms proposed in the literature in the problem space of scheduling for multi-hop wireless networks, specifically for (a) WiMAX mesh networks, (b) long distance multi-hop WiFi networks, and (c) Vehicular Ad-hoc Networks (VANETs). In general, these algorithms have several dimensions in terms of the assumptions made, the input space considered and the solution space generated. In this context, the goal of this survey is three-fold. Firstly, we classify the scheduling algorithms proposed in the literature based on following parameters: problem setting, problem goal, type of inputs and solution technique. Secondly, we describe different scheduling algorithms based on this classification framework. We specifically cover the state-of-the-art scheduling mechanisms proposed for generic multi-channel, multi-radio wireless mesh networks and in particular scheduling algorithms for WiMAX mesh networks, long distance mesh networks and vehicular ad-hoc networks. We describe scheduling algorithms which consider scheduling data, voice as well as video traffic. Finally, we compare these algorithms based on our classification parameters. We also critique individual mechanisms and point out the practicality and the limitations, wherever applicable. We observe that, the literature in the domain of scheduling for wireless mesh network is quite extensive, in terms of depth as well as breadth. Our classification framework helps in understanding the pros and cons of various aspects of scheduling for wireless multi-hop (popularly known as wireless mesh) networks. We also list desirable properties of any scheduling mechanism and use our classification framework to point out the open research issues in the space of scheduling for wireless mesh networks.

Evolutionary-based channel assignment in multi-radio multi-channel wireless mesh networks for multicast applications

The multi–radio multi–channel wireless mesh networks give rise to considerable improvement in network throughput. Due to the limited number of available orthogonal channels, interference is still a problematic issue in such networks. Besides, multicast is an effective mechanism for delivering data to a group of receivers. Channel assignment for multicast has only been addressed recently. Focusing on this issue, in this paper, we consider the multicast channel assignment problem to minimise the interference among multicast tree nodes. We develop a hybrid particle swarm optimisation (PSO) and tabu search approach for channel assignment. The use of tabu search as a local improvement procedure enables the proposed algorithm to overleap local optimum and show satisfactory performance. The proposed approach is applied to different network configurations, and its performance is compared with LCA, MCM, tabu search–based, and PSO–based algorithms. Simulation results show that the proposed method achieves superior performance in terms of interference.

A semi-dynamic, game based and interference aware channel assignment for multi-radio multi-channel wireless mesh networks

Channel assignment CA has been extensively researched for multi-radio wireless mesh networks WMNs, but it is still very challenging when it comes to its implementation. In this paper we propose a semi-dynamic and distributed CA mechanism called semi-dynamic interference aware channel assignment SICA based on game theory formulation. SICA is an interference aware, distributed CA which preserves the network connectivity without relying on a common channel nor central node for coordination between mesh routers. SICA applies a real time learner algorithm which assumes that nodes do not have perfect information about the network topology. To the best of our knowledge this is the first game formulation of CA which takes the co-channel interference into account. We have simulated SICA and compared against other channel assignment mechanisms proposed in the literature. Simulation results show that SICA outperforms other mechanisms.