Multi-radio Wireless Mesh Networks Research Articles

On the Relationship between Multicast/Broadcast Throughput and Resource Utilizations in Wireless Mesh Networks

This paper deals with the problem of multicast/broadcast throughput in multi-channel multi-radio wireless mesh networks that suffer from the resource constraints. We provide a formulation to capture the utilization of the network resources and derive analytical relationships for the network's throughput in terms of the node utilization, the channel utilization, and the number of transmissions. Our model relies on the on-demand quality of service multicast/broadcast sessions, where each admitted session creates a unique tree with a specific bandwidth. As an advantage, the derived relationships are independent of the type of tree built for each session and can be used for different protocols. The proposed formulation considers the channel assignment strategy and reflects both the wireless broadcast advantage and the interference constraint. We also offer a comprehensive discussion to evaluate the effects of load-balancing and number of transmissions on the network's throughput. Numerical results confirm the accuracy of the presented analysis.

On channel assignment and multicast routing in multi-channel multi-radio wireless mesh networks

Multicast is a key networking service, enabling one-shot delivery of information from a source to multiple destinations and is considered underlying for collaborating multimedia applications such as video conferencing, distance learning and other forms of content distributing over Multi-Channel Multi-Radio Wireless Mesh Networks MCMR WMNs. Multicast protocol as designed in these networks, however, is tightly coupled with the specifics of the nodes' channel-radio associations to realise minimum interference communication. The mainstream of research in WMN multicasting is oriented towards heuristic or meta-heuristic strategies which basically take on a sequential approach to solve the channel assignment and the multicast routing as two disjoint sub-problems. The resulting network configurations would be sub-optimal in this case. It is given that the cross-interaction between the two sub-problems is an effect of the problem's specifications. In this paper, first, we propose a cross-layer mathematical formulation of joint channel assignment and multicast tree construction in MCMR WMNs, which, opposed to the existing schemes guarantees optimal solution. The simulation results demonstrate that our cross-layer design outperforms the Level Channel Assignment LCA, Multi-Channel Multicast MCM, the Genetic Algorithm GA, Simulated Annealing SA and the Tabu Search TS-based methods proposed by Zeng et al. 2010 and Cheng et al. 2011 respectively, in terms of inter-channel interference. Second, since joint optimisation modelling has been relatively demanding in terms of complexity, we relax the optimality requirement and alternatively explore the option of a layered formulation in which to ensure an optimal solution for each sub-problem. Our alternative design is proved superior to the prior art in terms of interference minimisation too. We conduct an extensive series of simulations to analyse the optimality and complexity of our two design strategies. The overall result of the interference, is our optimality measurement. Also, complexity is evaluated in terms of the memory consumption as well as the required time to solve the multicast problem.

Channel Assignment for Throughput Optimization in Multichannel Multiradio Wireless Mesh Networks Using Network Coding

Compared to single-hop networks such as WiFi, multihop infrastructure wireless mesh networks (WMNs) can potentially embrace the broadcast benefits of a wireless medium in a more flexible manner. Rather than being point-to-point, links in the WMNs may originate from a single node and reach more than one other node. Nodes located farther than a one-hop distance and overhearing such transmissions may opportunistically help relay packets for previous hops. This phenomenon is called opportunistic overhearing/listening. With multiple radios, a node can also improve its capacity by transmitting over multiple radios simultaneously using orthogonal channels. Capitalizing on these potential advantages requires effective routing and efficient mapping of channels to radios (channel assignment (CA)). While efficient channel assignment can greatly reduce interference from nearby transmitters, effective routing can potentially relieve congestion on paths to the infrastructure. Routing, however, requires that only packets pertaining to a particular connection be routed on a predetermined route. Random network coding (RNC) breaks this constraint by allowing nodes to randomly mix packets overheard so far before forwarding. A relay node thus only needs to know how many packets, and not which packets, it should send. We mathematically formulate the joint problem of random network coding, channel assignment, and broadcast link scheduling, taking into account opportunistic overhearing, the interference constraints, the coding constraints, the number of orthogonal channels, the number of radios per node, and fairness among unicast connections. Based on this formulation, we develop a suboptimal, auction-based solution for overall network throughput optimization. Performance evaluation results show that our algorithm can effectively exploit multiple radios and channels and can cope with fairness issues arising from auctions. Our algorithm also shows promising gains over traditional routing solutions in which various channel assignment strategies are used.

Multisource Video On-Demand Streaming in Wireless Mesh Networks

We study the multisource video on-demand (VoD) application in multichannel multiradio wireless mesh networks. When a user initiates a new video request, the application can stream the video not only from the media servers, but also from the peers that have buffered the video. The multipath multisource video on-demand streaming has been applied in wired networks with great success. However, it remains a challenging task in wireless networks due to wireless interference. In this paper, we first focus on the problem of finding the maximum number of high-quality and independent paths from the user to the servers or peers for each VoD request by considering the effect of wireless interference. We formulate it as a constrained maximum independent paths problem and propose two efficient heuristic path discovery algorithms. Based on the multiple paths discovered, we further propose a joint routing and rate allocation algorithm, which minimizes the network congestion caused by the new VoD session. The algorithm is aware of the optimization for both existing and potential VoD sessions in the wireless mesh network. We evaluate our algorithms with real video traces. Simulation results demonstrate that our algorithm not only improves the average video streaming performance over all the coexisting VoD sessions in the network, but also increases the network's capacity of satisfying more subsequent VoD requests.

An optimization framework for monitoring multi-channel multi-radio wireless mesh networks

This paper studies an optimal monitoring problem for behavior-based detection in multi-channel multi-radio wireless mesh networks. In behavior-based detection, nodes overhear communications in their neighborhood to determine if the behaviors of their neighbors are legitimate. The objective of this work is to maximize the number of nodes being monitored by judiciously choosing a set of monitoring nodes and also channels for the chosen monitoring nodes. This problem is NP-hard, growing exponentially with the number of monitoring nodes. We develop three approximation algorithms, each of which achieves at least a constant factor of the optimum. Furthermore, one of our algorithms achieves the best possible approximation ratio among all polynomial-time algorithms, unless P=NP. We conduct simulations in random networks and scale-free networks to evaluate the coverage and the execution time of the three algorithms.

Using Partially Overlapping Channels to Improve Throughput in Wireless Mesh Networks

Wireless mesh networks have attracted great interest in the research community recently. Much effort has been devoted to maximizing the network performance using limited channel resources in a multichannel multiradio wireless mesh network. It is believed that the limited spectrum resource can be fully exploited by utilizing partially overlapping channels in addition to nonoverlapping channels in 802.11b/g networks. However, there are only few studies of channel assignment algorithms for partially overlapping channels. In this paper, we first formulate the optimal channel assignment problem with the goal of maximizing the overall network throughput or maximizing the throughput of a multicast application. For both cases, we present a greedy algorithm for partially overlapping channel assignment, and then propose a novel genetic algorithm, which has the potential to obtain better solutions. Through evaluation, we demonstrate that the overall network throughput can be dramatically improved by properly utilizing the partially overlapping channels. The genetic algorithm outperforms the greedy algorithm in mitigating the network interference, and therefore leads to higher network throughput. In addition, the multicast throughput can also be dramatically improved by using our algorithms compared to previous work.

Channel Re-assignment in Wireless Mesh Networks based on Link Load Estimation

A channel assignment scheme for multi-radio WMNs (Wireless Mesh Networks) to provide high-throughput paths especially for the highly loaded node with the best connectivity to the gateway(e.g. in terms of highest rate, lowest interference or both) is provided in this paper. We observed the flows on the links and data packets at each wireless access point in an existing wireless mesh backbone from logs files of traffic flows generated at gateway level. After observing, we estimate the traffic load for each network link using load estimation algorithm. We provide the links having maximum load to minimum interference channel i.e. non-interference channel based on IEEE 802.11. The performance evaluation shows that by using the proposed channel assignment, the network performance is improved.

Utility based channel assignment: A centralized channel assignment mechanism for multi radio multi channel wireless mesh networks

In this paper, we address the channel assignment problem in a multi-radio mesh network that involves assigning channels to radio interfaces for eliminating the effect of wireless interference. Due to the insufficient number of frequency channels and available radios per node, interference is still present which limits the available bandwidth on wireless links and eventually decreases the achievable throughput. In this paper, we investigate the effect of considering the diverse delivery probability of the wireless links on the channel assignment solutions. We show that it is possible to classify the wireless links and omit some of them to benefit from a more diverse-channel solution. We propose a new channel assignment mechanism aiming to minimize the interference over high performance links. Finally, a performance study is carried out to assess the effectiveness of our proposed algorithm. Evaluations show that the multi-channel network obtained from our proposed algorithm achieves significant improvement in terms of reducing the interference and increasing the network capacity. Key words: Wireless mesh network, channel assignment, multi-radio, multi-channel.

An Analysis of Reconfiguration Approaches for Recovery in Wireless Mesh Networks

Wireless Mesh Network (WMN) is one of the essential elements in the networks of the future because of its ability to provide high bandwidth wireless backbone covering a large physical region. Generally single radio mesh nodes operating on a single channel suffer from capacity issues and hence it is essential to equip mesh routers with multiple radios using multiple non overlapping channels. But during their lifetime, multi radio wireless mesh networks suffer from link failures caused by channel interference, dynamic obstacles, and applications bandwidth demands. This paper presents a detailed analysis of various reconfiguration techniques used to recover wireless mesh network from link failures and the issues to be addressed in order to maximize the network performance. Reconfiguration schemes make use of primitive link changes such as channel, radio and route switch operations to recover WMNs from link failures. In general, reconfiguration schemes generate a set of reconfiguration plans and select the best plan according to the optimality criteria defined specific to that particular scheme. The system cooperatively reconfigures network settings among all mesh routers based on this best reconfiguration plan and thus recover from link failure.

Interference-Aware Bandwidth Reservation in multi-radio multi-channel mesh networks

In this paper, we propose the Interference-Aware Bandwidth Reservation (IABR) scheme for providing flow admission control and bandwidth reservation for end-to-end flows in 802.11 multi-radio multi-channel wireless mesh networks. The effects of inter-flow and intra-flow interference have often been neglected in existing solutions, which can lead to inaccurate bandwidth estimation and reservation. IABR models both the current inter-flow interference from existing flows and the expected intra-flow interference of the incoming flow to make accurate estimation of the available bandwidth and perform admission control. Moreover, IABR exploits wireless link diversity between neighboring nodes in multi-radio multi-channel mesh networks to improve flow admission ratio and ensure efficient load-balancing. Simulation results show that IABR provides accurate bandwidth estimation, excellent load distribution and high flow admission ratio.

Experiences with a Metropolitan Multiradio Wireless Mesh Network: Design, Performance, and Application

Wireless mesh networks comprise nodes with multiple radio interfaces, and can provide low-cost high-speed Internet access or connectivity for data transfer. In this article we report our experiences and investigations with an experimental metropolitan multiradio mesh network that covers an area of approximately 60 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in the city of Heraklion, Crete. We present the design and deployment of the network, experiments to quantify the network's performance, and an application that runs on top of it and exploits it's low-cost wide-area connectivity. The metropolitan network consists of 16 nodes, among which six are core nodes, each with up to four 802.11a wireless interfaces and an additional wireless interface for management and monitoring. The distance between core mesh nodes varies from 1.6 to 5 km, and the mesh network contains two gateways that connect it to a wired network. Our performance experiments involve rate, power, and channel control for long-distance metropolitan links, and include investigations of the timescales for the operation for these mechanisms. Finally, we present a system for continuous online electromagnetic field monitoring and spectrum sensing, which utilizes the metropolitan mesh network for collecting wide-area measurements from low-cost EMF measurement devices.

LAMR: learning automata based multicast routing protocol for multi-channel multi-radio wireless mesh networks

Multicast routing is a crucial issue in wireless networks in which the same content should be delivered to a group of recipients simultaneously. Multicast is also considered as a key service for audio and video applications as well as data dissemination protocols over the last-mile backhaul Internet connectivity provided by multi-channel multi-radio wireless mesh networks (MCMR WMNs). The multicast problem is essentially related to a channel assignment strategy which determines the most suitable channel-radio associations. However, channel assignment brings about its own complications and hence, solving the multicast problem in MCMR WMNs will be more complicated than that of traditional networks. This problem has been proved to be NP-hard. In the major prior art multicast protocols developed for these networks, channel assignment and multicast routing are considered as two separate sub-problems to be solved sequentially. The work in this article is targeted at promoting the adoption of learning automata for joint channel assignment and multicast routing problem in MCMR WMNs. In the proposed scheme named LAMR, contrary to the existing methods, these two sub-problems will be solved conjointly. Experimental results demonstrate that LAMR outperforms the LCA and MCM proposed by Zeng et al. (IEEE Trans. Parallel. Distrib. Syst. 21(1):86---99, 2010) as well as the genetic algorithm-, tabu search-, and simulated annealing-based methods by Cheng and Yang (Int. J. Appl. Soft Comput. 11(2):1953---1964, 2011) in terms of achieved throughput, end-to-end delay, average packet delivery ratio, and multicast tree total cost.

A taxonomy of cross layer routing metrics for wireless mesh networks

AbstractMulti-hop, multi-channel, and multi-radio wireless mesh networks (WMNs) are emerging as promising field of wireless technology with self-organizing and self-healing features for internet and real time applications, i.e., VoIP and Video over IP. Interoperability feature of WMNs have made them to integrate easily with other network technologies like wired networks, WiFi, WiMax, MANETs, and cellular networks. WMNs are gaining popularity due to their high network throughput which highly depends on the routing procedures. Routing algorithms like optimized link state routing protocol and dynamic source routing make efficient routing decisions on the basis of routing metrics which actually predict the cost of link quality. Most of the routing protocols and routing metrics implemented in WMNs are actually designed for mobile ad hoc networks (MANETs). Since WMNs have different characteristics and limitations as compared to MANETs, so the routing metrics design for MANETs do not perform well in WMNs. Furthermore, quality of service (QoS) and throughput of the network in WMNs can be enhanced by using cross layer routing approach and by deploying multi-channel multi-radio (MCMR) scenarios in each relay node. This article discusses a design taxonomy, limitations and qualitative comparison of existing routing metrics for QoS in MCMR WMNs with respect to routing parameters, i.e., transmission rate, inter-flow interference, intra-flow interference, congestion, and channel diversity. Moreover, our taxonomy also opens the door up for new research areas in the design of cross layer routing metrics for MCMR radio WMNs for high throughput IP connectivity.

On the Use of Smart Ants for Efficient Routing in Wireless Mesh Networks

Routing in wireless mesh networks (WMNs) has been an active area of research for the last several years. In this paper, we address the problem of packet routing for efficient data forwarding in wireless mesh networks (WMNs) with the help of smart ants acting as intelligent agents. The aim of this paper is to study the use of such biologically inspired agents to effectively route the packets in WMNs. In particular, we propose AntMesh, a distributed interference-aware data forwarding algorithm which enables the use of smart ants to probabilistically and concurrently perform the routing and data forwarding in order to stochastically solve a dynamic network routing problem. AntMesh belongs to the class of routing algorithms inspired by the behaviour of real ants which are known to find a shortest path between their nest and a food source. In addition, AntMesh has the capability to effectively utilize the space/channel diversity typically common in multi radio WMNs and to discover high throughput paths with less interflow and intra-flow interference while conventional wireless network routing protocols fail to do so. We implement our smart ant-based routing algorithm in ns-2 and carry out extensive evaluation. We demonstrate the stability of AntMesh in terms of how quickly it adapts itself to the changing dynamics or load on the network. We tune the parameters of AntMesh algorithm to study the effect on its performance in terms of the routing load and end-to-end delay and have tested its performance under various network scenarios particularly fixed nodes mesh networks and also on mobile WMN scenarios. The results obtained show AntMesh's advantages that make it a valuable candidate to operate in mesh networks.

Online reconfiguration of channel assignment in Multi-Channel Multi-Radio wireless mesh networks

Efficient utilization of Multi Channel–Multi Radio (MC–MR) wireless mesh networks (WMNs) can be achieved only by intelligent channel assignment (CA) and Link Scheduling (LS). Due to the dynamic nature of traffic demand in WMNs, the CA has to be reconfigured whenever traffic demand changes, in order to achieve maximum throughput in the network. The reconfiguration of CA requires channel switching at radios which leads to disruption of ongoing traffic in the network. So, we have to consider this traffic disruption overhead while reconfiguring the network for traffic adaptation. The existing CA algorithms for MC–MR WMNs in the literature do not consider the reconfiguration overhead caused by the channel switching. In this paper, we propose a novel reconfiguration model that considers both network throughput and reconfiguration overhead to quantitatively evaluate a reconfiguration algorithm. Based on the reconfiguration model, we formulate the problem of reconfiguration of CA as a Mixed Integer Linear Program (MILP). We also propose an on-line heuristic algorithm for CA called Demand based State Aware channel Reconfiguration Algorithm (DeSARA) that finds the CA for the current traffic demand by considering the existing CA of the network to minimize the reconfiguration overhead. Through extensive simulations, we show the importance of considering the overhead in reconfiguration of CA, by comparing the performance of DeSARA with a static CA and a fully dynamic CA that does not consider the reconfiguration overhead. We also study the performance of the proposed algorithm with real network traces collected in a campus network to show its practicality.

Optimized Self Reconfigurable Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are being developed actively and deployed widely for a variety of applications, such as public safety, environment monitoring, and citywide wireless Internet services . They have also been evolving in various forms (e.g., using multiradio/channel systems to meet the increasing capacity demands by the above-mentioned and other emerging applications. However, due to heterogeneous and fluctuating wireless link conditions , preserving the required performance of such WMNs is still a challenging problem. . For example, some links of a WMN may experience significant channel interference from other coexisting wireless networks. Some parts of networks might not be able to meet increasing bandwidth demands from new mobile users and applications. The above problem in the WMNs is overcome by the proposed system i.e. autonomous network reconfiguration system (ARS) that allows a multiradio WMN(mr-WMN) to autonomously reconfigure its local network settings— channel, radio, and route assignment— for real-time recovery from link failures. This show that ARS outperforms existing failure-recovery schemes in improving channel-efficiency by more than 90% and in the ability of meeting the applications' bandwidth demands by an average of 200%.This paper presents shows that ARS decouples network reconfiguration from flow assignment and routing.This is the first step to solve optimization problem in giving best effort service to network failures is proposed. In this a threshold value is set for every node is the modification is proposed.When a node want to send packet from source to destination,it verify its threshold value,whether it reach its limit or not.When it reaches it limit,it choose another node to send data.It chooses it route with minimum path cost value and minimum delay time.With this consideration,some considerable amount of packet loss will be less when compared to the ARS system.

Load-balanced Multicast Tree Routing in Multi Channel Multi Radio Wireless Mesh Networks Using a New Cost Function

Wireless Mesh Network (WMN) is new emerging technology that offers low-cost high-bandwidth community wireless services. This type of network requires carefully assignment of resources and load balancing in order to provide the quality guarantees to traffic flows. Load balancing avoids the creation of bottleneck nodes, and increases the network efficiency. This paper addresses the problem of multicast load balancing in Multi-Channel Multi-Radio WMNs (MCMR-WMNs). In this regard, we introduce a novel load-aware dynamic cost function to weight the links of the network. Proposed cost function considers both the benefits of Wireless Broadcast Advantage (WBA) as well as the problem of load balancing. Also, we propose a Load-balanced Multicast Tree Routing (LMTR) algorithm which provides balanced multicast trees using the defined cost function. The proposed on-demand routing scheme not only minimizes the number of transmissions, but also tries to distribute the traffic among the nodes fairly and consequently decreases the interference in the network. We also demonstrate how proposed scheme can control the trade-off between load balancing and delay. Our extensive simulations in various networks with grid and random topologies show the efficiency of LMTR in load balancing. As you will see, LMTR significantly avoids the creation of bottleneck nodes and reduces the standard deviation of traffic load on mesh routers.

Optimization model for handoff-aware channel assignment problem for multi-radio wireless mesh networks

Optimal channel assignment (CA) in multi-radio wireless mesh networks is an NP-hard problem for which solutions usually leave several links interfering. Most of these solutions usually consider the overall throughput as the main optimization objective. However, other objectives have to be considered in order to provide better quality wireless connections to non stationary users. In this paper, we propose a multi-objective optimization model that, besides maximizing throughput, improves fairness and handoff experience of mesh clients. In this model, we use the Jain’s index to maximize users’ fairness and we allow same-channel assignments to links involved in the same high handoff traffic, thus reducing handoff-triggered re-routing characterized by its high latency. Then, we propose a centralized variable neighborhood search and a Tabu search heuristics to efficiently solve our model as an offline CA process. Moreover, in order to adapt to traffic dynamics caused especially by user handoffs, we propose an online CA scheme that carefully re-assigns channels to interfaces with the purpose of continuously minimizing the re-routing overhead/latency during user handoffs. We further improve this online scheme using load balancing. Simulation results show the good performance of our proposed approach in terms of delay, loss rate, overall throughput and fairness. Particularly, performance results of our online handoff-aware CA show the effectiveness of handoffs not involving path re-routing in decreasing the delay, especially when considering load balancing.

An energy efficient channel assignment and routing algorithm for multi-radio wireless mesh networks

Endowing mesh routers with multiple radios is a recent solution to improve the performance of wireless mesh networks. Solving the problem how to assign channels to radios has attracted a lot of attention in the recent years, partly because of the hardness of solving the channel assignment problem jointly with the routing problem. However, the approaches proposed in the literature so far have mainly focused on reducing interference or maximizing the throughput. Little attention has been paid to the energy consumption of wireless mesh networks, given that mesh nodes are usually connected to a power source. However, with the rising concerns about the energy consumed by communication infrastructures, it makes sense to consider the minimization of the energy consumption as an objective of the channel assignment and routing problem. Our work stems from the observation that an idle radio simply overhearing a frame consumes nearly the same power as the radio actually receiving the frame. Hence, energy may be saved by turning off a number of radios, if the performance of the network is not impaired. In this paper, we define the energy efficient channel assignment and routing problem, show that it is NP-hard and propose a heuristic algorithm. For the purpose of comparing the solution found by the proposed algorithm to the optimal solution, we also present two Mixed Integer Linear Programs (MILPs) that optimally solve the problem we address. Finally, we show the results of extensive simulation studies we conducted to assess the effectiveness of the proposed algorithm.

Modeling and Optimization of Muiticast End-to-End Delay in Multi-Radio Wireless Mesh Networks

Multi-radio wireless mesh network(MR-WMN) is one of the key access techniques in Mobile Internet.However,current 802.11-based MR-WMN is not able to provide low multicast end-to-end delay.To address this problem,we first propose a layered and analytical model by combining overlapping channel assignment with multipath routing strategies.The proposed model can be used as a guide on multicast design.It decoupled multicast delay into transmission delay in the MAC layer and queuing delay in the Mesh layer based on that it derived a new multicast routing metric that had low end-to-end delay.Second,we prove that finding the minimum global flow interference solution is a NP-Complete problem and the relationship between global flow interference and network node densities is distributed in accord with double-Pareto lognormal(dPlN) distribution.Based on these two results,the DCA algorithm is proposed in order to minimum global flow interference which can efficiently reduce the multicast transmission delay in MAC layer.Last,to avoid the best wireless link being congested,we propose the flow adaptive-based MMRA algorithm by making use of the MR-MED routing metric and the multipath routing design philosophy,which took local channel congestion into account and can efficiently reduce the queuing delay in Mesh layer.Simulation result and comparison of the common algorithm MCM both show that the proposed model accurately characterizes the multicast delay in multi-radio wireless mesh network and the combination of the DCA and MMRA algorithms efficiently reduce the multicast end-to-end delay.