Cluster‐based mobility management algorithms for wireless mesh networks

Wireless mesh networks (WMNs) have been the recent advancements and attracting more academicians and industrialists for their seamless connectivity to the internet. Radio resource is one among the prime resources in wireless networks, which is expected to use in an efficient way especially when the mobile nodes are on move. However, providing guaranteed quality of service to the mobile nodes in the network is a challenging issue. To accomplish this, we propose 2 clustering algorithms, namely, static clustering algorithm for WMNs and dynamic clustering algorithm for WMNs. In these algorithms, we propose a new weight‐based cluster head and cluster member selection process for the formation of clusters. The weight of the nodes in WMN is computed considering the parameters include the bandwidth of the node, the degree of node connectivity, and node cooperation factor. Further, we also propose enhanced quality of service enabled routing protocol for WMNs considering the delay, bandwidth, hopcount, and expected transmission count are the routing metrics. The performance of the proposed clustering algorithms and routing protocol are analyzed, and results show high throughput, high packet delivery ratio, and low communication cost compared with the existing baseline mobility management algorithms and routing protocols.     

On Routing in Multichannel Wireless Mesh Networks: Challenges and Solutions

Wireless mesh networks have emerged as a promising solution to providing cost-effective last-mile connectivity. Employing multiple channels is shown to be an effective approach to overcoming the problem of capacity degradation in multihop wireless networks. However, existing routing schemes that are designed for single-channel multihop wireless networks may lead to inefficient routing paths in multichannel WMNs. To fully exploit the capacity gain due to multiple channels, one must consider the availability of multiple channels and distribute traffic load among channels as well as among nodes in routing algorithms. In this article we focus on the routing problem in multichannel WMNs. We highlight the challenges in designing routing algorithms for multichannel WMNs and examine existing routing metrics that are designed for multichannel WMNs, along with a simulation-based performance study. We also address some open research issues related to routing in multichannel WMNs.     

Multi-radio multi-channel routing metrics in IEEE 802.11s based wireless mesh networks

IEEE 802.11s is one of the emerging standards designed to build wireless mesh networks which may serve to extend the coverage of access networks. The default IEEE 802.11s path selection protocol Hybrid Wireless Mesh Protocol (HWMP) is based on the radio-aware airtime link metric (ALM) that outperforms the hop-count metric in single channel multi-hop wireless networks. However, this metric may lead to capacity degradation when multiple channels and/or multi-radio are used. To fully exploit the capacity gain of multiple channels use, new routing metrics have been proposed such as weighted cumulative expected transmission time, metric of interference and channel switching, interference aware routing metric, exclusive expected transmission time, and normalized bottleneck link capacity. These metrics distribute the data traffic load among channels and/or radios to reach the final destination. In this paper, we provide a qualitative comparison study that considers the characteristics of these metrics. Indeed, we substitute ALM by these different metrics, and we evaluate the performance of HWMP through simulation. Obtained results allow us to identify the appropriate use case of each metric.     

A Multi-Objective Optimization Approach for Joint Channel Assignment and Multicast Routing in Multi-Radio Multi-Channel Wireless Mesh Networks

Multicast routing is an effective mechanism for delivering data to a group of receivers. Due to intrinsic property of air medium in wireless mesh networks (WMN), interference is an important issue in determining the data rate for multicast services. Interference reduction is handled by assigning multiple orthogonal channels to multiple radios in multi-radio multi-channel WMNs. Channel assignment is known to be a NP-complete problem. Most prior methods have solved multicast routing and channel assignment problems sequentially and have not considered the interplay between these two problems. Focusing on this issue, we address joint channel assignment and routing problem for multicast applications. In this paper, a novel technique based on a multi-objective genetic algorithm is proposed to build a delay constrained minimum cost multicast tree with minimum interference. We have examined the proposed algorithm on different network configurations. Experimental results demonstrate that our method finds better trees in terms of cost, delay, and interference compared to prior methods.     

无线Mesh网中基于信道感知的多径路由判据

无线Mesh网是一种新型的宽带无线接入网络,其中路由算法的设计是一个非常活跃的研究领域。WCETT路由判据仅适于单径路由协议,但是多路径路由能够提供负载平衡和较高的总带宽。为了提高网络性能,在综合考虑无线链路质量和信道间干扰的基础上,提出了一种新的多径路由判据CAM-WCETT。仿真结果表明,该方案能显著提高网络的吞吐量。     

Parallel Big Bang–Big Crunch Global Optimization Algorithm: Performance and its Applications to routing in WMNs

This paper presents the performance of Parallel Big Bang–Big Crunch (PB3C) global optimization algorithm on CEC-2014 test suite. The performance is compared with 16 other algorithms. It has been observed that PB3C gave best performance on 7 functions of the test bench. Out of seven, for 6 functions it gave the unmatched best performance whereas on one count its performance was equaled by other algorithm as well. Further this paper proposes a PB3C based new routing approach to wireless mesh networks (WMNs). Being dynamic; routing is a challenging issue in WMNs. The approach is a near shortest path route evaluation approach. The approach was simulated on MATLAB. The performance was compared with 7 other approaches namely ad hoc on-demand distance vector, dynamic source routing, ant colony optimization, biogeography based optimization, firefly algorithm, BAT and simple Big Bang–Big Crunch based approaches. For WMNs of size 1000 nodes and above the PB3C was observed to outperform rest of the 7 algorithms.     

A ring-based multicast routing topology with QoS support in wireless mesh networks

Wireless mesh networking (WMN) is an emerging technology for future broadband wireless access. The proliferation of the mobile computing devices that are equipped with cameras and ad hoc communication mode creates the possibility of exchanging real-time data between mobile users in wireless mesh networks. In this paper, we argue for a ring-based multicast routing topology with support from infrastructure nodes for group communications in WMNs. We study the performance of multicast communication over a ring routing topology when 802.11 with RTS/CTS scheme is used at the MAC layer to enable reliable multicast services in WMNs. We propose an algorithm to enhance the IP multicast routing on the ring topology. We show that when mesh routers on a ring topology support group communications by employing our proposed algorithms, a significant performance enhancement is realized. We analytically compute the end-to-end delay on a ring multicast routing topology. Our results show that the end-to-end delay is reduced about 33 %, and the capacity of multicast network (i.e., maximum group size that the ring can serve with QoS guarantees) is increased about 50 % as compared to conventional schemes. We also use our analytical results to develop heuristic algorithms for constructing an efficient ring-based multicast routing topology with QoS guarantees. The proposed algorithms take into account all possible traffic interference when constructing the multicast ring topology. Thus, the constructed ring topology provides QoS guarantees for the multicast traffic and minimizes the cost of group communications in WMNs.     

On a joint temporal-spatial multi-channel assignment and routing scheme in resource-constrained wireless mesh networks

Use of multiple orthogonal channels can significantly improve network throughput of multi-hop wireless mesh networks (WMNs). In these WMNs where multiple channels are available, channel assignment is done either in a centralized manner, which unfortunately shows a poor scalability with respect to the increase of network size, or in a distributed manner, where at least one channel has to be dedicated for exchanging necessary control messages or time synchronization has to be utilized for managing the duration of data packet transmission, causing excessive system overhead and waste of bandwidth resource. In this paper, we first formulate multi-channel assignment as a NP-hard optimization problem. Then a distributed, heuristic temporal-spatial multi-channel assignment and routing scheme is proposed, assuming every wireless node in the network is equipped with a single-radio interface. Here the gateway node is set to use all the channels sequentially in a round-robin fashion. This temporal scheme ensures all the nodes that need to directly communicate with the gateway node shall have a fair access to it. For those non-gateway nodes, a spatial scheme where channels are assigned based on their neighbors’ channel usage is adopted to exploit parallel communications and avoid channel interference among nodes. Furthermore, since the routing factors, including channel usage of neighbor nodes, node hop count, node memory size, and node communication history, are all considered along with the channel assignment, network performance, measured by packet delivery latency, channel usage ratio, and memory usage ratio, tends to be considerably enhanced. The simulation results have confirmed that, compared with a couple of well-known multi-channel assignment schemes, such as LCM [21] and ROMA [15], the proposed scheme shows substantial improvement in network throughput with a very modest collision level. In addition, the proposed scheme is highly scalable as the algorithm complexity is only linearly dependent on the total number of channels that are available in the network and the number of neighbors that a network node directly connects to.     

EFT: a high throughput routing metric for IEEE 802.11s wireless mesh networks

In this paper, we present a throughput-maximizing routing metric, referred to as expected forwarding time (EFT), for IEEE 802.11s-based wireless mesh networks. Our study reveals that most of the existing routing metrics select the paths with minimum aggregate transmission time of a packet. However, we show by analyses that, due to the shared nature of the wireless medium, other factors, such as transmission time of the contending nodes and their densities and loads, also affect the performance of routing metrics. We therefore first identify the factors that hinder the forwarding time of a packet. Furthermore, we add a new dimension to our metric by introducing traffic priority into our routing metric design, which, to the best of our knowledge, is completely unaddressed by existing studies. We also show how EFT can be incorporated into the hybrid wireless mesh protocol (HWMP), the path selection protocol used in the IEEE 802.11s draft standard. Finally, we study the performance of EFT through simulations under different network scenarios. Simulation results show that EFT outperforms other routing metrics in terms of average network throughput, end-to-end delay, and packet loss rate.     

Design and implementation of multicasting for multi-channel multi-interface wireless mesh networks

Multicasting is a useful communication method in wireless mesh networks (WMNs). Many applications in WMNs require efficient and reliable multicast communications, i.e., high delivery ratio with low overhead among a group of recipients. In spite of its significance, little work has been done on providing such multicast service in multi-channel WMNs. Traditional multicast protocols for wireless and multi-hop networks tend to assume that all nodes, each of which is equipped with a single interface, collaborate on the same channel. This single-channel assumption is not always true, as WMNs often provide nodes with multiple interfaces to enhance performance. In multi-channel and multi-interface (MCMI) WMNs, the same multicast data must be sent multiple times by a sender node if its neighboring nodes operate on different channels. In this paper, we try to tackle the challenging issue of how to design a multicast protocol more suitable for MCMI WMNs. Our multicast protocol builds multicast paths while inviting multicast members, and tries to allocate the same channel to neighboring members in a bottom-up manner. By unifying fixed channels of one-hop multicast neighbors, the proposed algorithm can improve the performance such as reducing multicast data transmission overhead and delay, while managing a successful delivery ratio. In order to prove such expectation on the performance, we have implemented and evaluated the proposed solution on the real testbed having the maximum 24 nodes, each of which is equipped with two IEEE 802.11a Atheros WLAN cards.     

Enhancing the Performance of Video Streaming in Wireless Mesh Networks

Multihop wireless mesh networks (WMNs) provide ubiquitous wireless access in a large area with less dependence on wired networks. However, some emerging applications with high bandwidth requirement and delay and loss constraints, such as video streaming, suffer poor performance in WMNs, since high compression rates and/or high packet loss rates deteriorate the video quality. In this paper, we propose a novel mechanism composed of (1) a network route selection scheme which provides paths for multiple video streams with the least interference, called Minimum Interference Route Selection (MIROSE) and (2) an optimization algorithm that determines the compression rates depending on the network condition, called Network State Dependent Video Compression Rate (NSDVCR) algorithm. Simulation results of the proposed mechanisms show the significant improvement of the video quality measured with a popular metric, Peak-Signal-to-Noise Ratio (PSNR), compared with standard routing and default compression rates.     

基于HWMP的先应树状路由算法研究

无线网状网是一种新兴的宽带无线网络接入技术,支持不同应用场景的无线接入。IEEE802.11s标准定义了一种默认的路由选择算法,称为混合无线网状网协议(HWMP)。HWMP将把树状路由为基础的先应路由模式和按需路由模式相结合。对先应路由模式进行改进,以减小网络开销,增强网络性能。从仿真结果可以看出,改进后的算法在数据包到达率、平均端到端时延和吞吐量指标上达到了更佳的性能。     

Efficient routing and centralized scheduling algorithms for IEEE 802.16 Mesh Networks

An IEEE 802.16 wireless system can provide broadband wireless access to subscriber stations and operate in mesh mode. The communication between a subscriber station and a base station can pass through one or more intermediate subscriber stations. The IEEE 802.16 standard provides a centralized scheduling mechanism that supports contention‐free and resource‐guarantee transmission services in mesh mode. However, the corresponding algorithm to this schedule is quite primitive in the standard. In this paper, we propose a more efficient way to realize this schedule by maximizing channel utilization. Our designs are divided into two phases: routing and scheduling. First, a routing tree topology is constructed from a given mesh topology by our proposed tree construction algorithm. Secondly, we allocate channel resources to the edges in the routing tree by our proposed scheduling algorithm. To further support the quality‐of‐service schedule, we extend our designs by addressing some issues such as service class, admission control and fairness. Simulation results show the superiority of our proposed algorithms over others. Copyright © 2011 John Wiley & Sons, Ltd.     

Cross-Layer Design for QoS in Wireless Mesh Networks

Cross-layer design for quality of service (QoS) in wireless mesh networks (WMNs) has attracted much research interest recently. Such networks are expected to support various types of applications with different and multiple QoS and grade-of-service (GoS) requirements. In order to achieve this, several key technologies spanning all layers, from physical up to network layer, have to be exploited and novel algorithms for harmonic and efficient layer interaction must be designed. Unfortunately most of the existing works on cross-layer design focus on the interaction of up to two layers while the GoS concept in WMNs has been overlooked. In this paper, we propose a unified framework that exploits the physical channel properties and multi-user diversity gain of WMNs and by performing intelligent route selection and connection admission control provides both QoS and GoS to a variety of underlying applications. Extensive simulation results show that our proposed framework can successfully satisfy multiple QoS requirements while it achieves higher network throughput and lower outage as compared to other scheduling, routing and admission control schemes.     

A QoS aware joint design for wireless mesh networks

Wireless mesh networks (WMNs) provide Internet access to remote areas and wireless connections on a metropolitan scale. In this paper, we focus on the problem of improving the gateway throughput in WMNs while achieving fairness and supporting quality-of-service (QoS) differentiation for end-users. To address this problem, we propose a new distributed dynamic traffic scheduling algorithm that supports different QoS requirements from different users. We also develop a joint weight-aware channel assignment and minimum expected delay routing mechanism. Simulation results demonstrate the performance of the proposed work in terms of the achieved throughput and minimized packet loss ratio and delay.     

Power-Efficient Spatial Reusable Channel Assignment Scheme in WLAN Mesh Networks

Interference has strong effect on the available bandwidth of wireless local area network (WLAN) based mesh networks. The channel assignment problem for multi-radio multi-channel multihop WLAN mesh networks is complex NP-hard, and channel assignment, routing and power control are tightly coupled. To mitigate the co-channel interference and improve capacity in multi-channel and multi-interface WLAN mesh networks, a power-efficient spatial reusable channel assignment scheme is proposed, which considers both channel diversity and spatial reusability to reduce co-channel interference by joint adjusting channel, transmission power and routing. In order to assign channel appropriately, an efficient power control scheme and a simple heuristic algorithm is introduced to achieve this objective, which adjust the channel and power level of each radio according to the current channel conditions so as to increase the opportunity of channel spatial reusability. The proposed channel assignment scheme also takes load, capacity and interference of links into consideration. Simulation results show the effectiveness of our approach and demonstrate that the proposed scheme can get better performance than other approaches in terms of throughput, blocking ratio, energy consumption and end-to-end delay.     

The Optimization of Combination Scheme in Cooperative Spectrum Sensing Based on the Practical Reporting Frame Format

Wireless mesh networks (WMNs) are emerged as prominent solution to provide seamless connection to the internet. WMNs are typically used for providing broadband wireless internet access to a large number of users and networks. Guaranteeing the quality of service to end users with efficient resource utilization is a challenging issue in WMNs. To accomplish this, we propose a hybrid routing protocol for wireless mesh networks. It is a combination of intra cluster routing protocol (ICR) and inter cluster routing protocol for mesh networks (ICMR). Intra cluster routing protocol is intended to facilitate the communication between mesh clients within a same cluster and inter cluster routing protocol (ICMR) intended to facilitate the communication for mesh clients from different clusters. Intra cluster routing protocol is a proactive type of routing protocol and inter cluster routing protocol is a reactive type of routing protocol. The performance of the proposed protocol is analyzed and the results shown superior performance compared to baseline routing protocols in terms of throughput, end to end delay, packet delivery ratio and jitter.     

Admission control on multipath routing in 802.11-based wireless mesh networks

Admission control (AC) is a mechanism for meeting bandwidth requirements of data transmissions. Early research on admission control for wireless mesh networks (WMNs) was centered around single-path routing. Compared to single-path routing, parallel multipath routing may offer more reliable network services and better load balancing. Applying admission control to multipath routing could further improve service quality, but it also faces a number of challenges. For example, transmission on one path may affect transmission on a neighboring path. Addressing these challenges, this paper presents an AC algorithm on parallel multipath routing for WMNs. In particular, we formulate an optimization problem for achieving the best service based on available bandwidth and bandwidth consumption of to-be-admitted data sessions. While solving this problem is a complex task, we devise an optimal algorithm for selecting two node-disjoint paths with rate allocation, and propose a distributed multipath routing and admission control protocol to achieve a near-optimal solution. Simulations show that MRAC is efficient and effective in meeting bandwidth requirements.     

Distributed Contention-Aware Call Admission Control for IEEE 802.11 Multi-Radio Multi-Rate Multi-Channel Wireless Mesh Networks

In this paper, we focus on call admission control (CAC) in IEEE 802.11 multi-radio multi-rate multi-channel (MR²-MC) wireless mesh networks (WMNs). CAC is the key component of QoS routing protocols. The goal of CAC is to protect existing flows from QoS violations and fully utilize available radio resource on channels. We propose a CAC mechanism, called Contention-Aware Multi-channel Call Admission Control (CMC), for MR²-MC WMNs based on IEEE 802.11 DCF. CMC is fully distributed, relies on local information to estimate the residual bandwidth of a path, and can be integrated into existing routing protocols for MR²-MC WMNs to provide QoS. We evaluate the performance of CMC via ns-2 simulations. The results show that CMC can precisely predict the end-to-end residual bandwidths of paths, successfully protects existing flows from QoS violations, and fully utilizes the bandwidths on channels.     

Efficient delay based scheduling with fairness in multi-hop wireless mesh networks

Some scheduling algorithms have been designed to improve the performance of multi-hop wireless mesh networks (WMNs) recently. However the end-to-end delay is seldom considered as the complexity of multi-hop topology and open wireless shared channel. This article proposes an efficient delay based scheduling algorithm with the concept of buffer-data- hops. Considering the demand satisfaction factor (DSF), the proposed algorithm can also achieve a good fairness performance. Moreover, with the interference-based network model, the scheduling algorithm can maximize the spatial reuse, compared to those graph-based scheduling algorithms. Detailed theoretical analysis shows that the algorithm can minimize the end-to-end delay and make a fair scheduling to all the links.