Backbone Wireless Mesh Networks Research Articles

Layer 3 wireless mesh networks: mobility management issues

Wireless Mesh Networks (WMNs) may be broadly classified into two categories: Layer 2 and Layer 3 WMNs. This article focuses on the Layer 3 WMN, which provides the same service interfaces and functionalities to the conventional mobile host (MH) as the conventional wireless local area network. Three essential design issues to realize seamless mobility management in the Layer 3 WMN are identified and systematically discussed in this article. They are IP address resolution, location management, and Media Access Control (MAC) address resolution. The Layer 3 WMN backbone requires systematic management of the IP and MAC addresses of each MH, which can be realized by four basic approaches: centralized management, home management, replication management, and distributed management. It is shown that the address pair management architecture is fundamental to realizing efficient packet forwarding and address resolution. Design guidelines are provided to realize Layer 3 WMN supporting seamless MH roaming, considering the applicability of address pair management architectures with regard to WMN scale and client mobility; this applicability is considered based on a qualitative evaluation of the management overhead and handover performance.

Clique-Based Utility Maximization in Wireless Mesh Networks

This study considers utility-based resource allocation in backbone wireless mesh networks (WMNs). Unlike single-hop cellular networks, a WMN has multi-hop transmissions with multiple contending links, and thus requires more careful design for resource allocation. To this end, we provide a clique-based method with efficient spatial reuse, which is then incorporated into proportionally fair scheduling (PFS) for fair resource management in WMNs. We call it a clique-based proportionally fair scheduling (CBPFS) algorithm. The linear and/or logarithmic rate models used to analyze PFS in single-hop cellular networks cannot be used to analyze CBPFS in backbone WMNs. Using stochastic approximation and recent results on rate modeling for Rayleigh fading channels, we conduct mathematical analysis and obtain a closed-form model to quantify CBPFS performance, without the need of the highly time-consuming ordinary differential equation (ODE) analysis. We use the derived analytical framework to estimate the link throughput of CBPFS and compare it with simulations. It is the first time a closed-form analytical model is developed to quantify the throughput of links in a multi-hop network where links are proportionally fair scheduled.

Flow admission control for multi-channel multi-radio wireless networks

Providing Quality of Service (QoS) is a major challenge in wireless networks. In this paper we propose a distributed call admission control protocol (DCAC) to do both bandwidth and delay guaranteed call admission for multihop wireless mesh backbone networks, by exploiting the multi-channel multi-radio (mc-mr) feature. We propose a novel routing metric for route setup, and present an efficient distributed algorithm for link reservation that satisfies the required bandwidth and reduces the delay by a local scheduling that minimizes one hop delay. To the best of our knowledge, this is the first distributed protocol that embeds mc-mr feature in Time Division Medium Access (TDMA) to do QoS call admission in wireless backbone networks. Extensive simulation studies show that our protocol significantly improves network performance on supporting QoS sessions compared with some widely used protocols.

MIMO Network Coding-Based PHY/MAC Protocol for Replacement of CSMA/CA in Efficient Two-Way Multihop Relay Networks

Backbone wireless mesh networks have attracted much of attention due to their wide-range applications. The use of CSMA/CA basedMAC protocols in mesh networks, however, leads to an inefficient resource utilization, and to high latency. Several alternative protocols including directional MAC, multichannel MAC only provide marginal improvement. Recently, a cross-layer design employing multiple antenna techniques and network coding called MIMO network coding was proposed. Owing to multiple access interference cancellation ability of MIMO, bi-directional flow multiplexing capability of network coding in combination with an efficient channel access scheme of TDMA/TDD, MIMO two-way relay provides significantly high end-to-end capacity. In this paper, MIMO network coding is considered as an alternative PHY/MAC protocol of CSMA/CA. This paper provides details of the protocol and develops network simulators for performance evaluation. Furthermore, an efficient retransmission scheme for transmission system employing network coding is proposed. The paper shows that MIMO network coding achieves significant network performance improvement with respect to CSMA/CA mesh networks. The proposed retransmission scheme is also shown to be effective in terms of resource usage as well as QoS guarantee.

Throughput Gateways-Congestion Trade-Off in Designing Multi-Radio Wireless Networks

In Wireless Mesh Networks (WMNs), traffic is mainly routed by WMN Backbone (WMNB) between the mesh clients and the Internet and goes through mesh gateways. Since almost all traffic has to pass through one of the MGs, the network may be unexpectedly congested at one or more of them, even if every mesh router provides enough throughput capacity. In this paper, we address the problem of congestion of gateways while designing WMNs. We propose a simultaneous optimization of three competing objectives, namely network deployment cost, interference between network channels and congestion of gateways while guaranteeing full coverage for mesh clients. We tailor a nature inspired meta-heuristic algorithm to solve the model whereby, several trade-off solutions are provided to the network planner to choose from. A comparative experimental study with different key parameter settings is conducted to evaluate the performance of the model.

Flow Oriented Channel Assignment for Multi-radio Wireless Mesh Networks

We investigate channel assignment for a multichannel wireless mesh network backbone, where each router is equipped with multiple interfaces. Of particular interest is the development of channel assignment heuristics for multiple flows. We present an optimization formulation and then propose two iterative flow oriented heuristics for the conflict-free and interference-aware cases, respectively. To maximize the aggregate useful end-to-end flow rates, both algorithms identify and resolve congestion at instantaneous bottleneck link in each iteration. Then the link rate is optimally allocated among contending flows that share this link by solving a linear programming (LP) problem. A thorough performance evaluation is undertaken as a function of the number of channels and interfaces/node and the number of contending flows. The performance of our algorithm is shown to be significantly superior to best known algorithm in its class in multichannel limited radio scenarios.

Queuing delay of backbone wireless mesh networks

The delay of a mesh-distributed backbone Wireless Mesh Network (WMN) was investigated. A short-path routing protocol based on traffic load balance was put forward. Considering the factors of routing protocol,network scale,the serving capability of gateways and mesh routers,the arriving rate of data packets,MMN's queuing delay was researched. In addition,the relation between queuing delay and capacity of the networks was discussed,and then the capacity based on the restriction of delay was given.

Design and implementation of MobiSEC: A complete security architecture for wireless mesh networks

Wireless mesh networks (WMNs) have emerged recently as a technology for next-generation wireless networking. They consist of mesh routers and clients, where mesh routers are almost static and form the backbone of WMNs. WMNs provide network access for both mesh and conventional clients. In this paper we propose MobiSEC, a complete security architecture that provides both access control for mesh users and routers as well as a key distribution scheme that supports layer-2 encryption to ensure security and data confidentiality of all communications that occur in the WMN. MobiSEC extends the IEEE 802.11i standard exploiting the routing capabilities of mesh routers; after connecting to the access network as generic wireless clients, new mesh routers authenticate to a central server and obtain a temporary key that is used both to prove their credentials to neighbor nodes and to encrypt all the traffic transmitted on the wireless backbone links. A key feature in the design of MobiSEC is its independence from the underlying wireless technology used by network nodes to form the backbone. Furthermore, MobiSEC allows seamless mobility of both mesh clients and routers. MobiSEC has been implemented and integrated in MobiMESH, a WMN implementation that provides a complete framework for testing and analyzing the behavior of a mesh network in real-life environments. Moreover, extensive simulations have been performed in large-scale network scenarios using Network Simulator. Numerical results show that our proposed architecture considerably increases the WMN security, with a negligible impact on the network performance, thus representing an effective solution for wireless mesh networking.

Gateways Placement in Backbone Wireless Mesh Networks

This paper presents a novel algorithm for the gateway placement problem in Backbone Wireless Mesh Networks (BWMNs). Different from existing algorithms, the new algorithm incrementally identifies gateways and assigns mesh routers to identified gateways. The new algorithm can guarantee to find a feasible gateway placement satisfying Quality-of-Service (QoS) constraints, including delay constraint, relay load constraint and gateway capacity constraint. Experimental results show that its performance is as good as that of the best of existing algorithms for the gateway placement problem. But, the new algorithm can be used for BWMNs that do not form one connected component, and it is easy to implement and use.

A flow-based network monitoring framework for wireless mesh networks

As an extension of wireless ad hoc and sensor networks, wireless mesh networks recently were developed as a key solution to provide high-quality multimedia services and applications, such as voice, data, and video, over wireless personal area networks, wireless local area networks, and wireless metropolitan area networks. A WMN has a hybrid network infrastructure with a backbone and an access network and usually is operated in both ad hoc and infrastructure modes with self-configuration and self-organization capabilities. In this article, we review security challenges, attacks, and countermeasures in the physical, medium access control (MAC), and network layers of wireless mesh backbone and access networks. We then extend the concept of traffic flow from IP networks and define meshflow in wireless mesh networks. Based on this new concept, we propose a comprehensive framework to realize network monitoring, user and router profiling, application and service balancing, and security protection in wireless mesh backbone networks. Practical issues and design trade-offs for implementing the proposed framework in real systems also are discussed.

Survivable and delay-guaranteed backbone wireless mesh network design

Backbone wireless mesh networks (BWMNs) consisting of wireless mesh routers are emerging alternatives to implementations of metropolitan area networks (MANs). In a BWMN, gateways connect to the Internet via wireline links and provide Internet access services for users. Due to the limited wireless channel bit rate, multiple gateways are usually required in a BWMN, which costs budget and takes time to set up. In this paper, we study the network topology design and the gateway arrangement so that the construction cost of a BWMN is minimal. Two algorithms, namely, the Predefined Gateway Set Algorithm (PGSA) and the Self-Constituted Gateway Algorithm (SCGA), are proposed for the BWMN design. A genetic algorithm and a proposed enhanced Djikstra's algorithm are employed to search for the low-cost network configuration with constraints such as survivability, link capacity, degree limitation and maximum tolerable delay. Computational results show that the PGSA can give an acceptable network configuration rapidly. In case the gateway cost is high, using the SCGA can lower the network construction cost at the expense of more computational time.

Wireless mesh networks

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and convent...

Wireless mesh networks: a survey

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.