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.     

Design and Performance Study for a Mobility Management Mechanism (WMM) Using Location Cache for Wireless Mesh Networks

Wireless mesh networks (WMNs) have emerged as one of the major technologies for 4G high-speed mobile networks. In a WMN, a mesh backhaul connects the WMN with the Internet, and mesh access points (MAPs) provide wireless network access service to mobile stations (MSs). The MAPs are stationary and connected through the wireless mesh links. Due to MS mobility in WMNs, mobility management (MM) is required to efficiently and correctly route the packets to MSs. We propose an MM mechanism named Wireless mesh Mobility Management (WMM). The WMM adopts the location cache approach, where mesh backhaul and MAPs (referred to as mesh nodes (MNs)) cache the MS's location information while routing the data for the MS. The MM is exercised when MNs route the packets. We implement the WMM and conduct an analytical model and simulation experiments to investigate the performance of WMM. We compare the signaling and routing cost between WMM and other existing MM protocols. Our study shows that WMM has light signaling overhead and low implementation cost.     

Multicast Routing in Wireless Mesh Networks: Minimum Cost Trees or Shortest Path Trees?

There exist two fundamental approaches to multicast routing: shortest path trees (SPTs) and minimum cost trees (MCTs). The SPT algorithms minimize the distance (or cost) from the sender to each receiver, whereas the MCT algorithms minimize the overall cost of the multicast tree. Due to the very large scale and unknown topology of the Internet, computing MCTs for multicast routing in the Internet is a very complex problem. As a result, the SPT approach is the more commonly used method for multicast routing in the Internet, because it is easy to implement and gives minimum delay from the sender to each receiver, a property favored by many real-life applications. Unlike the Internet, a wireless mesh network (WMN) has a much smaller size, and its topology can be made known to all nodes in the network. This makes the MCT approach an equally viable candidate for multicast routing in WMNs. However, it is not clear how the two types of trees compare when used in WMNs. In this article we present a simulation-based performance comparison of SPTs and MCTs in WMNs, using performance metrics, such as packet delivery ratio, end-to-end delay, and traffic impacts on unicast flows in the same network.     

无线Mesh网络路由协议研究

无线Mesh网络WMN（wireless mesh networks）是一种新型的无线网络,它融合了无线局域网（WLAN）和Ad Hoc网络的优势,成为宽带接入的一种有效手段。首先介绍了无线Mesh网的网络结构和特点．并在此基础上讨论了无线Mesh网络对路由协议的要求。无线Mesh网络的路由算法是Mesh领域的研究难点,通过分析比较4种针对WMN的路由协议,总结了现有的路由协议的优缺点,并对今后的研究方向做出了展望。     

Path diversified multi-QoS optimization in multi-channel wireless mesh networks

Wireless mesh networks (WMNs) have become a promising solution for quick and low-cost spreading of Internet accesses and other network services. Given the mesh topology, multiple paths are often available between node pairs, which thus naturally endorse path-diversified transmission. Unfortunately, like in wired networks, discovering completely disjoint paths in a WMN remains an intractable problem. It indeed becomes more challenging given the interferences across wireless channels in a WMN, not to mention that applications may demand heterogeneous QoS optimizations across different paths. The availability of multiple channels in advanced WMNs however sheds new lights into this problem. In this paper, we show that, as long as the best channels with different QoS metrics are not overlapped between neighboring node pairs, complete disjoint paths with heterogeneous QoS targets are available in a multi-channel WMN. We present efficient solutions to discover such paths, particularly for bandwidth- and delay-optimization. We also develop novel algorithms for accurately estimating path bandwidth and delay in the multi-channel environment. These lead to the design of a practical protocol that extends the classical Ad hoc On-demand Multi-path Distance Vector (AOMDV). Through extensive simulations, we show that our protocol yields significant improvement over state-of-the-art multi-path protocols in terms of both end-to-end throughput and delay.     

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.     

Selfishness in mesh networks: wired multihop MANETs

A wireless mesh network is a wired extension of a multihop ad hoc network that defines a new paradigm for broadband wireless Internet access. A packet originating from a mesh client is relayed collaboratively in a multihop fashion by the intermediate mesh routers toward an Internet gateway. All existing mesh routing protocols assume that each MR honestly participates in packet forwarding. This is valid only in a network managed by a single trusted authority. However, a community-based WMN can be formed by a group of independent MRs operated by different service providers. It is a real challenge to establish a priori trust in a multi-operator WMN. In such a situation, a selfish MR might be motivated to monopolize the wireless channel for itself by intentionally dropping others? packets. This results in severe performance degradation. Thus, enforcing collaboration is a determinant aspect in designing a secure and reliable WMN. In this article we analyze selfishness of MRs in a multi-operator WMN and explore its overall negative impact on network performance. We finally present a summary of various existing schemes with respect to detecting selfishness, analyze their usefulness in WMNs, and highlight their relative advantages and deficiencies.     

Cross Layer Secure and Resource-Aware On-Demand Routing Protocol for Hybrid Wireless Mesh Networks

Secure routing is one of the challenges offered by hybrid wireless mesh networks (WMNs). Researcher are implementing different approaches for mesh routing, but still need more efforts in terms of security, efficiency, deployment and capability with different scenarios and applications. Cross layer secure and resource-aware on demand routing (CSROR) protocol for hybrid WMN is designed to ensure routing security and fulfil different applications specific requirements for multimedia delivery and real-time transmissions. CSROR selects an optimum route on the basis of route security taking in consideration the different cross layer parameters. CSROR is not only resource aware approach but also resilient to different packet dropping attacks. It is evaluated in diverse range of hostile hybrid WMN scenarios.     

Oblivious routing in wireless mesh networks

As new network applications have arisen rapidly in recent years, it is becoming more difficult to predict the exact traffic pattern of a network. In consequence, a routing scheme based on a single traffic demand matrix often leads to a poor performance. Oblivious routing (Racke in Proceedings of the 43rd annual IEEE symposium on foundations of computer science 43–52, 2002) is a technique for tackling the traffic demand uncertainty problem. A routing scheme derived from this principle intends to achieve a predicable performance for a set of traffic matrixes. Oblivious routing can certainly be an effective tool to handle traffic demand uncertainty in a wireless mesh network (WMN). However, a WMN has an additional tool that a wireline network does not have: dynamic bandwidth allocation. A router in a WMN can dynamically assign bandwidth to its attached links. This capability has never been exploited previously in works on oblivious routing for a spatial time division multiple access (STDMA) based WMN. Another useful insight is that although it is impossible to know the exact traffic matrix, it is relatively easy to estimate the amount of the traffic routed through a link when the routing scheme is given. Based on these two insights, we propose a new oblivious routing framework for STDMA WMNs. Both analytical models and simulation results are presented in this paper to prove that the performance—in terms of throughput, queue lengths, and fairness—of the proposed scheme can achieve significant gains over conventional oblivious routing schemes for STDMA based WMNs.     

Improved network resilience of wireless mesh networks using MPLS and Fast Re-Routing techniques

The performance of a wireless mesh network (WMN) can be significantly affected by node failures and medium-term time-varying phenomena in the wireless channel, which may lead to significant interruptions in packet delivery service. Because of their nature, WMNs are often deployed with an inherent degree of redundancy. In principle, this flexibility might be exploited to cope with the link failure problem by temporarily re-routing ongoing traffic on alternate paths. However, the existing routing protocols cannot be used for this purpose, since they either rely on link-state updates, which happen on a longer time scale than the phenomena under consideration, or the decisions are taken by the source node, which does not know the status on intermediate links. In this paper we present a Fast Re-Routing enabled architecture that is optimized for WMNs and allows nodes to react to local node or link failures by activating a pre-configured alternate path to reach a two-hop neighbor. The proposed scheme is enabled by label switching/stacking. Alternate paths are created automatically during the path setup phase via a lightweight protocol derived from LDP. The solution is proved to be effective through a testbed implementation.     

无线Mesh网中一种基于综合准则的DSR扩展路由方法

无线Mesh网(Wireless Mesh Network:WMN)是一种新型的分布式宽带无线网络结构,相对于典型的移动Ad hoc网络,该网络由于具有节点移动性小、不受电池动力限制等特点,从而导致传统的移动Ad hoc路由协议不再适用.为了满足WMN多媒体业务传输的性能要求,WMN路由必须满足负载均衡、路由容错与网络容量等目标.本文首先介绍了当前几种已有的WMN路由协议,在此基础上,提出了一种适用于WMN的基于综合准则的动态源路由(Dynamic Source Routing:DSR)扩展路由方法,该方法综合考虑了投递率、剩余带宽以及节点负载等因素.分析与仿真结果表明,该算法极大地提高了网络吞吐量,并且达到了负载均衡的设计目标.     

A Hybrid Centralized Routing Protocol for 802.11s WMNs

Wireless mesh networks (WMNs) are being widely accepted as a critical wireless access solution for various applications. Due to minimal mobility in mesh nodes, a backbone topology can be effectively maintained in WMN using a proactive routing protocol. In IEEE 802.11s standard, a tree-based routing (TBR) protocol is adopted as a viable proactive routing protocol for a WMN with user traffic flowing to/from a wired network through a root (i.e., a mesh portal). However, the performance of the TBR protocol degrades rapidly as the user traffic becomes dominated by intra-mesh traffic. The reason is that the routing path through the root even for intra-mesh traffic unnecessarily overloads the root. Furthermore, the TBR performance becomes more severe when the network size of WMN is large, which could lead to the huge amount of intra-mesh traffic towards the root. To overcome these problems, we propose a new routing mechanism, root driven routing (RDR) protocol, for the root to quickly determine the best-metric route for any source-destination pair of intra-mesh traffic. For inter-mesh traffic, the original TBR protocol is employed. Thus, the hybrid centralized routing protocol that combines TBR and RDR and is adaptive to all traffic scenarios. Our simulation results reveal that the proposed RDR protocol outperforms the TBR protocol with much lower average end-to-end delay and much higher packet delivery ratio for intra-mesh traffic. The simulation results also provide some insight into the right tradeoff between the TBR protocol and the RDR protocol to achieve the best performance of the hybrid centralized routing protocol for WMNs.     

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.     

网络编码在无线Mesh网络中的研究与实现

Mesh网络沿用了Ad Hoc网络中的路由协议,但Mesh网络节点移动性高,路径的生存周期短,根据无线Mesh网络自身的动态特点进行路由协议的优化成为了研究的热点。COPE编码方案是针对Mesh网络中的单播特性提出的一种新的机会网络编码机制,能够提高网络的吞吐量。通过NS2仿真平台对AODV路由协议添加COPE网络编码方案,仿真结果表明在不同网络条件下,AODV和COPE的结合增加了无线节点的编码机会,使网络的吞吐量得到了有效的提高。     

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.     

Intelligent wireless mesh path selection algorithm using fuzzy decision making

Wireless mesh networks (WMNs) are expected to be widely deployed due to their ability to provide ubiquity, convenience, cost-efficiency, and simplicity for both service providers and end-users. Recently, the IEEE 802.11s standard introduces the hybrid wireless mesh protocol (HWMP) which is inspired by a combination of on-demand and tree-based pro-active routing algorithms. In this paper, we argue that the proposed unimetric path selection algorithm in the standard is not reliable. We introduce and examine a novel multimetric wireless mesh path selection algorithm using fuzzy decision making under realistic wireless channel conditions. The proposed path selection algorithm is designed to improve the performance of both re-active and pro-active routing protocols of HWMP for not only single-channel but also multi-channel WMNs. The reported results show the superior performance of the proposed path selection algorithm in terms of delay and packet delivery ratio without increasing overhead significantly. Although some fuzzy-based routing algorithms have been defined in literature recently, to the best of our knowledge, this paper is the first one to introduce and examine the use of fuzzy logic in the path selection of single- and multi-channel wireless local area network-based WMNs under realistic wireless channel conditions.     

基于MAODV无线Mesh网多播路由协议的优化

针对无线Mesh网(WMNs)现有的路由协议不能很好地解决多播视频业务对时延的要求,以Ad hoc网络中多播路由协议MAODV为基础,结合无线网络拓扑的动态变化,在WMN下提出一种基于路径优化的ROMAODV(Routing Optimization-MAODV)路由算法.此算法以很小的优化开销获得延时的大幅度减小,仿...     

A fast and reliable routing technique for wireless mesh networks

In wireless mesh networks (WMNs), real time communications (e.g., Voice over IP (VoIP) and interactive video communications) may often be interrupted as packets are frequently lost or delayed excessively. This usually happens due to the unreliability of wireless links or buffer overflows along the routing paths. The mesh connectivity within the WMN enables the capability to enhance reliability and reduce delay for such applications by using multiple paths for routing their packets. The vital components in multi‐path routing for achieving this are the pre‐determined formation of paths and the technique that the paths are deployed for packet traversal. Therefore, we propose a novel multi‐path routing protocol by introducing a new multi‐path organization and a traffic assignment technique. The designed technique dubbed as FLASH (Fast and reLiAble meSH routing protocol) discovers one primary path between a pair of source and destination based on a new proposed metric, and thereafter selects mini‐paths, which connect pairs of intermediate nodes along the primary path. The primary path and mini‐paths are concurrently deployed, as multiple copies of packets are routed through. This technique compensates for possible outage at intermediate wireless nodes or their corresponding wireless links along the primary path. Routing along mini‐paths is performed in such a way that redundant copies do not cause an excessive congestion on the network. The effectiveness of the proposed scheme is evaluated analytically and through extensive simulations under various load conditions. The results demonstrate the superiority of the proposed multi‐path organization in terms of reliability and satisfactory achievements of the protocol in enhancing delay and throughput compared to the existing routing protocols, especially for long distances and in congested conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Unified routing protocol based on passive bandwidth measurement in heterogeneous WMNs

The past few years have witnessed a surge of wireless mesh networks (WMNs)‐based applications and heterogeneous WMNs are taking advantage of multiple radio interfaces to improve network performance. Although many routing protocols have been proposed for heterogeneous WMNs, most of them mainly relied on hierarchical or cluster techniques, which result in high routing overhead and performance degradation due to low utilization of wireless links. This is because only gateway nodes are aware of all the network resources. In contrast, a unified routing protocol (e.g., optimal link state routing (OLSR)), which treats the nodes and links equally, can avoid the performance bottleneck incurred by gateway nodes. However, OLSR has to pay the price for unification, that is, OLSR introduces a great amount of routing overhead for broadcasting routing message on every interface. In this paper, we propose unified routing protocol (URP), which is based on passive bandwidth measurement for heterogeneous WMNs. Firstly, we use the available bandwidth as a metric of the unification and propose a low‐cost passive available bandwidth estimation method to calculate expected transmission time that can capture the dynamics of wireless link more accurately. Secondly, based on the estimated available bandwidth, we propose a multipoint relays selection algorithm to achieve higher transmission ability and to help accelerate the routing message diffusion. Finally, instead of broadcasting routing message on all channels, nodes running URP transmit routing message on a set of selected high bandwidth channels. Results from extensive simulations show that URP helps improve the network throughput and to reduce the routing overhead compared with OLSR and hierarchical routing. Copyright © 2016 John Wiley & Sons, Ltd.