Impacts of user-selfishness on cooperative content caching in social wireless networks

Cooperative caching can be an effective mechanism for reducing electronic content provisioning cost in Social Wireless Networks (SWNETs). These networks are formed by a collection of mobile data enabled devices physically gathering in settings such as university campus, malls, airport and other public places. In this paper, we first propose an optimal collaborative object caching policy in order to minimize the object provisioning cost in SWNETs with homogenous user requests and a peer-rebate model for promoting collaboration. Then using an analytical model we study the impacts of user selfishness on the provisioning cost and the earned rebate when certain nodes in an SWNET selfishly deviate from the optimal policy. User selfishness is motivated in order to either increase individually earned rebate or to reduce content provisioning cost. The analytical model is validated by experimental results from simulated SWNETs using the network simulator ns2.     

Responsive on-line gateway load-balancing for wireless mesh networks

We propose an adaptive online load-balancing protocol for multi-gateway Wireless Mesh Networks (WMNs) which, based on the current network conditions, balances load between gateways. Traffic is balanced at the TCP flow level and, as a result, the aggregate throughput, average flow throughput and fairness of flows improves. The proposed scheme (referred to as Gateway Load-Balancing, GWLB) is highly responsive, thanks to fast gateway selection and the fact that current traffic conditions are maintained up-to-date at all times without any overhead. It also effectively takes into account intra-flow and inter-flow interference when switching flows between gateway domains. We have found the performance achievable by routes used after gateway selection to be very close to the performance of optimal routes found by solving a MINLP formulation under the protocol model of interference. Through simulations, we analyze performance and compare with a number of proposed strategies, showing that GWLB outperforms them. In particular, we have observed average flow throughput gains of 128% over the nearest gateway strategy.     

High-throughput multicast routing metrics in wireless mesh networks

The stationary nature of nodes in a mesh network has shifted the main design goal of routing protocols from maintaining connectivity between source and destination nodes to finding high-throughput paths between them. Numerous link-quality-based routing metrics have been proposed for choosing high-throughput routing paths in recent years. In this paper, we study routing metrics for high-throughput tree or mesh construction in multicast protocols. We show that there is a fundamental difference between unicast and multicast routing in how data packets are transmitted at the link layer, and accordingly how the routing metrics for unicast routing should be adapted for high-throughput multicast routing. We propose a low-overhead adaptive online algorithm to incorporate link-quality metrics to a representative multicast routing protocol. We then study the performance improvement achieved by using different link-quality-based routing metrics via extensive simulation and experiments on a mesh-network testbed, using ODMRP as a representative multicast protocol.Our extensive simulation studies show that: (1) ODMRP equipped with any of the link-quality-based routing metrics can achieve higher throughput than the original ODMRP. In particular, under a tree topology, on average, ODMRP enhanced with link-quality routing metrics achieve up to 34% higher throughput than the original ODMRP under low multicast sending rate; (2) the improvement reduces to 21% under high multicast sending rate due to higher interference experienced by the data packets from the probe packets; (3) heavily penalizing lossy links is an effective way in the link-quality metric design to avoid low-throughput paths; and (4) the path redundancy from a mesh data dissemination topology in mesh-based multicast protocols provides another degree of robustness to link characteristics and reduces the additional throughput gain achieved by using link-quality-based routing metrics. Finally, our experiments on an eight-node testbed show that on average, ODMRP using SPP and PP achieves 14% and 17% higher throughput over ODMRP, respectively, validating the simulation results.     

Secure group communication in wireless mesh networks

Wireless mesh networks (WMNs) have emerged as a promising technology that offers low-cost community wireless services. The community-oriented nature of WMNs facilitates group applications, such as webcast, distance learning, online gaming, video conferencing, and multimedia broadcasting. Security is critical for the deployment of these services. Previous work focused primarily on MAC and routing protocol security, while application-level security has received relatively little attention. In this paper we focus on providing data confidentiality for group communication in WMNs. Compared to other network environments, WMNs present new challenges and opportunities in designing such protocols. We propose a new protocol framework, Secure Group Overlay Multicast (SeGrOM), that employs decentralized group membership, promotes localized communication, and leverages the wireless broadcast nature to achieve efficient and secure group communication. We analyze the performance and discuss the security properties of our protocols. We demonstrate through simulations that our protocols provide good performance and incur a significantly smaller overhead than a baseline centralized protocol optimized for WMNs.     

MrFair: Misbehavior-resistant fair scheduling in wireless mesh networks

It is a critical issue to ensure that nodes and/or flows have fair access to the network bandwidth in wireless mesh networks (WMNs). However, current WMNs based on IEEE 802.11 exhibit severe unfairness. Several scheduling schemes have been proposed to ensure fairness in WMNs. Unfortunately, all of them implicitly trust nodes in the network, and thus are vulnerable to the misbehavior of nodes participating in scheduling. In this paper, we address the threats to fair scheduling in WMNs resulting from node misbehavior and present a generic verification framework to detect such misbehavior. Moreover, we develop two verification schemes based on this framework for distributed and centralized authentication environments, respectively. We validate our approach by extending an existing fair scheduling scheme and evaluating it through simulation. The results show that our approach improves misbehavior detection with light performance overhead.     

DCNC: throughput maximization via delay controlled network coding for wireless mesh networks

Network coding (NC) can greatly improve the performance of wireless mesh networks (WMNs) in terms of throughput and reliability, and so on. However, NC generally performs a batch‐based transmission scheme, the main drawback of this scheme is the inevitable increase in average packet delay, that is, a large batch size may achieve higher throughput but also induce larger average packet delay. In this work, we put our focus on the tradeoff between the average throughput and packet delay; in particular, our ultimate goal is to maximize the throughput for real‐time traffic under the premise of diversified and time‐varying delay requirements. To tackle this problem, we propose DCNC, a delay controlled network coding protocol, which can improve the throughput for real‐time traffic by dynamically controlling the delay in WMNs. To define an appropriate control foundation, we first build up a delay prediction model to capture the relationship between the average packet delay and the encoding batch size. Then, we design a novel freedom‐based feedback scheme to efficiently reflect the reception of receivers in a reliable way. Based on the predicted delay and current reception status, DCNC utilizes the continuous encoding batch size adjustment to control delay and further improve the throughput. Extensive simulations show that, when faced with the diversified and time‐varying delay requirements, DCNC can constantly fulfill the delay requirements, for example, achieving over 95% efficient packet delivery ratio (EPDR) in all instances under good channel quality, and also obtains higher throughput than the state‐of‐art protocol. Copyright © 2014 John Wiley & Sons, Ltd.     

无线mesh网络安全研究

无线mesh网络（wireless mesh networks,WMN）是下一代网络中的新型技术,和传统网络不同,它不依赖任何固定的设施,主机可以相互依赖保持网络连接,WISP可以利用它提供快速、简单、低廉的网络部署,然而存在一个主要的问题是容易遭受攻击。介绍了无线mesh网络的体系机构以及特点,分析并研究其存在的安全性威胁以及现有的关键安全解决机制。     

Dynamic agent-based hierarchical multicast for wireless mesh networks

We propose and analyze a multicast algorithm named Dynamic Agent-based Hierarchical Multicast (DAHM) for wireless mesh networks that supports user mobility and dynamic group membership. The objective of DAHM is to minimize the overall network cost incurred. DAHM dynamically selects multicast routers serving as multicast agents for integrated mobility and multicast service management, effectively combining backbone multicast routing and local unicast routing into an integrated algorithm. As the name suggests, DAHM employs a two-level hierarchical multicast structure. At the upper level is a backbone multicast tree consisting of mesh routers with multicast agents being the leaves. At the lower level, each multicast agent services those multicast group members within its service region. A multicast group member changes its multicast agent when it moves out of the service region of the current multicast agent. The optimal service region size of a multicast agent is a critical system parameter. We propose a model-based approach to dynamically determine the optimal service region size that achieves network cost minimization. Through a comparative performance study, we show that DAHM significantly outperforms two existing baseline multicast algorithms based on multicast tree structures with dynamic updates upon member movement and group membership changes.     

Protocols and architectures for channel assignment in wireless mesh networks

The use of multiple channels can substantially improve the performance of wireless mesh networks. Considering that the IEEE PHY specification permits the simultaneous operation of three non-overlapping channels in the 2.4 GHz band and 12 non-overlapping channels in the 5 GHz band, a major challenge in wireless mesh networks is how to efficiently assign these available channels in order to optimize the network performance. We survey and classify the current techniques proposed to solve this problem in both single-radio and multi-radio wireless mesh networks. This paper also discusses the issues in the design of multi-channel protocols and architectures.     

VoIP traffic in wireless mesh networks: a MOS‐based routing scheme

Support of Voice over Internet Protocol (VoIP) services in wireless mesh networks requires implementation of efficient policies to support low‐delay data delivery. Multipath routing is typically supported in wireless mesh networks at the network level to provide high fault tolerance and load balancing because links in the proximity of the wireless mesh gateways can be very stressed and overloaded, thus causing scarce performance. As a consequence of using multipath solutions, lower delay and higher throughput can be supported also when a given path is broken because of mobility or bad channel conditions, and alternative routes are available. This can be a relevant improvement especially when assuming that real‐time traffic, such as VoIP, travels into the network. In this paper, we address the problem of Quality of Service (QoS) support in wireless mesh networks and propose a multipath routing strategy that exploits the Mean Opinion Score (MOS) metric to select the most suitable paths for supporting VoIP applications and performing adaptive load balancing among the available paths to equalize network traffic. Performance results assess the effectiveness of the proposed approach when compared with other existing methodologies. Copyright © 2015 John Wiley & Sons, Ltd.     

Simulation and analysis of node throughput using smart antenna in wireless mesh networks

Smart antenna technology is introduced to wireless mesh networks. Smart antennas based wider-range access medium access control (MAC) protocol (SWAMP) is used as MAC protocol for IEEE 802.11 mesh networks in this study. The calculation method of node throughput in chain and arbitrary topology is proposed under nodes fairness guarantee. Network scale and interference among nodes are key factors that influence node throughput. Node distribution pattern near the gateway also affects the node throughput. Experiment based on network simulator-2 (NS-2) simulation platform compares node throughput between smart antenna scenario and omni-antenna scenario. As smart antenna technology reduces the bottle collision domain, node throughput increases observably.     

基于传输路径质量的无线mesh网络可靠多播

提出了一种可靠多播网(RM)模型,探讨了无线链路和节点可靠性对多播路径选择的影响。首先,建立了无线链路的相关性和多播路径的可靠性模型,并提出了多播传输的可靠性判据;同时,结合首树算法和多路径树算法提出了构造可靠多播网的算法。可靠多播网具有并行的多播路径,通过在多播源节点和目的节点之间选择多播链路和节点构成了可靠的多播路径,提供了多播路径的"负荷分担"和"热备份"功能,从而支持了多播业务可靠性。     

Analytical model for approximating node throughputs in wireless mesh networks

This paper describes an analytical model and an associated algorithm for assessing the throughputs of each host in wireless mesh networks (WMNs). It provides a framework for studying WMNs, particularly when the performance and parameters in multiple protocol layers have to be jointly evaluated and optimized. From the point of the implementation, a simple recursive formula with N ? 1 iterations is used to obtain the throughput performance of N node WMNs. The produced expressions offer insights into understanding the performance of the individual nodes without referring to a specific medium access control layer or physical layer technology. The model serves as a general tool for capturing the characteristics of the WMNs. Using the model, the complexity of cross‐layer studies is reduced, thus allowing researchers to focus on the modelling of other associated layers. The paper explains the rationale behind the model and provides examples of scenarios for which it is suitable. It is validated using discrete event simulations in the OPNET network simulator. Copyright © 2012 John Wiley & Sons, Ltd.     

High throughput route selection in multi-rate wireless mesh networks

Most existing Ad-hoc routing protocols use the shortest path algorithm with a hop count metric to select paths. It is appropriate in single-rate wireless networks, but has a tendency to select paths containing long-distance links that have low data rates and reduced reliability in multi-rate networks. This article introduces a high throughput routing algorithm utilizing the multi-rate capability and some mesh characteristics in wireless fidelity （WiFi） mesh networks. It uses the medium access control （MAC） transmission time as the routing metric, which is estimated by the information passed up from the physical layer. When the proposed algorithm is adopted, the Ad-hoc on-demand distance vector （AODV） routing can be improved as high throughput AODV （HT-AODV）. Simulation results show that HT-AODV is capable of establishing a route that has high data-rate, short end-to-end delay and great network throughput.     

认知无线Mesh网络中基于马氏决策模型的MAC协议

为解决认知无线Mesh网络中专用控制信道较难获得的问题,提出一种基于POMDP的机会式频谱接入MAC协议,在不需要中心控制器和专用控制信道的协调下,实现动态频谱感知和接入。仿真结果表明,基于POMDP的接入策略能够有效提高网络频谱利用率和吞吐量,性能最优,而基于贪心算法的接入策略,在降低计算复杂度的同时,获得了较好的性能,实用性较强。     

Multi‐channel power‐controlled directional MAC for wireless mesh networks

Wireless Mesh Networks (WMNs) have emerged recently as a technology for providing high‐speed last mile connectivity in next‐generation wireless networks. Several MAC protocols that exploit multiple channels and directional antennas have been proposed in the literature to increase the performance of WMNs. However, while these techniques can improve the wireless medium utilization by reducing radio interference and the impact of the exposed nodes problem, they can also exacerbate the hidden nodes problem. Therefore, efficient MAC protocols need to be carefully designed to fully exploit the features offered by multiple channels and directional antennas. In this paper we propose a novel Multi‐Channel Power‐Controlled Directional MAC protocol (MPCD‐MAC) for nodes equipped with multiple network interfaces and directional antennas. MPCD‐MAC uses the standard RTS‐CTS‐DATA‐ACK exchange procedure. The novel difference is the transmission of the RTS and CTS packets in all directions on a separate control channel, while the DATA and ACK packets are transmitted only directionally on an available data channel at the minimum required power, taking into account the interference generated on already active connections. This solution spreads the information on wireless medium reservation (RTS/CTS) to the largest set of neighbors, while data transfers take place directionally on separate channels to increase spatial reuse. Furthermore, power control is used to limit the interference produced over active nodes. We measure the performance of MPCD‐MAC by simulation of several realistic network scenarios, and we compare it with other approaches proposed in the literature. The results show that our scheme increases considerably both the total traffic accepted by the network and the fairness among competing connections. Copyright © 2010 John Wiley & Sons, Ltd.     

Replication schemes for peer‐to‐peer content in wireless mesh networks with infrastructure support

Many mobile devices (e.g., smart phones, PDAs, portable computers) and wireless routers (e.g., WiFi access points) nowadays are equipped with ad hoc transmission mode. In a dense environment such as a college/office campus, this creates the possibility of forming a wireless mesh network (WMN) in which mobile users communicate with each other through multiple wireless hops. This allows mobile users to exchange (share) files over the free access WMN rather than a carrier frequency such as 3G and WiMax. We consider a peer‐to‐peer (P2P) content sharing setting in a WMN, wherein the mesh network operator over‐provision a number of mesh routers in the network with additional storage capacity and P2P‐aware devices that are programmed to cache and store P2P content. Those mesh routers act as caches and participants in P2P content sharing. The aim of this setting is to both reduce the cost of communications between peers within the WMN (i.e., reduce bandwidth and energy that P2P traffic consumes in the network), and enhance the performance of P2P content sharing (i.e., reduce the average P2P content download delay). Our main contribution in this paper is an optimum P2P content replication strategy at the participating mesh routers. In particular, we determine the optimum number of replicas for every P2P file such that the average access cost of all files in the network is minimized. We propose a centralized algorithm that enables the participating mesh routers to implement the optimal strategy. We further propose a distributed (low cost) algorithm for P2P content replication at the participating mesh routers, and show that the distributed algorithm mimics the optimal strategy very well. The analytical and simulation results show that our replication strategy significantly reduces the average overall cost of accessing P2P files in the WMN as compared with other commonly used replication strategies. Copyright © 2013 John Wiley & Sons, Ltd.     

An efficient mesh router nodes placement in wireless mesh networks based on moth-flame optimization algorithm

One of the most challenging tasks is deploying a wireless mesh network backbone to achieve optimum client coverage. Previous research proposed a bi-objective function and used a hierarchical or aggregate weighted sum method to find the best mesh router placement. In this work, to avoid the fragmented network scenarios generated by previous formulations, we suggest and evaluate a new objective function to maximize client coverage while simultaneously optimizing and maximizing network connectivity for optimal efficiency without requiring knowledge of the aggregation coefficient. In addition, we compare the performance of several recent meta-heuristic algorithms: Moth-Flame Optimization (MFO), Marine Predators Algorithm (MPA), Multi-Verse Optimizer (MVO), Improved Grey Wolf Optimizer (IGWO), Salp Swarm Algorithm (SSA), Grey Wolf Optimizer (GWO), Whale Optimization Algorithm (WOA), Harris Hawks Optimization (HHO), Particle Swarm Optimization (PSO), Sine Cosine Algorithm (SCA), and Slime Mould Algorithm (SMA). We empirically examined the performance of the proposed function using different settings. The results show that our proposed function provides higher client coverage and optimal network connectivity with less computation power. Also, compared to other optimization algorithms, the MFO algorithm gives higher coverage to clients while maintaining a fully connected network.     

无线mesh网中一种基于博弈论的公平性路由协议

提出一种基于博弈论的以树为拓扑结构的公平性路由协议.新的协议综合了先验式路由和按需路由,并且将路由计算和信道资源分配控制分布到树中的每个枝节点上,降低了根节点的负担,使其更适合于无线 mesh网的通信需求.仿真结果表明,新的路由协议改进了AODV、HWMP路由协议的端到端平均延迟和网络吞吐量,并且网络中各个无线节点占有的信道资源基本相近,满足公平性原则.     

Multi‐cost routing for energy and capacity constrained wireless mesh networks

We propose a class of novel energy‐efficient multi‐cost routing algorithms for wireless mesh networks, and evaluate their performance. In multi‐cost routing, a vector of cost parameters is assigned to each network link, from which the cost vectors of candidate paths are calculated using appropriate operators. In the end these parameters are combined in various optimization functions, corresponding to different routing algorithms, for selecting the optimal path. We evaluate the performance of the proposed energy‐aware multi‐cost routing algorithms under two models. In the network evacuation model, the network starts with a number of packets that have to be transmitted and an amount of energy per node, and the objective is to serve the packets in the smallest number of steps, or serve as many packets as possible before the energy is depleted. In the dynamic one‐to‐one communication model, new data packets are generated continuously and nodes are capable of recharging their energy periodically, over an infinite time horizon, and we are interested in the maximum achievable steady‐state throughput, the packet delay, and the energy consumption. Our results show that energy‐aware multi‐cost routing increases the lifetime of the network and achieves better overall network performance than other approaches. Copyright © 2011 John Wiley & Sons, Ltd.