A hierarchical architecture for detecting selfish behaviour in community wireless mesh networks

Wireless mesh networks (WMNs) consist of dedicated nodes called mesh routers which relay the traffic generated by mesh clients over multi-hop paths. In a community WMN, all mesh routers may not be managed by an Internet Service Provider (ISP). Limited capacity of wireless channels and lack of a single trusted authority in such networks can motivate mesh routers to behave selfishly by dropping relay traffic in order to provide a higher throughput to their own users. Existing solutions for stimulating cooperation in multi-hop networks use promiscuous monitoring or exchange probe packets to detect selfish nodes and apply virtual currency mechanism to compensate the cooperating nodes. These schemes fail to operate well when applied to WMNs which have a multi-radio environment with a relatively static topology. In this paper we, propose architecture for a community WMN which can detect selfish behaviour in the network and enforce cooperation among mesh routers. The architecture adopts a decentralized detection scheme by dividing the mesh routers into manageable clusters. Monitoring agents hosted on managed mesh routers monitor the behaviour of mesh routers in their cluster by collecting periodic reports and sending them to the sink agents hosted at the mesh gateways. To make the detection more accurate we consider the quality of wireless links. We present experimental results that evaluate the performance of our scheme.     

Matrix-based pairwise key establishment for wireless mesh networks

Wireless communication in wireless mesh networks (WMNs), like other types of wireless networks, is vulnerable to many malicious activities such as eavesdropping. As one of the fundamental security technologies, pairwise key establishment has been widely studied to secure wireless communication. In this paper, we propose a new matrix-based pairwise key establishment scheme for mesh clients in WMNs. A fact in WMNs is that mesh routers are more powerful than mesh clients, in both communication and storage. Motivated by this fact, expensive operations can be delegated to mesh routers to alleviate the overhead of mesh clients when establishing pairwise keys between them. Compared with other matrix-based schemes, our scheme has significant advantages: any two mesh clients can directly establish pairwise keys while communication and storage costs of mesh clients are significantly reduced.     

Local search methods for efficient router nodes placement in wireless mesh networks

Wireless Mesh Networks (WMNs) are an important networking infrastructure for providing cost-efficient broadband wireless connectivity to a group of users. WMNs are increasingly being used in urban, metropolitan and municipal area networks for deployment of medical, transport, surveillance systems, etc. The performance and operability of WMNs largely depends on placement of mesh routers nodes in the geographical area to achieve network connectivity and stability. The objective is to find an optimal and robust topology of the mesh router network to support intelligent telecommunication services to clients such as adaptive and flexible wireless Internet access, mobile data, voice, video in addition to supporting other preferred client services. In this work, we propose and evaluate local search methods for intelligent placement of mesh routers in WMNs with a two fold objective: maximizing the size of the giant component in the network and user coverage. Given a grid area where to distribute a given number of mesh router nodes, which can have different radio coverage, and a number of fixed clients a priori distributed in the given area, local search methods explore different local movements and incrementally improve the quality of the router nodes placement in terms of network connectivity and user coverage. We have experimentally evaluated the proposed local search methods through a benchmark of generated instances of varying sizes. Moreover, different distributions of mesh clients (Uniform, Normal, Exponential and Weibull) are used. The experimental evaluation showed the good performance of local search methods for optimizing network connectivity and user coverage in WMNs.     

Joint scheduling and routing algorithm with load balancing in wireless mesh network

Wireless mesh network (WMN) is a promising solution for last mile broadband internet access. Mesh nodes or mesh routers are connected via wireless links to form a multi-hop backbone infrastructure and improving throughput is the primary goal. While previous works mainly focused on either link level protocol design or complex mathematical model, in this paper, we investigate the performance gains from jointly optimizing scheduling and routing in a multi-radio, multi-channel and multi-hop wireless mesh network. Then, two optimization objectives are addressed by considering wireless media contention and spatial multiplexing. The first objective is to maximize throughput by exploiting spatial reuse while the second one is to ensure fairness among different links. We design a cross-layer algorithm by considering both MAC layer and network layer. Simulation results show that our joint optimization algorithm can significantly increase throughput as well as fairness.     

A genetic algorithm-based system for wireless mesh networks: analysis of system data considering different routing protocols and architectures

Wireless mesh networks (WMNs) are attracting a lot of attention from wireless network researchers. Node placement problems have been investigated for a long time in the optimization field due to numerous applications in location science. In our previous work, we evaluated WMN-GA system which is based on genetic algorithms (GAs) to find an optimal location assignment for mesh routers. In this paper, we evaluate the performance of four different distributions of mesh clients for two WMN architectures considering throughput, delay and energy metrics. For simulations, we used ns-3, optimized link state routing (OLSR) and hybrid wireless mesh protocols (HWMP). We compare the performance for Normal, Uniform, Exponential and Weibull distributions of mesh clients by sending multiple constant bit rate flows in the network. The simulation results show that for HWM protocol the throughput of Uniform distribution is higher than other distributions. However, for OLSR protocol, the throughput of Exponential distribution is better than other distributions. For both protocols, the delay and remaining energy are better for Weibull distribution.     

Design of certification authority using secret redistribution and multicast routing in wireless mesh networks

Wireless mesh networks (WMNs) should provide authentication and key management without a trusted third party because of their self-organizing and self-configuring characteristics. Several solutions to this problem have been proposed in mobile ad hoc networks (MANETs). But they are not optimal for WMNs because WMNs are with stationary mesh routers (MRs) that do not suffer from the limited power problem. In this paper, we design an architecture of mesh certification authority (MeCA) for WMNs. In MeCA, the secret key and functions of certification authority (CA) are distributed over several MRs. For secret sharing and redistribution, we develop the fast verifiable share redistribution (FVSR) scheme, which works for threshold cryptography and minimizes the possibility of secret disclosure when some shareholders are compromised by adversaries. MeCA adopts the multicasting based on Ruiz tree, which is optimal in reducing the operation overhead. It can update, revoke, and verify certificates of WMN nodes in a secure and efficient manner. Simulation results show that MeCA does not disclose its secret key even under severe attacks while incurring low overhead compared to other existing schemes in MANETs.     

Capacity bounds of deployment concepts for Wireless Mesh Networks

Local area wireless networks are like cellular systems: Stations associate to one out of several access points (APs), which connect to a wired backbone. Due to signal attenuation and transmission power limitations, radio connectivity is available only sufficiently close to an AP. In scenarios with a dense deployment of APs the wired backbone causes unprofitably high costs.A Wireless Mesh Network (WMN) serves to extend the coverage of APs by means of Mesh Points (MPs) that forward data between a station and an AP. This concept reduces deployment costs, but reduces also network capacity, owing to multiple transmissions of the same data packet on its multi-hop route.This paper analyzes how the capacity of cost-limited WMNs can be optimized. A layered model of a WMN specifying the typical characteristics of the network is used to calculate the upper capacity bound. Based on the heuristics developed, networks of more than 150 nodes (APs, MPs and stations) can be handled.We apply the method to investigate the combination of three measures for improving the WMN capacity: (i) concurrent scheduling of transmissions, (ii) application of directional antennas and (iii) variable number of MPs per AP. The capacity bounds for different combinations of the measures mentioned is computed and compared. Combined with a simple cost model, these results are useful to provide insight into the economical feasibility of WMNs for wireless Internet access.     

Multicast routing protocols in wireless mesh networks: a survey

Wireless mesh networks (WMNs) introduce a new type of network that has been applied over the last few years. One of the most important developing issues in WMNs is multicast routing, which is a key technology that provides dissemination of data to a group of members in an efficient way. In this article, after an introduction about the structure of a WMN, multicast routing algorithms and protocols in WMNs are surveyed in a detailed and efficient manner. Moreover, effort is made to scale the study into one of the important potential capabilities of multicast routing mechanisms in WMNs, which is taking advantage of using different channels and radios association. While nodes in a single-radio mesh network operating on single-channel have restrictions for capacity, equipping mesh routers with multiple radios using multiple channels can decrease the intention of capacity problem as well as increase the aggregate bandwidth available to the network and improving the throughput. Hence, the purpose of channel assignment is to decrease the interferences while increasing the network capacity and keeping the connectivity of the network. Therefore, this article investigates the multicast protocols considering a definition of three types of WMNs, based on channel-radio association including SRSC, SRMC and MRMC. In its follow, a classification for multicast routing algorithms regarding the achieved optimal solutions will be presented. Finally, a study of MRMC and its relevant problems will be offered, considering the joint channel assignment and the multicast tree construction problem.     

基于标识的无线Mesh网络接入认证协议

为解决无线Mesh网络节点高效、安全入网认证的问题,提出了一种新的基于标识认证的无线Mesh网络接入认证协议.该协议针对无线Mesh网络的特点,将标识认证体制引入到无线Mesh节点接入认证当中,并在标识认证的基础上一次性完成了入网节点的双向身份认证、网络认证和空口密钥的建立3个步骤.简化了认证的流程,减少了认证的时延,达到了分布式认证的效果,为大规模的节点接入提供了一种新的认证方案.通过BAN逻辑形式化方法证明了协议的安全性,通过效率分析说明了协议的高效性.     

Effects of population size for location-aware node placement in WMNs: evaluation by a genetic algorithm--based approach

Wireless mesh networks (WMNs) are cost-efficient networks that have the potential to serve as an infrastructure for advanced location-based services. Location service is a desired feature for WMNs to support location-oriented applications. WMNs are also interesting infrastructures for supporting ubiquitous multimedia Internet access for mobile or fixed mesh clients. In order to efficiently support such services and offering QoS, the optimized placement of mesh router nodes is very important. Indeed, such optimized mesh placement can support location service managed in the mesh and keep the rate of location updates low. This node location-based problem has been shown to be NP-hard and thus is unlikely to be solvable in reasonable amount of time. Therefore, heuristic methods, such as genetic algorithms (GAs), are used as resolution methods. In this paper, we deal with the effect of population size for location-aware node placement in WMNs. Our WMN-GA system uses GA to determine the positions of the mesh routers and mesh clients in the grid area. We used a location-aware node placement of mesh router in cells of considered grid area to maximize network connectivity and user coverage. We evaluate the performance of the proposed and implemented WMN-GA system for low and high density of clients considering different distributions and considering giant component and number of covered users parameters. The simulation results show that for low-density networks, with the increasing of population size, GA obtains better result. However, with the increase in the population size, the GA needs more computational time. The proposed system has better performance in dense networks like hot spots for Weibull distribution when the population size is big.     

Routing protocols in wireless mesh networks: challenges and design considerations

Wireless Mesh Networks (WMNs) are an emerging technology that could revolutionize the way wireless network access is provided. The interconnection of access points using wireless links exhibits great potential in addressing the “last mile” connectivity issue. To realize this vision, it is imperative to provide efficient resource management. Resource management encompasses a number of different issues, including routing. Although a profusion of routing mechanisms has been proposed for other wireless networks, the unique characteristics of WMNs (e.g., wireless backbone) suggest that WMNs demand a specific solution. To have a clear and precise focus on future research in WMN routing, the characteristics of WMNs that have a strong impact on routing must be identified. Then a set of criteria is defined against which the existing routing protocols from ad hoc, sensor, and WMNs can be evaluated and performance metrics identified. This will serve as the basis for deriving the key design features for routing in wireless mesh networks. Thus, this paper will help to guide and refocus future works in this area.

SafeMesh: A wireless mesh network routing protocol for incident area communications

Reliable broadband communication is becoming increasingly important during disaster recovery and emergency response operations. In situations where infrastructure-based communication is not available or has been disrupted, an Incident Area Network needs to be dynamically deployed, i.e. a temporary network that provides communication services for efficient crisis management at an incident site. Wireless Mesh Networks (WMNs) are multi-hop wireless networks with self-healing and self-configuring capabilities. These features, combined with the ability to provide wireless broadband connectivity at a comparably low cost, make WMNs a promising technology for incident management communications. This paper specifically focuses on hybrid WMNs, which allow both mobile client devices as well as dedicated infrastructure nodes to form the network and provide routing and forwarding functionality. Hybrid WMNs are the most generic and most flexible type of mesh networks and are ideally suited to meet the requirements of incident area communications. However, current wireless mesh and ad-hoc routing protocols do not perform well in hybrid WMN, and are not able to establish stable and high throughput communication paths. One of the key reasons for this is their inability to exploit the typical high degree of heterogeneity in hybrid WMNs. SafeMesh, the routing protocol presented in this paper, addresses the limitations of current mesh and ad-hoc routing protocols in the context of hybrid WMNs. SafeMesh is based on the well-known AODV routing protocol, and implements a number of modifications and extensions that significantly improve its performance in hybrid WMNs. This is demonstrated via an extensive set of simulation results. We further show the practicality of the protocol through a prototype implementation and provide performance results obtained from a small-scale testbed deployment.     

PEACE: A Novel Privacy-Enhanced Yet Accountable Security Framework for Metropolitan Wireless Mesh Networks

Recently, multihop wireless mesh networks (WMNs) have attracted increasing attention and deployment as a low-cost approach to provide broadband Internet access at metropolitan scale. Security and privacy issues are of most concern in pushing the success of WMNs for their wide deployment and for supporting service-oriented applications. Despite the necessity, limited security research has been conducted toward privacy preservation in WMNs. This motivates us to develop PEACE, a novel Privacy-Enhanced yet Accountable seCurity framEwork, tailored for WMNs. On one hand, PEACE enforces strict user access control to cope with both free riders and malicious users. On the other hand, PEACE offers sophisticated user privacy protection against both adversaries and various other network entities. PEACE is presented as a suite of authentication and key agreement protocols built upon our proposed short group signature variation. Our analysis shows that PEACE is resilient to a number of security and privacy related attacks. Additional techniques were also discussed to further enhance scheme efficiency.     

Zero-Degree algorithm for Internet GateWay placement in backbone wireless mesh networks

Internet GateWays (IGWs) are responsible for connecting the backbone wireless mesh networks (BWMNs) to the Internet/wired backbone. An IGW has more capabilities than a simple wireless mesh router (WMR) but is more expensive. Strategically placing the IGWs in a BWMN is critical to the Wireless Mesh Network (WMN) architecture. In order to solve the problem of IGWs placement in BWMNs, a novel algorithm is proposed in this paper. The new algorithm is involved in placing a minimum number of IGWs so that the Quality of Service (QoS) requirements are satisfied. Different from existing algorithms, this new algorithm incrementally identifies IGWs and prioritively assigns wireless mesh routers (WMRs) based on the computed degree of WMRs to identified IGWs. Performance evaluation results show that proposed algorithm outperforms other alternative algorithms by comparing the number of gateways placed in different scenarios. Furthermore, having control of the distribution of IGWs in order to locate them closest to available Internet/wired network connection points is an added advantage of this algorithm.     

Load-balanced mesh router migration for wireless mesh networks

Load-balancing among domains in a wireless mesh network (WMN) is normally achieved by changing the Internet attachment of mesh routers (MRs) that carry the traffic from mobile stations (MSs). The greediness of load-balancing algorithms may force MRs to frequently change their Internet attachments, and thus degrade network performance due to inter-domain mobility of the associated MSs. In this paper, we discuss the negative impact on the performance of MSs’ mobility, due to inter-domain reassignment of MR. A MR migration scheme is proposed to achieve a tradeoff between load-balancing and inter-domain reassignment of MR. The proposed load-balancing scheme for WMNs includes: an initialization procedure to divide a WMN into domains, and a load adjustment procedure to rebalance the traffic load among the neighboring domains when required. We also provide a framework for handling inter-domain mobility in support of multi-hop communication using the Multi-hop cellular IP. Our simulation results show that the proposed protocol effectively controls MR’s change in connectivity as well as MS’s mobility.     

Load-balanced AP association in multi-hop wireless mesh networks

Wireless mesh networks (WMNs) provide high-bandwidth wireless access, which makes it capable for multimedia services. A user in a WMN may be covered by multiple APs, while it should be associated with only one to access the Internet. Conventional IEEE 802.11 user-AP association mechanism for WLANs employs signal strength as the sole metric. However, this may lead to network congestion and performance degradation in multi-hop networks such as WMNs, especially for multimedia services that require a large bandwidth and a low latency. Thus AP association in WMNs becomes an important research issue. In this paper we propose a novel AP association approach LBAA, taking AP’s load-balancing, WMN’s multi-hop characteristic, and user’s RSSI into consideration. We first propose a centralized algorithm and then extend it to a distributed one, with the latter one more practical and convenient for deployment. Network throughput and max–min user fairness are improved by LBAA. Performance evaluation demonstrating the benefits of our approach is given through a series of experiments in terms of collision probability, access bandwidth, end-to-end throughput, and average RSSI.     

一种高吞吐量的IEEE 802．11Mesh网AP选择算法

现有的IEEE802．11mesh网访问点（AP）选择算法仅仅基于对mesh用户周围链路质量的测量，无法使用户获得高性能的Internet访问。本文提出了一种基于期望传输吞吐量（Expected Transmission Throughput，EXT）的AP选择算法，该算法同时考虑了mesh路由器访问网关的能力以及用户与路由器的连接时间，目的是使用户选择能够获得最大吞吐量的路由器进行连接。同时，本文针对mesh网络特点和用户的移动方式给出了实际可行的算法实现过程。本文使用NS2对算法进行了仿真，结果证明与传统的基于接收信号强度指示（RSSI）的算法相比，基于EXT的AP选择算法可以使用户的访问吞吐量得到较大提高。     

电子商务中无线Mesh网络方案安全性研究

采用WMN技术的电子商务方案可以实现视频监控、无线上网、语音通信、手持无线接入等功能,这些功能对WMN方案的安全性提出了严格的要求。文章从网络认证、路由选择等角度来分析电子商务活动中WMN方案安全性面临的挑战和相应的对策。     

Optimization models and methods for planning wireless mesh networks

In this paper novel optimization models are proposed for planning Wireless Mesh Networks (WMNs), where the objective is to minimize the network installation cost while providing full coverage to wireless mesh clients. Our mixed integer linear programming models allow to select the number and positions of mesh routers and access points, while accurately taking into account traffic routing, interference, rate adaptation, and channel assignment. We provide the optimal solutions of three problem formulations for a set of realistic-size instances (with up to 60 mesh devices) and discuss the effect of different parameters on the characteristics of the planned networks. Moreover, we propose and evaluate a relaxation-based heuristic for large-sized network instances which jointly solves the topology/coverage planning and channel assignment problems. Finally, the quality of the planned networks is evaluated under different traffic conditions through detailed system level simulations.     

Securing wireless mesh networks in a unified security framework with corruption-resilience

Wireless mesh networks (WMN) are expected to be widespread due to their excellent properties like low-cost deployment, easy arrangement and self-organization. Although some proposed security schemes for WMNs with various security objectives have been put forward recently, it is a challenge to employ a uniform cryptography context to achieve resilience to trust authority corruption and maintain trust relationships flexibly among different domains. In this paper, a unified security framework (USF) for multi-domain wireless mesh networks is proposed. The identity-based encryption and the certificateless signature are unified in the proposed cryptography operations utilizing bilinear groups to solve key escrow problem. To ensure secure muliti-hop communication in WMN, the intra and inter domain authentication and key agreement protocols are devised sophisticatedly to achieve perfect forward secrecy and attack-resilience. With the enhanced security properties in the USF scheme, when a trust authority is corrupted, parts of the WMN could be survivable in the local area if proper measures are taken. A formal security proof of the proposed authentication protocols is presented based on Universal Composable security theory. The detailed performance analysis shows that the enhanced security attributes are achieved with reasonable overhead.