Untraceable Authentication Protocol for IEEE802.11s Standard

In the current paper, a new handover authentication protocol for IEEE802.11s Wireless mesh networks is presented. The new protocol divides the network into a number of cells, each cell contains a number of access points and based on the concept of ticket authentication, the mesh user takes a new ticket when enters the region of a new cell which decreases the handover latency. Moreover, in the current paper, a new idea for ticket generation is proposed, called Chain Ticket Derivation Function (CTDF), which uses the concept of a chain. Using CTDF in our proposed protocol raises the level of privacy for the users. The security analysis presented in the paper showed more strengths in our proposed scheme. Two formal verification tools, AVISPA and BAN logic are used to test the proposed protocol.

Router and gateway node placement in wireless mesh networks for emergency rescue scenarios

The focus of this paper is on base functionalities required for UAV-based rapid deployment of an ad hoc communication infrastructure in the initial phases of rescue operations. The main idea is to use heterogeneous teams of UAVs to deploy communication kits that include routers, and are used in the generation of ad hoc Wireless Mesh Networks (WMN). Several fundamental problems are considered and algorithms are proposed to solve these problems. The Router Node Placement problem (RNP) and a generalization of it that takes into account additional constraints arising in actual field usage is considered first. The RNP problem tries to determine how to optimally place routers in a WMN. A new algorithm, the RRT-WMN algorithm, is proposed to solve this problem. It is based in part on a novel use of the Rapidly Exploring Random Trees (RRT) algorithm used in motion planning. A comparative empirical evaluation between the RRT-WMN algorithm and existing techniques such as the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) and Particle Swarm Optimization (PSO), shows that the RRT-WMN algorithm has far better performance both in amount of time taken and regional coverage as the generalized RNP problem scales to realistic scenarios. The Gateway Node Placement Problem (GNP) tries to determine how to locate a minimal number of gateway nodes in a WMN backbone network while satisfying a number of Quality of Service (QoS) constraints.Two alternatives are proposed for solving the combined RNP-GNP problem. The first approach combines the RRT-WMN algorithm with a preexisting graph clustering algorithm. The second approach, WMNbyAreaDecomposition, proposes a novel divide-and-conquer algorithm that recursively partitions a target deployment area into a set of disjoint regions, thus creating a number of simpler RNP problems that are then solved concurrently. Both algorithms are evaluated on real-world GIS models of different size and complexity. WMNbyAreaDecomposition is shown to outperform existing algorithms using 73% to 92% fewer router nodes while at the same time satisfying all QoS requirements.

Content Replication and Placement Schemes for Wireless Mesh Networks

<p>Recently, Wireless Mesh Networks (WMNs) have attracted much of interest from both academia and industry, due to their potential to provide an alternative broadband wireless Internet connectivity. However, due to different reasons such as multi-hop forwarding and the dynamic wireless link characteristics, the performance of current WMNs is rather low when clients are soliciting Web contents. Due to the evolution of advanced mobile computing devices; it is anticipated that the demand for bandwidth-onerous popular content (especially multimedia content) in WMNs will dramatically increase in the coming future. Content replication is a popular approach for outsourcing content on behalf of the origin content provider. This area has been well explored in the context of the wired Internet, but has received comparatively less attention from the research community when it comes to WMNs. There are a number of replica placement algorithms that are specifically designed for the Internet. But they do not consider the special features of wireless networks such as insufficient bandwidth, low server capacity, contention to access the wireless medium, etc. This thesis studies the technical challenges encountered when transforming the traditional model of multi-hop WMNs from an access network into a content network. We advance the thesis that support from packet relaying mesh routers to act as replica servers for popular content such as media streaming, results in significant performance improvement. Such support from infrastructure mesh routers benefits from knowledge of the underlying network topology (i.e., information about the physical connections between network nodes is available at mesh routers). The utilization of cross-layer information from lower layers opens the door to developing efficient replication schemes that account for the specific features of WMNs (e.g., contention between the nodes to access the wireless medium and traffic interference). Moreover, this can benefit from the underutilized resources (e.g., storage and bandwidth) at mesh routers. This utilization enables those infrastructure nodes to participate in content distribution and play the role of replica servers. In this thesis, our main contribution is the design of two lightweight, distributed, and scalable object replication schemes for WMNs. The first scheme follows a hierarchical approach, while the second scheme follows a flat one. The challenge is to replicate content as close as possible to the requesting clients and thus, reduce the access latency per object, while minimizing the number of replicas. The two schemes aim to address the questions of where and how many replicas should be placed in the WMN. In our schemes, we consider the underlying topology joint with link-quality metrics to improve the quality of experience. We show using simulation tests that the schemes significantly enhance the performance of a WMN in terms of reducing the access cost, bandwidth consumption and computation/communication cost.</p>

Content Replication and Placement Schemes for Wireless Mesh Networks

<p>Recently, Wireless Mesh Networks (WMNs) have attracted much of interest from both academia and industry, due to their potential to provide an alternative broadband wireless Internet connectivity. However, due to different reasons such as multi-hop forwarding and the dynamic wireless link characteristics, the performance of current WMNs is rather low when clients are soliciting Web contents. Due to the evolution of advanced mobile computing devices; it is anticipated that the demand for bandwidth-onerous popular content (especially multimedia content) in WMNs will dramatically increase in the coming future. Content replication is a popular approach for outsourcing content on behalf of the origin content provider. This area has been well explored in the context of the wired Internet, but has received comparatively less attention from the research community when it comes to WMNs. There are a number of replica placement algorithms that are specifically designed for the Internet. But they do not consider the special features of wireless networks such as insufficient bandwidth, low server capacity, contention to access the wireless medium, etc. This thesis studies the technical challenges encountered when transforming the traditional model of multi-hop WMNs from an access network into a content network. We advance the thesis that support from packet relaying mesh routers to act as replica servers for popular content such as media streaming, results in significant performance improvement. Such support from infrastructure mesh routers benefits from knowledge of the underlying network topology (i.e., information about the physical connections between network nodes is available at mesh routers). The utilization of cross-layer information from lower layers opens the door to developing efficient replication schemes that account for the specific features of WMNs (e.g., contention between the nodes to access the wireless medium and traffic interference). Moreover, this can benefit from the underutilized resources (e.g., storage and bandwidth) at mesh routers. This utilization enables those infrastructure nodes to participate in content distribution and play the role of replica servers. In this thesis, our main contribution is the design of two lightweight, distributed, and scalable object replication schemes for WMNs. The first scheme follows a hierarchical approach, while the second scheme follows a flat one. The challenge is to replicate content as close as possible to the requesting clients and thus, reduce the access latency per object, while minimizing the number of replicas. The two schemes aim to address the questions of where and how many replicas should be placed in the WMN. In our schemes, we consider the underlying topology joint with link-quality metrics to improve the quality of experience. We show using simulation tests that the schemes significantly enhance the performance of a WMN in terms of reducing the access cost, bandwidth consumption and computation/communication cost.</p>

Performance Evaluation of Routing Metrics for Community Wireless Mesh Networks

<p>With the growth of different types of Internet traffic there is a compelling need to provide better quality of service, especially, over the increasing number of wireless networks. Expected Transmission Count (ETX) is a high throughput route selection metric that measures link loss ratios. ETX of a path reflects the total number of packet transmissions (including retransmission) required to successfully deliver a data packet along that path. Expected Transmission Time (ETT) is an improvement of ETX. ETT of a path is a measure of the transmission time needed to successfully deliver a packet along the path. ETT measures the loss ratio and the bandwidth of the link. Both, ETX and ETT, in comparison to hop count, provide better route selection for routing protocols widely used in Wireless Mesh Networks (WMNs). Using minimum hop count to find the shortest path has been shown to be inadequate for WMNs, as the selected routes often include the weakest links. This thesis presents a performance evaluation comparing hop count, ETX and ETT when used with the Optimized Link State Routing version 2 (OLSRv2) protocol. This study is based on the wireless mesh topology of a suburban residential area in New Zealand, and analyses the performance of three common Internet traffic types in terms of throughput, end-to-end delay, jitter and packet loss ratio, and presents findings that are closer to the perspective of what an enduser experiences. Also, a grid network of 121 nodes was used to analyze how the metrics choose paths, the performance changes (for different path lengths) and other conditions that affect the performance of the three metrics.</p>

Performance Evaluation of Routing Metrics for Community Wireless Mesh Networks

<p>With the growth of different types of Internet traffic there is a compelling need to provide better quality of service, especially, over the increasing number of wireless networks. Expected Transmission Count (ETX) is a high throughput route selection metric that measures link loss ratios. ETX of a path reflects the total number of packet transmissions (including retransmission) required to successfully deliver a data packet along that path. Expected Transmission Time (ETT) is an improvement of ETX. ETT of a path is a measure of the transmission time needed to successfully deliver a packet along the path. ETT measures the loss ratio and the bandwidth of the link. Both, ETX and ETT, in comparison to hop count, provide better route selection for routing protocols widely used in Wireless Mesh Networks (WMNs). Using minimum hop count to find the shortest path has been shown to be inadequate for WMNs, as the selected routes often include the weakest links. This thesis presents a performance evaluation comparing hop count, ETX and ETT when used with the Optimized Link State Routing version 2 (OLSRv2) protocol. This study is based on the wireless mesh topology of a suburban residential area in New Zealand, and analyses the performance of three common Internet traffic types in terms of throughput, end-to-end delay, jitter and packet loss ratio, and presents findings that are closer to the perspective of what an enduser experiences. Also, a grid network of 121 nodes was used to analyze how the metrics choose paths, the performance changes (for different path lengths) and other conditions that affect the performance of the three metrics.</p>

Adaptive Multi-Channel Clustering in IEEE 802.11s Wireless Mesh Networks

WLAN mesh networks are one of the key technologies for upcoming smart city applications and are characterized by a flexible and low-cost deployment. The standard amendment IEEE 802.11s introduces low-level mesh interoperability at the WLAN MAC layer. However, scalability limitations imposed by management traffic overhead, routing delays, medium contention, and interference are common issues in wireless mesh networks and also apply to IEEE 802.11s networks. Possible solutions proposed in the literature recommend a divide-and-conquer scheme that partitions the network into clusters and forms smaller collision and broadcast domains by assigning orthogonal channels. We present CHaChA (Clustering Heuristic and Channel Assignment), a distributed cross-layer approach for cluster formation and channel assignment that directly integrates the default IEEE 802.11s mesh protocol information and operating modes, retaining unrestricted compliance to the WLAN standard. Our concept proposes further mechanisms for dynamic cluster adaptation, including subsequent cluster joining, isolation and fault detection, and node roaming for cluster balancing. The practical performance of CHaChA is demonstrated in a real-world 802.11s testbed. We first investigate clustering reproducibility, duration, and communication overhead in static network scenarios of different sizes. We then validate our concepts for dynamic cluster adaptation, considering topology changes that are likely to occur during long-term network operation and maintenance.