Showing papers on "Wireless mesh network published in 2009"

DRAND: Distributed Randomized TDMA Scheduling for Wireless Ad Hoc Networks

Abstract: This paper presents a distributed implementation of RAND, a randomized time slot scheduling algorithm, called DRAND. DRAND runs in O(delta) time and message complexity where delta is the maximum size of a two-hop neighborhood in a wireless network while message complexity remains O(delta), assuming that message delays can be bounded by an unknown constant. DRAND is the first fully distributed version of RAND. The algorithm is suitable for a wireless network where most nodes do not move, such as wireless mesh networks and wireless sensor networks. We implement the algorithm in TinyOS and demonstrate its performance in a real testbed of Mica2 nodes. The algorithm does not require any time synchronization and is shown to be effective in adapting to local topology changes without incurring global overhead in the scheduling. Because of these features, it can also be used even for other scheduling problems such as frequency or code scheduling (for FDMA or CDMA) or local identifier assignment for wireless networks where time synchronization is not enforced. We further evaluate the effect of the time-varying nature of wireless links on the conflict-free property of DRAND-assigned time slots. This experiment is conducted on a 55-node testbed consisting of the more recent MicaZ sensor nodes.

SOAR: Simple Opportunistic Adaptive Routing Protocol for Wireless Mesh Networks

Abstract: Multihop wireless mesh networks are becoming a new attractive communication paradigm owing to their low cost and ease of deployment. Routing protocols are critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along predetermined paths and face difficulties in coping with unreliable and unpredictable wireless medium. In this paper, we propose a simple opportunistic adaptive routing protocol (SOAR) to explicitly support multiple simultaneous flows in wireless mesh networks. SOAR incorporates the following four major components to achieve high throughput and fairness: 1) adaptive forwarding path selection to leverage path diversity while minimizing duplicate transmissions, 2) priority timer-based forwarding to let only the best forwarding node forward the packet, 3) local loss recovery to efficiently detect and retransmit lost packets, and 4) adaptive rate control to determine an appropriate sending rate according to the current network conditions. We implement SOAR in both NS-2 simulation and an 18-node wireless mesh testbed. Our extensive evaluation shows that SOAR significantly outperforms traditional routing and a seminal opportunistic routing protocol, ExOR, under a wide range of scenarios.

Wireless Mesh Networks

Abstract: Wireless telemedicine using GSM and GPRS technologies can only provide low bandwidth connections, which makes it difficult to transmit images and video. Satellite or 3G wireless transmission provides greater bandwidth, but the running costs are high. Wireless networks (WLANs) appear promising, since they can supply high bandwidth at low cost. However, the WLAN technology has limitations, such as coverage. A new wireless networking technology named the wireless mesh network (WMN) overcomes some of the limitations of the WLAN. A WMN combines the characteristics of both a WLAN and ad hoc networks, thus forming an intelligent, large scale and broadband wireless network. These features are attractive for telemedicine and telecare because of the ability to provide data, voice and video communications over a large area. One successful wireless telemedicine project which uses wireless mesh technology is the Emergency Room Link (ER-LINK) in Tucson, Arizona, USA. There are three key characteristics of a WMN: self-organization, including self-management and self-healing; dynamic changes in network topology; and scalability. What we may now see is a shift from mobile communication and satellite systems for wireless telemedicine to the use of wireless networks based on mesh technology, since the latter are very attractive in terms of cost, reliability and speed.

Fiber-wireless (FiWi) access networks: A survey

Abstract: This article provides an up-to-date survey of hybrid fiber-wireless (FiWi) access networks that leverage on the respective strengths of optical and wireless technologies and converge them seamlessly. FiWi networks become rapidly mature and give rise to new powerful access network solutions and paradigms. The survey first overviews the state of the art, enabling technologies and future developments of wireless and optical access networks, respectively, paying particular attention to wireless mesh networks and fiber to the home networks. After briefly reviewing some generic integration approaches of EPON and WiMAX networks, several recently proposed FiWi architectures based on different optical network topologies and WiFi technology are described. Finally, technological challenges toward the realization and commercial adoption of future FiWi access networks are identified.

Remote monitoring and control system comprising mesh and time synchronization technology

Abstract: A remote monitoring and control system comprising synchronized wireless MESH technology for remote monitoring and control of utility grids (e.g., utility meters), commodity distribution networks, industrial equipment, and infrastructure including remote disconnection/connection and self-generating power.

Load management in wireless mesh communications networks

Abstract: Methods and systems for providing a network and routing protocol for utility services are disclosed. A method includes discovering a utility network. Neighboring nodes are discovered and the node listens for advertised routes for networks from the neighbors. The node is then registered with one or more utility networks, receiving a unique address for each network registration. Each upstream node can independently make forwarding decisions on both upstream and downstream packets, i.e., choose the next hop according to the best information available to it. The node can sense transient link problems, outage problems and traffic characteristics. Information is used to find the best route out of and within each network. Each network node maintains multi-egress, multi-ingress network routing options both for itself and the node(s) associated with it. The node is capable of several route maintenance functions utilizing the basic routing protocol and algorithms.

Gateways Placement in Backbone Wireless Mesh Networks

Abstract: 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.

Design and evaluation of a hierarchical on-chip interconnect for next-generation CMPs

Abstract: Performance and power consumption of an on-chip interconnect that forms the backbone of Chip Multiprocessors (CMPs), are directly influenced by the underlying network topology. Both these parameters can also be optimized by application induced communication locality since applications mapped on a large CMP system will benefit from clustered communication, where data is placed in cache banks closer to the cores accessing it. Thus, in this paper, we design a hierarchical network topology that takes advantage of such communication locality. The two-tier hierarchical topology consists of local networks that are connected via a global network. The local network is a simple, high-bandwidth, low-power shared bus fabric, and the global network is a low-radix mesh. The key insight that enables the hybrid topology is that most communication in CMP applications can be limited to the local network, and thus, using a fast, low-power bus to handle local communication will improve both packet latency and power-efficiency. The proposed hierarchical topology provides up to 63% reduction in energy-delay-product over mesh, 47% over flattened butterfly, and 33% with respect to concentrated mesh across network sizes with uniform and non-uniform synthetic traffic. For real parallel workloads, the hybrid topology provides up to 14% improvement in system performance (IPC) and in terms of energy-delay-product, improvements of 70%, 22%, 30% over the mesh, flattened butterfly, and concentrated mesh, respectively, for a 32-way CMP. Although the hybrid topology scales in a power- and bandwidth-efficient manner with network size, while keeping the average packet latency low in comparison to high radix topologies, it has lower throughput due to high concentration. To improve the throughput of the hybrid topology, we propose a novel router micro-architecture, called XShare, which exploits data value locality and bimodal traffic characteristics of CMP applications to transfer multiple small flits over a single channel. This helps in enhancing the network throughput by 35%, providing a latency reduction of 14% with synthetic traffic, and improving IPC on an average 4% with application workloads.

Which Wireless Technology for Industrial Wireless Sensor Networks? The Development of OCARI Technology

Abstract: In this paper, we present an industrial development of a wireless sensor network technology called OCARI: optimization of communication for ad hoc reliable industrial networks. It targets applications in harsh environments such as power plants and warships. OCARI is a wireless-communication technology that supports mesh topology and power-aware ad hoc routing protocol aimed at maximizing the network lifetime. It is based on IEEE 802.15.4 physical layer with deterministic media access control layer for time-constrained communication. During the nontime-constrained communication period, its ad hoc routing strategy uses an energy-aware optimized-link state-routing proactive protocol. An OCARI application layer (APL) is based on ZigBee application support sublayer and APL primitives and profiles to provide maximum compatibility with ZigBee applications. To fully assess this technology, extensive tests are done in industrial facilities at ElectricitEacute De France R&D as well as at Direction des Constructions Navales Services. Our objective is then to promote this specification as an open standard of industrial wireless technology.

Rapidly-Deployable Mesh Network Testbed

Abstract: This paper describes a wireless mesh network testbed for research in rapid deployment and autoconfiguration of mesh nodes. Motivated by the needs of first responders and military personnel arriving to an incident area, we developed and tested an automated deployment algorithm that indicates when a mesh node needs to be deployed as the coverage area grows. Conventional radios can experience severe coverage limitations inside structures such as hi-rise buildings, subterranean buildings, caves, and underground mines. The approach examined here is to deploy wireless relays that extend coverage through multihop communication using a deployment algorithm that employs physical layer measurements. A flexible platform based on IEEE 802.11 radios has been implemented and tested in a subterranean laboratory complex where conventional public safety radios have no coverage. Applications tested include two-way voice, data, and location information. This paper describes the testbed, presents experimental results, and recommends areas for further study and development in rapidly-deployable multihop networks.

A system and method for implementing mesh network communications using a mesh network protocol

Abstract: The following describes data structures, communication protocol formats and process flows for controlling and facilitating secure communications between the nodes of a mesh network, such as utility meters and gateway nodes comprising a utility network. The enabled processes include association, information exchange, route discovery and maintenance and the like for instituting and maintaining a secure mesh network.

Practical, distributed channel assignment and routing in dual-radio mesh networks

Abstract: Realizing the full potential of a multi-radio mesh network involves two main challenges: how to assign channels to radios at each node to minimize interference and how to choose high throughput routing paths in the face of lossy links, variable channel conditions and external load. This paper presents ROMA, a practical, distributed channel assignment and routing protocol that achieves good multi-hop path performance between every node and one or more designated gateway nodes in a dual-radio network. ROMA assigns non-overlapping channels to links along each gateway path to eliminate intra-path interference. ROMA reduces inter-path interference by assigning different channels to paths destined for different gateways whenever possible. Evaluations on a 24-node dual-radio testbed show that ROMA achieves high throughput in a variety of scenarios.

Practical defenses against pollution attacks in intra-flow network coding for wireless mesh networks

Abstract: Recent studies show that network coding can provide significant benefits to network protocols, such as increased throughput, reduced network congestion, higher reliability, and lower power consumption. The core principle of network coding is that intermediate nodes actively mix input packets to produce output packets. This mixing subjects network coding systems to a severe security threat, known as a \emph{pollution attack}, where attacker nodes inject corrupted packets into the network. Corrupted packets propagate in an epidemic manner, depleting network resources and significantly decreasing throughput. Pollution attacks are particularly dangerous in wireless networks, where attackers can easily inject packets or compromise devices due to the increased network vulnerability.In this paper, we address pollution attacks against network coding systems in wireless mesh networks. We demonstrate that previous solutions to the problem are impractical in wireless networks, incurring an unacceptably high degradation of throughput. We propose a lightweight scheme, DART, that uses time-based authentication in combination with random linear transformations to defend against pollution attacks. We further improve system performance and propose EDART, which enhances DART with an optimistic forwarding scheme. A detailed security analysis shows that the probability of a polluted packet passing our verification procedure is very low. Performance results using the well-known MORE protocol and realistic link quality measurements from the Roofnet experimental testbed show that our schemes improve system performance over 20 times compared to previous solutions.

Multirate Anypath Routing in Wireless Mesh Networks

Abstract: In this paper, we present a new routing paradigm that generalizes opportunistic routing in wireless mesh networks. In multirate anypath routing, each node uses both a set of next hops and a selected transmission rate to reach a destination. Using this rate, a packet is broadcast to the nodes in the set and one of them forwards the packet on to the destination. To date, there is no theory capable of jointly optimizing both the set of next hops and the transmission rate used by each node. We bridge this gap by introducing a polynomial-time algorithm to this problem and provide the proof of its optimality. The proposed algorithm runs in the same running time as regular shortest-path algorithms and is therefore suitable for deployment in link-state routing protocols. We conducted experiments in a 802.11b testbed network, and our results show that multirate anypath routing performs on average 80% and up to 6.4 times better than anypath routing with a fixed rate of 11 Mbps. If the rate is fixed at 1 Mbps instead, performance improves by up to one order of magnitude. I. INTRODUCTION The high loss rate and dynamic quality of links make routing in wireless mesh networks extremely challenging (1). Anypath routing 1 has been recently proposed as a way to circumvent these shortcomings by using multiple next hops for each destination (3)-(6). Each packet is broadcast to a forwarding set composed of several neighbors, and the packet must be retransmitted only if none of the neighbors in the set receive it. Therefore, while the link to a given neighbor is down or performing poorly, another nearby neighbor may receive the packet and forward it on. This is in contrast to single-path routing where only one neighbor is assigned as the next hop for each destination. In this case, if the link to this neighbor is not performing well, a packet may be lost even though other neighbors may have overheard it. Existing work on anypath routing has focused on wireless networks that use a single transmission rate. This approach, albeit straightforward, presents two major drawbacks. First, using a single rate over the entire network underutilizes available bandwidth resources. Some links may perform well at a higher rate, while others may only work at a lower rate. Secondly and most importantly, the network may become disconnected at a higher bit rate. We provide experimental measurements from a 802.11b testbed which show that this phenomenon is not uncommon in practice. The key problem is that higher transmission rates have a shorter radio range, which reduces network density and connectivity. As the bit rate in- creases, links becomes lossier and the network eventually gets disconnected. Therefore, in order to guarantee connectivity, single-rate anypath routing must be limited to low rates. In multirate anypath routing, these problems do not exist; however, we face different challenges. First, we must find 1 We use the term anypath rather than opportunistic routing, since oppor- tunistic routing is an overloaded term also used for opportunistic contacts (2).

Ad Hoc and Neighborhood Search Methods for Placement of Mesh Routers in Wireless Mesh Networks

Abstract: With the fast development in wireless technologies and wireless devices, Wireless Mesh Networks (WMN) are becoming and important networking infrastructure, especially due to their low cost of deployment and maintenance. A main issue in deploying WMNs is the optimal placement of mesh routers to achieve network connectivity and stability through the maximization of the size of the giant component in the network and user coverage. In this work we evaluate ad hoc and neighborhood search methods for placement of mesh routers in WMNs. Routers are assumed having their own coverage area, oscillating between minimum and maximum values. Given a deployment area where to distribute the mesh router nodes and a number of fixed clients a priori distributed in the given area, ad hoc methods explore different topologies such as placement in diagonals, in corners of the area, in hotspots, etc.~and the resulting network connectivity and user coverage are measured. We have experimentally evaluated the considered ad hoc methods through a benchmark of generated instances as stand alone methods and as initializing methods of evolutionary algorithms. For each ad hoc method, different distributions of mesh clients (Normal, Exponential and Weibull), are considered and the size of the giant component and user coverage parameters are reported. Further, we considered neighborhood search methods for optimal placement of mesh routers as more powerful methods for achieving near optimal placements of mesh router nodes. The experimental evaluation showed the good performance of a swap-based movement neighborhood search, which achieved good connectivity of the network in few phases of neighborhood search exploration.

Minimizing End-to-End Delay: A Novel Routing Metric for Multi-Radio Wireless Mesh Networks

Abstract: This paper studies how to select a path with the minimum cost in terms of expected end-to-end delay (EED) in a multi-radio wireless mesh network Different from the previous efforts, the new EED metric takes the queuing delay into account, since the end-to-end delay consists of not only the transmission delay over the wireless links but also the queuing delay in the buffer In addition to minimizing the end-to-end delay, the EED metric implies the concept of load balancing We develop EED- based routing protocols for both single-channel and multi-channel wireless mesh networks In particular for the multi-radio multi- channel case, we develop a generic iterative approach to calculate a multi-radio achievable bandwidth (MRAB) for a path, taking the impacts of inter/intra-flow interference and space/channel diversity into account The MRAB is then integrated with EED to form the metric of weighted end-to-end delay (WEED) As a byproduct of MRAB, a channel diversity coefficient can be defined to quantitatively represent the channel diversity along a given path Both numerical analysis and simulation studies are presented to validate the performance of the routing protocol based on the EED/WEED metric, with comparison to some well- known routing metrics I INTRODUCTION Routing in wireless mesh networks has been a hot re- search area in recent years, with the objective to achieve as high throughput as possible over the network The main methodology adopted by most of the existing work is selecting path based on interference-aware or load-balancing routing metrics to reduce network-wide channel contentions It has been revealed that the capacity of a single-radio multi-hop wireless network can not scale up with the network size, due to the co-channel interference (1)-(3) The multi-radio multi-channel connection has been widely considered as an efficient approach to increase the wireless network capacity (8) Design of efficient routing schemes for multi-radio multi- channel wireless mesh network is much more challenging compared to the single-channel case Many popular multimedia applications, eg, voice over IP, IPTV, and on-line gaming, have strict delay requirement In this paper, we aim at designing a routing metric to minimize the end-to-end delay, considering not only the transmission delay at the medium access control (MAC) layer, but also the queuing delay at the network layer Most of the previous studies focus only on the transmission delay of the packet

Comparison of two routing metrics in OLSR on a grid based mesh network

Abstract: Predicting the performance of ad hoc networking protocols for mesh networks has typically been performed by making use of software based simulation tools. Experimental study and validation of such predictions is a vital to obtaining more realistic results, but may not be possible under the constrained environment of network simulators. This paper presents an experimental comparison of OLSR using the standard hysteresis routing metric and the ETX metric in a 7 by 7 grid of closely spaced Wi-Fi nodes to obtain more realistic results. The wireless grid is first modelled to extract its ability to emulate a real world multi-hop ad hoc network. This is followed by a detailed analysis of OLSR in terms of hop count, routing traffic overhead, throughput, delay, packet loss and route flapping in the wireless grid using the hysteresis and ETX routing metric. It was discovered that the ETX metric which has been extensively used in mesh networks around the world is fundamentally flawed when estimating optimal routes in real mesh networks and that the less sophisticated hysteresis metric shows better performance in large dense mesh networks.

A Cross-Layer Framework for Association Control in Wireless Mesh Networks

Abstract: The user association mechanism specified by the IEEE 802.11 standard does not consider the channel conditions and the AP load in the association process. Employing the mechanism in its plain form in wireless mesh networks we may only achieve low throughput and low user transmission rates. In this paper we design a new association framework in order to provide optimal association and network performance. In this framework we propose a new channel-quality based user association mechanism inspired by the operation of the infrastructure-based WLANs. Besides, we enforce our framework by proposing an airtime-metric based association mechanism that is aware of the uplink and downlink channel conditions as well as the communication load. We then extend the functionality of this mechanism in a cross-layer manner taking into account information from the routing layer, in order to fit it in the operation of wireless mesh networks. Lastly, we design a hybrid association scheme that can be efficiently applied in real deployments to improve the network performance. We evaluate the performance of our system through simulations and we show that wireless mesh networks that use the proposed association mechanisms are more capable in meeting the needs of QoS-sensitive applications.

A channel and rate assignment algorithm and a layer-2.5 forwarding paradigm for multi-radio wireless mesh networks

Abstract: The availability of cost-effective wireless network interface cards makes it practical to design network devices with multiple radios which can be exploited to simultane-ously transmit/receive over different frequency channels. It has been shown that using multiple radios per node increases the throughput of multi-hop wireless mesh networks. However, multi-radios create several research challenges. A fundamental problem is the joint channel assignment and routing problem, i.e., how the channels can be assigned to radios and how a set of flow rates can be determined for every network link in order to achieve an anticipated objective. This joint problem is NP-com-plete. Thus, an approximate solution is developed by solving the channel assignment and the routing problems separately. The channel assignment problem turns out to be the problem to assign channels such that a given set of flow rates are schedulable and itself is shown to be also NP-complete. This paper shows that not only the channels but also the transmission rates of the links have to be properly selected to make a given set of flow rates schedulable. Thus, a greedy heuristic for the channel and rate assignment problem is developed. Algorithms to schedule the resulting set of flow rates have been proposed in the literature, which require synchronization among nodes and hence modified coordination functions. Unlike previous work, in this paper a forwarding paradigm is developed to achieve the resulting set of flow rates while using a standard MAC. A bi-dimensional Markov chain model of the proposed forwarding paradigm is presented to analyze its behavior. Thorough performance studies are con-ducted to: a) compare the proposed greedy heuristic to other channel assignment algorithms; b) analyze the behavior of the forwarding paradigm through numerical simulations based on the Markov chain model; c) simulate the operations of the forwarding paradigm and evaluate the achieved network throughput.

The role of zigbee technology in future data communication system

Abstract: ZigBee is an IEEE 802.15.4 standard for data communications with business and consumer devices. It is designed around low-power consumption allowing batteries to essentially last forever. The ZigBee standard provides network, security, and application support services operating on top of the IEEE 802.15.4 Medium Access Control (MAC) and Physical Layer (PHY) wireless standard. It employs a suite of technologies to enable scalable, self-organizing, self-healing networks that can manage various data traffic patterns. ZigBee is a low-cost, low-power, wireless mesh networking standard. The low cost allows the technology to be widely deployed in wireless control and monitoring applications, the low power-usage allows longer life with smaller batteries, and the mesh networking provides high reliability and larger range.ZigBee has been developed to meet the growing demand for capable wireless networking between numerous lowpower devices. In industry ZigBee is being used for next generation automated manufacturing, with small transmitters in every device on the floor, allowing for communication between devices to a central computer. This new level of communication permits finely-tuned remote monitoring and manipulation.

Realistic mobility simulation of urban mesh networks

Abstract: It is a truism that today's simulations of mobile wireless networks are not realistic. In realistic simulations of urban networks, the mobility of vehicles and pedestrians is greatly influenced by the environment (e.g., the location of buildings) as well as by interaction with other nodes. For example, on a congested street or sidewalk, nodes cannot travel at their desired speed. Furthermore, the location of streets, sidewalks, hallways, etc. restricts the position of nodes, and traffic lights impact the flow of nodes. And finally, people do not wander the simulated region at random, rather, their mobility depends on whether the person is at work, at lunch, etc. In this paper, realistic simulation of mobility for urban wireless networks is addressed. In contrast to most other mobility modeling efforts, most of the aspects of the presented mobility model and model parameters are derived from surveys from urban planning and traffic engineering research. The mobility model discussed here is part of the UDel Models, a suite of tools for realistic simulation of urban wireless networks. The UDel Models simulation tools are available online.

Cognitive radio for next-generation wireless networks: an approach to opportunistic channel selection in ieee 802.11-based wireless mesh

Abstract: 'Cognitive radio' has emerged as a new design paradigm for next-generation wireless networks that aims to increase utilization of the scarce radio spectrum (both licensed and unlicensed). Learning and adaptation are two significant features of a cognitive radio transceiver. Intelligent algorithms are used to learn the surrounding environment, and the knowledge thus obtained is utilized by the transceiver to choose the frequency band (i.e., channel) of transmission as well as transmission parameters to achieve the best performance. In this article we first provide an overview of the different components to achieve adaptability in a cognitive radio transceiver and discuss the related approaches. A survey of the cognitive radio techniques used in the different wireless systems is then presented. To this end, a dynamic opportunistic channel selection scheme based on the cognitive radio concept is presented for an IEEE 802.11-based wireless mesh network.

A low-radix and low-diameter 3D interconnection network design

Abstract: Interconnection plays an important role in performance and power of CMP designs using deep sub-micron technology. The network-on-chip (NoCs) has been proposed as a scalable and high-bandwidth fabric for interconnect design. The advent of the 3D technology has provided further opportunity to reduce on-chip communication delay. However, the design of the 3D NoC topologies has important distinctions from 2D NoCs or off-chip interconnection networks. First, current 3D stacking technology allows only vertical inter-layer links. Hence, there cannot be direct connections between arbitrary nodes in different layers — the vertical connection topology are essentially fixed. Second, the 3D NoC is highly constrained by the complexity and power of routers and links. Hence, low-radix routers are preferred over high-radix routers for lower power and better heat dissipation. This implies long network latency due to high hop counts in network paths. In this paper, we design a low-diameter 3D network using low-radix routers. Our topology leverages long wires to connect remote intra-layer nodes. We take advantage of the start-of-the-art one-hop vertical communication design and utilize lateral long wires to shorten network paths. Effectively, we implement a small-to-medium sized clique network in different layers of a 3D chip. The resulting topology generates a diameter of 3-hop only network, using routers of the same radix as 3D mesh routers. The proposed network shows up to 29% of network latency reduction, up to 10% throughput improvement, and up to 24% energy reduction, when compared to a 3D mesh network.

Security in Wireless Ad Hoc and Sensor Networks

Abstract: About the Authors. Preface. Acknowledgements. List of Acronyms. Part One Wireless Ad Hoc, Sensor and Mesh Networking. 1 Introduction. 1.1 Information Security. 1.2 Scope of the Book. 1.3 Structure of the Book. 1.4 Electronic Resources for the Book. 1.5 Review Questions. 2 Wireless Ad Hoc, Sensor and Mesh Networks. 2.1 Ad Hoc Networks and Applications. 2.2 Sensor and Actuator Networks. 2.3 Mesh Networks. 2.4 Tactical Communications and Networks. 2.5 Factors Influencing the Design of Wireless Ad Hoc, Sensor and Mesh Networks. .6 Review Questions. 3 The Wireless Medium. 3.1 Wireless Channel Fundamentals and Security. 3.2 Advanced Radio Technologies. 3.3 Review Questions. 4 Medium Access and Error Control. 4.1 Medium Access Control. 4.2 Error Control. 4.3 Wireless Metropolitan Area Networks. 4.4 Wireless Local Area Networks. 4.5 Wireless Personal Area Networks. 4.6 Review Questions. 5 Routing. 5.1 Internet Protocol and Mobile IP. 5.2 Routing in Wireless Ad Hoc Networks. 5.3 Routing in Wireless Sensor and Actuator Networks. 5.4 Review Questions. 6 Reliability, Flow and Congestion Control. 6.1 Reliability. 6.2 Flow and Congestion Control. 6.3 Review Questions. 7 Other Challenges and Security Aspects. 7.1 Localization and Positioning. 7.2 Time Synchronization. 7.3 Addressing. 7.4 Data Aggregation and Fusion. 7.5 Data Querying. 7.6 Coverage. 7.7 Mobility Management. 7.8 Cross-layer Design. 7.9 Review Questions. Part Two Security in Wireless Ad Hoc, Sensor and Mesh Networking. 8 Security Attacks in Ad Hoc, Sensor and Mesh Networks. 8.1 Security Attacks. 8.2 Attackers. 8.3 Security Goals. 8.4 Review Questions. 9 Cryptography. 9.1 Symmetric Encryption. 9.2 Asymmetric Encryption. 9.3 Hash Functions and Message Authentication Code. 9.4 Cascading Hashing. 9.5 Review Questions. 10 Challenges and Solutions: Basic Issues. 10.1 Bootstrapping Security in Ad Hoc Networks. 10.2 Bootstrapping Security in Sensor Networks. 10.3 Key Distribution, Exchange and Management. 10.4 Authentication Issues. 10.5 Integrity. 10.6 Review Questions. 11 Challenges and Solutions: Protection. 11.1 Privacy and Anonymity. 11.2 Intrusion Detection. 11.3 Defense Against Traffic Analysis. 11.4 Access Control and Secure Human-Computer Interaction. 11.5 Software-Based Anti-Tamper Techniques. 11.6 Tamper Resilience: Hardware Protection. 11.7 Availability and Plausibility. 11.8 Review Questions. 12 Secure Routing. 12.1 Defense Against Security Attacks in Ad Hoc Routing. 12.2 Secure Ad Hoc Routing Protocols. 12.3 Further Reading. 12.4 Review Questions. 13 Specific Challenges and Solutions. 13.1 SPINS: Security Protocols for Sensor Networks. 13.2 Quarantine Region Scheme for Spam Attacks. 13.3 Secure Charging and Rewarding Scheme. 13.4 Secure Node Localization. 13.5 Secure Time Synchronization. 13.6 Secure Event and Event Boundary Detection. 13.7 Review Questions. 14 Information Operations and Electronic Warfare. 14.1 Electronic Support. 14.2 Electronic Attack. 14.3 Electronic Protection. 14.4 Review Questions. 15 Standards. 15.1 X.800 and RFC 2828. 15.2 Wired Equivalent Privacy (WEP). 15.3 Wi-Fi Protected Access (WPA). References. Index.

Capacity and delay of hybrid wireless broadband access networks

Abstract: An optical network is too costly to act as a broadband access network. On the other hand, a pure wireless ad hoc network with n nodes and total bandwidth of W bits per second cannot provide satisfactory broadband services since the pernode throughput diminishes as the number of users goes large. In this paper, we propose a hybrid wireless network, which is an integrated wireless and optical network, as the broadband access network. Specifically, we assume a hybrid wireless network consisting of n randomly distributed normal nodes, and m regularly placed base stations connected via an optical network. A source node transmits to its destination only with the help of normal nodes, i.e., in the ad hoc mode, if the destination can be reached within L (L /spl geq/ 1) hops from the source. Otherwise, the transmission will be carried out in the infrastructure mode, i.e., with the help of base stations. Two transmission modes share the same bandwidth of W bits/sec. We first study the throughput capacity of such a hybrid wireless network, and observe that the throughput capacity greatly depends on the maximum hop count L and the number of base stations m. We show that the throughput capacity of a hybrid wireless network can scale linearly with n only if m = Omega(n), and when we assign all the bandwidth to the infrastructure mode traffics. We then investigate the delay in hybrid wireless networks. We find that the average packet delay can be maintained as low as Theta(1) even when the per-node throughput capacity is Theta(W).

The availability and reliability of wireless multi-hop networks with stochastic link failures

Abstract: The network reliability and availability in wireless multi-hop networks can be inadequate due to radio induced interference. It is therefore common to introduce redundant nodes. This paper provides a method to forecast how the introduction of redundant nodes increases the reliability and availability of such networks. For simplicity, it is assumed that link failures are stochastic and independent, and the network can be modelled as a random graph. First, the network reliability and availability of a static network with a planned topology is explored. This analysis is relevant to mesh networks for public access, but also provides insight into the reliability and availability behaviour of other categories of wireless multi-hop networks. Then, by extending the analysis to also consider random geometric graphs, networks with nodes that are randomly distributed in a metric space are also investigated. Unlike many other random graph analyses, our approach allows for advanced link models where the link failure probability is continuously decreasing with an increasing distance between the two nodes of the link. In addition to analysing the steady-state availability, the transient reliability behaviour of wireless multi-hop networks is also found. These results are supported by simulations.

A genetic approach to joint routing and link scheduling for wireless mesh networks

Abstract: Wireless mesh networks are an attractive technology for providing broadband connectivity to mobile clients who are just on the edge of wired networks, and also for building self-organized networks in places where wired infrastructures are not available or not deemed to be worth deploying. This paper investigates the joint link scheduling and routing issues involved in the delivery of a given backlog from any node of a wireless mesh network towards a specific node (which acts as a gateway), within a given deadline. Scheduling and routing are assumed to be aware of the physical interference among nodes, which is modeled in the paper by means of a signal-to-interference ratio. Firstly, we present a theoretical model which allows us to formulate the task of deriving joint routing and scheduling as an integer linear programming problem. Secondly, since the problem cannot be dealt with using exact methods, we propose and use a technique based on genetic algorithms. To the best of our knowledge, these algorithms have never been used before for working out these kinds of optimization problems in a wireless mesh environment. We show that our technique is suitable for this purpose as it provides a good trade-off between fast computation and the overall goodness of the solution found. Our experience has in fact shown that genetic algorithms would seem to be quite promising for solving more complex models than the one dealt with in this paper, such as those including multiple flows and multi-radio multi-channels.

Channel assignment for multicast in multi-channel multi-radio wireless mesh networks

Abstract: One of the most effective approaches to enhance the throughput capacity of wireless mesh networks (WMN) is to use systems with multiple channels and multiple radios per node. Multi-channel multi-radio (MCMR) networks require efficient channel assignment (CA) algorithms to determine which channel a link should use for data transmission in order to maximize network throughput. The problem of CA has been studied extensively for unicast communications, but addressed only recently for multicast. We propose a CA algorithm named Minimum interference Multi-channel Multi-radio Multicast (M4) that minimizes interference among nodes in a multicast routing tree and uses both orthogonal and overlapping channels such as those in IEEE 802.11b-g systems. Simulation results show that M4 outperforms the Multi Channel Multicast algorithm proposed. in various scenarios with respect to average packet delivery ratio, throughput and end-to-end delay. Copyright © 2008 John Wiley & Sons, Ltd.

Quality of service and power aware forwarding rules for mesh points in wireless mesh networks

Abstract: Apparatus, methods and computer program products provide quality of service and power aware forwarding rules for mesh points in wireless mesh networks by monitoring frame flow to and from a first mesh point in the wireless mesh network; and in dependence on the monitored frame flow, setting a power management mode of the first mesh point. The first mesh point monitors, for example, the power save mode and mesh deterministic access status of peer modes and selects power save and frame transmission modes in dependence on the monitored information.