MESH NETWORK

Wireless mesh networking is an exciting new technology that has applications in defence, metro-area Internet access, and transient networks (e.g: disaster recovery, conventions). In this paper, we describe the design and implementation of a self-configuring, secure infrastructure mesh network architecture, called MeshCluster, composed using multi-radio network nodes. A subset of radio interfaces on these nodes are used for providing network access to end-devices whereas other radio interface are used for relaying packets to nearest Internet gateway. We identify four key design problems: (1) auto-configuration of MeshCluster nodes and relay infrastructure, (2) single and multipath routing in the relay infrastructure using routing metrics, (3) load balancing in the relay infrastructure, and (4) support for end-device mobility across access interfaces of mesh network. For each of these problems, we describe in detail our design, prototype implementation, and performance results.

Mesh networks are multi-hop wireless networks that can be used as a low cost infrastructure for community and city-wide access networks. In this context, support for killer applications such as cooperative services and mobile multimedia applications are in great demand. This mini-course presents the main challenges and solutions for providing mobility, quality of service (QoS) and multicasting in wireless mesh

Advances in wireless personal area networks have made the practical deployment of various services possible, which until a few years ago was considered extremely costly or labor intensive. We build such a wireless sensor network for precision agriculture where real time data of the climatological and other environmental properties are sensed and relayed to a central repository. The architecture comprises of three distinct sections -(a) the sensor-nodes (b) the wireless mesh network and (c) the actuation components. The sensors are selected based on the properties suited for the most common crops and we identify four such attributes. The sensor network is based on the IEEE-802.15.4 standard and we develop a new static routing algorithm suited for the sensing application. The algorithm overrides the deficiency of the Hierarchical Routing scheme inherent in the ZigBee specification where the C skip addressing algorithm limits the possible depth of the network topology due to address wastage. The new algorithm maintains the hierarchical network topology and thus ensures routing at its optimal best. The algorithms for both addressing and routing are provided. The actuation components are also a part of mesh network and are activated wirelessly for controlling irrigation and fertigation.

A novel model for detecting leaks in complex pipeline network systems has been developed. The model derives from the theory of Liapunov stability criteria. A leak is detected if the resulting eigenvalues from the deviation flow matrix have values less than a predetermined value. An advanced mesh network algorithm was used to decompose the complex pipeline network system into sub-networks. The flow model (equations of motion and continuity) which incorporates a leaking factor, k L , is solved by a numerical technique that uses the method of characteristics and an implicit finite function. The unsteady state flow matrix of the complex pipeline network system was analysed using a modified Hardy Cross algorithm, where the velocity and pressure were computed for each node and pipeline loop in the complex network. The plots for the characteristic pressure and velocity eigenvalues show that pressure measurements are faster parameters for leak detection than volume measurements. Volume measurements appear to be suitable for larger leak systems and longer response time.

Over the last two decades free-space optical communication (FSO) has become more and more interesting as an adjunct or alternative to radio frequency communication. Free-space optical (FSO) communication links are most susceptible to a tremendous amount of variability and offer a real challenge for efficient, robust system design.one method of transmitting information from one place to another by sending pulses of light through an optical fiber is Fiber-optic communication , FSO communication systems will provide a large dynamic range of performance through most cases .It is a line-of-sight (LOS) technology that transmits a modulated beam of visible or infrared light through the atmosphere for broadband communications. In a way similar to fiber optical communications, free space optics uses a light emitting diode (LED) or laser (light amplification by stimulated emission of radiation) as a point source for data transmission. However, in free space optics, an energy beam is collimate...

The IEEE 802.16 WiMax standard provides a mechanism for creating multi-hop mesh, which can be deployed as a high speed wide-area wireless network. To realize the full potential of such high-speed IEEE 802.16 mesh networks, two efficient wireless radio resource allocation extensions were developed. The objective of this paper is to propose an efficient approach for increasing the utilization of WiMax mesh through appropriate design of multi-hop routing and scheduling. As multiple-access interference is a major limiting factor for wireless communication systems, we adopt here an interference-aware cross-layer design to increase the throughput of the wireless mesh network. In particular, our scheme creates a tree-based routing framework, which along with scheduling is interference aware and results in a much higher spectral efficiency. Performance evaluation results show that the proposed interference-aware scheme achieves significant throughput enhancement over the basic IEEE 802.16 mesh network.

In recent years, there has been an upsurge of interest in multihop-augmented infrastructurebased networks in both industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and coverage extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to Working Group 4 of the Wireless World Research Forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.

Mesh networks are multi-hop wireless networks emerging as a low cost infrastructure for community access networks and digital cities. In this context, support for killer applications such as cooperative services and mobile multimedia applications are the in great demand. This mini-course aims at presenting, in a theoretical way, main problems, solutions and challenges for providing security in wireless mesh networks. The course has three main focuses: the mesh networks contextualization; Security issues in wireless mesh networks, with your challenges and deficiency and; the main proposals found in the literature.

We evaluate several routing protocols for mobile, wireless, ad hoc networks via packet level simulations. The protocol suite includes routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, end-to-end delay and routing load for a given traffic and mobility model. It is observed that the new generation of on-demand routing protocols use much lower routing load. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and delay performance.

The admittance summation method is efficient in short circuit analysis of radial and weakly meshed networks. It is especially powerful if all node loads can be represented as any combination of constant impedance and constant current load component. However, in the existing literature one cannot find any explanation how to handle power transformer in that approach. For that reason, the corresponding equations have been developed in this paper along with a procedure for development of a three-winding transformer admittance matrix. In addition, a procedure for handling an arbitrary load was proposed. A large number of tests were performed and results were compared with that obtained by the previously published method. As an illustration, some of the results for single fault currents are presented. It can be concluded that the proposed approach makes the admittance summation method capable to take into account all network elements in a proper way.

This paper describes an INtrusion-tolerant routing protocol for wireless SEnsor NetworkS (INSENS). INSENS securely and efficiently constructs tree-structured routing for wireless sensor networks (WSNs). The key objective of an INSENS network is to tolerate damage caused by an intruder who has compromised deployed sensor nodes and is intent on injecting, modifying, or blocking packets. To limit or localize the damage caused by such an intruder, INSENS incorporates distributed lightweight security mechanisms, including efficient oneway hash chains and nested keyed message authentication codes that defend against wormhole attacks, as well as multipath routing. Adapting to WSN characteristics, the design of INSENS also pushes complexity away from resource-poor sensor nodes towards resource-rich base stations. An enhanced single-phase version of INSENS scales to large networks, integrates bidirectional verification to defend against rushing attacks, accommodates multipath routing to multiple base stations, enables secure joining/leaving, and incorporates a novel pairwise key setup scheme based on transitory global keys that is more resilient than LEAP. Simulation results are presented to demonstrate and assess the tolerance of INSENS to various attacks launched by an adversary. A prototype implementation of INSENS over a network of MICA2 motes is presented to evaluate the cost incurred. q 2005 Published by Elsevier B.V. Computer Communications xx (xxxx) 1-15 www.elsevier.com/locate/comcom 0140-3664/$ -see front matter q 2005 Published by Elsevier B.V.

IEEE 802.15.4 is an emerging next generation wireless standard specifically designed for low-rate wireless personal area networks (LR-WPAN) which suit wireless sensor networks applications. It attempts to provide a low cost, low power and short range wireless networking. The QoS is more challenging in heterogeneous wireless sensors networks where a diverse mixture of sensors for monitoring temperature, pressure, and humidity are deployed to monitor the phenomena, thereby introducing different reading rates at these sensors. In this paper, we have simulated the performance analysis of Quality of Service parameters of WSN based on IEEE 802.15.4 mesh topology using reactive MANET routing in QualNet 4.5 on multiple traffic types. The data packet delivery ratio, average end-to-end delay, total energy consumption and network lifetime are investigated as the performance metrics. The results show that DSR and DYMO perform better than AODV in mesh topology non beacon enabled mode.

Advances in semiconductor technology have resulted in the creation of miniature medical embedded systems that can wirelessly monitor the vital signs of patients. These lightweight medical systems can aid providers in large disasters who become overwhelmed with the large number of patients, limited resources, and insufficient information. In a mass casualty incident, small embedded medical systems facilitate patient care, resource allocation, and real-time communication in the Advanced Health and Disaster Aid Network (AID-N). We present the design of electronic triage tags on lightweight, embedded systems with limited memory and computational power. These electronic triage tags use noninvasive, biomedical sensors (pulse oximeter, electrocardiogram, and blood pressure cuff) to continuously monitor the vital signs of a patient and deliver pertinent information to first responders. This electronic triage system facilitates the seamless collection and dissemination of data from the incident site to key members of the distributed emergency response community. The real-time collection of data through a mesh network in a mass casualty drill was shown to approximately triple the number of times patients that were triaged compared with the traditional paper triage system.

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-ofthe-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.

This paper is based on the Mesh network. Meshcomm helps to create a mesh network in the desired area to establish on-demand communication and to avoid casualties. Here we are using a chip called NodeMcu to provide a temporary network. The basic ideology is to connect the NodeMcu's with each other and create a mesh network. These nodes will be deployed in a way that they will provide emergency network covering the area these are deployed in. People in need will connect to this network using Wi-Fi on their mobiles. Once they are connected to the network they will receive a pop-up message, using that they can communicate to the rescue team or with each other.

Packet-based on-chip networks are increasingly being adopted in complex System-on-Chip (SoC) designs supporting numerous homogeneous and heterogeneous functional blocks. These Network-on-Chip (NoC) architectures are required to not only provide ultra-low latency, but also occupy a small footprint and consume as little energy as possible. Further, reliability is rapidly becoming a major challenge in deep sub-micron technologies due to the increased prominence of permanent faults resulting from accelerated aging effects and manufacturing/testing challenges.

Wireless mesh networks hold promises to provide robust and high-throughput data delivery to wireless users. In a mesh network, high-speed Access Points (HAPs), equipped with advanced antennas, communicate with each other over wireless channels and form an indoor/outdoor broadband backhaul. This backbone efficiently forwards user traffic to a few gateway APs (GAPs), which additionally have high-speed connections to the wired Internet. In this paper, we describe ROMER, a resilient and opportunistic routing solution for mesh networks. ROMER balances between long-term route stability and shortterm opportunistic performance. It builds a runtime, forwarding mesh on a per-packet basis that offers a set of candidate routes. The actual forwarding path by each packet opportunistically adapts to the dynamic channel condition and exploits the highestrate wireless channels at the time. To improve resilience against lossy links, HAP failures or HAPs under DoS attacks, ROMER delivers redundant data copies in a controlled and randomized manner over the candidate forwarding mesh. We evaluate the effectiveness of ROMER through both simulations and analysis.

This paper is an introduction to survivability of WDM networks. All the main optical protection techniques proposed as far as now for the WDM layer are classified and reviewed. In particular, commonly adopted protection strategies for ring and mesh networks are explained. Moreover, off-line planning of WDM networks able to support path protection is briefly introduced. Finally, an example of heuristic network-capacity optimization is presented, discussing results obtained by considering a case-study network.

In general, there is a well recognized need to study cascading failures in inter-dependent societal infrastructures. Here, we conduct a systematic study of human-initiated cascading failures in certain critical inter-dependent societal infrastructures. In particular, we analyze cascades that occur in these inter-dependent infrastructures due to behavioral adaptations in response to a crisis. We focus on three coupled systems here: (i) cellular and mesh networks, (ii) transportation networks and (iii) social phone call networks. The three systems are closely coupled -indeed wireless cellular network traffic is greatly influenced by the spatio-temporal calling patterns of individuals. In such crises, changes in individual behavioral lead to altered calling patterns and activities, which influence the urban transport network. In turn, this affects the loads on wireless networks. The interaction between these systems and their co-evolution poses significant technical challenges for representing and reasoning about these systems. In contrast to system dynamics models for studying these interacting infrastructures, we develop interaction-based models in which individuals and infrastructure elements are represented in detail and are placed in a common geographic coordinate system. Using the detailed representation, we study the impact of a chemical plume that has been released in a densely populated urban region. Authorities order evacuation of the affected area and this leads to individual behavioral adaptation wherein individuals drive to pre-specified evacuation shelters. They also use the wireless networks for coordination among family members and information sharing. These two behavioral adaptations, cause flash-congestions in the urban transport network and the wireless network. We analyze how extended periods of unanticipated road congestion can result in failure of infrastructures, starting with the servicing base stations in the congested area. Finally, we study the criticality and robustness of the various base stations and measure how congestion in the transportation network impacts communication infrastructure.

Many state-of-the-art wireless systems, such as long distance mesh networks and high bandwidth networks using mm-wave frequencies, require high gain antennas to overcome adverse channel conditions. These networks could be greatly aided by adaptive beamforming antenna arrays, which can significantly simplify the installation and maintenance costs (e.g., by enabling automatic beam alignment). However, building large, low cost beamforming arrays is very complicated. In this paper, we examine the main challenges presented by large arrays, starting from electromagnetic and antenna design and proceeding to the signal processing and algorithms domain. We propose 3-dimensional antenna structures and hybrid RF/digital radio architectures that can significantly reduce the complexity and improve the power efficiency of adaptive array systems. We also present signal processing techniques based on adaptive filtering methods that enhance the robustness of these architectures. Finally, we present computationally efficient vector quantization techniques that significantly improve the interference cancellation capabilities of analog beamforming architectures.

A new decomposition method is presented that includes the network through ac modeling within the hydrothermal scheduling optimization process including the losses. In short-term hydrothermal scheduling, the transmission network is typically modeled with dc power flow techniques. Such modeling, however, can lead to impractical solutions when it is verified with ac power flow. Another proposal considers in thermal systems the ac network modeling but not the optimization of losses. The approach presented here addresses issues such as congestion management and control of service quality that often arise in large and weakly meshed networks-the typical pattern of power systems in Latin America. Generalized Benders decomposition and traditional, well-known optimization techniques are used to solve this problem. The master problem stage defines the generation levels by regarding the inter-temporal constraints, whereas the subproblem stage determines both the active and the reactive economical dispatches for each time interval of the load curve. It meets the electrical constraints through a modified ac optimal power flow (OPF). Another important contribution is the inclusion of accelerating techniques aimed at reducing the number of iterations and CPU time. The methodology was proven in a real system and test systems. Results are discussed in this paper.

Although IEEE 802.15.4 is being considered as a promising standard for low-cost low-power Wireless Sensor Networks (WSNs), several issues in the specification are still open. One of those open issues is how to build a synchronized multi-hop mesh network for power efficient, scalable, and robust networking. In fact, while the current specification supports multi-hop networking using peer-to-peer topology, it restricts its use to the beaconless mode. This paper presents an extension to the current IEEE 802.15.4 standard in which mesh networking in the low power beacon mode is enabled through the use of distributed beacon scheduling. The work presented in this paper has been implemented on top of the Open-ZB IEEE 802.15.4 implementation within the TinyOS operating system. The feasibility of our proposal is demonstrated and evaluated through both physical test-bed and computer based emulation.

A number of disasters in various places of the planet have caused an extensive loss of lives, severe damages to properties and the environment, as well as a tremendous shock to the survivors. For relief and mitigation operations, emergency responders are immediately dispatched to the disaster areas. Ubiquitous and robust communications during the emergency response operations are of paramount importance. Nevertheless, various reports have highlighted that after many devastating events, the current technologies used, failed to support the mission critical communications, resulting in further loss of lives. Inefficiencies of the current communications used for emergency response include lack of technology inter-operability between different jurisdictions, and high vulnerability due to their centralized infrastructure. In this article, we propose a flexible network architecture that provides a common networking platform for heterogeneous multi-operator networks, for interoperation in case of emergencies. A wireless mesh network is the main part of the proposed architecture and this provides a back-up network in case of emergencies. We first describe the shortcomings and limitations of the current technologies, and then we address issues related to the applications and functionalities a future emergency response network should support. Furthermore, we describe the necessary requirements for a flexible, secure, robust, and QoS-aware emergency response multi-operator architecture, and then we suggest several schemes that can be adopted by our proposed architecture to meet those requirements. In addition, we suggest several methods for the re-tasking of communication means owned by independent individuals to provide support during emergencies. In order to investigate the feasibility of multimedia transmission over a wireless mesh network, we measured the performance of a video streaming application in a real wireless metropolitan multi-radio mesh network, showing that the mesh network can meet the requirements for high quality video transmissions.

Mesh networks are multi-hop wireless networks emerging as a low cost infrastructure for community access networks and digital cities. In this context, support for killer applications such as cooperative services and mobile multimedia applications are the in great demand. This mini-course aims at presenting, in a theoretical way, main problems, solutions and challenges for providing security in wireless mesh networks. The course has three main focuses: the mesh networks contextualization; Security issues in wireless mesh networks, with your challenges and deficiency and; the main proposals found in the literature.

There is a potential for significant cost, footprint and power savings by eliminating unnecessary Opto-Electronic (OE) conversions on a signal path in a core optical mesh network. This paper addresses and clarifies some fundamental issues surrounding all-optical networking and all-optical switching and analyzes the tradeoffs between transparent (no OE conversions) and opaque networking (with OE conversions). It investigates a number of networking and interface compatibility issues that arise for an opaque network with transparent switches and presents a number of ways on how this issues can be addressed.

This paper describes a system design approach for a wireless sensor network based application that is to be used to measure temperature and humidity as well as being fitted with a smoke detector. Such a device can be used as an early warning fire detection system in ...

This paper shows a development of an RFID (Radio Frequency IDentification) user authorization (access control system) using wireless ZigBee communication network. The system is designed with the topology of one Master and multiple Slave nodes. Idea is to manage a data base on the Master node which is connected to the Slave nodes through a wireless link. Slave node consists of an RFID reader, LCD touch screen and XBee wireless module. Master node communicates with the LabView application through an Ethernet interface. A program development is shown for both nodes, including all the peripheral modules. The proposed system's major advantage over the existing systems is wireless communications. Wireless network uses XBee wireless modules and can be formed as a mesh network, where an end node server as a router, thus extending the range of the network.

Nowadays, critical control systems are a fundamental component contributing to the overall performance of critical infrastructures in our society, most of which belong to the industrial sector. These complex systems include in their design different types of information and communication technology systems, such as wireless (mesh) sensor networks, to carry out control processes in real time. This fact has meant that several communication standards, such as Zigbee PRO, WirelessHART, and ISA100.11a, have been specified to ensure coexistence, reliability, and security in their communications. The main purpose of this paper has been to review these three standards and analyze their security. We have identified a set of threats and potential attacks in their routing protocols, and we consequently provide recommendations and countermeasures to help Industry protect its infrastructures.

a b s t r a c t 24 Wireless mesh networks (WMNs) have emerged recently as a technology for next-genera-25 tion wireless networking. They consist of mesh routers and clients, where mesh routers are 26 almost static and form the backbone of WMNs. WMNs provide network access for both 27 mesh and conventional clients. 28 In this paper we propose MobiSEC, a complete security architecture that provides both 29 access control for mesh users and routers as well as a key distribution scheme that sup-30 ports layer-2 encryption to ensure security and data confidentiality of all communications 31 that occur in the WMN. 32 MobiSEC extends the IEEE 802.11i standard exploiting the routing capabilities of mesh 33 routers; after connecting to the access network as generic wireless clients, new mesh rou-34 ters authenticate to a central server and obtain a temporary key that is used both to prove 35 their credentials to neighbor nodes and to encrypt all the traffic transmitted on the wire-36 less backbone links. 37 A key feature in the design of MobiSEC is its independence from the underlying wireless 38 technology used by network nodes to form the backbone. Furthermore, MobiSEC allows 39 seamless mobility of both mesh clients and routers. 40 MobiSEC has been implemented and integrated in MobiMESH, a WMN implementation 41 that provides a complete framework for testing and analyzing the behavior of a mesh net-42 work in real-life environments. Moreover, extensive simulations have been performed in 43 large-scale network scenarios using Network Simulator. 44 Numerical results show that our proposed architecture considerably increases the WMN 45 security, with a negligible impact on the network performance, thus representing an effec-46 tive solution for wireless mesh networking. 47 Ó 2009 Published by Elsevier B.V. 48 49 50

The designer of a system on a chip (SoC) that connects IP cores through a network on chip (NoC) needs methods to support application performance evaluation. Two key aspects these methods have to address are the generation and evaluation of network traffic. Traffic generation allows injecting packets in the network according to application constraint specifications such as transmission rate and end-to-end latency. Performance evaluation helps in computing latency and throughput at network channels/interfaces, as well as to identify congestion and hotspots. This paper reviews related works in traffic generation and performance evaluation for mesh topology NoCs, and proposes general methods for both aspects. Three parameters are used here to define traffic generation: packet spatial distribution, packet injection rate and packet size. Two types of methods to evaluate performance in NoCs are discussed: (i) external evaluation, a common strategy found in related works, where the network is considered as a black box and traffic results are obtained only from the external network interfaces; (ii) internal evaluation, where performance is computed in each network channel. The paper presents the result of experiments conducted in an 8x8 mesh network, varying the routing algorithms and the number of virtual channels. The main contribution of this work is the set of methods for internal NoC evaluation, which help designers to optimize the network under different traffic scenarios.

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 multihop 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.

We present a measurement study of a large-scale urban WiFi mesh network consisting of more than 250 Mesh Access Points (MAPs), with paying customers that use it for Internet access. Our study, involved collecting multi-modal data, e.g., through continuous gathering of SNMP logs, syslogs, passive traffic capture, and limited active measurements in different parts of the city. Our study is split into four components -planning and deployment of the mesh, success of mesh routing techniques, likely experience of users, and characterization of how the mesh is utilized. During our data collection process that spanned 8 months, the network changed many times due to hardware and software upgrades. Hence to present a consistent view of the network, the core dataset used in this paper comes from a two week excerpt of our dataset. This part of the dataset had more than 1.7 million SNMP log entries (from 224 MAPs) and more than 100 hours of active measurements. The scale of the study allowed us to make many important observations that are critical in planning and using WiFi meshes as an Internet access technology. For example, our study indicates that the last hop 2.4GHz wireless link between the mesh and the client is the major bottleneck in client performance. Further we observe that deploying the mesh access points on utility poles results in performance degradation for indoor clients that receive poor signal from the access points.

Wireless Mesh Networks (WMNs) have gained a lot of attention recently. Features such as self-configuration, selfhealing and the low cost of equipment and deployment make WMN technology a promising platform for a wide range of applications. Traditional ad-hoc routing protocols are typically used to deal with the dynamic nature of these networks, which is mainly due to mobility. However, these protocols typically suffer from a number of shortcomings, such as high routing overhead and limited scalability. More recently, it has been shown that multi-path ad-hoc routing protocols have a number of advantages over their single-path counterparts, including reduced overhead and increased reliability. This motivates the work presented in this paper, which provides a comparison of AOMDV and DSR-MP, the multi-path variants of AODV and DSR. We specifically study the performance of these protocols in a hybrid wireless mesh network, where static mesh routers and mobile clients collaborate to implement network functionality such as routing and packet forwarding. Based on extensive simulations, we present a comparative analysis covering performance metrics such as packet loss, latency and path optimality.

Data centers' energy consumption has attracted global attention because of the fast growth of the information technology (IT) industry. Up to 60% of the energy consumed in a data center is used for cooling in wasteful ways as a result of lack of environmental information and overcompensated cooling systems. In this project, a wireless sensor network for data-enter environmental monitoring was developed to improve energy efficiency and to optimize data-center performance. The sensor network consists of a suite of sensor nodes for data sensing, a router node to relay sensed data, and a coordinator node to establish a network, receive the data, and process the data. The prototype sensor network was built on Arduino open source hardware with a seamlessly integrated XBee RF module and configured to operate within the ZigBee mesh network standard. A 24-hour test run at Argonne's data center demonstrated that the wireless networked environmental monitoring solution is easy to integrate and manage with the existing IT infrastructure, while delivering better visibility into the data center's 3D temperature and humidity distribution and substantial improvements in energy efficiency.

Innovative asynchronous circuits are central to the Ethernet switch chips from Intel's Switch and Router Division (formerly Fulcrum Microsystems). These circuits are complex, and it can be hard to gauge their benefits since there are few direct comparisons. For this paper, we apply the technology and tool flow developed for these commercial products to a familiar benchmark: a network of general purpose processors on a chip. The processor is a single-issue 32-bit integer RISC core, a fromscratch implementation mostly compatible with the MIPS R3000. The network uses a 16-port 32-bit fully connected Nexus crossbar. We achieve greater scalability by linking these crossbars in a 2D mesh with clusters of 8 cores and 4 cardinal and 4 diagonal links per tile. Each core has 64KB of local memory and can access the memory of any other core in the mesh. Our design makes heavy use of the Proteus synthesis, place & route flow, as well as existing custom cells. It required only a few man-months of effort to develop a complete gate-level design and physical floorplan which can run simple C programs such as Dhrystone. A few more man-months will produce a test chip, expected in 2013.

Based on the IEEE 802.15.4 LR-WPAN standard, the ZigBee standard has been proposed to interconnect simple, low rate, and battery powered wireless devices. The deployment of ZigBee networks is expected to facilitate numerous applications, such as home-appliance networks, home healthcare, medical monitoring, consumer electronics, and environmental sensors. An effective routing scheme in a ZigBee network is particularly important in that it is the key to achieve resource (e.g., bandwidth and energy) efficiency in ZigBee networks. Routing in a ZigBee network is not exactly the same as in a MANET. In particular, while Full Function Devices (FFD) can serve as network coordinators or network routers, Reduced Function Devices (RFD) can only associate and communicate with FFDs in a ZigBee network. Therefore, different from traditional MANET routing algorithms, which only take into account node mobility to figure out a best route to a given destination, node heterogeneity plays an important role in ZigBee network routing. In this paper, we perform extensive evaluation, using NS-2 simulator, to study the impact of node heterogeneity on ZigBee mesh network routing. The results show that the ZigBee mesh routing algorithm exhibits significant performance difference when the network is highly heterogenous. We also reveal that the node type and the role of the node plays a critical role in deciding routing performances.

The scene of electric power systems has changed drastically and will continue to do so in the years to come. Causes of this evolution are the liberalization of the electricity markets and the increased use of intermittent renewable energy. Uncertainty in the transmitted power and congestion of the lines raise the need for new technologies. High voltage direct current (HVDC) is one of these emerging technologies that may have a major impact, and more specifically voltage source converter (VSC) HVDC. The main part of this paper is to verify the feasibility, technical as well as economic, of VSC HVDC on loss minimization in meshed networks. The losses of the different components of a VSC HVDC link are studied and the impact of the installation on overall system losses in meshed networks is verified through simulations. Simulations are performed on two networks: the small IEEE 14 bus network and the larger IEEE 118 bus network. The networks are investigated in their original state and in a state of increased loading. Finally, an economic analysis is performed to investigate the economic feasibility of VSC HVDC on loss reduction in meshed networks.

Data centers' energy consumption has attracted global attention because of the fast growth of the information technology (IT) industry. Up to 60% of the energy consumed in a data center is used for cooling in wasteful ways as a result of lack of environmental information and overcompensated cooling systems. In this project, a wireless sensor network for data-enter environmental monitoring was developed to improve energy efficiency and to optimize data-center performance. The sensor network consists of a suite of sensor nodes for data sensing, a router node to relay sensed data, and a coordinator node to establish a network, receive the data, and process the data. The prototype sensor network was built on Arduino open source hardware with a seamlessly integrated XBee RF module and configured to operate within the ZigBee mesh network standard. A 24-hour test run at Argonne's data center demonstrated that the wireless networked environmental monitoring solution is easy to integrate and manage with the existing IT infrastructure, while delivering better visibility into the data center's 3D temperature and humidity distribution and substantial improvements in energy efficiency.

Wireless mesh networks hold promises to provide robust and high-throughput data delivery to wireless users. In a mesh network, high-speed Access Points (HAPs), equipped with advanced antennas, communicate with each other over wireless channels and form an indoor/outdoor broadband backhaul. This backbone efficiently forwards user traffic to a few gateway APs (GAPs), which additionally have high-speed connections to the wired Internet. In this paper, we describe ROMER, a resilient and opportunistic routing solution for mesh networks. ROMER balances between long-term route stability and shortterm opportunistic performance. It builds a runtime, forwarding mesh on a per-packet basis that offers a set of candidate routes. The actual forwarding path by each packet opportunistically adapts to the dynamic channel condition and exploits the highestrate wireless channels at the time. To improve resilience against lossy links, HAP failures or HAPs under DoS attacks, ROMER delivers redundant data copies in a controlled and randomized manner over the candidate forwarding mesh. We evaluate the effectiveness of ROMER through both simulations and analysis.