Showing papers on "Wireless WAN published in 2007"

Embracing wireless interference: analog network coding

Abstract: Traditionally, interference is considered harmful. Wireless networks strive to avoid scheduling multiple transmissions at the same time in order to prevent interference. This paper adopts the opposite approach; it encourages strategically picked senders to interfere. Instead of forwarding packets, routers forward the interfering signals. The destination leverages network-level information to cancel the interference and recover the signal destined to it. The result is analog network coding because it mixes signals not bits.So, what if wireless routers forward signals instead of packets? Theoretically, such an approach doubles the capacity of the canonical 2-way relay network. Surprisingly, it is also practical. We implement our design using software radios and show that it achieves significantly higher throughput than both traditional wireless routing and prior work on wireless network coding.

In-network aggregation techniques for wireless sensor networks: a survey

Abstract: In this article we provide a comprehensive review of the existing literature on techniques and protocols for in-network aggregation in wireless sensor networks. We first define suitable criteria to classify existing solutions, and then describe them by separately addressing the different layers of the protocol stack while highlighting the role of a cross-layer design approach, which is likely to be needed for optimal performance. Throughout the article we identify and discuss open issues, and propose directions for future research in the area

Physical Layer Network Coding

Abstract: A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). The goal of this paper is to show how the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacityboosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to “straightforward” network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. PNC can yield higher capacity than straightforward network coding when applied to wireless networks. We believe this is a first paper that ventures into EM-wavebased network coding at the physical layer and demonstrates its potential for boosting network capacity. PNC opens up a whole new research area because of its implications and new design requirements for the physical, MAC, and network layers of ad hoc wireless stations. The resolution of the many outstanding but interesting issues in PNC may lead to a revolutionary new paradigm for wireless ad hoc networking.

Pervasive healthcare and wireless health monitoring

Abstract: With an increasingly mobile society and the worldwide deployment of mobile and wireless networks, the wireless infrastructure can support many current and emerging healthcare applications. This could fulfill the vision of "Pervasive Healthcare" or healthcare to anyone, anytime, and anywhere by removing locational, time and other restraints while increasing both the coverage and the quality. In this paper, we present applications and requirements of pervasive healthcare, wireless networking solutions and several important research problems. The pervasive healthcare applications include pervasive health monitoring, intelligent emergency management system, pervasive health-care data access, and ubiquitous mobile telemedicine. One major application in pervasive healthcare, termed comprehensive health monitoring is presented in significant details using wireless networking solutions of wireless LANs, ad hoc wireless networks, and, cellular/GSM/3G infrastructure-oriented networks. Many interesting challenges of comprehensive wireless health monitoring, including context-awareness, reliability, and, autonomous and adaptable operation are also presented along with several high-level solutions. Several interesting research problems have been identified and presented for future research.

60 GHz wireless communications: emerging requirements and design recommendations

Abstract: Multiple GHz of internationally available, unlicensed spectrum surrounding the 60 GHz carrier frequency has the ability to accommodate high-throughput wireless communications. While the size and availability of this free spectrum make it very attractive for wireless applications, 60 GHz implementations must overcome many challenges. For example, the high attenuation and directional nature of the 60 GHz wireless channel as well as limited gain amplifiers and excessive phase noise in 60 GHz transceivers are explicit implementation difficulties. The challenges associated with this channel motivate commercial deployment of short-range wireless local area networks, wireless personal area networks, and vehicular networks. In this paper we detail design tradeoffs for algorithms in the 60 GHz physical layer including modulation, equalization, and space-time processing. The discussion is enhanced by considering the limitations in circuit design, characteristics of the effective wireless channel (including antennas), and performance requirements to support current and next generation 60 GHz wireless communication applications.

An overview of wireless structural health monitoring for civil structures

Abstract: Wireless monitoring has emerged in recent years as a promising technology that could greatly impact the field of structural monitoring and infrastructure asset management. This paper is a summary of research efforts that have resulted in the design of numerous wireless sensing unit prototypes explicitly intended for implementation in civil structures. Wireless sensing units integrate wireless communications and mobile computing with sensors to deliver a relatively inexpensive sensor platform. A key design feature of wireless sensing units is the collocation of computational power and sensors; the tight integration of computing with a wireless sensing unit provides sensors with the opportunity to self-interrogate measurement data. In particular, there is strong interest in using wireless sensing units to build structural health monitoring systems that interrogate structural data for signs of damage. After the hardware and the software designs of wireless sensing units are completed, the Alamosa Canyon Bridge in New Mexico is utilized to validate their accuracy and reliability. To improve the ability of low-cost wireless sensing units to detect the onset of structural damage, the wireless sensing unit paradigm is extended to include the capability to command actuators and active sensors.

An Analysis of Wireless Network Coding for Unicast Sessions: The Case for Coding-Aware Routing

Abstract: A recent approach, COPE, for improving the throughput of unicast traffic in wireless multi-hop networks exploits the broadcast nature of the wireless medium through opportunistic network coding. In this paper, we analyze throughput improvements obtained by COPE-type network coding in wireless networks from a theoretical perspective. We make two key contributions. First, we obtain a theoretical formulation for computing the throughput of network coding on any wireless network topology and any pattern of concurrent unicast traffic sessions. Second, we advocate that routing be made aware of network coding opportunities rather than, as in COPE, being oblivious to it. More importantly, our work studies the tradeoff between routing flows "close to each other" for utilizing coding opportunities and "away from each other" for avoiding wireless interference. Our theoretical formulation provides a method for computing source-destination routes and utilizing the best coding opportunities from available ones so as to maximize the throughput. We handle scheduling of broadcast transmissions subject to wireless transmit/receive diversity and link interference in our optimization framework. Using our formulations, we compare the performance of traditional unicast routing and network coding with coding-oblivious and coding-aware routing on a variety of mesh network topologies, including some derived from contemporary mesh network testbeds. Our evaluations show that a route selection strategy that is aware of network coding opportunities leads to higher end-to-end throughput when compared to coding-oblivious routing strategies.

Robust key generation from signal envelopes in wireless networks

Abstract: The broadcast nature of a wireless link provides a natural eavesdropping and intervention capability to an adversary. Thus, securing a wireless link is essential to the security of a wireless network, and key generation algorithms are necessary for securing wireless links. However, traditional key agreement algorithms can be very costly in many settings, e.g. in wireless ad-hoc networks, since they consume scarce resources such as bandwidth and battery power.Traditional key agreement algorithms are not suitable for wireless ad-hoc networks since they consume scarce resources such as bandwidth and battery power.This paper presents a novel approach that couples the physical layer characteristics of wireless networks with key generation algorithms. It is based on the wireless communication phenomenon known as the principle of reciprocity which states that in the absence of interference both transmitter and receiver experience the same signal envelope. The key-observation here is that the signal envelope information can provide to the two transceivers two correlated random sources that provide sufficient amounts of entropy which can be used to extract a cryptographic key. In contrast, it is virtually impossible for a third party, which is not located at one of the transceiver's position, to obtain or predict the exact envelope; thus retrieve the key. Since in the presence of interference strict reciprocity property can not be maintained; our methodology is based on detecting deep fades to extract correlated bitstrings. In particular, we show how a pair of transceivers can reconcile such bitstrings and finally flatten their distribution to reach key agreement. In our constructions we use cryptographic tools related to randomness extraction and information reconciliation. We introduce "secure fuzzy information reconciliators" a tool that enables us to describe robust key generation systems in our setting. Finally we provide a computational study that presents a simulation of a wireless channel that demonstrates the feasibility of our approach and justifies the assumptions made in our analysis.

Wirelessly controlling unmanned aircraft and accessing associated surveillance data

Abstract: Controlling an unmanned aerial vehicle (UAV) may be accomplished by using a wireless device (e.g., cell phone) to send a control message to a receiver at the UAV via a wireless telecommunication network (e.g., an existing cellular network configured primarily for mobile telephone communication). In addition, the wireless device may be used to receive communications from a transmitter at the UAV, wherein the wireless device receives the communications from the transmitter via the wireless network. Examples of such communications include surveillance information and UAV monitoring information.

Wireless Sensor Networks and Applications: a Survey

Abstract: Summary In this research work, a survey on Wireless Sensor Networks (WSN) and their technologies, standards and applications was carried out. Wireless sensor networks consist of small nodes with sensing, computation, and wireless communications capabilities. Many routing, power management, and data dissemination protocols have been specifically designed for WSNs where energy awareness is an essential design issue. Routing protocols in WSNs might differ depending on the application and network architecture. A multidisciplinary research area such as wireless sensor networks, where close collaboration between users, application domain experts, hardware designers, and software developers is needed to implement efficient systems. The flexibility, fault tolerance, high sensing fidelity, low cost, and rapid deployment characteristics of sensor networks create many new and exciting application areas for remote sensing. In the future, this wide range of application areas will make sensor networks an integral part of our lives. However, realization of sensor networks needs to satisfy the constraints introduced by factors such as fault tolerance, scalability, cost, hardware, topology change, environment, and power consumption.

PPR: partial packet recovery for wireless networks

Abstract: Bit errors occur in wireless communication when interference or noise overcomes the coded and modulated transmission. Current wireless protocols may use forward error correction (FEC) to correct some small number of bit errors, but generally retransmit the whole packet if the FEC is insufficient. We observe that current wireless mesh network protocols retransmit a number of packets and that most of these retransmissions end up sending bits that have already been received multiple times, wasting network capacity. To overcome this inefficiency, we develop, implement, and evaluate a partial packet recovery (PPR) system.PPR incorporates two new ideas: (1) SoftPHY, an expanded physical layer (PHY) interface that provides PHY-independent hints to higher layers about the PHY's confidence in each bit it decodes, and (2) a postamble scheme to recover data even when a packet preamble is corrupted and not decodable at the receiver.Finally, we present PP-ARQ, an asynchronous link-layer ARQ protocol built on PPR that allows a receiver to compactly encode a request for retransmission of only those bits in a packet that are likely in error. Our experimental results from a 31-node Zigbee (802.15.4) testbed that includes Telos motes with 2.4 GHz Chipcon radios and GNU Radio nodes implementing the 802.15.4 standard show that PP-ARQ increases end-to-end capacity by a factor of 2x under moderate load.

Energy-Efficient Resource Allocation in Wireless Networks

Abstract: This paper shows that game theory can be used as a unifying framework to study radio resource management in a variety of wireless networks with different service criteria It focuses on infrastructure networks where users transmit to a common concentration point such as a base station in a cellular network or an access point Since most of the terminals in a wireless network are battery-powered, energy efficiency is crucial to prolonging the life of the terminals Also, in most practical scenarios, distributed algorithms are preferred over centralized ones Throughout this article it focuses on distributed algorithms with emphasis on energy efficiency A family of power control games is presented for energy-efficient resource allocation in wireless code-division multiple-access (CDMA) networks and give discussions and conclusions

Wireless security through RF fingerprinting

Abstract: The process of identifying radio transmitters by examining their unique transient characteristics at the beginning of transmission is called RF fingerprinting. The security of wireless networks can be enhanced by challenging a user to prove its identity if the fingerprint of a network device is unidentified or deemed to be a threat. This paper addresses the problem of identifying an individual node in a wireless network by means of its RF fingerprint. A complete identification system is presented, including data acquisition, transient detection, RF fingerprint extraction, and classification subsystems. The classification performance of the proposed system has been evaluated from experimental data. It is demonstrated that the RF fingerprinting technique can be used as an additional tool to enhance the security of wireless networks.

CogMesh: A Cluster-Based Cognitive Radio Network

Abstract: As the radio spectrum usage paradigm shifting from the traditional command and control allocation scheme to the open spectrum allocation scheme, wireless ad-hoc networks meet new opportunities and challenges. The open spectrum allocation scheme has potential to provide those networks more capacity, and make them more flexible and reliable. However, the freedom brought by the new spectrum allocation scheme introduces spectrum management and network coordination challenges. Moreover, wireless ad-hoc networks usually rely on a common control channel for operation. Such a control channel may, however, not always available in an open spectrum allocation scheme due to the interference and the need for coexistence with primary users of the spectrum. Instead, common channels most likely exist in a local area.In this paper, we propose a cluster-based framework to form a wireless mesh network in the context of open spectrum sharing. Clusters are constructed by neighbor nodes sharing local common channels, and the network is formed by interconnecting the clusters gradually. We identify issues in such a network and provide mechanisms for neighbor discovery, cluster formation, network formation, and network topology management. The unique feature of this network is its ability to intelligently adapt to the network and radio environment change.

Centralized wireless network for multi-room large properties

Abstract: Method and devices for use in a centralized wireless network are provided. The centralized wireless network employs a wireless communication protocol to communicate with various devices throughout the network. In addition to communication, the protocol may be used to control and monitor various aspects of the devices throughout the network.

System and method for monitoring and optimizing network performance to a wireless device

Abstract: A system for monitoring and optimizing network performance to a wireless device including a wireless router in communication with the wireless device for transmitting and receiving RF signals between the wireless router and the wireless device, the wireless router configured to determine network performance information of the wireless network; concatenate the network performance information into data packets; a packet network switch in communication with the wireless router for communicating the data packets between the wireless router and the packet network switch; and a network management device in communication with the packet network switch for instructing the packet network switch to route the data packets to the wireless router based on the network performance information to optimize the network performance to the wireless device. A method for monitoring and optimizing network performance to a wireless device is also included.

Flush: a reliable bulk transport protocol for multihop wireless networks

Abstract: We present Flush, a reliable, high goodput bulk data transport protocol for wireless sensor networks. Flush provides end-to-end reliability, reduces transfer time, and adapts to time-varying network conditions. It achieves these properties using end-to-end acknowledgments, implicit snooping of control information, and a rate-control algorithm that operates at each hop along a flow. Using several real network topologies, we show that Flush closely tracks or exceeds the maximum goodput achievable by a hand-tuned but fixed rate for each hop over a wide range of path lengths and varying network conditions. Flush is scalable; its effective bandwidth over a 48-hop wireless network is approximately one-third of the rate achievable over one hop. The design of Flush is simplified by assuming that different flows do not interfere with each other, a reasonable restriction for many sensornet applications that collect bulk data in a coordinated fashion, like structural health monitoring, volcanic activity monitoring, or protocol evaluation. We collected all of the performance data presented in this paper using Flush itself.

Multi-interface wireless adapter and network bridge

Abstract: Among other things, a wireless device is disclosed for enabling communication with a gateway device within a user premises. The wireless device includes a wireless local area network transceiver for bidirectional wireless data communication at the premises, an interface for wired communication, a processor for converting data between the wireless and wired interfaces. The wireless device receives instructions from the gateway device via the transceiver or the interface and implements conversion and communication control functions to implement a selected one of a plurality of wireless-wired adaptations for communications flowing between the selected one of the transceiver and the interface and the other of the transceiver and the interface for communication within the user premises for application service delivered by the gateway device.

Sensor networks based on wireless devices

Abstract: Techniques for using wireless devices to implement sensor networks are described. For cognitive radio, a wireless device obtains measurements for a first system (e.g., a broadcast system) with which the wireless device is not in communication. The wireless device sends the measurements and associated location information and/or timestamps via a second system (e.g., a cellular system). A server receives measurements from a number of wireless devices and determines the coverage of the first system based on the measurements. For other applications, a wireless device obtains sensor information from at least one sensor at the wireless device and sends the sensor information and associated location information and/or timestamps via a wireless system. A server receives the sensor information and associated information from a number of wireless devices, aggregates the sensor information, and constructs a map. The wireless device may develop a user profile based on the sensor information and associated information.

Automated network selection in a heterogeneous wireless network environment

Abstract: Service delivery in a heterogeneous all-IP wireless network environment requires the selection of an optimal access network. Selection of a non-optimal network can result in undesirable effects such as higher costs or poor service experience. Network selection in such an environment is influenced by several factors, and currently a complete solution is not available to solve this problem. This article describes a comprehensive decision making process to rank candidate networks for service delivery to the terminal. The proposed mechanism is based on a unique decision process that uses compensatory and non-compensatory multi-attribute decision making algorithms jointly to assist the terminal in selecting the top candidate network

Prediction-Based Routing for Vehicular Ad Hoc Networks

Abstract: Development in short-range wireless LAN (WLAN) and long-range wireless WAN (WWAN) technologies have motivated recent efforts to integrate the two. This creates new application scenarios that were not possible before. Vehicles with only WLAN radios can use other vehicles that have both WLAN and WWAN radios as mobile gateways and connect to the Internet while on the road. The most difficult challenge in the scenario is to deal with frequent route breakages due to dynamic mobility of vehicles on the road. Existing routing protocols that are widely used for mobile ad hoc networks are reactive in nature and wait until existing routes break before constructing new routes. The frequent route failures result in a significant amount of time needed for repairing existing routes or reconstructing new routes. In spite of the dynamic mobility, the motion of vehicles on highways is quite predictable compared to other mobility patterns for wireless ad hoc networks, with location and velocity information readily available. This can be exploited to predict how long a route will last between a vehicle requiring Internet connectivity and the gateway that provides a route to the Internet. Successful prediction of route lifetimes can significantly reduce the number of route failures. In this paper, we introduce a prediction-based routing (PBR) protocol that is specifically tailored to the mobile gateway scenario and takes advantage of the predictable mobility pattern of vehicles on highways. The protocol uses predicted route lifetimes to preemptively create new routes before existing ones fail. We study the performance of this protocol through simulation and demonstrate significant reductions in route failures compared to protocols that do not use preemptive routing. Moreover, we find that the overhead of preemptive routing is kept in check due to the ability of PBR to predict route lifetimes.

Negotiated wireless peripheral security systems

Abstract: Methods, apparatus, and business techniques are disclosed for use in mobile network communication systems. A mobile unit such as a smart phone is preferably equipped with a wireless local area network connection and a wireless wide area network connection. The local area network connection is used to establish a position-dependent ecommerce network connection with a wireless peripheral supplied by a vendor. The mobile unit is then temporarily augmented with the added peripheral services supplied by the negotiated wireless peripheral. Systems and methods allow the mobile unit to communicate securely with a remote server, even when the negotiated wireless peripheral is not fully trusted. Also mobile units, wireless user peripherals, and negotiated wireless peripherals that project a non-area constrained user interface image on a display surface are taught.

Topology Control for Wireless Sensor Networks

Abstract: Topology control is one of the most fundamental problems in wireless sensor networks. It is of great importance for prolonging network lifetime, reducing radio interference, increasing the efficiency of MAC (media access control) protocols and routing protocols, among other things. This paper makes a full-scale introduction to the advancement of research on topology control. Firstly, the topology control problem and the design objectives are clearly presented. Secondly, an introduction is made to representative research efforts, along with analyses and comparisons, in two aspects, power control and sleep scheduling, respectively. At the same time, the defects of those efforts are clearly pointed out. Finally, existing problems, open issues and research trends are analyzed and

A Low-delay Protocol for Multihop Wireless Body Area Networks

Abstract: Wireless body area networks (WBANs) form a new and interesting area in the world of remote health monitoring. An important concern in such networks is the communication between the sensors. This communication needs to be energy efficient and highly reliable while keeping delays low. Mobility also has to be supported as the nodes are positioned on different parts of the body that move with regard to each other. In this paper, we present a new cross-layer communication protocol for WBANs: CICADA or Cascading Information retrieval by Controlling Access with Distributed slot Assignment. The protocol sets up a network tree in a distributed manner. This tree structure is subsequently used to guarantee collision free access to the medium and to route data towards the sink. The paper analyzes CICADA and shows simulation results. The protocol offers low delay and good resilience to mobility. The energy usage is low as the nodes can sleep in slots where they are not transmitting or receiving.

Energy-efficient wireless sensor network design and implementation for condition-based maintenance

Abstract: A new application architecture is designed for continuous, real-time, distributed wireless sensor networks. We develop a wireless sensor network for machinery condition-based maintenance (CBM) in small machinery spaces using commercially available products. We develop a hardware platform, networking architecture, and medium access communication protocol. We implement a single-hop sensor network to facilitate real-time monitoring and extensive data processing for machine monitoring. A new radio battery consumption model is presented and the battery consumption equation is used to select the most suitable topology and design an energy efficient communication protocol for wireless sensor networks. A new streamlined matrix formulation is developed that allows the base station to compute the best periodic sleep times for all the nodes in the network. We combine scheduling and contention to design a hybrid MAC protocol, which achieves 100p collision avoidance by using our modified RTS-CTS contention mechanism known as UC-TDMA protocol. A LabVIEW graphical user interface is described that allows for signal processing, including FFT, various moments, and kurtosis. A wireless CBM sensor network implementation on a heating and air conditioning plant is presented as a case study.

Seamless roaming for dual-mode wimax/wifi stations

Abstract: An examplary embodiment providing for one or more improvements includes a method for use in a mobile station operating in a multi-protocol wireless network environment (Fig. 1) that supports a first wireless communication protocol and a second wireless communication protocol wherein the network environment allows the mobile station to seamlessly roam utilizing the first and second wireless communication protocols (100, 110, 120) The method includes establishing a first link layer connection using the first wireless communication protocol, and a second link layer connection using the second wireless communication protocol wherein a single mobile identifier, corresponding to the mobile station, is used in the first and second connections.

Wireless Network Coding: Opportunities & Challenges

Abstract: Wireless networks suffer from a variety of unique problems such as low throughput, dead spots, and inadequate support for mobility. However, their characteristics such as the broadcast nature of the medium, spatial diversity, and significant data redundancy, provide opportunities for new design principles to address these problems. There has been recent interest in employing network coding in wireless networks. This paper explores the case for network coding as a unifying design paradigm for wireless networks, by describing how it addresses issues of throughput, reliability, mobility, and management. We also discuss the practical challenges facing the integration of such a design into the network stack.

User plane uplink time difference of arrival (U-TDOA)

Abstract: A system for locating a mobile wireless device is configured to communicate with a wireless communications system via a control plane and a user plane. The user plane includes a data channel, and the system includes a server configured to communicate via the data channel with a wireless device to be located. The server obtains from the wireless device information useful for tasking the wireless location system. The information useful for tasking may include information indicative of at least one cell site neighboring a serving cell site with which the wireless device is communicating. This may include information indicative of a serving cell site, a reverse channel through which the wireless device is communicating, and/or a hopping pattern, etc. The system may be used, for example, in connection with a GSM or UMTS wireless communications system.

Dynamically created and expanded wireless network

Abstract: A system and method for the establishment and maintenance of wireless network, such as wireless network enabling access to the World Wide Web. The network can be created by its users as part of social network activity. The users are using automated resources discovery, verification and mapping as a comprehensive wireless resources search engine. Once few locations are mapped as wireless service “hot spots,” the service area can be expanded as users keep discovering and mapping more resources. These existing wireless Internet access resources could be mined by users to create spontaneous wireless network providing wide area high-speed data service.