Showing papers on "Wi-Fi array published in 2006"

XORs in the air: practical wireless network coding

Abstract: This paper proposes COPE, a new architecture for wireless mesh networks. In addition to forwarding packets, routers mix (i.e., code) packets from different sources to increase the information content of each transmission. We show that intelligently mixing packets increases network throughput. Our design is rooted in the theory of network coding. Prior work on network coding is mainly theoretical and focuses on multicast traffic. This paper aims to bridge theory with practice; it addresses the common case of unicast traffic, dynamic and potentially bursty flows, and practical issues facing the integration of network coding in the current network stack. We evaluate our design on a 20-node wireless network, and discuss the results of the first testbed deployment of wireless network coding. The results show that COPE largely increases network throughput. The gains vary from a few percent to several folds depending on the traffic pattern, congestion level, and transport protocol.

Mesh network stroke monitoring appliance

Abstract: A health care monitoring system for a person includes one or more wireless nodes forming a wireless mesh network; a wearable appliance having a sound transducer coupled to the wireless transceiver; and a heart attack or stroke attack sensor coupled to the wireless mesh network to communicate patient data over the wireless mesh network to detect a heart attack or a stroke attack.

Interference-Aware Channel Assignment in Multi-Radio Wireless Mesh Networks

Abstract: The capacity problem in wireless mesh networks can be alleviated by equipping the mesh routers with multiple radios tuned to non-overlapping channels However, channel assignment presents a challenge because co-located wireless networks are likely to be tuned to the same channels The resulting increase in interference can adversely affect performance This paper presents an interference-aware channel assignment algorithm and protocol for multi-radio wireless mesh networks that address this interference problem The proposed solution intelligently assigns channels to radios to minimize interference within the mesh network and between the mesh network and co-located wireless networks It utilizes a novel interference estimation technique implemented at each mesh router An extension to the conflict graph model, the multi-radio conflict graph, is used to model the interference between the routers We demonstrate our solution’s practicality through the evaluation of a prototype implementation in a IEEE 80211 testbed We also report on an extensive evaluation via simulations In a sample multi-radio scenario, our solution yields performance gains in excess of 40% compared to a static assignment of channels

Antennas And Propagation for Body-Centric Wireless Communications

Abstract: In this paper, on-body propagation modelling has been investigated applying various numerical computational techniques. Propagation measurements with body-worn antennas have been carried out at 2.4 GHz inside and outside an anechoic chamber respectively for narrowband communication channel characterisation. Both simulation and measurement results have been also obtained at the UWB (ultra wide-band) band.

Mesh network monitoring appliance

Abstract: A health care monitoring system for a person includes one or more wireless nodes forming a wireless mesh network; a wearable appliance having a sound transducer coupled to the wireless transceiver; and a bioelectric impedance (BI) sensor coupled to the wireless mesh network to communicate BI data over the wireless mesh network to detect a heart attack or a stroke attack.

Medium Access Control protocols for ad hoc wireless networks: A survey

Abstract: Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work.

Capacity of wireless erasure networks

Abstract: In this paper, a special class of wireless networks, called wireless erasure networks, is considered. In these networks, each node is connected to a set of nodes by possibly correlated erasure channels. The network model incorporates the broadcast nature of the wireless environment by requiring each node to send the same signal on all outgoing channels. However, we assume there is no interference in reception. Such models are therefore appropriate for wireless networks where all information transmission is packetized and where some mechanism for interference avoidance is already built in. This paper looks at multicast problems over these networks. The capacity under the assumption that erasure locations on all the links of the network are provided to the destinations is obtained. It turns out that the capacity region has a nice max-flow min-cut interpretation. The definition of cut-capacity in these networks incorporates the broadcast property of the wireless medium. It is further shown that linear coding at nodes in the network suffices to achieve the capacity region. Finally, the performance of different coding schemes in these networks when no side information is available to the destinations is analyzed

Wireless power transmission systems and methods

Abstract: Methods, apparatus, and articles of manufacture to power a device using wirelessly transmitted power are disclosed. Initially, a wireless base unit obtains a request for wireless power. The wireless base unit then determines a power requirement associated with a wireless field unit and compares the power requirement to a remaining power capacity of the wireless base unit. The wireless base unit then transmits power wirelessly to the wireless field unit based on the comparison of the power requirement to the remaining power capacity. The wirelessly transmitted power is associated with powering a field device operatively coupled to the wireless field unit.

Local area network having multiple channel wireless access

Abstract: A communication network having at least one access point supports wireless communication among a plurality of wireless roaming devices via a first and a second wireless channel. The access point comprises a first and a second transceiver. The first and second transceivers operate on the first and second wireless channels, respectively. Each of the plurality of wireless roaming devices are capable of communicating on the first and second wireless channel. In one embodiment, the first wireless channel is used to exchange data, while the second channel is used to manage such exchanges as well as access to the first channel. In an alternate embodiment, both channels are used to support communication flow, however the first channel supports a protocol that is more deterministic than that of the second channel. Allocation of ones of the plurality of wireless roaming devices from one channel to the next may occur per direction from the access point. It may also result from decisions made by each of the wireless roaming devices made independent of the access point. For example, a decision may be made based on the data type being transferred or based on the current channel load. Such factors may also be used by the access point for allocation determinations. In addition, allocation may be based on the type of roaming device involved, such as allocating peripherals to a slower channel.

MIMO-OFDM wireless systems: basics, perspectives, and challenges

Abstract: Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency division multiplexing (MIMO-OFDM) is an attractive air-interface solution for next-generation wireless local area networks (WLANs), wireless metropolitan area networks (WMANs), and fourth-generation mobile cellular wireless systems. This article provides an overview of the basics of MIMO-OFDM technology and focuses on space-frequency signaling, receiver design, multiuser systems, and hardware implementation aspects. We conclude with a discussion of relevant open areas for further research

CRAWDAD: a community resource for archiving wireless data at Dartmouth

Abstract: Wireless network researchers are seriously starved for data about how real users, applications, and devices use real networks under real network conditions. CRAWDAD, a Community Resource for Archiving Wireless Data at Dartmouth, is a new NSF-funded project to build a wireless network data archive for the research community. We host wireless data, and provide tools and documents to make it easy to collect and use wireless network data. We hope that this resource will help researchers identify and evaluate real and interesting problems in mobile and pervasive computing. This report outlines the CRAWDAD project, the kick-off work-shop that was held at MobiCom 2005, and the latest news. how real users, applications, and devices use real networks under real conditions, and how mobile users actually move about. This data helps us to identify and understand the real problems, to evaluate possible solutions, and to evaluate new applications and services.

A cross-layer scheduling algorithm with QoS support in wireless networks

Abstract: Scheduling plays an important role in providing quality of service (QoS) support to multimedia communications in various kinds of wireless networks, including cellular networks, mobile ad hoc networks, and wireless sensor networks. The authors propose a scheduling algorithm at the medium access control (MAC) layer for multiple connections with diverse QoS requirements, where each connection employs adaptive modulation and coding (AMC) scheme at the physical (PHY) layer over wireless fading channels. Each connection is assigned a priority, which is updated dynamically based on its channel and service status; the connection with the highest priority is scheduled each time. The authors' scheduler provides diverse QoS guarantees, uses the wireless bandwidth efficiently, and enjoys flexibility, scalability, and low implementation complexity. Its performance is evaluated via simulations

Rf interconnected hvac system and security system

Abstract: An interconnected wireless HVAC (heating, ventilation, air conditioning) system and wireless security system, which are interconnected and communicate with each other through the use of a common wireless technology, including the same selected frequency, modulation and a set of common protocols. The Wireless HVAC system includes wireless thermostats, which can communicate with and control both the HVAC system and the security system, and the wireless security system includes wireless controls or keypads, which can communicate with and control both the security system and the HVAC system. The universal wireless infrastructure can be expanded to provide communication or control of additional user or manufacturer installed wireless devices or systems through the universal wireless home infrastructure.

Detecting identity-based attacks in wireless networks using signalprints

Abstract: Wireless networks are vulnerable to many identity-based attacks in which a malicious device uses forged MAC addresses to masquerade as a specific client or to create multiple illegitimate identities. For example, several link-layer services in IEEE 802.11 networks have been shown to be vulnerable to such attacks even when 802.11i/1X and other security mechanisms are deployed. In this paper we show that a transmitting device can be robustly identified by its signalprint, a tuple of signal strength values reported by access points acting as sensors. We show that, different from MAC addresses or other packet contents, attackers do not have as much control regarding the signalprints they produce. Moreover, using measurements in a testbed network, we demonstrate that signalprints are strongly correlated with the physical location of clients, with similar values found mostly in close proximity. By tagging suspicious packets with their corresponding signalprints, the network is able to robustly identify each transmitter independently of packet contents, allowing detection of a large class of identity-based attacks with high probability.

Indoor Localization System using RSSI Measurement of Wireless Sensor Network based on ZigBee Standard.

Abstract: To verify the validity of our previously reported autonomous indoor localization system in an actual environment, we implemented it in a wireless sensor network based on the ZigBee standard The system automatically estimates the distance between sensor nodes by measuring the RSSI (received signal strength indicator) at an appropriate number of sensor nodes Through experiments, we clarified the validity of our data collection and position estimation techniques The results show that when the deployment density of sensor nodes was set to 027 nodes/ , the position estimation error was reduced to 15-2 m

An energy-efficient ant-based routing algorithm for wireless sensor networks

Abstract: Wireless Sensor Networks are characterized by having specific requirements such as limited energy availability, low memory and reduced processing power. On the other hand, these networks have enormous potential applicability, e.g., habitat monitoring, medical care, military surveillance or traffic control. Many protocols have been developed for Wireless Sensor Networks that try to overcome the constraints that characterize this type of networks. Ant-based routing protocols can add a significant contribution to assist in the maximisation of the network lifetime, but this is only possible by means of an adaptable and balanced algorithm that takes into account the Wireless Sensor Networks main restrictions. This paper presents a new Wireless Sensor Network routing protocol, which is based on the Ant Colony Optimization metaheuristic. The protocol was studied by simulation for several Wireless Sensor Network scenarios and the results clearly show that it minimises communication load and maximises energy savings.

Medical device wireless adapter

Abstract: The invention relates generally to a medical device wireless adapter, and more particularly, to a module that adapts an existing legacy or newly designed medical device to a healthcare provider's wireless infrastructure.

Channel-aware distributed detection in wireless sensor networks

Abstract: This paper reviews the classical decentralized decision theory in the light of new constraints and requirements. The central theme that transcends various aspects of signal processing design is that an integrated channel-aware approach needs to be taken for optimal detection performance given the available resources.

Method and apparatus for communicating emergency information using wireless devices

Abstract: A method and apparatus for providing emergency notification by a wireless mobile device in response to triggering a sensor. A detection system, which may be located within a vehicle, comprises one or more sensors configured to sense an emergency event and transmit a message via a wireless link regarding the emergency event. For example, the wireless mobile device may be programmed to call a predetermined emergency number such as E911, and transmit data including position and other information from the mobile device to the emergency number in response to the received message.

Method and apparatus for wireless network security

Abstract: In one embodiment, the present invention is a method and apparatus for wireless network security. In one embodiment, a method for securing a wireless computing network includes receiving a communication from an unidentified transmitter, identifying the transmitter in accordance with a fingerprint generated from one or more radio frequency signal characteristics extracted from the communication, and taking action in response to an identity of the transmitter.

Peer-to-peer communication in ad hoc wireless network

Abstract: For a peer-to-peer call in an ad hoc wireless network, a wireless device performs discovery of a target wireless device, performs authentication of the target wireless device and generates a session key (e.g., using a pre-shared key or a certificate provisioned on the wireless device), forms an ad hoc wireless network with the target wireless device, and communicates peer-to-peer with the target wireless device via the ad hoc wireless network. The wireless device may perform discovery with a list of identifiers for wireless devices designated to communicate with this wireless device. The wireless device may derive a service set identifier (SSID) used to identify the ad hoc wireless network based on its user-specific identifier (e.g., its phone number) and/or a user-specific identifier for the target wireless device. The wireless device may also performs IP address discovery using the user-specific identifier for the target wireless device.

Wireless network with adaptive autonomous location push

Abstract: A method of providing location-based services includes transmitting a first location criterion from a wireless network server to a wireless device. The method also includes evaluating whether a physical location of the wireless device satisfies the first location criterion. The process of evaluating is performed in part using the wireless device. When the first location criteria is satisfied, the method further includes transmitting an indication from the wireless device to the server that the first location criterion has been satisfied.

A Client-Driven Approach for Channel Management in Wireless LANs

Abstract: We propose an efficient client-based approach for channel management (channel assignment and load balancing) in 802.11-based WLANs that lead to better usage of the wireless spectrum. This approach is based on a “conflict set coloring” formulation that jointly performs load balancing along with channel assignment. Such a formulation has a number of advantages. First, it explicitly captures interference effects at clients. Next, it intrinsically exposes opportunities for better channel re-use. Finally, algorithms based on this formulation do not depend on specific physical RF models and hence can be applied efficiently to a wide-range of in-building as well as outdoor scenarios. We have performed extensive packet-level simulations and measurements on a deployed wireless testbed of 70 APs to validate the performance of our proposed algorithms. We show that in addition to single network scenarios, the conflict set coloring formulation is well suited for channel assignment where multiple wireless networks share and contend for spectrum in the same physical space. Our results over a wide range of both simulated topologies and in-building testbed experiments indicate that our approach improves application level performance at the clients by upto three times (and atleast 50%) in comparison to current best-known techniques.

Signal threshold adaptation for vertical handoff in heterogeneous wireless networks

Abstract: The convergence of heterogeneous wireless access technologies has been envisioned to characterize the next generation wireless networks. In such converged systems, the seamless and efficient handoff between different access technologies (vertical handoff) is essential and remains a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics results in handoff asymmetry that differs from the traditional intra-network handoff (horizontal handoff) problem. In the case where one network is preferred, the vertical handoff decision should be carefully executed, based on the wireless channel state, network layer characteristics, as well as application requirements. In this paper, we study the performance of vertical handoff using the integration of 3G cellular and wireless local area networks as an example. In particular, we investigate the effect of an application-based signal strength threshold on an adaptive preferred-network lifetime-based handoff strategy, in terms of the signalling load, available bandwidth, and packet delay for an inter-network roaming mobile. We present an analytical framework to evaluate the converged system performance, which is validated by computer simulation. We show how the proposed analytical model can be used to provide design guidelines for the optimization of vertical handoff in the next generation integrated wireless networks.

The 802.11n MIMO-OFDM Standard for Wireless LAN and Beyond

Abstract: An overview is given of the new IEEE 80211n standard This is the first wireless LAN standard based on MIMO-OFDM, a technique pioneered by Airgo Networks to give a significant performance increase in both range and rate relative to conventional wireless LAN Performance results show that net user throughputs over 100 Mbps are achievable, which is about four times larger than the maximum achievable throughput using IEEE 80211a/g For the same throughput, MIMO-OFDM achieves a range that is about 3 times larger than non-MIMO systems This significant improvement in range-rate performance makes MIMO-OFDM the ideal solution not only for wireless LAN, but also for home entertainment networks and 4G networks

On accurate measurement of link quality in multi-hop wireless mesh networks

Abstract: This paper presents a highly efficient and accurate link-quality measurement framework, called EAR (Efficient and Accurate link-quality monitoR), for multi-hop wireless mesh networks, that has several salient features. First, it exploits three complementary measurement schemes: passive, cooperative, and active monitoring. EAR maximizes the measurement accuracy by (i) dynamically and adaptively adopting one of these schemes and (ii) opportunistically exploiting the nicast application traffic present in the network, while minimizing the measurement overhead. Second, EAR effectively identifies the existence of wireless link asymmetry by measuring the quality of each link in both directions of the link, thus improving the utilization of network capacity by up to 114%. Finally, its reliance on both the network layer and the IEEE 802.11-based device driver solutions makes EAR easily deployable in existing multi-hop wireless mesh networks without system recompilation or MAC firmware modification. EAR has been evaluated extensively via both ns-2-based simulation and experimentation on our Linux-based implementation. Both simulation and experimentation results have shown EAR to provide highly accurate link-quality measurements with minimum overhead.

Advanced triggers for location-based service applications in a wireless location system

Abstract: Method and systems are employed by a wireless location system (WLS) for locating a wireless device operating in a geographic area served by a wireless communications system. An exemplary method includes monitoring a set of signaling links of the wireless communications system, and detecting at least one predefined signaling transaction occurring on at least one of the predefined signaling links. Then, in response to the detection of the at least one predefined network transaction, at least one predefined location service is triggered.

System and Method for Determining Geographic Location of Wireless Computing Devices

Abstract: System for enabling a wireless computing device to determine its position includes a server with a database of identification and positional information about wireless beacons and a wireless computing device arranged to wirelessly communicate using the Internet with the server. The server determines the geographic location of the wireless computing device upon receiving data from the wireless computing device relating to reception of signals by the wireless computing device from at least one wireless beacon and analysis of the signals in light of the information contained in the database of the server. The server applies a calculation algorithm which determines the geographic location of the wireless computing device upon input of identification and signal strength information about the wireless beacon(s) derived from the received signals.