Showing papers on "Wireless published in 2001"

Investigating the energy consumption of a wireless network interface in an ad hoc networking environment

Abstract: Energy-aware design and evaluation of network protocols requires knowledge of the energy consumption behavior of actual wireless interfaces. But little practical information is available about the energy consumption behavior of well-known wireless network interfaces and device specifications do not provide information in a form that is helpful to protocol developers. This paper describes a series of experiments which obtained detailed measurements of the energy consumption of an IEEE 802.11 wireless network interface operating in an ad hoc networking environment. The data is presented as a collection of linear equations for calculating the energy consumed in sending, receiving and discarding broadcast and point-to-point data packets of various sizes. Some implications for protocol design and evaluation in ad hoc networks are discussed.

Cognitive radio for flexible mobile multimedia communications

Abstract: Wireless multimedia applications require significant bandwidth, some of which will be provided by third-generation (3G) services. even with substantial investment in 3G infrastructure, the radio spectrum allocated to 3G will be limited. Cognitive radio offers a mechanism for the flexible pooling of radio spectrum using a new class of protocols called formal radio etiquettes. This approach could expand the bandwidth available for conventional uses (e.g., police, fire and rescue) and extend the spatial coverage of 3G in a novel way. Cognitive radio is a particular extension of software radio that employs model-based reasoning about users, multimedia content, and communications context. This paper characterizes the potential contributions of cognitive radio to spectrum pooling and outlines an initial framework for formal radio-etiquette protocols.

Providing quality of service over a shared wireless link

Abstract: We propose an efficient way to support quality of service of multiple real-time data users sharing a wireless channel. We show how scheduling algorithms exploiting asynchronous variations of channel quality can be used to maximize the channel capacity (i.e., maximize the number of users that can be supported with the desired QoS).

Physical layer driven protocol and algorithm design for energy-efficient wireless sensor networks

Abstract: The potential for collaborative, robust networks of microsensors has attracted a great deal of research attention. For the most part, this is due to the compelling applications that will be enabled once wireless microsensor networks are in place; location-sensing, environmental sensing, medical monitoring and similar applications are all gaining interest. However, wireless microsensor networks pose numerous design challenges. For applications requiring long-term, robust sensing, such as military reconnaissance, one important challenge is to design sensor networks that have long system lifetimes. This challenge is especially difficult due to the energy-constrained nature of the devices. In order to design networks that have extremely long lifetimes, we propose a physical layer driven approach to designing protocols and algorithms. We first present a hardware model for our wireless sensor node and then introduce the design of physical layer aware protocols, algorithms, and applications that minimize energy consumption of the system. Our approach prescribes methods that can be used at all levels of the hierarchy to take advantage of the underlying hardware. We also show how to reduce energy consumption of non-ideal hardware through physical layer aware algorithms and protocols.

Distributed topology control for power efficient operation in multihop wireless ad hoc networks

Abstract: The topology of wireless multihop ad hoc networks can be controlled by varying the transmission power of each node. We propose a simple distributed algorithm where each node makes local decisions about its transmission power and these local decisions collectively guarantee global connectivity. Specifically, based on the directional information, a node grows it transmission power until it finds a neighbor node in every direction. The resulting network topology increases the network lifetime by reducing the transmission power and reduces traffic interference by having low node degrees. Moreover, we show that the routes in the multihop network are efficient in power consumption. We give an approximation scheme in which the power consumption of each route can be made arbitrarily close to the optimal by carefully choosing the parameters. Simulation results demonstrate significant performance improvements.

Spread Spectrum Communications Handbook

Abstract: This reference deals with spread spectrum systems, which are beginning to find new applications such as CDMA cellular networks and wireless personal communications networks. Theory is covered where appropriate although the focus is on practical issues, including an in-depth look at multiple access communications and positioning systems applications.

Handbook of Antennas in Wireless Communications

Abstract: From the Publisher: The move toward worldwide wireless communications continues at a remarkable pace, and the antenna element of the technology is crucial to its success. With contributions from more than 30 international experts, the Handbook of Antennas in Wireless Communications brings together all of the latest research and results to provide engineering professionals and students with a one-stop reference on the theory, technologies, and applications for indoor, hand-held, mobile, and satellite systems.Beginning with an introduction to wireless communications systems, it offers an in-depth treatment of propagation prediction and fading channels. It then explores antenna technology with discussion of antenna design methods and the various antennas in current use or development for base stations, hand held devices, satellite communications, and shaping beams. The discussions then move to smart antennas and phased array technology, including details on array theory and beamforming techniques. Space diversity, direction-of-arrival estimation, source tracking, and blind source separation methods are addressed, as are the implementation of smart antennas and the results of field trials of systems using smart antennas implemented. Finally, the hot media topic of the safety of mobile phones receives due attention, including details of how the human body interacts with the electromagnetic fields of these devices.Its logical development and extensive range of diagrams, figures, and photographs make this handbook easy to follow and provide a clear understanding of design techniques and the performance of finished products. Its unique, comprehensive coverage written by top experts in their fields promises tomake the Handbook of Antennas in Wireless Communications the standard reference for the field.

System and method for measuring wireless device and network usage and performance metrics

Abstract: Systems and methods for measuring wireless device and wireless network usage and performance metrics are set forth. The system includes at least one wireless device, and data gathering software installed on the wireless device for collecting device parametric data, network parametric data, event data. A control center may receive, store and process said device parametric data, network parametric data, and event data.

An analysis of the optimum node density for ad hoc mobile networks

Abstract: An ad hoc mobile network is a collection of nodes, each of which communicates over wireless channels and is capable of movement. Wireless nodes have the unique capability of transmission at different power levels. As the transmission power is varied, a tradeoff exists between the number of hops from source to destination and the overall bandwidth available to individual nodes. Because both battery life and channel bandwidth are limited resources in mobile networks, it is important to ascertain the effects different transmission powers have on the overall performance of the network. This paper explores the nature of this transmission power tradeoff in mobile networks to determine the optimum node density for delivering the maximum number of data packets. It is shown that there does not exist a global optimum density, but rather that, to achieve this maximum, the node density should increase as the rate of node movement increases.

An efficient protocol for realizing cooperative diversity in wireless networks

Abstract: We develop two variants of an energy-efficient cooperative diversity protocol that combats fading induced by multipath propagation in wireless networks, The underlying techniques build upon the classical relay channel and related work and exploit space diversity available at distributed antennas through coordinated transmission and processing by cooperating radios. While applicable to any wireless setting, these protocols are particularly attractive in ad-hoc or peer-to-peer wireless networks, in which radios are typically constrained to employ a single antenna. Substantial energy-savings resulting from these protocols can lead to reduced battery drain, longer network lifetime, and improved network performance in terms of, e.g., capacity.

A power controlled multiple access protocol for wireless packet networks

Abstract: Multiple access-based collision avoidance MAC protocols have typically used fixed transmission power, and have not considered power control mechanisms based on the distance of the transmitter and receiver in order to improve spatial channel reuse. This work proposes PCMA, a power controlled multiple access wireless MAC protocol within the collision avoidance framework. PCMA generalizes the transmit-or-defer "on/off" collision avoidance model of current protocols to a more flexible "variable bounded power" collision suppression model. The algorithm is provisioned for ad hoc networks and does not require the presence of base stations to manage transmission power (i.e. it is decentralized). The advantage of implementing a power controlled protocol in an ad-hoc network is that source-destination pairs can be more tightly packed into the network allowing a greater number of simultaneous transmissions (spectral reuse). Our initial simulation results show that the PCMA can improve the throughput performance of the non-power controlled IEEE 802.11 by a factor of 2 with potential for additional scalability as source-destination pairs become more localized, thus providing a compelling reason for migrating to a new power controlled multiple access wireless MAC protocol standard.

Wireless system protocol for telemetry monitoring

Abstract: A wireless, programmable system for medical monitoring includes a base unit (18) and a plurality of individual wireless, remotely programmable biosensor transceivers (20). The base unit (18) manages the transceivers (20) by issuing registration, configuration, data acquisition, and transmission commands using wireless techniques. Physiologic data from the wireless transceivers (20) are demultiplexed and supplied via a standard interface to a conventional monitor (914) for display. Initialization, configuration, registration, and management routines for the wireless transceivers and the base unit are also described.

Automatic and seamless vertical roaming between wireless local area network (WLAN) and wireless wide area network (WWAN) while maintaining an active voice or streaming data connection: systems, methods and program products

Abstract: A Mobile Station (MS) is able to vertically roam in either direction between two different networks, i.e., WWAN and WLAN. The MS is equipped with a dual mode Radio for WWAN and WLAN transmissions. The WLAN Radio is linked to a WLAN Enterprise Gateway Controller (EGC) via a first air link and the WWAN Radio is linked to a WWAN Base Transceiver Station (BTS) via a second air link. An outgoing VoIP call from the WLAN Radio to a remote party on the WWAN will transition or seamlessly switch over to a WWAN connection when the MS detects packet error rates, frequent scale back or consistent signal degradation.

Method and apparatus for optimization of wireless multipoint electromagnetic communication networks

Abstract: Exploiting the substantive reciprocity of internode channel responses through dynamic, adaptive modification of receive and transmit weights, enables locally enabled global optimization of a multipoint, wireless electromagnetic communications network of communication nodes. Each diversity-channel-capable node uses computationally efficient exploitation of pilot tone data and diversity-adaptive signal processing of the weightings and the signal to further convey optimization and channel information which promote local and thereby network-global efficiency. The preferred embodiment performs complex digital signal manipulation that includes a linear combining and linear distribution of the transmit and receive weights, the generation of piloting signals containing origination and destination node information, as well as interference-avoiding pseudorandom delay timing, and both symbol and multitione encoding, to gain the benefit of substantive orthogonality at the physical level without requiring actual substantive orthogonality at the physical level.

Research challenges in wireless networks of biomedical sensors

Abstract: Implanted biomedical devices have the potential to revolutionize medicine. Smart sensors, which are created by combining sensing materials with integrated circuitry, are being considered for several biomedical applications such as a glucose level monitor or a retina prosthesis. These devices require the capability to communicate with an external computer system (base station) via a wireless interface. The limited power and computational capabilities of smart sensor based biological implants present research challenges in several aspects of wireless networking due to the need for having a bio-compatible, fault-tolerant, energy-efficient, and scalable design. Further, em bedding thesesensors in humans add additional requirements. For example, the wireless networking solutions should be ultra-safe and reliable, work trouble-free in different geographical locations (although implants are typically not expected to move; they shouldn't restrict the movements of their human host), and require minimal maintenance. This necessitates application-specific solutions which are vastly different from traditional solutions.In this paper, we describe the potential of biomedical smart sensors. We then explain the challenges for wireless networking of human-embedded smart sensor arrays and our preliminary approach for wireless networking of a retina prosthesis. Our aim is to motivate vigorous research in this area by illustrating the need for more application-specific and novel approaches toward developing wireless networking solutions for human-implanted smart sensors.

Method and system for wireless voice channel/data channel integration

Abstract: A system and method for wireless communication is disclosed. In one embodiment of a method, a user of a wireless device initiates a communication session during which a wireless data session can be triggered from a voice session and a voice session can be triggered from a wireless data session. During the communication session, data is shared between the wireless data channel and the voice channel.

Tripling the capacity of wireless communications using electromagnetic polarization

Abstract: Wireless communications are a fundamental part of modern information infrastructure. But wireless bandwidth is costly, prompting a close examination of the data channels available using electromagnetic waves. Classically, radio communications have relied on one channel per frequency, although it is well understood that the two polarization states of planar waves allow two distinct information channels; techniques such as 'polarization diversity' already take advantage of this. Recent work has shown that environments with scattering, such as urban areas or indoors, also possess independent spatial channels that can be used to enhance capacity greatly. In either case, the relevant signal processing techniques come under the heading of 'multiple-input/multiple-output' communications, because multiple antennae are required to access the polarization or spatial channels. Here we show that, in a scattering environment, an extra factor of three in channel capacity can be obtained, relative to the conventional limit using dual-polarized radio signals. The extra capacity arises because there are six distinguishable electric and magnetic states of polarization at a given point, rather than two as is usually assumed.

Wireless communication networks for providing remote monitoring of devices

Abstract: Wireless communication networks for monitoring and controlling a plurality of remote devices are provided. Briefly, one embodiment of a wireless communication network may comprise a plurality of wireless transceivers having unique identifiers. Each of the plurality of wireless transceivers may be configured to receive a sensor data signal from one of the plurality of remote devices and transmit an orginal data message using a predefined wireless communication protocol. The original data message may comprise the corresponding unique identifier and sensor data signal. Each of the plurality of wireless transceivers may be configured to receive the original data message transmitted by one of the other wireless transceivers and transmit a repeated data message using the predefined communication protocol. The repeated data message may include the sensor data signal and the corresponding unique identifier. Furthermore, at least one of the plurality of wireless transceivers may be further configured to provide the original data messages and the repeated data messages to a site controller connected to a wide area network. The site controller may be configured to manage communications between the wireless communication network and a host computer connected to the wide area network.

Locating a mobile station using a plurality of wireless networks and applications therefor

Abstract: A location is disclosed for wireless telecommunication infrastructures. The systems output requested locations of hand sets or mobile stations (MS) based on, e.g., AMPS, NAMPS, CDMA or TDMA communication standards. The system determines both local MS locations, and more global MS location requests via, e.g., Internet communication. The system uses a plurality of mobile station locating technologies, including those based on, e.g., (1) two-way TOA and TDOA; (2) home base stations and (3) distributed antenna provisioning. The system is useful for 911 emergency calls, tracking, routing, people and animal location including applications for confinement to and exclusion from certain areas. The system is particularly useful for estimating a location of an MS using information received from a commercial mobile radio service provider (CMRS) for which the MS is not registered for subscriber services.

Wireless Communications and Networks

Abstract: From the Publisher: This is the first guide to wireless technology with the pedagogical breadth, depth, and discipline needed to help both professionals and students master the entire field. Legendary networking author William Stallings presents thorough, up-to-date introductions to every key aspect of wireless communications and networking: technology, architecture, types of wireless networks, design approaches, applications, standards, and more.Stallings begins with the fundamentals of data transmission: signals, channels, analog and digital data transmission, and multiplexing, circuit-switched and packet-switched networks, and the role of protocols such as TCP/IP. With these basics understood, he moves on to the unique components and technologies of wireless networks. The book includes detailed chapters on antennas and propagation; signal encoding techniques; spread spectrum; coding; and error control. Stallings offers in-depth coverage of satellite-based wireless networks; analog, TDMA, CDMA, and 3G cellular; cordless systems; Wireless Local Loop; Mobile IP; and WAP. The book also contains a full section of wireless LANs, including in-depth coverage of IEEE 802.11 and Bluetooth standards. William Stallings' accompanying Web site includes extensive bonus resources, including PDF transparency masters, PowerPoint slides, and book updates.For all students and professionals in the fields of information technology, networking, and data communications — including current and future network designers, implementers, administrators, managers, and customers.

An overview of the Bluetooth wireless technology

Abstract: The Bluetooth/sup TM/ wireless technology is designed as a short-range connectivity solution for personal, portable, and handheld electronic devices. Since May 1998 the Bluetooth SIG has steered the development of the technology through the development of an open industry specification, including both protocols and application scenarios, and a qualification program designed to assure end-user value for Bluetooth products. This article highlights the Bluetooth wireless technology.

y do tngrs luv 2 txt msg

Abstract: "Text messaging"--using a mobile phone to send a message--has changed how teenagers use wireless phones to communicate and coordinate. While the media reports rapid growth in text messaging, less is known about why teenagers have adopted it. In this paper, we report findings from a study of teenagers' text messaging practices. Specifically, we show that teenagers use text messages to: arrange and adjust times to talk, coordinate with friends and family, and chat. Moreover, we argue that the reasons teenagers find text messaging quick, cheap, and easy to use, are grounded in their social context. Finally, we show that teenagers encounter three problems when text messaging understanding evolving language, determining intent from content, and addressing messages.

Low-power wireless sensor networks

Abstract: Wireless distributed microsensor systems will enable fault tolerant monitoring and control of a variety of applications. Due to the large number of microsensor nodes that may be deployed and the need for long system lifetimes, replacing the battery is not an option. Sensor systems must utilize the minimal possible energy while operating over a wide range of operating scenarios. This paper presents an overview of the key technologies required for low-energy distributed microsensors. These include power aware computation/communication component technology, low-energy signaling and networking, system partitioning based on computation and communication tradeoffs, and a power aware software infrastructure.

Location and Time Sensitive Wireless Calendaring

Abstract: A computer-implemented method provides location-sensitive and time-sensitive calendaring to a wireless device, such as a cell phone, pager, PDA, etc. A user's calendar is maintained with a number of appointments, start times and end times for the appointments, meeting place and a list of attendees for the appointments. When the present time reading is within a predetermined minimum of a meeting start time of an appointment of a calendar user, the location of the user is determined based on the location of the wireless device. The location of the meeting place is also determined. Using historical data (of the user or others), the estimated time of arrival of the user at the meeting place is determined. If the estimated time of arrival is after the meeting start time, then a late message may be sent to the user and/or to the other meeting attendees.

Adaptive approaches to relieving broadcast storms in a wireless multihop mobile ad hoc network

Abstract: In a multihop mobile ad hoc network, broadcasting is an elementary operation to support many applications. In (Ni et al., 1999), it is shown that naively broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which we refer to as the broadcast storm problem. Several threshold-based schemes are shown to perform better than flooding in (Ni et al., 1999). However, how to choose thresholds also poses a dilemma between reachability and efficiency under different host densities. We propose several adaptive schemes, which can dynamically adjust thresholds based on local connectivity information. Simulation results show that these adaptive schemes can offer better reachability as well as efficiency as compared to the results in (Ni et al., 1999).

Distributed topology construction of Bluetooth personal area networks

Abstract: Wireless ad hoc networks have been a growing area of research. While there has been considerable research on the topic of routing in such networks, the topic of topology creation has not received due attention. This is because almost all ad hoc networks to date have been built on top of a single channel, broadcast based wireless media, such as 802.11 or IR LANs. For such networks the distance relationship between the nodes implicitly (and uniquely) determines the topology of the ad hoc network. Bluetooth is a promising new wireless technology, which enables portable devices to form short-range wireless ad hoc networks and is based on a frequency hopping physical layer. This fact implies that hosts are not able to communicate unless they have previously discovered each other by synchronizing their frequency hopping patterns. Thus, even if all nodes are within direct communication range of each other, only those nodes which are synchronized with the transmitter can hear the transmission. To support any-to-any communication, nodes must be synchronized so that the pairs of nodes (which can communicate with each other) together form a connected graph. Using Bluetooth as an example, this paper first provides deeper insights into the issue to link establishment in frequency hopping wireless systems. It then introduces the Bluetooth topology construction protocol (BTCP), an asynchronous distributed protocol for constructing scatternets which starts with nodes that have no knowledge of their surroundings and terminates with the formation of a connected network satisfying all connectivity constraints posed by the Bluetooth technology. To the best of our knowledge, the work presented in this paper is the first attempt at building Bluetooth scatternets using distributed logic and is quite "practical" in the sense that it can be implemented using the communication primitives offered by the Bluetooth 1.0 specifications.

Toward self-organized mobile ad hoc networks: the terminodes project

Abstract: This article provides a technical overview of mobile ad hoc networks and describes their long-term potential. It covers current research, and describes major technical challenges, including networking, real-time services, and software. It shows that by their very nature, mobile ad hoc networks can bring a paradigm shift in the way networks are organized and operated, and can even lead to a fundamental change in the relationships between information technology and societal organization. As an illustration of these concepts, the article also contains an overall description of our long-term research project, called terminodes.

Quality of service

Abstract: The application relates to quality of service. In particular, the application relates to enabling user-controlled alteration of the quality of service in a wireless communication between a subscriber device and a communication system.

Patient medication iv delivery pump with wireless communication to a hospital information management system

Abstract: A wireless communication system (9) from an IV medication infusion pump to a hospital information management system (HIMS) is disclosed. The system includes an IV pump (10) having pump operation circuitry (41) for monitoring preselected characteristics of pump operation indicative of IV administration of medication to a patient. A transmitter (45) is connected to the pump operation circuitry (41) for transmitting a wireless pump signal representing the preselected pump operation characteristics. The wireless pump transmitter (45) communicates with a hospital information management system (HIMS) (60). The HIMS (60) includes a receiver (61) capable of receiving the pump signal representing the pump operation characteristics and also includes a computer (57) capable of storing and displaying the pump operation characteristics represented by the received wireless pump signal.

Supporting service differentiation in wireless packet networks using distributed control

Abstract: This paper investigates differentiated services in wireless packet networks using a fully distributed approach that supports service differentiation, radio monitoring, and admission control. While our proposal is generally applicable to distributed wireless access schemes, we design, implement, and evaluate our framework within the context of existing wireless technology. Service differentiation is based on the IEEE 802.11 distributed coordination function (DCF) originally designed to support best-effort data services. We analyze the delay experienced by a mobile host implementing the IEEE 802.11 DCF and derive a closed-form formula. We then extend the DCF to provide service differentiation for delay-sensitive and best-effort traffic based on the results from the analysis. Two distributed estimation algorithms are proposed. These algorithms are evaluated using simulation, analysis, and experimentation. A virtual MAC (VMAC) algorithm passively monitors the radio channel and estimates locally achievable service levels. The VMAC estimates key MAC level statistics related to service quality such as delay, delay variation, packet collision, and packet loss. We show the efficiency of the VMAC algorithm through simulation and consider significantly overlapping cells and highly bursty traffic mixes. In addition, we implement and evaluate the VMAC in an experimental differentiated services wireless testbed. A virtual source (VS) algorithm utilizes the VMAC to estimate application-level service quality. The VS allows application parameters to be tuned in response to dynamic channel conditions based on "virtual delay curves." We demonstrate through simulation that when these distributed victual algorithms are applied to the admission control of the radio channel then a globally stable state can be maintained without the need for complex centralized radio resource management.