Showing papers on "Wireless published in 1996"

Principles of mobile communication

Abstract: Principles of Mobile Communication, Third Edition, is an authoritative treatment of the fundamentals of mobile communications. This book stresses the "fundamentals" of physical-layer wireless and mobile communications engineering that are important for the design of "any" wireless system. This book differs from others in the field by stressing mathematical modeling and analysis. It includes many detailed derivations from first principles, extensive literature references, and provides a level of depth that is necessary for graduate students wishing to pursue research on this topic. The book's focus will benefit students taking formal instruction and practicing engineers who are likely to already have familiarity with the standards and are seeking to increase their knowledge of this important subject. Major changes from the second edition: 1. Updated discussion of wireless standards (Chapter 1). 2. Updated treatment of land mobile radio propagation to include space-time correlation functions, mobile-to-mobile (or vehicle-to-vehicle) channels, multiple-input multiple-output (MIMO) channels, improved simulation models for land mobile radio channels, and 3G cellular simulation models. 3. Updated treatment of modulation techniques and power spectrum to include Nyquist pulse shaping and linearized Gaussian minimum shift keying (LGMSK). 4. Updated treatment of antenna diversity techniques to include optimum combining, non-coherent square-law combining, and classical beamforming. 5. Updated treatment of error control coding to include space-time block codes, the BCJR algorithm, bit interleaved coded modulation, and space-time trellis codes. 6. Updated treatment of spread spectrum to include code division multiple access (CDMA) multi-user detection techniques. 7. A completely new chapter on multi-carrier techniques to include the performance of orthogonal frequency division multiplexing (OFDM) on intersymbol interference (ISI) channels, OFDM residual ISI cancellation, single-carrier frequency domain equalization (SC-FDE), orthogonal frequency division multiple access (OFDMA) and single-carrier frequency division multiple access (SC-FDMA). 8. Updated discussion of frequency planning to include OFDMA frequency planning. 9. Updated treatment of CDMA cellular systems to include hierarchical CDMA cellular architectures and capacity analysis. 10. Updated treatment of radio resource management to include CDMA soft handoff analysis. Includes numerous homework problems throughout.

Pfinder: real-time tracking of the human body

Abstract: Pfinder is a real-time system for tracking and interpretation of people. It runs on a standard SGI Indy computer, and has performed reliably on thousands of people in many different physical locations. The system uses a multi-class statistical model of color and shape to obtain a 2-D representation of head and hands in a wide range of viewing conditions. These representations are useful for applications such as wireless interfaces, video databases, and low-bandwidth coding, without cumbersome wires or attached sensors.

Multi-user detection for DS-CDMA communications

Abstract: Direct-sequence code-division multiple access (DS-CDMA) is a popular wireless technology. In DS-CDMA communications, all of the users' signals overlap in time and frequency and cause mutual interference. The conventional DS-CDMA detector follows a single-user detection strategy in which each user is detected separately without regard for the other users. A better strategy is multi-user detection, where information about multiple users is used to improve detection of each individual user. This article describes a number of important multiuser DS-CDMA detectors that have been proposed.

Mobile Computing

Abstract: From the Publisher: The rapid development of wireless digital communication technology has created capabilities that software systems are only beginning to exploit. The falling cost of both communication and of mobile computing devices (laptop computers, hand-held computers, etc.) is making wireless computing affordable not only to business users but also to consumers. Mobile computing is not a "scaled-down" version of the established and well-studied field of distributed computing. The nature of wireless communication media and the mobility of computers combine to create fundamentally new problems in networking, operating systems, and information systems. Furthermore, many of the applications envisioned for mobile computing place novel demands on software systems. Although mobile computing is still in its infancy, some basic concepts have been identified and several seminal experimental systems developed. Mobile Computing contains chapters that describe these concepts and systems, and the book describes applications that are currently being deployed and tested. Mobile Computing serves as a valuable reference book and may also be used as a text for a course on the subject.

Method and apparatus for electronically accessing and distributing personal health care information and services in hospitals and homes

Abstract: This new and unique method and apparatus is used for the distribution and administration of medical services, entertainment services, electronic medical records, educational information, etc. to a patient's individual electronic patient care station (PCS) interconnected to a master library (ML) which stores data in digital compressed format, through a local medical information network. The patient/medical personnel interact with this medical information network through the unique PCS and receives the requested service or data from the master library. The data is then displayed either on the associated television set or video monitor or through wireless/IR communications to a peripheral personal data assistant (pen based computer technology) The data for text, audio, and video information is all compressed digitally to facilitate distribution and only decompressed at the final stage before viewing/interaction.

Position location using wireless communications on highways of the future

Abstract: With the advances in wireless communications and low-power electronics, accurate position location may now be accomplished by a number of techniques which involve commercial wireless services. Emerging position location systems, when used in conjunction with mobile communications services, will lead to enhanced public safety and revolutionary products and services. The fundamental technical challenges and business motivations behind wireless position location systems are described, and promising techniques for solving the practical position location problem are treated.

Digital beamforming in wireless communications

Abstract: From the Publisher: Explosive growth of wireless communications is demanding increased system capacity for mobile communications satellites - and the expert authors of this first-of-a-kind book explore a promising, cost-effective solution: digital beamforming (DBF) technology. In definitive detail, the authors explain why increasing the bandwidth of existing channels or allocating new frequency bands may not be feasible and why frequency reuse is becoming the most practical means for increasing system capacity. First they review the principles of DBF technology. Then they discuss beamforming techniques and results, state-of-the-art supportive technologies, and promising applications for wireless communications - complete with 165 figures, 300 equations, plus techniques and findings of researchers in related fields. This book is an excellent tutorial or reference for understanding, designing, developing, and applying DBF systems in wireless communications. Communications engineers, technicians, managers, researchers, and graduate students alike will find solutions to four key problems: • Improving a wireless communications system's immunity to multipath fading • Reducing co-channel interference in a wireless communications system • Increasing system capacity of a wireless communications system • Achieving greater antenna array calibration accuracy

Hearing aid with wireless remote processor

Abstract: A hearing aid or audio communication system includes an earpiece (10) that can be hidden in the ear canal, and which communicates wirelessly with a remote processor unit, or RPU (16), that enhances audio signals and can be concealed under clothing. Sounds from the environnment are picked up by a microphone (12) in the earpiece and sent with other information over a two-way wireless link (17) to the RPU (16). The wireless link (17) uses microwaves for component miniaturization. Furthermore, use of radar technology to implement the wireless link (17), with an RPU (16) interrogator and earpiece (10) transponder, reduces earpiece size and power, as no microwave oscillator is needed in the earpiece (10). Optional secondary wireless link circuitry (19) can be used between the RPU (16) and a cellular telephone system or other sources of information. Electronic voice recognition and response can control system operation.

Performance evaluation and enhancement of the CSMA/CA MAC protocol for 802.11 wireless LANs

Abstract: The IEEE 802.11 protocol for wireless local area networks adopts a CSMA/CA protocol with exponential backoff as medium access control technique. As the throughput performance of such a scheme becomes critical when the number of mobile stations increases, in this paper we propose an adaptive contention window mechanism, which dynamically selects the optimal backoff window according to the estimate of the number of contending stations. We show that this technique leads to stable behavior, and it outperforms the standard protocol when the network load and the number of mobile stations are high. We also investigate the CSMA/CA with the optional RTS/CTS technique, and we show that our adaptive technique reaches better performance only when the packet size is short. Finally, the performance of a system environment with hidden terminals show that the RTS/CTS mechanism, which can also be used in conjunction with the adaptive contention window mechanism, provides significant improvements.

System and method for providing protocol translation and filtering to access the world wide web from wireless or low-bandwidth networks

Abstract: An interface between a protected computer or computer network and the World Wide Web (WWW). The interface comprises a split proxy system that encapsulates TCP/IP transmissions into a script transmission, which is not subject to problems in high latency systems, thereby greatly improving WWW access, via a wireless modem or other low-bandwidth communications network. The split proxy interface also provides compression, encryption and filtering capabilities and allows receipt of unsolicited transmissions from the service provider for such purposes as automatically updating or configuring WWW access software.

Movement-based location update and selective paging for PCS networks

Abstract: This paper introduces a mobility tracking mechanism that combines a movement-based location update policy with a selective paging scheme. Movement-based location update is selected for its simplicity. It does not require each mobile terminal to store information about the arrangement and the distance relationship of all cells. In fact, each mobile terminal only keeps a counter of the number of cells visited. A location update is performed when this counter exceeds a predefined threshold value. This scheme allows the dynamic selection of the movement threshold on a per-user basis. This is desirable as different users may have very different mobility patterns. Selective paging reduces the cost for locating a mobile terminal in the expense of an increase in the paging delay. We propose a selective paging scheme which significantly decreases the location tracking cost under a small increase in the allowable paging delay. We introduce an analytical model for the proposed location tracking mechanism which captures the mobility and the incoming call arrival patterns of each mobile terminal. Analytical results are provided to demonstrate the cost-effectiveness of the proposed scheme under various parameters.

Wireless transaction and information system

Abstract: A financial information and transaction system utilizes wireless communication in connection with portable terminals. In this system, a terminal is connected to the financial institution via a wireless or cellular telephone hook-up. Smart cards are utilized to verify authorization for transactions, thereby minimizing potential security problems which could otherwise result from use of a mobile terminal. Alternately, a smart card is advantageously utilized not only for authorization, but also to maintain a secure record of available funds. The system not only provides the functionality of an ATM network, but also provides non-financial services, thereby forming an integrated system.

Wireless communications application specific enabling method and apparatus

Abstract: A method and apparatus for wireless communication on an existing wireless communication network comprising taking existing data and manipulating the data to create manipulated data. The manipulated data is then translated into an application specific message. The application specific message is applied to control and communicate with an application specific apparatus, whereby wireless communication on the existing wireless communication network is provided without causing any disruption, system overloading, or limitation on normal system communication activity.

Enhancing throughput over wireless LANs using channel state dependent packet scheduling

Abstract: Unlike wired networks, packets transmitted on wireless channels are often subject to burst errors which cause back to back packet losses. Most wireless LAN link layer protocols recover from packet losses by retransmitting lost segments. When the wireless channel is in a burst error state, most retransmission attempts fail thereby causing poor utilization of the wireless channel. Furthermore, in the event of multiple sessions sharing a wireless link, FIFO packet scheduling can cause the HOL blocking effect, resulting in unfair sharing of the bandwidth. This observation leads to a new class of packet dispatching methods which explicitly take the wireless channel characteristics into consideration in making packet dispatching decisions. We compare a variety of channel state dependent packet (CSDP) scheduling methods with a view towards enhancing the performance of the transport layer sessions. Our results indicate that by employing a CSDP scheduler at the wireless LAN device driver level, significant improvement in the channel utilization can be achieved in typical wireless LAN configurations.

Mobile Wireless Communications

Abstract: Wireless communication has become a ubiquitous part of modern life, from global cellular telephone systems to local and even personal-area networks. This 2004 book provides a tutorial introduction to digital mobile wireless networks, illustrating theoretical underpinnings with a wide range of real-world examples. The book begins with a review of propagation phenomena, and goes on to examine channel allocation, modulation techniques, multiple access schemes, and coding techniques. GSM and IS-95 systems are reviewed and 2.5G and 3G packet-switched systems are discussed in detail. Performance analysis and accessing and scheduling techniques are covered, and the book closes with a chapter on wireless LANs and personal-area networks. Many worked examples and homework exercises are provided and a solutions manual is available for instructors. The book is an ideal text for electrical engineering and computer science students taking courses in wireless communications. It will also be an invaluable reference for practising engineers.

Wireless remote telemetry system

Abstract: A wireless remote telemetry system which uses low-cost remote communication devices operating on existing wireless communication systems in order to provide real-time reading and control of remote devices. In an embodiment applicable to utility service, consumption of electrical power among a population of customers is measured by a utility metering system having a wireless communication capability. The metering system comprises a remote metering unit which communicates with a central controller over existing wireless communication systems, such as cellular base stations, using existing communication standards. The remote metering unit transmits various messages over a shared random access channel to a central controller. The central controller transmits messages to the remote metering unit over a paging channel. The remote metering unit may operate in a half-duplex mode only. Furthermore, the remote metering unit may provide a gateway to advanced consumer services at the remote location.

CDMA for wireless personal communications

Abstract: From the Publisher: Code Division Multiple Access (CDMA) is a hot topic. Until now, it has only been used in satellite and military systems, but engineers are starting to recognize certain advantages it has over FDMA and TDMA for use in cellular radio. This book provides the first comprehensive analysis of the theory and practical applications of CDMA. Authored by a recognized expert in the field, it fills a gap in current literature by explaining the use of CDMA in different environments, presenting CDMA as a multiple access protocol for wireless indoor, outdoor, and land mobile satellite communication systems. This is cutting-edge information for all those involved in the future of wireless personal communications. It enables engineers, researchers and students to: ? Compare wired (cable) and wireless network systems ? Understand multiple access protocols ? Learn hybrid CDMA ? Apply CDMA to various mobile systems ? Investigate multiple access schemes for future wireless communication systems You'll gain a complete overview of CDMA, as well as useful solutions to the general problems of wireless communications as they relate to CDMA protocol, and recommended techniques to enhance the performance of a CDMA-based wireless personal communication system. Because the author recognizes that CDMA will have to be implemented in phases, he also addresses the practicalities of the coexistence of CDMA and TDMA. Complete with 180 illustrations, 400 equations, practical examples, and appendices.

Wireless packet data distributed communications system

Abstract: A two-way satellite communications system includes an Earth station communicating with a plurality of remote terminals using a network access protocol that facilitates low power consumption by the terminals. The Earth station generates forward link TDM packet data transmissions on one or more satellite channels, and detects, despreads and decodes multiple concurrent return link slotted CDMA packet transmissions on one or more satellite channels. It communicates through a wired connection with a packet processing center which ultimately both delivers return link packet data to end-customers and receives forward link packet data from end-customers. The remote terminals receive, process and act upon forward link TDM transmissions on one or more satellite channels, and generate slotted spread spectrum CDMA transmissions on the return link on one or more satellite channels. The remote terminals communicate with a local digital data source and/or sink, digitize one or more local analog sensor signals, enter into a sleep mode to minimize the terminal's power consumption, and access the satellite communications network in accordance with the system network access protocol.

Concentrated subscriber wireless remote telemetry system

Abstract: A concentrated subscriber wireless remote telemetry system which uses low-cost remote communication devices operating on existing wireless communication systems in order to provide real-time reading and control of remote devices. The metering system comprises at least one powerline remote metering device which collects and forwards telemetry data to an associated wireless remote telemetry device. The wireless remote telemetry device relays the telemetry data to a central controller over existing wireless communication systems, such as cellular base stations, using existing communication standards. The wireless remote metering device transmits various messages over a shared random access channel to the central controller. The central controller transmits messages to the wireless remote metering unit over a paging channel. The wireless remote metering unit may operate in a half-duplex mode only. Furthermore, the wireless remote metering unit may provide a gateway to advanced consumer services at the remote location.

Spread spectrum transceiver module utilizing multiple mode transmission

Abstract: A data transceiver module for digital data communications in a portable hand-held data terminal has multiple data spread spectrum modes which include direct sequence and frequency function modulation algorithms. The transceiver module has multiple user or program configurable data rates, modulation, channelization and process gain in order to maximize the performance of radio data transmissions and to maximize interference immunity. Various module housings, which may be PCMCIA type, are able to be mated with a suitably designed data terminal. Media access control protocols and interfaces of multiple nominal operational frequencies are utilized. Wireless access devices in a cell based network each consider a variety of factors when choosing one of a plurality of modes of wireless operation and associated operating parameters. Such selection defines a communication channel to support wireless data, message and communication exchanges. In further embodiments, the wireless access devices also support a second channel, a busy/control channel, for managing communication on the main communication channel and to overcome roaming and hidden terminal problems. Roaming terminal devices are also configured to support the dual channel design. Such configuration in both circumstances may involve the use of a multimode radio that is timeshared between the two channels or two radios, one dedicated to each channel.

Measurement and analysis of the error characteristics of an in-building wireless network

Abstract: There is general belief that networks based on wireless technologies have much higher error rates than those based on more traditional technologies such as optical fiber, coaxial cable, or twisted pair wiring. This difference has motivated research on new protocol suites specifically for wireless networks. While the error characteristics of wired networks have been well documented, less experimental data is available for wireless LANs.In this paper we report the results of a study characterizing the error environment provided by AT&T WaveLAN, a commercial product designed for constructing 2 Mb/s in-building wireless networks. We evaluated the effects of interfering radiation sources, and of attenuation due to distance and obstacles, on the packet loss rate and bit error rate. We found that under many conditions the error rate of this physical layer is comparable to that of wired links. We analyze the implications of our results on today's CSMA/CA based wireless LANs and on future pico-cellular shared-medium reservation-based wireless networks.

Wireless telecommunications system utilizing CDMA radio frequency signal modulation in conjunction with the GSM A-interface telecommunications network protocol

Abstract: A method and apparatus for operating a wireless telecommunication system utilizing code division multiple access (CDMA) over-the-air with a Global System for Mobile (GSM) communications A-interface based network is described. A CDMA radio frequency (RF) signal interface provides a bi-directional interface to a subscriber unit (50), and a Global System for Mobile (GSM) communications A-interface SS7 transport provides a bi-directional interface with GSM mobile services switching center (MSC) (52). Additionally, a transparent message transport (44) is provided over which signaling messages defined in the GSM A-interface protocol are exchanged between the GSM MSC (52) and a subscriber unit (50).

Spatio-temporal coding for wireless communications

Abstract: A compact model is derived for the multiple-input multiple output (MIMO), dispersive, spatially selective wireless communication channel. The multivariate information capacity behavior is then analyzed for various input and output antenna configurations. For high SNR conditions, the MIMO channel can exhibit a capacity slope in bits per dB of power increase that is proportional to the minimum of the number multipath components, the number of input antennas, or the number of output antennas. The discrete matrix multitone (DMMT) is proposed as an asymptotically optimal, practical spatio-temporal coding structure. Experimental examples that support the theoretical results are presented.

A trace-based approach for modeling wireless channel behavior

Abstract: The loss behavior of wireless networks has become the focus of many recent research efforts. Although it is generally agreed that wireless communications experience higher error rates than wireline, the nature of these lossy links is not fully understood. This paper describes an effort to characterize the loss behavior of the AT&T WaveLAN, a popular in-building wireless interface. Using a trace-based approach, packet loss information is recorded, analyzed, and validated. Our results indicate that WaveLAN experiences an average packet error rate of 2 to 3 percent. Further analysis reveals that these errors are not independent, making it hard to model them with a simple two-state Markov chain. We derive another model based on the distributions of the error and error-free length of the packet streams. For validation, we modulate both the error models and the traces in a simulator. Trace-driven simulations yield an average TCP throughput of about 5 percent less than simulations using our best error model.

adaptive mobile multimedia networks

Abstract: The authors consider a networking environment in which the users are mobile, the topology changes, code division multiple access (CDMA) provides multiple wireless channels, the bandwidth of a given link is unpredictable and possibly very low, the error rates are extremely high and variable, major interference occurs when multiple transmissions take place over (possibly different) links on the same or different codes, real-time multimedia traffic must be supported as well as datagram traffic, there is no stable communication infrastructure, and there is no central control. They consider the problem of developing a design prototyping methodology, performance evaluation techniques, and networking algorithms to support a rapidly deployable radio network for such an environment. The network must be capable of providing guaranteed quality of service (QoS) to real-time multimedia traffic in a mobile, wireless, multihop radio network with no fixed infrastructure (e.g., no base stations). Another element of the environment with which they deal is that of multihop communications. They focus on two layers of key importance in multimedia wireless network design, namely compression algorithms and adaptivity in the voice/video applications layer, and network algorithms at the wireless subnet layer. Simulation tools are used to evaluate our design as well as to provide a path toward their implementation in software.

Wireless 911 emergency location

Abstract: A system arrangement and method are disclosed for determining location of a wireless mobile unit involved in a call for public emergency assistance (e.g. a "911" call). The system is cost-effective in that it makes extensive use of existing telecommunication infrastructures, and does not require either special hardware or software at either the mobile unit site or the emergency assistance center handling a call. The system features shared use of a computer and specially defined database among a plurality of mobile switching offices serving a larger plurality of mobile base stations, the latter serving an even larger plurality of antenna and transceiving sites within predefined cellular regions. Signal strength measurements at the base stations are passed through the switching offices to a shared computer, and the latter uses the measurements to calculate a small area for which it would be practical to conduct a search if the mobile unit user requiring assistance is unable to help in determining his/her location. The calculated area and database are used to furnish the emergency assistance center handling the call with a detailed mapping of the calculated area, highlighting specific features (terrain, buildings, signs, etc.) that could be used to question the caller in a manner likely to produce responses from which the caller's location could be either precisely fixed or at least narrowed to a small part of the mapped area.

Wireless LANs and mobile networking: standards and future directions

Abstract: The emerging widespread use of wireless LAN systems together with the users' desire for such systems to interoperate has created a requirement for standards. Many standards bodies are currently defining standards for wireless systems that relate to different layers of the networking protocol stack. Of these, two influential physical and data link layer standards, IEEE 802.11 and the European HIPERLAN, are described. The article then considers the network layer by discussing extensions that are being made to the widely used Internet protocol (IP) to deal with mobility (wired or wireless). The final standards that are discussed relate to wireless link management. The article concludes by speculating on future directions for wireless LAN systems.

Energy-efficient caching for wireless mobile computing

Abstract: Caching can reduce the bandwidth requirement in a mobile computing environment. However, due to battery power limitations, a wireless mobile computer may often be forced to operate in a doze (or even totally disconnected) mode. As a result, the mobile computer may miss some cache invalidation reports broadcast by a server, forcing it to discard the entire cache contents after waking up. In this paper, we present an energy-efficient cache invalidation method, called GCORE (Grouping with COld update-set REtention), that allows a mobile computer to operate in a disconnected mode to save the battery while still retaining most of the caching benefits after a reconnection. We present an efficient implementation of GCORE and conduct simulations to evaluate its caching effectiveness. The results show that GCORE can substantially improve mobile caching by reducing the communication bandwidth (or energy consumption) for query processing.

Wireless ATM: a perspective on issues and prospects

Abstract: In this article the author examines several key issues in wireless ATM and even offers possible resolutions for some. The primary differences that distinguish wireless from wireline communications are presented, together with a short summary of so-called second-generation digital cellular system concepts. The operation of a wireline ATM network, especially with regard to those aspects bearing on the feasibility of wireless extension, is briefly reviewed, as well as some key technologies which may be very important enablers for wireless ATM, and some possible approaches for enabling bandwidth on demand (the media access problem) and maintaining service quality guarantees (the cell handoff problem), respectively. Finally, a possible format for signaling and synchronization, needed to "tie it all together", is presented.