Showing papers on "Communications system published in 2000"

Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple-access communications

Abstract: Attractive features of time-hopping spread-spectrum multiple-access systems employing impulse signal technology are outlined, and emerging design issues are described. Performance of such communications systems in terms of achievable transmission rate and multiple-access capability are estimated for both analog and digital data modulation formats under ideal multiple-access channel conditions.

Computer-based communication system and method using metadata defining a control-structure

Abstract: An automated communications system operates to transfer data, metadata and methods from a provider computer to a consumer computer through a communications network. The transferred information controls the communications relationship, including responses by the consumer computer, updating of information, and processes for future communications. Information which changes in the provider computer is automatically updated in the consumer computer through the communications system in order to maintain continuity of the relationship. Transfer of metadata and methods permits intelligent processing of information by the consumer computer and combined control by the provider and consumer of the types and content of information subsequently transferred. Object oriented processing is used for storage and transfer of information. The use of metadata and methods further allows for automating may of the actions underlying the communications, including communication acknowledgements and archiving of information. Service objects and partner servers provide specialized data, metadata, and methods to providers and consumers to automate many common communications services and transactions useful to both providers and consumers. A combination of the provider and consumer programs and databases allows for additional functionality, including coordination of multiple users for a single database.

Digital Communication over Fading Channels: A Unified Approach to Performance Analysis

Abstract: FUNDAMENTALS. Fading Channel Characterization and Modeling. Types of Communication. MATHEMATICAL TOOLS. Alternative Representations of Classical Functions. Useful Expressions for Evaluating Average Error Probability Performance. New Representations of Some PDF's and CDF's for Correlative Fading Applications. OPTIMUM RECEPTION AND PERFORMANCE EVALUATION. Optimum Receivers for Fading Channels. Performance of Single Channel Receivers. Performance of Multichannel Receivers. APPLICATION IN PRACTICAL COMMUNICATION SYSTEMS. Optimum Combining: A Diversity Technique for Communication Over Fading Channels in the Presence of Interference. Direct--Sequence Code--Division Multiple Access. FURTHER EXTENSIONS. Coded Communication Over Fading Channels. INDEX.

Wireless multicarrier communications

Abstract: Relying on basic tools such as eigensignals of linear time-invariant systems, linear and circular block convolution, and fast Fourier transforms (FFTs), this article develops a systematic discrete-time framework and designs novel systems for single- and multiuser wireless multicarrier communications-a field rich in signal processing challenges that holds great potential in various applications including audio/video broadcasting, cable television, modem design, multimedia services, mobile local area networks, and future-generation wideband cellular systems. Wireless multicarrier (MC) communication systems utilize multiple complex exponentials as information-bearing carriers. MC transmissions thus retain their shape and orthogonality when propagating through linear time-dispersive media, precisely as eigensignals do when they pass through linear time-invariant (LTI) systems.

A review of lithium niobate modulators for fiber-optic communications systems

Abstract: The current status of lithium-niobate external-modulator technology is reviewed with emphasis on design, fabrication, system requirements, performance, and reliability. The technology meets the performance and reliability requirements of current 2.5-, 10-, and 40-Gb/s digital communication systems, as well as CATV analog systems. The current trend in device topology is toward higher data rates and increased levels of integration. In particular, multiple high-speed modulation functions, such as 10-Gb/s return-to-zero pulse generation plus data modulation, have been achieved in a single device.

Fading Channels: InformationTheoretic and Communications Aspects

Abstract: In this paper we review the most peculiar and interesting information-theoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information theory of fading channels, by emphasizing capacity as the most important performance measure. Both single-user and multiuser transmission are examined. Further, we describe how the structure of fading channels impacts code design, and finally overview equalization of fading multipath channels.

Method of using a communications device together with another communications device, a communications system, a communications device and an accessory device for use in connection with a communications device

Abstract: A method of using a first communications device, such as a mobile telephone, together with at least one other communications device, such as a telephone, comprises the steps of playing back audio signals in the first communications device, transmitting the same audio signals to the other communications device, and playing back the audio signals in the other communications device. By transmitting the audio signals played back in the first communications device to the other device and playing them back there, shared audio listening is achieved and in this way the communications devices can be used also for the shared listening to e.g. music. Thus it is possible for two persons present at different locations to listen to the same audio signals simultaneously or at least almost simultaneously.

Microwave and Rf Design of Wireless Systems

Abstract: From the Publisher: This book offers a quantitative and design-oriented presentation of the analog RF aspects of modern wireless telecommunications and data transmission systems from the antenna to the baseband level. It takes an integrated approach to topics such as antennas and proagation, microwave systems and circuits and communication systems.

Communication system and method

Abstract: A system and method for establishing communication with any one of a variety of different wireless communication devices including through the provision of a short range transceiver assembly so as to provide data communication from a sender to the wireless communication device either over the Internet, utilizing an Internet access facility, such as a computer, or alternatively using an over-the-air network, compatible with the communication device. The wireless communication device is structured to operate on either of at least two independent frequencies for communication with the computer or with the over-the-air network, dependent on predetermined parameters including the acceptance of a unique identifier or code and/or the positioning of the wireless communication device, within a predetermined vicinity range relative to the computer. An auto switching capability establishes data communication with the computer or with the over-the-air network, dependent on whether the identification and vicinity parameters have been met.

A computationally efficient Doppler compensation system for underwater acoustic communications

Abstract: A Doppler compensation system is presented which is suitable for high-data-rate acoustic communication between rapidly moving platforms such as autonomous underwater vehicles. The proposed approach provides a generic preprocessor to conventional adaptive receiver structures with only a marginal increase in computational load and hardware cost. The preprocessor employs a novel Doppler estimation technique and efficient sample rate conversion to remove Doppler shift induced by platform velocity and acceleration. Performance predicted by simulation is compared to that of sea trials of a prototype communication system in the North Sea. Successful communication is demonstrated at 16 kbit/s with a transmitting platform moving at up to /spl plusmn/2.6 m/s.

System and method for providing group communication services in an existing communication system

Abstract: The present invention is a system and method for providing group communication services in an existing communication system. Group communications are enabled by installing a communications manager in a data network such as the Internet. The communications manager acts as a configurable switch, allowing communications from any group member to be transmitted to all other group members. The communications processed by the communications manager take the form of data packets, suitable for transmission over the data network. The data packets are generated by communication devices operating within the communication system. The use of the communications manager further allows users of other communication systems and devices to participate in group communications with each other.

Single- and Multi-carrier Quadrature Amplitude Modulation : Principles and Applications for Personal Communications, WLANs and Broadcasting

Abstract: Single- and Multi-carrier Quadrature Amplitude Modulation Principles and Applications for Personal Communications, WLANs and Broadcasting L. Hanzo Department of Electronics and Computer Science, University of Southampton, UK W. Webb Motorola, Arlington Heights, USA formerly at Multiple Access Communications Ltd, Southampton, UK T. Keller Ubinetics, Cambridge Technology Centre, Melbourn, UK formerly at Department of Electronics and Computer Science, University of Southampton, UK Motivated by the rapid evolution of wireless communication systems, this expanded second edition provides an overview of most major single- and multi-carrier Quadrature Amplitude Modulation (QAM) techniques commencing with simple QAM schemes for the uninitiated through to complex, rapidly-evolving areas, such as arrangements for wide-band mobile channels. Targeted at the more advanced reader, the multi-carrier modulation based second half of the book presents a research-orientated outlook using a variety of novel QAM-based arrangements. * Features six new chapters dealing with the complexities of multi-carrier modulation which has found applications ranging from Wireless Local Area Networks (WLAN) to Digital Video Broadcasting (DVB) * Provides a rudimentary introduction for readers requiring a background in the field of modulation and radio wave propagation * Discusses classic QAM transmission issues relevant to Gaussian channels * Examines QAM-based transmissions over mobile radio channels * Incorporates QAM-related orthogonal techniques, considers the spectral efficiency of QAM in cellular frequency re-use structures and presents a QAM-based speech communications system design study * Introduces Orthogonal Frequency Division Multiplexing (OFDM) over both Gaussian and wideband fading channels By providing an all-encompassing self-contained treatment of single- and multi- carrier QAM based communications, a wide range of readers including senior undergraduate and postgraduate students, practising engineers and researchers alike will all find the coverage of this book attractive.

Information network interrogation of an implanted device

Abstract: A communication system is provided which permits of communication between a deployed implantable medical device (IMD) and a computing resource capable of storing and distributing patient and device data. A deployed IMD may be polled by a network interface external to the host patient, and data may be received by wireless communication. This data may be transmitted to a computer for storage and distribution, and changes to a treatment or instruction regimen, or firmware or software upgrades, may then be transmitted to the network interface for immediate or eventual loading into the IMD via wireless communication. The system is adapted to provide communication service between multiple IMDs deployed in a patient or a number of patients.

Method and wireless systems using multiple antennas and adaptive control for maximizing a communication parameter

Abstract: A method of maximizing a communication parameter, such as data capacity, signal quality or throughput of a channel between a transmit unit (12) with M transmit antennas (18A...18M) and a receive unit (14) with N receive antennas (34A...34N) and a communication system employing the method. The data is first processed to produce parallel spatial-multiplexed streams SMi, where i=1...k, which are converted or mapped to transmit signals TSp, where p=1...M, assigned for transmission from the M transmit antennas (18A...18M). Corresponding receive signals RSj, where j=1...N, are received by the N receive antennas (34A...34N) of the receiver and used to assess a quality parameter, such as a statistical signal parameter or a parameter of the data. The quality parameter is used to adaptively adjust k as well as other parameters to transmit antennas such that the communication parameter of the channel is maximized.

CMOS Data Converters for Communications

Abstract: CMOS Data Converters for Communications distinguishes itself from other data converter books by emphasizing system-related aspects of the design and frequency-domain measures. It explains in detail how to derive data converter requirements for a given communication system (baseband, passband, and multi-carrier systems). The authors also review CMOS data converter architectures and discuss their suitability for communications. The rest of the book is dedicated to high-performance CMOS data converter architecture and circuit design. Pipelined ADCs, parallel ADCs with an improved passive sampling technique, and oversampling ADCs are the focus for ADC architectures, while current-steering DAC modeling and implementation are the focus for DAC architectures. The principles of the switched-current and the switched-capacitor techniques are reviewed and their applications to crucial functional blocks such as multiplying DACs and integrators are detailed. The book outlines the design of the basic building blocks such as operational amplifiers, comparators, and reference generators with emphasis on the practical aspects. To operate analog circuits at a reduced supply voltage, special circuit techniques are needed. Low-voltage techniques are also discussed in this book. CMOS Data Converters for Communications can be used as a reference book by analog circuit designers to understand the data converter requirements for communication applications. It can also be used by telecommunication system designers to understand the difficulties of certain performance requirements on data converters. It is also an excellent resource to prepare analog students for the new challenges ahead.

Method and apparatus for minimizing storage of common attachment files in an e-mail communications server

Abstract: The present invention provides an e-mail communications system that minimizes the number of duplicate copies of common attachment files to e-mail communications that are stored in the mail store of an e-mail server. When the e-mail server receives an e-mail attachment file that is larger than a threshold size, the server performs a database search for another copy of the attachment file in the mail store. If another copy is located, the system creates a pointer in the mail store that associates the located attachment file with the e-mail for the additional recipient(s). Attachment files are deleted only after the recipients of the associated e-mail communications delete each of the respective e-mails.

Highly reliable power line communications system

Abstract: An electric power line communication system (20) operates with an electric power distribution system to provide through premises power distribution lines (28) highly reliable communication links among receiving devices (26, 32, 40, 46, 68, 112) electrically coupled orlocated in proximity to the premises power distribution lines. A power line transceiver (22,30, 34) is designed to transmit and receive through the premises power distribution lines modulated carrier signals conveying information over the communication links. The powerline transceiver operates in a transmitter mode as an intentional radiator to emit modulated carrier signals by transmitting them at a frequency band and a power level sufficient to form by electrical conduction a communication link with a modulated carrier signal receiving device.

Method and apparatus for communicating with medical device systems

Abstract: A wearable telemetry arrangement is used with a medical information communications device in a telemetry system for communicating with an implantable medical device. In an example embodiment, the telemetry arrangement includes an article configured and arranged to be physically coupled to and donned on a body. In addition, an antenna member is located on the article that is configured and arranged to establish a communications link between the implanted device and the medical communications system. The telemetry arrangement of the present invention provides a reliable and non-invasive system that conveniently and chronically collects cardiac and other implanted medical device data. Further, the system is adaptable to patient management modules and portals to provide remote connectivity to web-based platforms and data management systems.

Method for informing a user of a communication device where to obtain a product and communication system employing same

Abstract: A communication system ( 100 ) employs a method for informing a user of a communication device (e.g., 101 ) where to obtain a product. The communication system determines an approximate location of the communication device and whether a particular requested product or one or more other potentially desirable products are available in a general vicinity of the device. When the particular or potentially desirable product is so available, a context engine server ( 109 ) of the communication system conveys a product information request and optionally other purchaser-related information to multiple product providers ( 120 ). The context engine server receives responses to the product information request from at least some of the product providers, wherein at least some of the responses preferably include offers to pay respective advertising fees. The context engine server generates a list of product providers based on the responses and provides the list to the communication device for display to the device user.

Dynamic bandwidth monitor and adjuster for remote communications with a medical device

Abstract: A communication system is provided which allows real-time communication between a deployed implantable medical device (IMD) and a computing resource capable of storing and distributing patient and device data. A deployed IMD may be polled by a network interface external to the host patient, and data may be received by wireless real-time communication in a manner which ensures secure and reliable information exchange. A bandwidth or baud rate monitor is used to verify the viability of the network-IMD connection for the intended use and then monitors the connection to ensure that bandwidth remains reliable. An alert feature notifies the user of any threatening bandwidth onset. This feature allows vibrant exchange of real-time information from the patient-IMD to a medical provider or system expert.

The future generations of mobile communications based on broadband access technologies

Abstract: The forthcoming mobile communication systems are expected to provide a wide variety of services, from high-quality voice to high-definition videos, through high data rate wireless channels anywhere in the world. The high data rate requires broad frequency bands, and sufficient broadband can be achieved in higher frequency bands such as microwave, Ka-band, and millimeter-wave. Broadband wireless channels have to be connected to broadband fixed networks such as the Internet and local area networks. The future-generation systems will include not only cellular phones, but also many new types of communication systems such as broadband wireless access systems, millimeter-wave LANs, intelligent transport systems, and high altitude stratospheric platform station systems. Key to the future generations of mobile communications are multimedia communications, wireless access to broadband fixed networks, and seamless roaming among different systems. This article discusses future-generation mobile communication systems.

Method and apparatus for determining the position of a mobile communication device using low accuracy clocks

Abstract: A position location communication system (10) determines the position of a master radio (12) using a round-trip messaging scheme in which the time of arrive (TOA) of ranging messages is accurately determined to yield the range estimates required to calculate the position of the master radio via trilateration. The master radio transmits outbound ranging messages to plural reference radios (14, 16, 18, 20) which respond by transmitting reply ranging messages. Upon reception of the reply ranging message, the master radio determines the range to the reference radio from the signal propagation time calculated by subtracting the far-end turn around time from the round-trip elapsed time. Any combination of fixed or mobile radios of known positions can be used as the reference radios for another mobile radio in the system, thereby providing adaptability under varying transmission conditions. The individual radios do not need to be synchronized to a common time reference, thereby eliminating the need for highly accurate system clocks.

Angle diversity for nondirected wireless infrared communication

Abstract: We outline the benefits and challenges of using angle diversity in nondirected wireless infrared (IR) communications systems. Multiple transmitter beams and multiple narrow field-of view receivers reduce the path loss, multipath distortion, and background noise of the channel, which leads to improved range. We also discuss practical considerations for multielement angle diversity systems, including channel characterization and suboptimal detection techniques. Maximal-ratio combining provides nearly optimal performance up to 100 Mb/s for the angle diversity systems considered. The design and performance of a prototype angle diversity IR communication system are discussed. The prototype can maintain 70 Mb/s at a P/sub e/ of 10/sup -9/ over a 4-m range.

Personal communication device

Abstract: A communication system provides two-way wireless communication between a user and at least one remote device. The communication system comprises at least one earpiece (400) worn by the user and a personal communication device (100) for receiving and transmitting signals over a wireless link to and from the earpiece. The personal communication device (100) includes voice recognition circuitry (140) which recognizes and interprets voice commands of the user. The personal communication device is configured to determine a remote device to receive each of the voice commands, and transmits the appropriate voice commands to the remote device, accordingly.

Interference suppression in cdma systems

Abstract: A receiver of the present invention addresses the need for improved interference suppression without the number of transmissions by the power control system being increased, and, to this end, provides a receiver for a CDMA communications system which employs interference subspace rejection to tune a substantially null response to interference components from selected signals of other user stations. Preferably, the receiver also tunes a substantially unity response for a propagation channel via which a corresponding user's signal was received. The receiver may be used in a base station or in a user/mobile station.

Wearable communication system

Abstract: A portable data input or computer system includes an input/output device such as a keyboard and a display, another data input device such as an optical bar code scanner, and a data processor module. To scan bar code type indicia, the operator points the scanner at the bar code and triggers the scanner to read the indicia. All the system components are distributed on an operator's body and together form a personal area system (PAS). Components may include a scanner or imager, a wrist unit, a headpiece including an eyepiece display, speaker and a microphone. Components within a particular PAS communicate with each other over a personal area network (PAN). Individual PASs may be combined into a network of PASs called a PAS cluster. PASs in a particular PAS cluster can communicate with each other over another wireless communication channel. Individual PAS can gain access to a Local Area Network (LAN) and/or a Wide Area Network (WAN) via an access point. Individual PASs can use devices, such as servers and PCs situated either on the LAN or the WAN to retrieve and exchange information. Individual PAS components can provide automatic speech and image recognition. PAS components may also act a telephone, a pager, or any other communication device having access to a LAN or a WAN. Transmission of digitized voice and/or video data can be achieved over an Internet link.

Method and apparatus for dynamically grouping communication units in a communication system

Abstract: A display-based terminal (101) employs a method and apparatus for dynamically grouping communication units (105-113) operating in a communication system (100). The display-based terminal displays a map (300, 400) to a user of the terminal that indicates, among other things, locations of communication units in at least a portion of the communication system. The terminal receives the user's selection of communication units from the map and an identification of at least one talkgroup with which the selected units are to become members. The communication units may be selected individually, as a group (e.g., using 'click and drag' rectangling techniques), or both. After communication units have been selected from the map, the terminal automatically groups the selected units into the indicated talkgroup. If the terminal user desires to ungroup a previously grouped communication unit, the user selects the unit from the map and the terminal automatically removes the newly selected unit from the talkgroup.

Low earth orbit distributed gateway communication system

Abstract: A method for operating a communication system includes steps of: (a) receiving a call for a user terminal at a satellite system gateway, the call originating from another user terminal; (b) examining a database to determine if the called user terminal is located within a coverage area of the satellite system gateway; and (c) if yes, formulating a paging message and transmitting the paging message to the called user terminal via at least one satellite. Upon the called user terminal responding to the page, the method further: (d) establishes the call using satellite system resources, (e) designates one of the calling or called user terminals as a call manager for the duration of the call, and (f) makes a temporary assignment of satellite system resources to the call manager user terminal for use in managing the remainder of the call. The step of establishing the call includes a step of assigning at least an initial channel/circuit pair to each of the user terminals. A call synopsis is transmitted from the call manager user terminal to the gateway at the completion of the call, and the gateway employs the call synopsis when transmitting billing-related information from the gateway to another gateway with which one or both of the user terminals has an affiliation. The other gateway could be a virtual gateway that serves a localized region within the service region of the gateway. At the completion of the call the assigned satellite system resources are relinquished. Also disclosed are methods and apparatus for extending the effective service regions of gateways and virtual gateways through a gateway-to-gateway diversity technique, wherein gateways are interconnected for providing user terminal traffic and signalling information between themselves at call setup and during a call.

Dual receiver for a on-board entertainment system

Abstract: A communication system is provided for use with a mobile platform. The communication system can be configured to store video data on-board to allow pseudo-live or live broadcasts to be played as the mobile platform traverses a number of broadcasts regions. The mobile platforms can be automobiles, aircraft, boats, ships, trains, or other vehicles. The communication system allows Internet access, movies, and other entertainment and business functions to be performed.

Adaptive power control in a mobile radio communications system

Abstract: An efficient and effective power control in a mobile communications system is provided that adapts to rapidly changing radio transmission conditions in varying and often unpredictable situations The value of a signal parameter detected from a signal received by a radio transceiver is compared with a desired signal parameter value, and a difference is determined A transmit power control command is sent to the radio transceiver and may instruct, for example, an increase or decrease in the level of radio transmit power Included with the transmit power control command is a power control indicator indicating whether a first or a second type of power control adjustment should be used by the radio transceiver depending upon the determined difference In one example embodiment, the power control indicator is a single flag bit A first value indicates that the first type of power control adjustment should be used; the second value indicates that the second type of power control adjustment should be used In any event, the power control indicator itself does not include specific details of the first or second type of power control adjustment Because only the indicator is sent (and not the details), signaling overhead and bandwidth consumption related to frequently sent power control commands are kept to a minimum The specific details of the first and second power control adjustments are initially stored in to the radio transceiver Such details may be updated when desirable, but the frequency of such updating is likely to be infrequent Alternatively, a power control indicator may be communicated using techniques other than adding one or more flag bits to a fast transmit power control message to effect a change in power control type as long as signaling overhead is not significantly increased