Showing papers on "Communications system published in 2002"

Adaptive modulation and MIMO coding for broadband wireless data networks

Abstract: Link adaptation techniques, where the modulation, coding rate, and/or other signal transmission parameters are dynamically adapted to the changing channel conditions, have emerged as powerful tools for increasing the data rate and spectral efficiency of wireless data-centric networks. While there has been significant progress on understanding the theoretical aspects of time adaptation in LA protocols, new challenges surface when dynamic transmission techniques are employed in broadband wireless networks with multiple signaling dimensions. Those additional dimensions are mainly frequency, especially in multicarrier systems, and space in multiple-antenna systems, particularly multiarray multiple-input multiple-output communication systems. We give an overview of the challenges and promises of link adaptation in future broadband wireless networks. We suggest guidelines to help in the design of robust, complexity/cost-effective algorithms for these future wireless networks.

Resource allocation for MIMO-OFDM communication systems

Abstract: Techniques to schedule terminals for data transmission on the downlink and/or uplink in a MIMO-OFDM system based on the spatial and/or frequency “signatures” of the terminals. A scheduler forms one or more sets of terminals for possible (downlink or uplink) data transmission for each of a number of frequency bands. One or more sub-hypotheses may further be formed for each hypothesis, with each sub-hypothesis corresponding to (1) specific assignments of transmit antennas to the terminal(s) in the hypothesis (for the downlink) or (2) a specific order for processing the uplink data transmissions from the terminal(s) (for the uplink). The performance of each sub-hypothesis is then evaluated (e.g., based on one or more performance metrics). One sub-hypothesis is then selected for each frequency band based on the evaluated performance, and the one or more terminals in each selected sub-hypothesis are then scheduled for data transmission on the corresponding frequency band.

Method and apparatus for utilizing channel state information in a wireless communication system

Abstract: Techniques for transmitting data from a transmitter unit to a receiver unit in a multiple-input multiple-output (MIMO) communication system. In one method, at the receiver unit, a number of signals are received via a number of receive antennas, with the received signal from each receive antenna comprising a combination of one or more signals transmitted from the transmitter unit. The received signals are processed to derive channel state information (CSI) indicative of characteristics of a number of transmission channels used for data transmission. The CSI is transmitted back to the transmitter unit. At the transmitter unit, the CSI from the receiver unit is received and data for transmission to the receiver unit is processed based on the received CSI.

Radio Over Fiber Technologies for Mobile Communications Networks

Abstract: Basic Microwave Properties of Optical Links - Insertion Loss and Noise Figure Concepts. A Brief Summary. Direct-Modulated Optical Links. Optical Links of External Intensity Modulation. Heterodyning Microwave/Millimeter Wave Optical Links. Low Cost Optical Fiber Links for Remote Antenna Feeding - Introduction. Requirements for Remote Antenna Feeding Links. Comparison Between Coax and Fiber-Optic Remote Antenna Feeding Links. Laser and Photodiode Nonlinearities and Their Influence on Link Performance. Laser Diode Noise and Its Influence on Link Performance. Low Cost Fiber-Optic Links. Fiber and Multicarrier Effects. Linearization of Fiber-Optic Links. Low Cost Laser Diode Driver and Photoreceiver Design for Fiber-Optic Remote Antenna Feeding Links. Extended Low Cost Fiber-Optic Link Concepts and Applications. Sub-Carrier Optical Fiber Transmission Systems: Fiber-Optic Transmission of Microwave Signals - Fiber-Optic Transmission of Microwave 64-QAM Signals. 256-QAM Sub-Carrier Transmission Using Coding. Laser Nonlinearity Compensation for SCM Applications. Radio Over Fiber Systems for Mobile Applications - Introduction. Coverage Problems. Competing Solutions. Advantages of Radio Over Fiber. Current Technologies. Emerging Technologies. Economic Aspects. Evolution to 3G. Conclusions. Fiber-Optic Radio Networking/Radio Highway Networks/Software Radio NW - Introduction. Various Types of Radio Highway. FDMA. TDMA. CDMA. Chirp Multiple Access (CMA). WCDMA Radio Over Fiber For Mobile Microcellular Communication Networks - WCDMA Computer Simulation Model. Evaluation of the Impact of Spreading Bandwidth. Using The Simulation Approach to Investigate Handover Algorithm performance. The Feasibility of Using Similar Macrodiversity-Combining Technique in the Uplink of ROF Microcellular Systems. Theoretical and Simulation Analysis of Power Control Performance for WCDMA ROF Microcellular Systems. Radio Over Fiber: Current Applications and Future Potential Advantages and Challenges for a Powerful Technology - ROF in the World. Market Acceptance and Competitive Analysis. Third Generation Technological Challenge. Industrial Possibility for ROF and Wireless Infrastructure Convergence. Commercial Advantages Associated With ROF. ROF Multiple Services Communication Systems - Road-to-Vehicle Communications. Wireless Local Loop Systems. Potential for Future Communication Systems. Conclusion.

Communications system using rings architecture

Abstract: Systems and methods are provided for implementing: a rings architecture for communications and data handling systems; an enumeration process for automatically configuring the ring topology; automatic routing of messages through bridges; extending a ring topology to external devices; write-ahead functionality to promote efficiency; wait-till-reset operation resumption; in-vivo scan through rings topology; staggered clocking arrangement; and stray message detection and eradication. Other inventive elements conveyed include: an architectural overview of a packet processor; a programming model for a packet processor; an instruction pipeline for a packet processor; and use of a packet processor as a module on a rings-based architecture. Additional inventive elements conveyed include: an architectural overview of a communications processor; a data path protocol support model for a communications processor; an exemplary network processor employed as the core packet processor for the communications processor; an exemplary rings-based SOC switch fabric architecture; and a variety of quality of support features.

Object-based on-line transaction infrastructure

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.

Trading computation for bandwidth: reducing communication in distributed control systems using state estimators

Abstract: Describes a new framework for distributed control systems in which estimators are used at each node to estimate the values of the outputs at the other nodes. The estimated values are then used to compute the control algorithms at each node. When the estimated value deviates from the true value by more than a pre-specified tolerance, the actual value is broadcast to the rest of the system; all of the estimators are then updated to the current value. By using the estimated values instead of true value at every node, a significant saving in the required bandwidth is achieved, allowing large-scale distributed control systems to be implemented effectively. The stability, performance, and expected communication frequency of the reduced communication system are analyzed in detail. Simulation and experimental results validating the effectiveness and communication savings of the framework are also presented.

Internet based home communications system

Abstract: An Internet based home communications system for allowing a homeowner to monitor and control various features of their home from a distant location via a global computer network. The inventive system comprises a plurality of control devices positioned within a home, a control unit in communication with the plurality of control devices wherein the control unit is connected to a global computer network (i.e. Internet), and a data center having server computers connected to the global computer network and in communication with the control unit. The homeowner can view, monitor and control features of their home through the web page such as viewing interior images of their home or adjusting the thermostat for the interior of their home. In addition, the control unit may notify the appropriate supplier when propane or food becomes low within the home through the global computer network.

The FTT-CAN protocol: why and how

Abstract: The requirement for flexible operation is becoming increasingly important in modern industrial systems. This requirement has to be supported at all system levels, including the field level in process industry, as well as the cell and machine control levels in manufacturing industry, where fieldbus-based communication systems are commonly found. Furthermore, typical applications at these levels require both time- and event-triggered communication services, in most cases under stringent timing constraints, to convey state data in the former case and alarms and management data in the latter. However, neither the requirement for flexible operation under guaranteed timeliness nor for joint support of time and event-triggered traffic are efficiently fulfilled by most of existing fieldbus systems. This paper presents a new protocol, flexible time-triggered communication on controller area network, which fulfills both requirements: it supports time-triggered communication in a flexible way as well as being an efficient combination of both time- and event-triggered traffic with temporal isolation. These types of traffic are handled by two complementary subsystems, the synchronous and the asynchronous messaging systems, respectively. The paper includes a justification for the new protocol as well as its description and worst case temporal analysis for both subsystems. This analysis shows the capability of the protocol to convey real-time traffic of either type.

Simulation and Software Radio for Mobile Communications

Abstract: Introduction. General Definition of Simulation Tools, Performance Evaluation for Digital Modulation Techniques. Orthogonal Frequency Division Multiplexing (OFDM) Transmission System. Code Division Multiplexing (CDM) Transmission System. Cellular Telecommunication System. Packet Telecommunications System. Software Radio Communication System.

Enhanced wireless packet data communication system, method, and apparatus applicable to both wide area networks and local area networks

Abstract: A cellular wireless packet data communication system containing transmit-only endpoint device (HA40, HA50) which transmit to receive-only base stations (B1, B2, BN). The system is configured to allow for large area coverage (e.g., a metropolitan area) with far fewer number base stations than are required with conventional two-way cellular systems. The base station coverage areas are configured to overlap, allowing for reception of packets at multiple base stations. A data concentrator (HA60) resolves redundantly received messages. The network is configurable as a WAN, a LAN, or a combination of the two. Novel modulation techniques (e.g., a 16QAM submodulation together with a 7FSK modulation) are used such that low cost components can be used in the transmitters and receivers while achieving outstanding probability of success performance. The endpoint devices are battery operated and accordingly, are designed for low power consumption and multi-year battery life. The system is used in a variety of applications including remote monitoring and mobile communications.

Method and apparatus for controlling uplink transmissions of a wireless communication system

Abstract: Techniques to partition and allocate the available system resources among cells in a communication system, and to allocate the resources in each cell to terminals for data transmission on the uplink. In one aspect, adaptive reuse schemes are provided wherein the available system resources may be dynamically and/or adaptively partitioned and allocated to the cells based on a number of factors such as the observed interference levels, loading conditions, system requirements, and so on. A reuse plan is initially defined and may be redefined to reflect changes in the system. In another aspect, the system resources may be partitioned such that each cell is allocated a set of channels having different performance levels. In yet another aspect, terminals in each cell are scheduled for data transmission (e.g., based on their priority or load requirements) and assigned channels based on their tolerance to interference and the channels' performance.

Chaos communications-principles, schemes, and system analysis

Abstract: This paper provides a comprehensive overview of chaotic communication methods and schemes with emphasis on digital schemes. Starting from general demands for communications, the general communication system structure is introduced. From this basic viewpoint, different classical and chaotic modulation and demodulation methods are treated and classified. For the performance analysis and comparison, a discrete-time statistical calculus is developed and applied to chaotic signal processing schemes. Discrete-time baseband models are developed, which are suitable for a statistical performance analysis. Analysis results for various example systems are provided and compared. New decoder structures are proposed and included in the comparative studies.

Personal medical device communication system and method

Abstract: A personal and/or institutional health and wellness communications system, which may be used for a variety of emergency and non-emergency situations using two-way communication devices and a bi-directional communication network. In one application two-way pagers are adapted for use in the system. In one application cellular devices are adapted for use in the system. In one application an assisted living response center is established using various embodiments of the present personal and/or institutional communications system. The system provides multiple levels of prioritization, authentication of person (task, step, process or order), and confirmation via interrogation of person, device, or related monitor. One embodiment provides a method for receiving, evaluating and responding to calls received from a subscriber, patient, related party, or health care provider or health care system.

Systems and methods for delivering information within a group communications system

Abstract: System and methods for delivering information include a communications network defined by at least a wireless telephone network (22) coupled to a computer network (24), where the communications network is associated with a plurality of communication devices (14, 16, 18, 20) that define a group communications net. A communications manager (32) is operable to provide a group communication session by receiving a data packet from one member of the group communications net and transmitting the data packet through the computer network to at least one of the other members of the group communications net. A message module (28) having a plurality of informational messages is associated with the communications manager, and a delivery module (30) is coupled to each of the message module, the communications manager, and the communications network. The delivery module is operable to monitor the group communication session and to deliver one of the plurality of informational massages to the group communications net. Further, methods of billing a user for participation in the group communications session include discounting an amount due based on receipt of informational messages.

Retrodirective arrays for wireless communications

Abstract: This article reports the recent progress in active and passive retrodirective arrays using phase-conjugation techniques. The arrays presented here are designed for wireless communications in microwave bands and have other features in addition to self-phasing aspects such that they can be applied to practical communication systems. The reliance on purely analog circuitry offers system simplicity and high-speed response. The self-beam-steering feature potentially offers the improvement of communication link gain between an interrogator and a retrodirective array, reducing the burden on transmitting and receiving amplifiers. By implementing a receiving function, it has been demonstrated that retrodirective arrays can also be used in bidirectional communications in either a full or semiduplex manner, initiating a new class of transceiver architecture.

Method and system for encrypted network management and intrusion detection

Abstract: A network security system includes a system data store capable of storing a variety of data associated with an encrypted computer network and communications transmitted thereon, a communication interface supporting communication over a communication channel and a system processor. Data corresponding to communications transmitted over the encrypted communication network are received. One or more tests are applied to the received data to determine whether a particular communication represents a potential security violation. An alarm may be generated based upon the results of the applied test or tests.

Method and apparatus for enabling group communication services in an existing communication system

Abstract: An apparatus to form a group of communication devices over a distributed network is claimed. A first node establishes a first channel with a first communication device. At least one second node establishes at least one second channel with at least one second communication device. A controller electrically connected to the first node and the at least one second node comprises a database module. The database module comprises identification information of each of the communication devices of the group. The controller is dynamically configurable such that any single communication device of the group is capable of sending packet data through its respective channel to the other communication devices of the group.

Last leg utility grid high-speed data communication network having virtual local area network functionality

Abstract: A power line based communication system includes a power line termination module, a plurality of power line gateways, and a plurality of power line nodes. The power line termination module manages data for local area networks within the power line based communication system. The plurality of power line gateways is arranged in sets of power line gateways, wherein each set of power line gateways constitutes a local area network. Each of the plurality of power line nodes is operably coupled to the power line termination module via a high-speed communication path. In addition, each power line node is operably coupled to set of power line gateways, i.e., to a local area network, via power lines of a local transformer. Each of the power line nodes receives data for its respective LAN from the power line termination module and provides the data to the power line gateways of its LAN via the power lines of the local transformer. Virtual local area networks are enabled between the power line termination module and the power line gateways.

Virtual antenna array

Abstract: A method of transmitting data across an electronic data communication system comprising a plurality of terminals that can send and receive data in the form of electromagnetic waves to and from at least one of the terminals, which method comprises the steps of: (a) identifying at least one control terminal, at least one target terminal and at least two relaying terminals from the plurality of terminals; and (b) using the control terminal to instruct the at least two relaying terminals to receive and relay data intended for the at least one target terminal, so that the at least one target terminal can receive data directly from at least one terminal and from the at least two relaying terminals, thereby increasing capacity of the system.

Method and system of retransmission

Abstract: The present invention relates to a method and system of transmissions and retransmissions of packet data in a communications system, where the communications system uses switched channels, switching between rates or channels of different characteristics, and connection control and management in such a system. Particularly, the invention relates to radio resource management in a Universal Mobile Telecommunications System, UMTS, or WCDMA system allowing for use of compatible protocols for non-switched and switched channels.

Communication system and techniques for transmission from source to destination

Abstract: A system and method for transmitting and presenting streaming digital information signals that optimizes performance in the context of goodput, throughput, delay, receiver buffer requirements and tolerance to loss and jitter. The method provides ordering packets of information based on a priority associated with each of the packets; managing the flow of the packets into and out of a buffer; adjusting the rate at which the packets are provided to a communication medium; and transmitting and retransmitting the packets as needed.

OFDM signal communication system, OFDM signal transmitting device and OFDM signal receiving device

Abstract: An OFDM signal communication system used in broadband mobile communication, achieves stable operation under severe frequency selective fading environments, giving high quality. The OFDM signal communication system which transmits OFDM signals over the same radio frequency from N transmitting antennas, has an inverse matrix computer for computing an N×N inverse matrix constituted by propagation coefficients for respective propagation paths between each of N transmitting antennas and each of N receiving antennas, and a subcarrier demodulator which separates the signals of the respective propagation paths, based on the obtained inverse matrix.

Wireless systems and interference avoidance

Abstract: Motivated by the emergence of programmable radios, we seek to understand a new class of communication system where pairs of transmitters and receivers can adapt their modulation/demodulation method in the presence of interference to achieve better performance. Using signal to interference ratio as a metric and a general signal space approach, we present a class of iterative distributed algorithms for synchronous systems which results in an ensemble of optimal waveforms for multiple users connected to a common receiver (or colocated independent receivers). That is, the waveform ensemble meets the Welch (1974) bound with equality and, therefore, achieves minimum average interference over the ensemble of signature waveforms. We derive fixed points for a number of scenarios, provide examples, look at ensemble stability under user addition and deletion as well as provide a simplistic comparison to synchronous code-division multiple-access. We close with suggestions for future work.

Ultra wide bandwidth spread-spectrum communications system

Abstract: An ultra wide bandwidth, high speed, spread spectrum communications system uses short wavelets of electromagnetic energy to transmit information through objects such as walls or earth. The communication system uses baseband codes formed from time shifted and inverted wavelets to encode data on a RF signal. Typical wavelet pulse durations are on the order of 100 to 1000 picoseconds with a bandwidth of approximately 8 GHz to 1 GHz, respectively. The combination of short duration wavelets and encoding techniques are used to spread the signal energy over an ultra wide frequency band such that the energy is not concentrated in any particular narrow band (e.g. VHF: 30-300 MHz or UHF: 300-1000 MHz) and is not detected by conventional narrow band receivers so it does not interfere with those communication systems. The use of pulse codes composed of time shifted and inverted wavelets gives the system according to the present invention has a spatial resolution on the order of 1 foot which is sufficient to minimize the negative effects of multipath interference and permit time domain rake processing.

Intelligent multi-media display communication system

Abstract: Interactive, low power, collapsible, intelligent, multi-media display systems (100) for use as hand-held, portable communications devices are disclosed. A display communications device according to the invention can include a housing (102) that contains a processor, radio transceiver means for transmitting and receiving radio signals, and a collapsible display (106) that is mechanically coupled to the housing and electrically coupled to the processor. The display can have a surface area that is larger than any cross-sectional area of the housing. The processor can be adapted to extract display data from input radio signals, and to provide a representation of the display data to the display.

Dynamic digital communication system control

Abstract: Control of a digital communication system having a plurality of communication lines on which signals are transmitted and received is implemented using a variety of methods and systems. According to one embodiment of the present invention, a method is implemented where the signals are affected by interference during transmission and each of the communication lines has at least one transmitter and at least one receiver. A model is created of the interference characteristics due to the signals carried on the communication lines. Interference characteristics for a line are determined based on the model and actual signals carried on other communication lines different from the line for which the characteristics are being determined. Actual interference is compensated for on the communication line using the determined interference characteristics.

Implementation and performance of cooperative control of shunt active filters for harmonic damping throughout a power distribution system

Abstract: This paper proposes the cooperative control of multiple active filters based on voltage detection for harmonic damping throughout a power distribution system. The arrangement of a real distribution system would be changed according to system operation, and/or fault conditions. In addition, shunt capacitors and loads are individually connected to, or disconnected from, the distribution system. Independent control might make multiple active filters produce unbalanced compensating currents. This paper presents hardware and software implementations of cooperative control for two active filters. Experimental results verify the effectiveness of the cooperative control with the help of a communication system.

Method and apparatus for adaptive carrier allocation and power control in multi-carrier communication systems

Abstract: An apparatus and process for allocating carriers in a multi-carrier system is described. In one embodiment, the process comprises determining a location (E, D, C, B, A; fig. 6) of a subscriber (520) with respect to a base station (510), selecting carriers from a band of carriers to allocate to the subscriber (520) according to the location of the subscriber with respect to the base station (510), and allocating selected carriers to the subscriber (520).