Showing papers on "Relay published in 2001"

Method of monitoring quality of communication for each flow

Abstract: A packet switch identifies a communication flow carried across an IP network, observes the communication flow, and acquires statistics data thereof, such as the number of packets that passed through the switch, the number of discarded packets, time at which the packets arrived at the switch, and time at which the packets were sent out from the switch. The packet switch continues to acquire the statistics data on the communication flow while the communication flow continues. If the packet switch performs a relay function, it sends the locally obtained statistics data to the adjoining packet switch placed downstream. If the packet switch is a node placed on either end edge of the network, it gathers the statistics data obtained by and delivered from other switches in the network and sends the gathered statistics data to the network management system.

Linked network switch configuration

Abstract: A network device having a plurality of ports including address resolution logic (ARL), a first switch, a second switch, and a CPU. The first and second switches include groups of ports which are a subset of the plurality of ports and are numbered by different numbering schemes, rate control logic for performing rate control functions related to switching data packets between the network ports, and local communications channels for transmitting messages between the groups of ports and the rate control logic. The first switch is configured to generate a rate control message and relay the rate control message to the second switch, and the second switch is configured to generate a second rate control message based on the first rate control message, where the second rate control message is different than the first message.

MEM relay for reconfigurable RF circuits

Abstract: We describe a microelectromechanical (MEM) relay technology for high-performance reconfigurable RF circuits. This microrelay, fabricated using surface micromachining, is a metal contact relay with electrical isolation between signal and drive lines. This relay provides excellent switching performance over a broad frequency band (insertion loss of 0.1 dB and isolation of 30 dB at 40 GHz), versatility in switch circuit configurations (microstrip and coplanar, shunt and series), and the capability for monolithic integration with high-frequency electronics. In addition, this MEM relay technology has demonstrated yields and lifetimes that are promising for RF circuit implementation.

Coding for relay channels with confidential messages

Abstract: We consider a relay channel where a relay helps the transmission of messages from one sender to one receiver. The relay is considered not only as a sender that helps the message transmission but as a wire-tapper who can obtain some knowledge about the transmitted messages. In this paper we study the coding problem of the relay channel under the situation that some of transmitted messages are confidential to the relay. A security of such confidential messages is measured by the conditional entropy. We derive an explicit inner bound of the capacity region characterized with the set of transmission rates for which messages are reliably transmitted and the security of confidential messages is larger than a prescribed level.

Satellite communications system using multiple earth stations

Abstract: A satellite communications system uses multiple ground station and one or more stellites for communicating between mobile subscribers and a land-based communications network, such as the PSTN or the Internet. Multiple ground stations geographically dispersed minimize tool charges incurred routing calls from a mobile subscriber through the land network by reducing the need for long-distance calling. Further, because each ground station communicates with a given satellite using the same frequency spectrum, the subscriber capacity of the system increases and/or bandwidth requirements for the communications link between ground stations and satellites may be reduced. The present system uses ground-based beamforming techniques enabling each satellite to transmit signal in multiple transmission beams, each beam supporting one or more mobile subscribers. Each beam may reuse the same frequency spectrum, thereby increasing the number of subscribers supported by each satellite. Multiple ground stations cooperatively relay signals through a given satellite in a manner complementary with ground-based beamforming.

New multi-ended fault location design for two- or three-terminal lines

Abstract: This paper presents a new fault location system for multiterminal power transmission lines. The algorithm used by this system is suitable for inclusion in a numerical protection relay, which communicates with remote relay(s) over a protective relaying channel. The data volume communicated between relays is sufficiently small to be easily transmitted using a digital protection channel. The new algorithm does not require data alignment, pre-fault load flow information, phase selection information, and does not perform iterations to calculate the distance to the fault. Pre-fault load flow, zero-sequence mutual coupling, fault resistance, power system nonhomogeneity, and current infeeds from other line terminals or tapped loads do not affect the fault location accuracy.

High precision linear motor control via relay-tuning and iterative learning based on zero-phase filtering

Abstract: In this paper, with a modest amount of modeling effort, a feedback-feedforward control structure is proposed for precision motion control of a permanent magnet linear motor for applications which are inherently repetitive in terms of the motion trajectories. First, a proportional-integral-derivative (PID) feedback controller is designed using an automatic relay tuning method. An iterative learning controller based on zero-phase filtering is applied as feedforward controller to the existing relay-tuned PID feedback controller to enhance the trajectory tracking performance by utilizing the experience gained from the repeated execution of the same operations. Experimental results are presented to demonstrate the practical appeal and effectiveness of the proposed scheme.

A fast adaptive digital distance protection

Abstract: This paper presents a new adaptive technique which can improve the performance of digital distance protection under high resistance earth fault conditions. In this technique, the relay operating characteristic is divided into certain and uncertain fault regions. The certain region is a preset fixed region which is obtained by the system studies under different operating conditions. The faults in the certain region are tripped quite instantly. However, for the other faults an adaptive routine is instigated which uses prefault system data available from a low speed communication channel such as SCADA or RTU. The distance relay with necessary data can provide a reliable trip decision for the whole line length in zone-1 setting. The results of computer simulation show the improvement of sensitivity and selectivity of the relay.

Distributed compression for sensor networks

Abstract: We consider the problem of efficiently transmitting sets of spatially correlated observations in a distributed sensor network without requiring inter-node communication to exploit the correlation. Specifically, we provide a construction for quantizer design given a training set, and a distributed compression scheme to efficiently relay the quantized observations to a central decoder.

Inter-network relay unit and transfer scheduling method in the same

Abstract: An inter-network relay unit is provided that is capable of simultaneously achieving guaranteed minimum bandwidth and priority control (including relay priority, discard priority, delay priority, etc.). A rate controller outputs relatively high priority packets from priority queues as guaranteed traffic based on guaranteed bandwidth for each link. Relatively low priority packets left in the priority queues are marked for preferential discard and output as best-effort traffic by an aging timer. When an output port is congested, an output queue portion discards only the marked packets. Thus, traffic having a plurality of relay priorities can use the guaranteed minimum bandwidth effectively and the guaranteed minimum bandwidth can be secured, irrespective of change in traffic volume for each relay priority level.

A theoretical characterization of the multihop wireless communications channel with diversity

Abstract: This paper provides a theoretical characterization of the multihop wireless communications channel with diversity, wherein intermediate terminals relay information employing spatial diversity techniques. Two channel models are proposed and developed: one where each intermediate terminal combines, digitally decodes, and re-encodes the received signals from all preceding terminals and the other where each intermediate terminal simply combines and amplifies the received signals from all preceding terminals. These models are compared, through analysis and simulations, with the single-hop reference channel on the basis of probability of outage and probability of error. Both models achieve significant gains over the single-hop reference channel, with the amplified relaying model outperforming the decoded relaying model despite noise propagation.

Compact non-contact electrical switch

Abstract: A compact non-contact electrical switch for use in an electrical box mounted on a wall has a capacitance sensor for detecting a presence of a hand placed adjacent to the switch and for generating a first data bit, and a CPU for receiving the data bit and for calculating a power output in response to the first data bit. The CPU generates a control signal for controlling a triac or relay and thus the power supplied to an electrical circuit passing through the box, for on/off and optionally dimmer control responsive to the proximity of the hand.

Software models for relays

Abstract: This paper reviews the past and present uses of relay models. It discusses the various types of models, what information is required to build such models and the model validation process. Examples of present and possible future use of software models are given.

Electronic circuit breaker

Abstract: The electronic circuit breaker comprises an input (A, B) for connection to a power-supply network and an output (C, D) for connection to a load (Z). Set between the input and the output are a switch (7), a relay (8) and a limitation block (9), which controls the switch (7) to cause at least partial inhibition thereof in the event of overcurrent. Moreover provided is a microprocessor (13), which is connected to the limitation block (9) to inhibit power supply to the load (Z).

Radio network, relay node, core node, relay transmission method used in the same and program thereof

Abstract: A radio network can select a route of minimum path loss among entire relay routes and can set the relay route satisfactorily resistive against interference. The radio network has a core node connected to a wired network, relay nodes each relaying at least one of a down-link data packet transmitted from the core node and an up-link data packet directed toward the core node, and a terminal station capable of transmission and reception of data packet with both of the core node and the relay node. The relay node has total path loss to be minimum at least one of between relay nodes includes in a relay route of the data packet and between the relay node and the core node.

Methods and apparatus for reducing signal degradation

Abstract: A single frequency relay station receives a signal from a master station, and retransmits it. Before retransmitting the signal, the relay station uses a digital filter to subtract from the signal components which arise from multipath interference and coupling interference. The coefficients used by the digital filter are derived from characteristics of the multipath interference and the overall transfer function of the relay station. These are derived by turning off the retransmission, so that the multipath interference can be estimated from the received signal, and commencing the retransmission again, to determine the transfer function. A simplified inverse fast Fourier transform is used to simplify the calculations.

Electric power steering apparatus

Abstract: In an electric power steering apparatus, a switch means (40) is provided with a shutoff means (70) which extends from one to another of at least two fixed contact points so as to shut off an extension of a foreign material which allows an electrical continuity of the fixed contact points, between the at least two fixed contact points among four fixed contact points including fixed contact points (a, b) of a first relay (50) and fixed contact points (c, d) of a second relay (60).

A Novel Digital Distance Relaying Technique for Transmission Line Protection

Abstract: Parallel transmission lines often pose more difficult protection problems than single lines. In the case of parallel lines, a number of problems arise when using the distance protection. This paper discusses problems associated with parallel line distance relaying schemes and presents a novel technique to overcome these problems. Two relays instead of four are proposed for the double lines. One relay is located at the beginning and another one at the end. Each relay is fed by three voltage and six current signals from the two lines. The suggested technique is based on the comparison of the measured impedance of corresponding phases. So, the complexity of the possible types of faults, high path fault resistance, mutual effects, current in-feed, inter-system faults are solved. Moreover, 100% of line is protected and the problem of balance-point locations is avoided. Alternative transient program models the power system and simulates different fault conditions.

Ofdm multiple upstream receiver network

Abstract: A communications system for transferring signals from a wireless transmitter to a hub station, comprising a wireless transmitter configured to transmit a data signal using multiple sub-carriers, a plurality of base stations each configured to receive the multiple sub-carrier data signal and relay the multiple sub-carrier data signal to a hub station; and a hub station configured to receive and combine the multiple sub-carrier data signals from the plurality of base stations. The wireless transmitter may use an orthogonal frequency division modulation (OFDM) scheme to transmit portions of the data signal in parallel on multiple sub-carriers.

Communications relay device, communications relay method, communications terminal apparatus and program storage medium

Abstract: A system capable of switching terminals while continuously receiving data on terminals monitored by a relay device such as a gateway. In devices such as a gateway for relaying data, the session status of the terminal under control is monitored and the relay processing status of data received externally over a network is changed according to requests such as pause, list, resume and call from a terminal, and the dynamic data address is changed or the relay of data is temporarily halted (pause). The present structure allows the user (client) to change the terminal receiving the data and change the receive processing status so that data can be continuously received on the terminal used after switching terminals.

An Impedance-Based CT Saturation Detection Algorithm for Bus-Bar Differential Protection

Abstract: This paper presents an algorithm for current transformer (CT) saturation detection based on the measurement of the power system source impedance seen at the relay location. The algorithm estimates this source impedance using a short-data window impedance-estimation algorithm and samples taken from the CT secondary current and bus-bar voltage. Following the changes on the impedance seen at the relay location, the algorithm is able to detect a CT saturation and send a blocking order to a fast tripping bus-bar differential relay.

Differential protective relay for electrical buses with improved immunity to saturation of current transformers

Abstract: A differential protective relay and method for a microprocessor-based bus differential protective relay that ensures fast and sensitive operation under internal fault conditions and offers improved stability during external fault and other non-internal fault conditions. The method uses a two-slope differential characteristic to cope with small CT transformation errors without reducing relay sensitivity. The method can also use a saturation detector to switch dynamically between the 1-out-of-2 and 2-out-of-2 operating mode depending whether or not the CTs saturate. In a 2-out-of-2 operating mode, both the differential and directional elements must confirm a fault for the relay to trip. In a 1-out-of-2 mode, if saturation is not detected, the relay can trip without checking the fault direction.

Robust self-tuning PID controller for nonlinear systems

Abstract: We propose a robust self-tuning PID controller suitable for nonlinear systems. The control system employs a preload relay (P_Relay) in series with a PID controller. The P_Relay ensures a high gain to yield a robust performance. However, it also incurs a chattering phenomenon. In this paper, instead of viewing the chattering as an undesirable yet inevitable feature, we use it as a naturally occurring signal for tuning and re-tuning the PID controller as the operating regime digresses. No other explicit input signal is required. Once the PID controller is tuned for a particular operating point, the relay may be disabled and chattering ceases correspondingly. However, it is invoked when there is a change in set-point to another operating regime. In this way, the approach is also applicable to time-varying systems as the PID tuning can be continuous, based on the latest set of chattering characteristics. Simulation results for the level control of fluid in a spherical tank using the scheme are also presented.

Network system using dedicated downlink network and bidirectional network

Abstract: A packet relay device for processing a request message of a prescribed protocol on behalf of a radio terminal is provided at a first sub-network which is capable of communications in the downlink direction with respect to the radio terminal only. Then, a request message encapsulated in an IP packer is transferred from the radio terminal to the packet relay device through the second sub-network which is capable of communications in both uplink direction and the downlink direction with respect to the radio terminal, and a response message corresponding to the request message is transferred from the packet relay device to the radio terminal, so that it becomes possible for the radio terminal to execute a prescribed protocol with respect to the first sub-network.

Functional separation of internal and external controls in network devices

Abstract: The present invention provides a network device, such as a network switch or a router, having a high degree of modularity and reliability The network device includes a data plane and a control plane The data plane relays datagrams between a pair of receive and transmit network interface ports The control plane runs management and control operations, such as routing and policing algorithms which provide the data plane with instructions on how to relay cells/packets/frames Further, the control plane includes an internal control device (40a-40b) that is primarily responsible for managing the internal resources of the network device, and a separate external control device that is primarily responsible for operations relating to the interfacing of the network device with an external environment

Data relay method, its apparatus, and data relay system using the apparatus

Abstract: A plurality of relay apparatuses are provided within an IP network of an ISP, and these relay apparatuses are connected to each other by logical tunnels. Each relay apparatus determines the type of a destination address at the Layer 2 level from the data loaded from a host device. When the type is for broadcast, the relay apparatus identifies a tunnel as a relay destination from the data contents set in correlation with destination addresses at the Layer 3 level, and transmits the data only to the relevant relay destination tunnel.

Combining connections for parallel access to multiple frame relay and other private networks

Abstract: Methods, configured storage media, and systems are provided for communications using two or more frame relay or point-to-point networks in parallel to provide load balancing across network connections, greater reliability, and/or increased security. A controller provides access to two or more private networks in parallel, through direct or indirect network interfaces. When one attached network fails, the failure is sensed by the controller and traffic is routed through one or more other private networks. When all attached networks are operating, the controller preferably balances the load between them.

New magnetizing inrush restraining algorithm for power transformer protection

Abstract: Large power transformers belong to a class of vital and very expensive components in electric power systems. Accordingly, high demands are imposed on power transformer protective relays. The operating conditions of transformer protection, however, do not make the relaying task easy. Protection of large power transformers is one of the most challenging problems in the area of power system relaying. Magnetizing inrush inhibit is one the issues. Traditional second harmonic restraining technique may face security problems as the level of the second harmonic may drop below the reasonable threshold setting (around 20%) permanently or for several power system cycles during magnetizing inrush conditions. This is particularly true for modern transformers with magnetic cores built with improved materials, but it has a bearing upon old designs as well. Numerical relays capable of performing sophisticated signal processing functions enable the relay designer to re-visit the classical protection principles and enhance the relay performance, facilitating faster, more secure and dependable protection for power transformers. A new magnetizing inrush restraining technique presented in this paper uses the angular relationship between the first and second harmonics of the differential current. Thus, the technique adds a new dimension to the traditional approach that measures the magnitude ratio only between the fundamental frequency component and the second harmonic.