Showing papers on "Relay published in 2002"

The role of the thalamus in the flow of information to the cortex

Abstract: The lateral geniculate nucleus is the best understood thalamic relay and serves as a model for all thalamic relays. Only 5-10% of the input to geniculate relay cells derives from the retina, which is the driving input. The rest is modulatory and derives from local inhibitory inputs, descending inputs from layer 6 of the visual cortex, and ascending inputs from the brainstem. These modulatory inputs control many features of retinogeniculate transmission. One such feature is the response mode, burst or tonic, of relay cells, which relates to the attentional demands at the moment. This response mode depends on membrane potential, which is controlled effectively by the modulator inputs. The lateral geniculate nucleus is a first-order relay, because it relays subcortical (i.e. retinal) information to the cortex for the first time. By contrast, the other main thalamic relay of visual information, the pulvinar region, is largely a higher-order relay, since much of it relays information from layer 5 of one cortical area to another. All thalamic relays receive a layer-6 modulatory input from cortex, but higher-order relays in addition receive a layer-5 driver input. Corticocortical processing may involve these corticothalamocortical 're-entry' routes to a far greater extent than previously appreciated. If so, the thalamus sits at an indispensable position for the modulation of messages involved in corticocortical processing.

On the capacity of wireless networks: the relay case

Abstract: Gupta and Kumar (see IEEE Transactions an Information Theory, vol.46, no.2, p.388-404, 2000) determined the capacity of wireless networks under certain assumptions, among them point-to-point coding, which excludes for example multi-access and broadcast codes. We consider essentially the same physical model of a wireless network under a different traffic pattern, namely the relay traffic pattern, but we allow for arbitrarily complex network coding. In our model, there is only one active source/destination pair, while all other nodes assist this transmission. We show code constructions leading to achievable rates and derive upper bounds from the max-flow min-cut theorem. It is shown that lower and upper bounds meet asymptotically as the number of nodes in the network goes to infinity, thus proving that the capacity of the wireless network with n nodes under the relay traffic pattern behaves like log n bits per second. This demonstrates also that network coding is essential: under the point-to-point coding assumption considered by Gupta et al., the achievable rate is constant, independent of the number of nodes. Moreover, the result of this paper has implications' and extensions to fading channels and to sensor networks.

Method and apparatus for supporting communications between a computing device within a network and an external computing device

Abstract: A network communication bridge establishes communication between a computing system within a protected network and an external computing system. A registrar is positioned outside the protected network and registers authorized users. The registrar determines if the computing device associated with the user is publicly addressable, and for those computing devices that are not publicly addressable, the computing device maintains a persistent communication session with a bridge proxy server. The bridge proxy server employs a reversal or relaying technique to enable communication between two systems that cannot ordinarily establish communication with each other, based on characteristics of the two systems. If at least one party to a communication is publicly addressable, then a reversal technique is employed. If neither party to the communication is publicly addressable, then both parties have a persistent session with their respective bridge proxy server, and the bridge proxy server acts as a “relay service” for communications between the initiator and the recipient. The invention can be implemented as a separate application or as an enhancement to the Session Initiation Protocol (SIP).

Performance analysis of two-hop relayed transmissions over Rayleigh fading channels

Abstract: Closed form expressions for the statistics of the harmonic mean of two independent exponential variates are presented. These statistical results are then applied to study the performance of wireless communication systems with non-regenerative relays over flat Rayleigh fading channels. It is shown that these results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, outage probability formulas for noise limited systems are obtained. Furthermore, outage capacity and bit error rate (BER) expressions for binary differential phase shift keying are derived. Finally, comparisons between regenerative and non-regenerative systems are presented. Numerical results show that the former systems clearly outperform the latter ones for low average signal-to-noise-ratio (SNR). They also show that the two systems have similar performance at high average SNR.

A new optimal approach for coordination of overcurrent relays in interconnected power systems

Abstract: In this paper, a new method for optimum coordination of overcurrent relays is proposed. The proposed method is based on only constraints. Minimization is inherently included by setting the time dials to minimum and increasing their values gradually. Configuration changes of the network are taken into account. The method does not need any initial solution. It can consider both linear and nonlinear relay characteristics models. The optimal settings of overcurrent relays for 8-Bus and England Norweb networks are obtained and comparison between the new method and existing methods is made.

Method and system for distributing data in a network

Abstract: A data distribution method is disclosed which can realize autonomous or private data distribution between user terminals in a network environment such as the Internet. In this method, the respective nodes exchange topology information indicating a connection relationship between upstream nodes and downstream nodes, and relay stream data from the upstream nodes to the downstream nodes. Each node arbitrarily separates from the network and connects to an upstream node in accordance with a predetermined condition.

Coverage enhancement through two-hop relaying in cellular radio systems

Abstract: Digital relaying is a technique that uses certain mobile terminals that have good communication links with the base station to act as relay nodes for those that do not have. With this technique, the signal quality at the destination is expected to improve since the signal only goes through favorable links and, at each intermediate node, the signal is decoded and re-encoded (so that no noise is propagated) before forwarding. One of the major costs of relaying is that additional channels are needed. We investigated the effect of using different schemes for selecting channels - among those already used in the adjacent cells - for relaying on performance improvement. Our simulation results show that not only can relaying improve the performance; but also, with power control this improvement is quite insensitive to the channel selection scheme. Furthermore, with small cell radii where there is a potential for high interference level, only a low relay node transmit power is sufficient to improve the system performance significantly.

Distributed space-time coded protocols for exploiting cooperative diversity in wireless networks

Abstract: We develop and analyze space-time coded cooperative diversity protocols for combating multipath fading across multiple protocol layers in a wireless network. The protocols exploit spatial diversity available among a collection of distributed terminals that relay messages for one another in such a manner that the destination terminal can average the fading, even though it is unknown a priori which terminals will be involved. In particular, a source initiates transmission to its destination, and many relays potentially receive the transmission. Those terminals that can fully decode the transmission utilize a space-time code to cooperatively relay to the destination. We demonstrate that these protocols achieve full spatial diversity in the number of cooperating terminals, not just the number of decoding relays, and can be used effectively for higher spectral efficiencies than repetition-based schemes. We discuss issues related to space-time code design for these protocols, emphasizing codes that readily allow for appealing distributed versions.

Multi-user spatial diversity in a shadow-fading environment

Abstract: In a wireless network, communication between a source and a destination mobile station (DMS) fails to establish if the source or the DMS is located inside a deep shadow-fading region. In this situation, intermediate mobile stations may be used to relay the signal between the two nodes. In a cellular system the source is a base station (BS) and the DMS is a weak mobile station (MS) while in an ad-hoc network, the source and the DMS are two nodes of the network. In this paper we study the scheme of "multi-user spatial diversity" as a new method of diversity to combat the undesired shadow-fade situation. We study the case where one or several mobile stations (MSs) relay the signal between the source and the DMS, in a shadow-fading environment. We derive a formula for the average outage probability of the received signal to noise ratio at the DMS, when M intermediate MSs relay the signal from the source to the DMS according to a particular protocol. The outage probability improves as the number of the relays increases.

An adaptive scheme to prevent undesirable distance protection operation during voltage instability

Abstract: An adaptive algorithm to prevent undesirable distance protection operations during voltage instability is proposed. The algorithm is based on mathematical logic blocks and uses the rate of change of voltage as an additional relay criteria to increase the relay security with respect to voltage instability. Studies are based on simulations using two different test systems; a 15-bus system developed by the authors and the Nordic32 system. The investigation shows that undesirable zone 3 distance relay operations can be the difference between a blackout and a recovering system during voltage instability. However, simulations have shown that the adaptive algorithm may save the system from a collapse. Although the algorithm prevents mal-trips due to voltage instability, the reach of the distance relay will not be restricted.

Determination of the optimum routine test and self-checking intervals in protective relaying using a reliability model

Abstract: Relaying reliability is generally separated into the two different aspects of dependability and security. The reliability of a protection relay can be improved by carrying out routine maintenance or by including built-in monitoring and self-checking facilities during the design stages. A Markov model is described in this paper which can be used to examine these features. The model also recognizes common-cause failures, temporary and permanent faults and the associated clearing times, operation of back-up protection, and relay mal-trips. Studies have been conducted to illustrate the expected reliability benefits by inclusion of monitoring and self-checking facilities within the relay.

Network system capable of selecting optimal route according to type of transmitted data

Abstract: A network system, enabling the quality of the data to be ensured and efficient use can be made of the network, including at least one network relay apparatus provided with a discriminating unit for discriminating the type of data transmitted, a selecting unit for selecting the optimal route for each string of data in accordance with the discriminated type and destination, and a holding unit for holding the optimal routing information for each type of data and destination and sending received data toward the optimal route.

Limit cycles with chattering in relay feedback systems

Abstract: Relay feedback has a large variety of applications in control engineering. Several interesting phenomena occur in simple relay systems. In the paper, scalar linear systems with relay feedback are analyzed. It is shown that a limit cycle where part of the limit cycle consists of fast relay switchings can occur. This chattering is analyzed in detail and conditions for approximating it by a sliding mode are derived. A result on existence of limit cycles with chattering is given, and it is shown that the limit cycles can have arbitrarily many relay switchings each period. Limit cycles with regular sliding modes are also discussed. Examples illustrate the results.

Multi-functional hybrid contactor

Abstract: A multi-functional hybrid contactor has a motor protection function against an abnormal state in addition to the starting, running and stopping of the motor, the same effect as the case that an electronic motor protection relay (EMPR) is connected in parallel can be obtained with only one multi-functional hybrid contactor. Also, the size of the product is much reduced compared to the case that the electric motor protection relay (EMPR) is connected in parallel, and its cost can be reduced. In addition, since the semiconductor switch is turned on only in the initial stage of starting and stopping, the rated current capacity and size of the semiconductor switch can be considerably reduced compared to the conventional soft starting method in which the semiconductor switch is used for controlling of all of starting, running and stopping.

The impact of FACTS device on digital multifunctional protective relays

Abstract: In this paper, the results of the application of multifunctional relays for the protection of compensated lines with FACTS devices is presented. The impact of different FACTS devices on the protective relays behavior is investigated. Since the distance relay is of great concern in transmission lines, the role of the applied protective algorithm in the presence of FACTS devices is presented. It is shown that different methods to perform the distance measurement in multifunctional relays could be effective in accurate discrimination. Some of them may be immune to the variations that would be caused by FACTS devices. The results indicate the importance of the protective relay specifications in the protection of the compensated lines.

An adaptive distance relay and its performance comparison with a fixed data window distance relay

Abstract: This paper describes the design, implementation and testing of an adaptive distance relay. The relay uses a fault detector to determine the inception of a fault and then uses data windows of appropriate length for estimating phasors and seen impedances. Hardware and software of the proposed adaptive relay are also described in this paper. The relay was tested using a model power system and a real-time playback simulator. Performance of the relay was compared with a fixed data window distance relay. Some results are reported in this paper. These results indicate that the adaptive distance relay provides faster tripping in comparison to the fixed data window distance relay.

Integrated cellular and ad hoc relay (iCAR) systems: pushing the performance limits of conventional wireless networks

Abstract: Performance of iCAR system - a new load balancing scheme in wireless networks - is analyzed. Traffic capacity enhancement of the iCAR system with respect to the conventional cellular system, without any load balancing, is evaluated. It is shown that, with a moderate amount of relay coverage, perfect load balancing can be achieved, thus enabling the system to support maximum possible traffic intensity for a given grade of service.

Method for relay transmission in a mobile communication system

Abstract: A method of relay transmission in a mobile communication system. The mobile communication system includes at least one base station and a plurality of user equipments (UEs). When one of the UEs attempts to send a message to the base station, this one of the UEs, referred to as a requesting UE, is capable of using the method of relay transmission to send messages to the base station via another one or more UEs, referred to as relay UEs. The method of relay transmission includes the following steps. First, a relay request confirmation procedure for the requesting UE and the relay UE is performed. Second, a base station confirmation procedure for the requesting UE, the relay UE, and the base station is executed. Next, an identity authentication procedure for the requesting UE, the relay UE, and the base station is performed. After that, a relay start confirmation procedure for the requesting UE and the relay UE is executed. Finally, a relay transmission procedure for the requesting UE, the relay UE, and the base station is performed, wherein the requesting UE sends the message to the base station via the relay UE. According to the invention, high data rate transmission can be achieved even if the requesting UE is distant from the base station, and thus communication quality can be improved, with a reduced cost.

Relay connection management program, relay connection management method, relay connection management apparatus and recording medium which stores relay connection management program

Abstract: A relay system stores destination information of both end systems for which communications are relayed, the sequence number of the one of the end systems is connected with a high quality transmission path, an ACK response number, a re-transmission count, etc. in a connection management table. Upon receiving a re-transmitted packet from the one of end systems, the relay system searches for the connection management table containing a matching sequence number, and increments the re-transmission count in the table by 1. If the re-transmission count has not reached a certain number, the relay system relays the re-transmitted packet as it is to the other end system.

Efficient, high fidelity transmission of modulation schemes through power-constrained remote relay stations by local transmit predistortion and local receiver feedback

Abstract: A system for pre-distorting samples derived from modulated data symbols to compensate, at least in part, for non-linear operation of a power amplifier in a power-constrained remote relay station. A symbol mapper maps successive renderings of an input alphabet into successive modulation symbols such as but not limited to 16-QAM or 64-QAM symbols. Pre-distortion logic pre-distorts samples derived from the symbols, and logic incorporates samples derived from the pre-distorted samples into a transmission signal. The transmission signal is amplified and transmitted over a communications link to the remote relay station. The system may employ a feedback loop to measure the amount of residual distortion still present is a signal relayed from the relay station and derived from the transmission signal. Responsive to this measured residual distortion, the system dynamically adjusts the amount of pre-distortion (at various input levels) which should be applied to its input samples, to drive the distortion to near-zero or zero, given enough adaptation time.

On the asymptotic capacity of Gaussian relay networks

Abstract: We determine the asymptotic capacity of a Gaussian multiple-relay channel as the number of relays tends to infinity The upper bound is an application of the cut-set theorem, and the lower bound follows from an argument involving uncoded transmission Hence, this paper gives one more example where the cut-set bound is achievable, and one more example where uncoded transmission achieves optimal performance In the latter sense, the result is an extension of the work of Gastpar, Rimoldi and Vetterli (see IEEE Trans Info Theory, May 2001) The arguments of this paper are also relevant to wireless networks, yielding an asymptotic capacity result

Wireless relay system

Abstract: PROBLEM TO BE SOLVED: To provide a wireless relay system that is applied to a wireless communication system adopting a single carrier so as to reduce the cost resulting from non-electric source. SOLUTION: In this wireless relay system, a main relay section 2A of a relay facility 2 is installed in a substantial communication area wherein a mobile station 1A is located, a forward relay section 2B is installed at a place apart from the main relay section 2A and around which a communication area is separately to be set, a direct modulation laser diode 2A3 converts a high frequency signal CU received by an antenna 2A5 of the main relay section 2A into a laser beam signal, which is transmitted to the forward relay section 2B through an optical fiber cable 5, a photodiode 2B2 converts the laser beam signal into an electric signal, and a transmission antenna 2B4 transmits the signal as a radio wave, which a mobile station 1B can receive. An external optical modulator 2B1 converts a high frequency signal CD transmitted from the mobile station 1B and received by a reception antenna 2B3 of the forward relay section 2B into a modulated laser beam signal, which is transmitted to the main relay section 2A through an optical fiber cable 4, a photodiode 2A2 converts the modulated laser beam signal into an electric signal a transmission reception antenna 2A5 transmits as a radio wave, which the mobile station 1A can receive. COPYRIGHT: (C)2004,JPO

Interrogation-based relay routing for ad hoc satellite networks

Abstract: Future Earth and space science missions are envisioned to be implemented using a flexible, distributed architecture consisting of a constellation of dynamically deployed or configured satellites that are networked together into an integrated information system. These satellites form an ad hoc network characterised by a frequently changing topology and potentially sparse and intermittent connectivity, which pose unique challenges to routing. We propose interrogation-based relay routing for ad hoc satellite networks, where the satellites interrogate each other to learn more about network topology and nodal capacity to make intelligent routing decisions. Simulations have been conducted to study the effects of satellite density and orbital patterns on throughput and delivery ratio.

Intake air quantity control system for internal combustion engine

Abstract: Intake air quantity control system, for internal combustion engine, ensuring improved response behaviors incorporates an abnormality supervisor and a fail-safe controller in a duplex CPU system configuration. System includes throttle valve control motor, engine driving machinery, load relay for supplying electric power to a throttle valve, peripheral auxiliary equipment, an alarm display device, main CPU for controlling the throttle valve control motor and the engine driving machinery, subsidiary CPU for controlling a load relay and the peripheral auxiliary equipment through cooperation with the main CPU, sensor groups and, serial interfaces for enabling signals to be transferred between the main CPU and the subsidiary CPU, and an abnormal event storage device for electrically deenergizing the load relay while electrically energizing the alarm display device.

A physical laboratory for protective relay education

Abstract: Undesirable but unavoidable natural events or human errors will occur to disrupt normal power system operation. Engineers must apply protective relay systems for the most probable events based on practical judgment to minimize service interruptions and damage to the equipment. Understanding the performance and limitations of different protective relay systems is vital in their application. One can explain the philosophy of system protection, the basic theory of a protective relay system, and the relay algorithms from classroom sessions and/or computer simulation. However, it is difficult, if not impossible, to evaluate the actual performance and possible misoperation of a relay in the field just through computer simulation or benchtop testing. This paper introduces the usage of the Power System Simulation Laboratory at the Energy Systems Research Center to enhance the teaching and research activities in relay education. A brief description of the laboratory configuration and the design of the relay testing station are presented. Some sample examples to illustrate the use of this facility for undergraduate and graduate education in protective relay systems are also included in this paper.

A novel approach using a FIRANN for fault detection and direction estimation for high-voltage transmission lines

Abstract: This paper presents a novel approach to fault detection, faulted phase selection, and direction estimation based on artificial neural networks (ANNs). The suggested approach uses the finite impulse response artificial neural network (FIRANN) with the same structure and parameters in each relaying location. Our main objective in this work is to find a fast relay design with a detection time not dependent on fault conditions (i.e., current transformer saturation, dynamic arcing faults, short-circuit level, and system topology) and that uses only unfiltered voltage and current samples at 2 kHz. The suggested relay, which we have named FIRANN-DSDST, is composed of a FIRANN together with post-processing elements. The FIRANN is trained globally using training patterns from more than one relaying position in order to be as general as possible. The FIRANN is trained using an improved training algorithm, which depends on a new synaptic weights updating method, which we have named the mixed updating technique. The proposed relay is trained using training patterns created by simulating a real 400-kV network from the Spanish transmission network (REE). Finally, the proposed relay is tested using simulated and real fault data. The results encourage the use of this technology in a protective relaying field.

Load model effects on distance relay settings

Abstract: The purpose of this paper is to study load model effects on distance protective relay settings in Taipower's transmission system. Five load models have been used in order to explore the effects of load characteristics on relay settings: (1) static ZIP model, (2) dynamic motor model, (3) composite model, (4) PTI IEEE model, and (5) exponential model. The major points of this study include (1) setting of impedance values for the three distance protective relay zones and the protection against loss of synchronicity in the outermost periphery, (2) exploring the effects of load models on impedance angles at the time of distance relay tripping, (3) study whether the load model will cause a malfunction in the distance relay when the system swings due to a sudden change in the power system, (4) analyze the coordination of the blocking time of the out-of-step blocking relay during system power swings, and (5) propose how to select a better load model for accuracy in relay settings.

Vehicle with switched supplemental energy storage system for engine cranking

Abstract: A vehicle having an internal combustion engine, a cranking motor, and a battery includes a double-layer capacitor characterized by a capacitance greater than 150 farads, and a low internal resistance. First and second electrical paths interconnect the capacitor with the cranking motor. A control circuit is coupled between the positive and negative terminals of at least one of the capacitor and battery, and this control circuit includes a switch that applies a variable control voltage to a relay in response to the position of the switch. The relay is included in one of the electrical paths, and the relay isolates the capacitor from the cranking motor when switched to the open-circuit condition by the control voltage and enables the capacitor to supply cranking current to the cranking motor when the control voltage places the relay in the closed-circuit condition.