• Title/Summary/Keyword: Wire link

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Performance Issues with General Packet Radio Service

  • Chakravorty, Rajiv;Pratt, Ian
    • Journal of Communications and Networks
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    • v.4 no.4
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    • pp.266-281
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    • 2002
  • The General Packet Radio Service (GPRS) is being deployed by GSM network operators world-wide, and promises to provide users with “always-on” data access at bandwidths comparable to that of conventional fixed-wire telephone modems. However, many users have found the reality to be rather different, experiencing very disappointing performance when, for example, browsing the web over GPRS. In this paper, we examine the causes, and show how unfortunate interactions between the GPRS link characteristics and TCP/IP protocols lead to poor performance. A performance characterization of the GPRS link-layer is presented, determined through extensive measurements taken over production networks. We present measurements of packet loss rates, bandwidth availability, link stability, and round-trip time. The effect these characteristics have on TCP behavior are examined, demonstrating how they can result in poor link utilization, excessive packet queueing, and slow recovery from packet losses. Further, we show that the HTTP protocol can compound these issues, leading to dire WWW performance. We go on to show how the use of a transparent proxy interposed near the wired-wireless border can be used to alleviate many of these performance issues without requiring changes to either client or server end systems.

Transmission Characteristics on Wire-Driven Links of a Bridge Transported Servo Manipulator for the ACP Equipment Maintenance (사용후핵연료 차세대관리 공정장치 유지보수용 천정이동 서보 매니퓰레이터 와이어 구동부 동작특성)

  • 박병석;진재현;송태길;김성현;윤지섭
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.2 no.3
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    • pp.189-199
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    • 2004
  • A bridge transported servo manipulator (BTSM) system for the advanced spent fuel conditioning process (ACP) has been developed to overcome the limitation of access, which is a drawback of mechanical master-slave manipulators (MSM) for the equipment maintenance. The servo manipulator is composed of a slave manipulator attached to the telescoping tubesets equipped with the overhead bridge installed at a hot cell and a master manipulator installed at an out-of-hot cell. Each manipulator has 7 degrees-of-freedom (DOF): a body rotation, an upper-arm tilt, a lower-arm tilt, a lower-arm rotation, a wrist pan & tilt, and a grasp motion. A wire-driven mechanism for a lower-arm rotation, a wrist pan and tilt, and a grasp motion of the manipulator has been adopted to increase the handling capacity compared to the manipulator weight and decrease the friction. The main disadvantage of the wire-driven mechanism is that if one link is in motion, other links can be affected. In this paper, the transmission characteristics among the wire-driven links have been formulated to overcome this drawback. The unexpected behaviors are confirmed by analyses of transmission characteristics as well as experiments. Also, the experimental results show that the unexpected behaviors are greatly decreased by the proposed compensation equations.

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Battery Energy Storage System Based Controller for a Wind Turbine Driven Isolated Asynchronous Generator

  • Singh, Bhim;Kasal, Gaurav Kumar
    • Journal of Power Electronics
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    • v.8 no.1
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    • pp.81-90
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    • 2008
  • This paper presents an investigation of a voltage and frequency controller for an isolated asynchronous generator (IAG) driven. by a wind turbine and supplying 3-phase 4-wire loads to the isolated areas where a grid is not accessible. The control strategy is based on the indirect current control of the VSC (voltage source converter) using the frequency PI controller. The proposed controller consists of three single-phase IGBT (Insulated Gate Bipolar Junction Transistor) based VSC, which are connected to each phase of the IAG through three single phase transformers and a battery at their DC link. The controller has the capability of controlling reactive and active powers to regulate the magnitude and frequency of the generated voltage, harmonic elimination, load balancing and neutral current compensation. The proposed isolated system is modeled and simulated in MATLAB using Simulink and PSB (Power System Block-set) toolboxes to verify the performance of the controller.

Development of a Network System for Monitoring Coastal Oceanographic Data (연안 해양학적 자료 수집을 위한 관측망 시스템의 개발)

  • Kim, Sang-Bong;Gam, Byeong-O;Gang, Byeong-Cheol;Kim, Dong-Gyu
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.139-146
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    • 1998
  • This paper introduces a network system for monitoring coastal oceanographic data. The network system consists of three parts such as the buoy to observe oceanographic data, the local site to collect data transferred from buoys, and the host site to construct the oceanographic data-base and to share the information for monitoring coastal oceanographic data. The buoy has a one-board microcomputer to manage and to acquire coastal environment data in real-time. A wireless and wire communication technique is employed in order to transfer data measured by buoys and to link local and host sites, respectively. In measuring coastal environment data, this system shows more cost-effective way than the presents conventional. In addition, the realtime monitoring system continuously from various sites with the network systems.

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IO BOARD DESIGN OF NEXT GENERATION SATELLITE USING THE SPACE WIRE INTERFACE

  • Kwon Ki-Ho;Kim Day-Young;Choi Seung-Woon;Lee Jong-In
    • Bulletin of the Korean Space Science Society
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    • 2004.10b
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    • pp.223-226
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    • 2004
  • This paper presents a feasibility study of an advanced IO board design for the next generation of low-earth orbit satellites. Advanced IO board design includes sensor interface, NO, D/A, Digital Module, Serial Module etc, and allows to process increasing data rates between IO board and CPU board. The higher data rate involved in modem IO board additionally introduce issues such as noise, fault tolerance, command and data handling, limited pin count and power consumption problems. The experience in KOMPSAT-l and 2 program with this kind of problems resulted in using SMCS chip set, a high speed serial link technology based on IEEE-1355 (Space Wire Protocol) (ESA-ESTEC 2003, Parkes 1999), as a standard for next generation of satellite IO board design.

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Experimental and numerical investigation of wire rope devices in base isolation systems

  • Calabrese, Andrea;Spizzuoco, Mariacristina;Losanno, Daniele;Barjani, Arman
    • Earthquakes and Structures
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    • v.18 no.3
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    • pp.275-284
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    • 2020
  • The scope of this study is the comparison between experimental results of tests performed on a base isolated building using helical wire rope isolators (WRs), and results of Nonlinear Response History Analyses (NRHAs) performed using SAP 2000, a commercial software for structural analysis. In the first stage of this research, WRs have been tested under shear deformation beyond their linear range of deformation, and analytical models have been derived to describe the nonlinear response of the bearings under different directions of loading. On the following stage, shaking table tests have been carried out on a 1/3 scale steel model isolated at the base by means of curved surface sliders (CSS) and WRs. The response of the structure under ground motion excitation has been compared to that obtained using numerical analyses in SAP 2000. The feasibility of modelling the nonlinear behavior of the tested isolation layer using multilinear link elements embedded in SAP 2000 is discussed in this paper, together with the advantages of using WRs as supplemental devices for CSSs base isolated structures.

Clock Skew Optimization Using Link-Edge Insertion (연결-에지 추가 기법을 이용한 클락 스큐 최적화)

  • 정공옥;류광기신현철정정화
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.1009-1012
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    • 1998
  • An efficient algorithm for clock skew optimization is proposed in this paper. It construct a new clock routing topology which is the generalized graph model while previous methods uses tree-structured routing topology. Edge-insertion technique is used in order to reduce the clock skew. A link-edge is inserted repeatedly between two sinks whose delay difference is large and the distance is small. As a result, the delay of a sink which has the longer delay is decreased and the clock skew is reduced. The proposed algorithm is implemented in C programming language. From the experimental results, we can get the total wire length minimization under the given skew bound.

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Comparison about TCP and Snoop protocol on wired and wireless integrated network (유무선 혼합망에서 TCP와 Snoop 프로토콜 비교에 관한 연구)

  • Kim, Chang Hee
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.5 no.2
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    • pp.141-156
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    • 2009
  • As the TCP is the protocol designed for the wired network that packet loss probability is very low, because TCP transmitter takes it for granted that the packet loss by the wireless network characteristics is occurred by the network congestion and lowers the transmitter's transmission rate, the performance is degraded. The Snoop Protocol was designed for the wired network by putting the Snoop agent module on the BS(Base Station) that connect the wire network to the wireless network to complement the TCP problem. The Snoop agent cash the packets being transferred to the wireless terminal and recover the loss by resending locally for the error occurred in the wireless link. The Snoop agent blocks the unnecessary congestion control by preventing the dupack (duplicate acknowledgement)for the retransmitted packet from sending to the sender and hiding the loss in the wireless link from the sender. We evaluated the performance in the wired/wireless network and in various TCP versions using the TCP designed for the wired network and the Snoop designed for the wireless network and evaluated the performance of the wired/wireless hybrid network in the wireless link environment that the continuous packet loss occur.

MSD가 존재하는 시편에 대한 잔류강도 평가

  • 신규인;김태순;박재학
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 1998.05a
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    • pp.77-82
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    • 1998
  • The residual strength of a specimen with MSD was investigated experimentally and numerically. The used materials for specimens are 2024-T3 and S50C. In each specimen, one main crack and 4 small cracks are machined by using electrical discharge wire cutting and saw cutting. The residual strengths are measured for 3 cases of crack configurations, and the measured values are compared with the values obtained numerically by using elasto-plastic average uncracked ligament stress link-up criteria.

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