• Title/Summary/Keyword: network gains

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Design and Implementation of Dual Wideband Dipole Type Antenna for the Reception of S-DMB and 2.4/5 GHz WLAN Signals (S-DMB와 2.4/5 GHz WLAN 신호 수신을 위한 이중 광대역 다이폴형 안테나의 설계 및 구현)

  • Kim, Sung-Min;Yang, Woon-Geun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.11 s.114
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    • pp.1021-1029
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    • 2006
  • In this paper, we designed and implemented a dual wideband dipole type antenna for the reception of S-DMB (Satellite Digital Multimedia Broadcasting) and 2.4/5 GHz WLAN(Wireless Local Area Network) signals. The proposed antenna based on conventional monopole type dual band antenna was implemented as planar wideband dipole type antenna with the volume of $8{\times}33.8{\times}1.68mm^3$. The proposed antenna is printed type on FR4 substrate of 1.6 mm thick and composed of a dipole type antenna for low frequency band and two symmetric structured resonance elements for high frequency band. We confirmed antenna area with dense surface current for each frequency band with simulation. By varying the length of the antenna area with dense surface current, we could vary resonance frequency of each frequency band separately. Impedance bandwidths$(VSWR{\leq}2)$ are 362 MHz(14.23 %) for 2 GHz band and 1188 MHz(22.13, %) for 5 GHz band which show wideband characteristic. Measured maximum gains were 4.33 dBi for 2 GHz band and 5.48 dBi for 5 GHz band which showed improved performance. And the implemented antenna has a good omni-directional radiation pattern characteristic.

A Cell Loss Constraint Method of Bandwidth Renegotiation for Prioritized MPEG Video Data Transmission in ATM Networks (ATM망에서 우선 순위가 주어진 MPEG 비디오 데이터 전송시 대역폭 재협상을 통한 셀 손실 방지 기법)

  • Yun, Byoung-An;Kim, Eun-Hwan;Jun, Moon-Seog
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.7
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    • pp.1770-1780
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    • 1997
  • Our problem is improvement of image quality because it is inevitable cell loss of image data when traffic congestion occurs. If cells are discarded indiscriminately in transmission of MPEG video data, it occurs severe degradation in quality of service(QOS). In this paper, to solve this problem, we propose two method. The first, we analyze the traffic characteristics of an MPEG encoder and generate high priority and low priority data stream. During network congestion, only the least low priority cells are dropped, and this ensures that the high priority cells are successfully transmitted, which, in turn, guarantees satisfactory QoS. In this case, the prioritization scheme for the encoder assigns components of the data stream to each priority level based on the value of a parameter ${\beta}$. The second, Number of high priority cells are increased when value of ${\beta}$ is large. It occurs the loss of high priority cell in the congestion. To prevent it, this paper is regulated to data stream rate as buffer occupancy with UPC controller. Therefore, encoder's bandwidth can be calculated renegotiation of the encoder and networks. In this paper, the encoder's bandwidth requirements are characterized by a usage parameter control (UPC) set consisting of peak rate, burstness, and sustained rate. An adaptive encoder rate control algorithm at the Networks Interface Card(NIC) computes the necessary UPC parameter to maintain the user specified quality of service. Simulation results are given for a rate-controlled VBR video encoder operating through an ATM network interface which supports dynamic UPC. These results show that dynamic bandwidth renegotiation of prioritized data stream could provided bandwidth saving and significant quality gains which guarantee high priority data stream.

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Distributed satellite-terrestrial diversity schemes using turbo coded STC (터보부호화된 시공간부호를 이용한 위성-지상 분산 다이버시티 기법)

  • Park, Un-Hee;Kim, Young-Min;Kim, Soo-Young;Kim, Hee-Wook;Ahn, Do-Seob
    • Journal of Satellite, Information and Communications
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    • v.4 no.2
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    • pp.28-33
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    • 2009
  • In this paper, we evaluate the performance of various diversity techniques which can contribute to provide efficient multimedia broadcasting services via hybrid/integrated satellite and terrestrial network. Space-time coding can achieve the diversity gain in a multi-path environment without additional bandwidth requirement. Recent study results reported that satellite systems can achieve high diversity gains by appropriate utilization of STC and/or forward error correction. Based on these previous study results, we present various cooperative diversity techniques by combing STC and rate compatible turbo codes in order to realize the transmit diversity for the mobile satellite system. The satellite and several terrestrial repeaters operate in unison to send the encoded signals, so that receiver may realize diversity gain. The results demonstrated in this paper can be utilized in future system implementation.

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Query Optimization with Metadata Routing Tables on Nano-Q+ Sensor Network with Multiple Heterogeneous Sensors (다중 이기종 센서를 보유한 Nano-Q+ 기반 센서네트워크에서 메타데이타 라우팅 테이블을 이용한 질의 최적화)

  • Nam, Young-Kwang;Choe, Gui-Ja;Lee, Byoung-Dai;Kwak, Kwang-Woong;Lee, Kwang-Yong;Mah, Pyoung-Soo
    • Journal of KIISE:Computing Practices and Letters
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    • v.14 no.1
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    • pp.13-21
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    • 2008
  • In general, data communication among sensor nodes requires more energy than internal processing or sensing activities. In this paper, we propose a noble technique to reduce the number of packet transmissions necessary for sending/receiving queries/results among neighboring nodes with the help of context-aware routing tables. The important information maintained in the context-aware routing table is which physical properties can be measured by descendent nodes reachable from the current node. Based on the information, the node is able to eliminate unnecessary packet transmission by filtering out the child nodes for query dissemination or result relaying. The simulation results show that up to 80% of performance gains can be achieved with our technique.

Band-Rejected UWB Antenna Using Unit Cells of FSS (FSS 단위 셀을 이용한 대역저지 UWB 안테나)

  • Lee, Chang Yong;Jung, Chang Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.7
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    • pp.3431-3436
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    • 2013
  • Band-notched ultra-wideband (UWB) antennas using frequency selective surfaces (FSSs) are presented. The proposed antennas utilized the band rejection characteristic of typical FSS unit cells. We loaded the FSS unit cells on the same plane of planar UWB antenna. These antennas are designed to reject the interference from the wireless local area network band, 5.15-5.825 GHz in the UWB band, 3.1-10.6 GHz. The measured peak gains of the proposed antennas are more than 2 dBi at both operation edge and center frequencies, and sufficient to apply for commercial purpose. The antennas are small size and planar shape for the purpose of the small mobile application, and enhanced design freedom by using various existing FSS unit cells.

On discrete nonlinear self-tuning control

  • Mohler, R.-R.;Rajkumar, V.;Zakrzewski, R.-R.
    • 제어로봇시스템학회:학술대회논문집
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    • 1991.10b
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    • pp.1659-1663
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    • 1991
  • A new control design methodology is presented here which is based on a nonlinear time-series reference model. It is indicated by highly nonlinear simulations that such designs successfully stabilize troublesome aircraft maneuvers undergoing large changes in angle of attack as well as large electric power transients due to line faults. In both applications, the nonlinear controller was significantly better than the corresponding linear adaptive controller. For the electric power network, a flexible a.c. transmission system (FACTS) with series capacitor power feedback control is studied. A bilinear auto-regressive moving average (BARMA) reference model is identified from system data and the feedback control manipulated according to a desired reference state. The control is optimized according to a predictive one-step quadratic performance index (J). A similar algorithm is derived for control of rapid changes in aircraft angle of attack over a normally unstable flight regime. In the latter case, however, a generalization of a bilinear time-series model reference includes quadratic and cubic terms in angle of attack. These applications are typical of the numerous plants for which nonlinear adaptive control has the potential to provide significant performance improvements. For aircraft control, significant maneuverability gains can provide safer transportation under large windshear disturbances as well as tactical advantages. For FACTS, there is the potential for significant increase in admissible electric power transmission over available transmission lines along with energy conservation. Electric power systems are inherently nonlinear for significant transient variations from synchronism such as may result for large fault disturbances. In such cases, traditional linear controllers may not stabilize the swing (in rotor angle) without inefficient energy wasting strategies to shed loads, etc. Fortunately, the advent of power electronics (e.g., high-speed thyristors) admits the possibility of adaptive control by means of FACTS. Line admittance manipulation seems to be an effective means to achieve stabilization and high efficiency for such FACTS. This results in parametric (or multiplicative) control of a highly nonlinear plant.

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Design and Fabrication of X-band Wideband Array Antenna for SAR Applications (SAR를 위한 X-band 광대역 배열 안테나의 설계 및 제작)

  • Won Young-Jin;Lee Young-Ju;Kong Young-Kyun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.2 s.105
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    • pp.184-192
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    • 2006
  • Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the $16{\times}16$ array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and honeycomb cores, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that this antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of $5^{\circ}$ and $5^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna will be applicable to the wideband SAR system.

Research about a Data Consistency hold Cost Using a Relocation Technique in Mobile Computing Environment (이동컴퓨팅 환경에서 재배치 기법을 이용한 데이터 일관성 유지비용에 관한 연구)

  • Choi, Kang-Hee
    • Journal of the Korea Computer Industry Society
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    • v.7 no.4
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    • pp.299-308
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    • 2006
  • Recently, A method of using the replicated database on a server to get new data without mis sing any information has been being studied in mobile computing environment. So far we ha ye used the Static Replica Allocation(SRA) for the replication which is the method of the replication on the server. This method is to replicate the data on the replica server after $\underline{a}$ moving host is transferred to a cell. Since the network of the SRA is very good, and if there are few moving users, no trouble will happen. But if there is no moving users in a cell, the data will not be shared. Therefore, this paper is about the study of the method of relocation after replicating the data to the cells for the users(User Select Replica Allocation : USRA). We also analyze the access rate and the possibility which are closely related to the moving frequency of the mobile hosts and the numbers of the cells. As a result, We show that the 5% lower access cost and the $2%\sim2.5%$ gains are achieved from the low mobility of the mobile hosts. We also show that t he extension function of USRA reduces the cost by 1.7% and it is influenced by the numbers of the cells.

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Applied Method of Energy Harvesting for Multi-Relay Environment (다중 중계기 환경에 대한 에너지 하베스팅의 적용 방안)

  • Kim, Tae-Wook;Kong, Hyung-Yun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.14 no.6
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    • pp.69-74
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    • 2014
  • In this paper, an energy harvesting scheme is investigated in the multi-relay cooperation communication. Our proposal is to maximize the diversity gain and overcome the disadvantages of the limited power wireless devices. The best relay is selected based on the maximizing channel gains from source to relays so that the harvested energy at selected relay is best. If an internal power of the best relay is lower than a defined target power, the best relay will harvest the energy from the source, and the help of the source-destination link is changed to the second best relay. By this operation method, the diversity gain is maintained and the performance of the network is improved. Finally, performance of the proposed protocol is analyzed in terms of bit error rate, utilization efficiency, power collection efficiency.

Design of Tag Antenna without Shadow Zone in Readable Pattern (인식 음영 구역을 제거한 RFID 태그 안테나 설계)

  • Cho, Chi-Hyun;Choo, Ho-Sung;Park, Ik-Mo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.12 s.103
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    • pp.1206-1212
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    • 2005
  • In this paper, we propose a novel antenna structure which uses the electric and magnetic currents so as to eliminate nulls on their radiation pattern. The tag antenna was matched to the conjugate impedance of the commercial tag chip using the modified double T matching network. The radiation efficiency is about $90\%$, and the bandwidth($S_{11}< -10 dB$) is 848${\~}$926 MHz. Also it shows the gain deviation between the maximum and minimum gains about 4 dB at any direction of the tag antenna at the operating frequency. The readable range of the tag is 1.7${\~}$2.4 m for an arbitrary rotation angle of the tag with a commercial tag chip.