• Title/Summary/Keyword: 대역폭 제어

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Tunable bragg filter of $Si_3N_4-SiO_2$ waveguide using thermooptic effect (열광학 효과를 이용한 $Si_3N_4-SiO_2$ 도파로 가변 브래그필터)

  • 이형종;정환재
    • Korean Journal of Optics and Photonics
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    • v.3 no.4
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    • pp.244-251
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    • 1992
  • Buried Bragg filters of single mode $Si_{3}N_{4}$ rib waveguide with a cover layer of $SiO_{2}$ and grating at the interface of $Si_{3}N_{4}$ and $SiO_{2}$ are designed and fabricated. Etching of the grating on $Si_{3}N_{4}$ waveguide core by buffered HF showed uniform etching with good control up to 1 nm. This buried type of Bragg filters are immune to contamination of the surface of device. The mode index and bandwidth of filters are determined by measurements of the transmission spectrum of Bragg filters and compared with that of calculation. Waveguide Bragg filters loaded with the micro-heater of Cr film and the cladding of silicone rubber are made to control the Brag wavelength of the filter. As a result the filter wavelength of the device moved by 0.41 nm for 10 mA current to the shorter side of wavelength proportional to the square of the current.

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Testbed Implementation and Performance Evaluation of High Speed Transport Protocols using TEIN2 Networks (TEIN2를 활용한 고대역 전송계층 프로토콜 테스트베드 구축 및 성능 분석)

  • Lee, Gi-Ra;So, Sang-Ho;Choi, Yun-Chul;Park, Man-Kyu;Lee, Jae-Yong;Kim, Byung-Chul;Kim, Dae-Young
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.2
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    • pp.104-113
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    • 2009
  • Recently, high-speed Internet users and broadband network infrastructure are increasing. However, the TCP protocol widely used in the Internet is an appropriate transport only for the legacy Internet, it is inefficient for traffic transport for network environments with large bandwidth-delay product. In order to remedy this problem, there have been many researches about improved congestion control algorithms for broadband networks. In these studies, most of performance evaluation has been done by simulations. In this paper, after we reviewed the proposed high bandwidth transport layer protocols, we implemented a real testbed, measured the performance and analyzed the problems of high-speed transport protocols through the international research network TEIN2 between three nations, Korea, China, and Germany.

Design of Wideband RF Frequency Measurement System with EP2AGX FPGA (EP2AGX FPGA를 이용한 광대역 고주파신호의 주파수 측정장치 설계)

  • Lim, Joong-Soo
    • Journal of the Korea Convergence Society
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    • v.8 no.7
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    • pp.1-6
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    • 2017
  • This paper presents the design of a frequency measurement device using ADC, EP2AGX FPGA and STM32 processor to accurately measure the frequency of a broadband high frequency signal. The ADC device used in this paper has a sampling frequency of 250 MSPS and a processing frequency bandwidth of 100 MHz. Due to its high sampling frequency, it is difficult to process in ordinary computers or processors, so we implemented the frequency measurement algorithm using the Altra EP2AGX FPGA. The measured frequency is sent to the direction detection controller in real time and fused with the phase signal to calculate the incident azimuth angle of the high frequency signal. The designed frequency measurement device is about 0.2 Mhz in frequency measurement error and 30% less than Anaren DFD-x, which is considered to contribute greatly to the design of radio monitoring and direction detection device.

X-Band Phased Array Antenna Module for the Beam Compensation of an Aircraft Wing Mounted Antenna (항공기 날개 탑재 안테나의 빔 보상을 위한 X-대역 위상 배열 안테나 모듈)

  • Choi, Woo-Yeol;Seo, Jung-Hoon;Kim, Hyun-Ho;Baek, Kun-Woo;Hong, Sung-Yong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.27 no.11
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    • pp.978-986
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    • 2016
  • X-band phased array antenna module for the compensation of deformed beam direction by wing deformation is designed and fabricated. The phased array antenna module consists of array antenna, phase shifter, power divider and control circuit. To select out the best component, the variation of radiation pattern by wing bending and phase error of components is simulated. The fabricated phased array antenna module shows an antenna gain of 5.84 dBi, a return loss of 13.6 dB and a bandwidth of 10.6 % at 9.375 GHz. The test bed was set up to verify the performance of beam direction compensation. This test confirmed that the main beam direction of array antenna has been well restored under wing bending of 9 %.

A Trellis-Coded 3-Dimensional OFDM System (격자 부호화 3차원 직교 주파수분할다중화 시스템)

  • Li, Shuang;Kang, Seog Geun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.21 no.9
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    • pp.1635-1641
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    • 2017
  • In this paper, a trellis-coded 3-dimensional (3-D) orthogonal frequency division multiplexing (OFDM) system is presented and its performance is analyzed. Here, a set-partitioning technique for trellis coding with respect to a 3-D signal constellation is also presented. We show theoretically that the proposed system, which exploits a trellis coding scheme with recursive systematic convolutional codes (RSC) of code rate R = 1/3 and 2/3, can improve symbol error rate (SER) up to 7.8 dB as compared with the uncoded OFDM system in an additive white Gaussian noise (AWGN) channel. Computer simulation confirms that the theoretical analysis of the proposed system is very accurate. It is, therefore, considered that the proposed trellis-coded 3-D OFDM system is well suited for the high quality digital transmission system without increase in the available bandwidth.

Theoretical Performance Analysis between Attack Prevention Schemes and Attack Mitigation Schemes (공격차단 기법과 공격경감 기법 간 이론적 성능 분석)

  • Ko Kwang-Sun;Eom Young-Ik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.7 s.349
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    • pp.84-92
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    • 2006
  • To defeat abnormal traffic driven by DoS (Denial-of-Service) or DDoS (Distributed DoS), there has been a variety of researches or studies in a few decades. In this paper, we present the results of theoretical performance analysis between attack prevention schemes and attack mitigation schemes. The former is a scheme that prevents abnormal incoming traffic from forwarding into a specific network based on filtering rules, and the latter is a scheme that makes some perimeter or intermediate routers, which exist on the traffic forwarding path, prevent abnormal traffic based on their own abnormal traffic information, or that mitigates abnormal traffic by using quality-of-service mechanisms at the gateway of the target network. The aspects of theoretical performance analysis are defined as the transit rates of either normal traffic or false-positive traffic after an attack detection routine processes its job, and we also present the concrete network bandwidth rates to control incoming traffic.

Adaptive Redundancy Scheme Using Channel State Estimation in Wireless LANs (무선 랜에서 채널 상태를 고려한 적응적 전송 방법)

  • 김선명;조영종
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.41 no.7
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    • pp.9-19
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    • 2004
  • WLAN (Wireless Local Area Networks) needs error recovery and flow control schemes to support reliable multicast protocol. Limited wireless bandwidth, as well as queuing losses caused by the asymmetric wired/wireless interactions, demands more effective approaches for reducing packet losses. Moreover, since the wireless channel is a shared broadcast medium, if sender receives feedback information simultaneously from several receivers, the feedback delays data frame transmission of forward direction by introducing channel congestion and burden at the sender. Therefore, it is important to minimize the amount of feedback information from receivers. In this paper, we propose an ARS(Adaptive Redundancy Scheme) that combines FEC(Forward Error Correction) using channel state estimation and ARQ(Automatic Repeat Request) both to reduce the amount of feedback information and the number of retransmissions and to guarantee high data reliability in a WLAN multicast environment. Performance of the proposed scheme is evaluated by means of analysis and simulations in AWGN and Rayleigh fading channels. The results show that the proposed scheme reduces the amount of feedback information and the number of retransmissions and guarantees high data reliability, while keeping throughput efficiency similarly with the conventional FEC and ARQ scheme.

Media-aware and Quality-guaranteed Rate Adaptation Algorithm for Scalable Video Streaming (미디어 특성과 네트워크 상태에 적응적인 스케일러블 비디오 스트리밍 기법에 관한 연구)

  • Jung, Young-H.;Kang, Young-Wook;Choe, Yoon-Sik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.5B
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    • pp.517-525
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    • 2009
  • We propose a quality guaranteed scalable video streaming service over the Internet using a new rate adaptation algorithm. Because video data requires much more bandwidth rather than other types of service, therefore, quality of video streaming service should be guaranteed while providing friendliness with other service flows over the Internet. To successfully provide this, we propose a framework for providing quality-guaranteed streaming service using two-channel transport layer and rate adaptation of scalable video stream. In this framework, baseline layer for scalable video is transmitted using TCP transport for minimum qualify service. Enhancement layers are delivered using TFRC transport with layer adaptation algorithm. The proposed framework jointly uses the status of playout buffer in the client and the encoding rate of layers in media contents. Therefore, the proposed algorithm can remarkably guarantee minimum quality of streaming service rather than conventional approaches regardless of network congestion and the encoding rate variation of media content.

An Approach for Multi-User Multimedia Requests Service to Overlay Multicast Trees (다중 사용자의 멀티미디어 요구 서비스를 위한 오버레이 멀티캐스트 트리의 구성과 복구 방안)

  • Kang, Mi-Young;Yang, Hyun-Jong;Nam, Ji-Seung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.12B
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    • pp.1058-1065
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    • 2008
  • In the Internet, as computer resource is developed, multimedia data request being increase more and more. It is effective way that process both high capacity-data and real-time data. Overlay Multicast is an effective method for efficient utilization of system resources and network bandwidth without using hardware customization. Overlay Multicast is an effective method for multimedia data service to multi-users. Multicast tree reconstruction is required when a non-leaf host leaves or fails. In this paper, relay-frame interval is selected as revealed network-state with jitter. In our proposal, multi-user service control algorithm gives a delay effect in multimedia request time. The simulation results show that our proposal takes shorter period of time than the other algorithms to reconstruct a similar tree and that it is a more effective way to deal with a lot of nodes that have lost their multi-user nodes.

Design of the Satellite Beacon Receiver Using Array Based Digital Filter (다중배열 디지털필터를 이용한 위성비콘 수신기 설계)

  • Lee, Kyung-Soon;Koo, Kyung-Heon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.27 no.10
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    • pp.909-916
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    • 2016
  • The beacon receiver is an equipment which detects and measures the signal strength of transmitting satellite beacon signal. Beacon signals transmitted by satellites are low power continuous wave(CW) signals without any modulation intended for antenna steering to satellite direction and power control purposes on the earth. The beacon signal detection method using a very narrow band analog filter and RSSI(Received Signal Strength Intensity) has been typically used. However, it requires the implementation to track the frequency at the beacon receiver, thus a beacon frequency variation of the satellite due to temperature changes and long-term operation. Therefore, in this paper, the beacon signal detection receiver is designed by using a very narrow band digital filter array for a faster acquisition and SNR(Signal to Noise Ratio) method detection. For this purpose, by calculating the satellite link budget with the rain attenuation between satellite and ground station, and then extracting the received $C/N_o$ of the beacon signal, this work derives the bandwidth and the array number of the configured digital filter that gives the required C/N.