• Title/Summary/Keyword: Digital Duplex

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A Study on the ECM(Echo Cancelling Method) Design for Digital Transmission over the Two-Hire Loops (2선 선로에 Digital 전송을 위한 ECM(Echo Cancelling Method) 설계에 관한 연구)

  • Lim, C.S.;Chung, H.C.;Kim, Y.K.;Lee, H.S.
    • Proceedings of the KIEE Conference
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    • 1987.07b
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    • pp.947-949
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    • 1987
  • This paper describes the design of echo cancslling method(ECM) for transmission with full-duplex which ie transmitted on "2B+D"(144kbps)data through two-wire loop plants. The design objective is 40dB attenuation with a signal-to-noise ratio of $10{\sim}20dB$. Since the transhybrid loos can be as low as $6{\sim}10dB$, the required attenuation of the echo signal is on the order of $50{\sim}55dB$. The used algorithms based on the sign algorithm, and have been improved by using adoptive reference voltage level algorithm.

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The study on the WiBro digital optic repeater design (휴대인터넷 디지털 광 중계기 설계에 대한 연구)

  • Ahn Jun-Bae;Ryoo Kyoo-Tae
    • 한국정보통신설비학회:학술대회논문집
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    • 2006.08a
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    • pp.35-38
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    • 2006
  • Using the repeaters is indispensable to WiBro services. Repeater types are distinguished by usage, output power and required performance. In the paper, we have studied on the WiBro digital optic repeater design which has excellent performance characteristic than any other repeaters. WiBro has specific characteristic on modulation method TDD(Time Division Duplex)/OFDMA(Orthogonal Frequency Division Multiple Access) so that it demands specified H/W to design WiBro repeater. Switching technique has been introduced because of TDD characteristic in each amplifier on the repeater. Time Advance technique has been considered because of OFDM characteristic among RAS(Radio Access Station) and repeater. In this paper, we have studied on these techniques to increase repeater cell coverage and distance between RAS and repeater.

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One Chip 반향 제거기를 위한 알고리즘 개발에 관한 연구

  • 강정신;백인천;박상봉;박노경;차균현
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.15 no.8
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    • pp.689-697
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    • 1990
  • This paper proposes ADAPTIVE STOCHASTIC ITERATION ALGORITHM that can be used for the full-duplex digital data transmission over existing twisted-pair cables. The canceller step size changes according to the residual echo level. Thus convergence speed increases by an order of magnitude over the conventional stochastic interation alogorithm. And it can be combined with the sequential type adaptive digital filter that simplifies the conventional echo canceller circuit. Thus it is suitable for LSI implementation. Theoretical analysis on two algorithms is carried out and the algorithm simulation program is developed.

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A Design and Evaluation of Protocol for VBR Service in Wireless Multimedia Network (멀티미디어 무선 네트워크에서 가변비트율 서비스를 위한 프로토콜의 설계 및 성능평가)

  • Lim Jae-Hwan
    • Journal of Digital Contents Society
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    • v.2 no.1
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    • pp.93-102
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    • 2001
  • In this paper we proposed a wireless MAC Protocol called DTDD/PS (Dynamic Time Division Duplex using Poll/Select scheme), and throughput performance is evaluated using computer simulation. Simulation results indicate that the proposed DTDD/PS protocol increases the limitation of allowable loads that guarantee duality of services by dynamic allocation of slot based on the system status. Also the proposed protocol is shown to maintain stable throughput even in the case of traffic variations.

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A Study on Efficient Evolution of Cable HFC Network (케이블 HFC 네트워크의 효율적인 진화 방안 연구)

  • Kwon, Ho-Jin;Moon, Joon-Woo
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2018.06a
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    • pp.31-34
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    • 2018
  • 최근 유무선 트래픽의 지속적인 증가에 대응하기 위해선 가입자 네트워크의 양적 확충은 물론, 새로운 인터넷 기술을 개발하고 그 구조를 재설계하는 등의 투자가 이루어지고 있다. 특히 차세대 미디어 서비스 등의 인터넷 수요 및 대역폭에 대한 요구가 증가로 인하여 가입자 망 진화의 필요성이 계속해서 이야기되고 있다. 정부에서는 10기가 인터넷 상용화를 목표로 '10기가 인터넷 상용화 촉진 선도 시범 사업'을 추진하고 있으며, KT와 SK브로드밴드 등 주요 통신사에서도 10Gbps 인터넷 상용화를 추진하고 있다. 이에 케이블 사업자도 인터넷 경쟁력 확보를 위해 HFC망 진화 방안에 대한 연구가 필요하다. 우선 상하향 10Gbps 전송이 가능한 DOCSIS 3.1 도입을 위해 망 장비 교체나 업그레이드 없이 주파수 확보가 이루어 져야 하며, 상향 전송 속도 확대를 위해 북미에서 표준화 진행중인 FDX(Full-Duplex) DOCSIS 도입을 위해 망 구조를 개선해야 한다.

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Performance of Full Duplex Switched Ethenlet Systems with a Dual Traffic Regulator for Avionic Data Buses (이중 트래픽 조절기능이 있는 항공데이터버스용 전이중 이더넷 교환시스템의 성능 분석)

  • Kim, Seung-Hwan;Yoon, Chong-Ho;Park, Pu-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.2
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    • pp.89-96
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    • 2009
  • As increasing the number of digital control devices installed on aircrafts and their transmission speed, various digital data buses have been introduced to provide reliable and high-speed characteristics. These characteristics of avionics data bus are highly related on the fault-tolerant performance which can make minimize jitter and loss during data transfer. In this paper, we concerned about a new traffic shaping scheme for increasing the reliability of Avionics Full Duplex Switched Ethernet (AFDX) systems based on ARINC 664 standard. We note that the conventional AFDX with a single regulator per virtual link system may produce aggregated traffics as the number of virtual links increasing. The aggregated traffic results in large jitters among frames. To remedy for the jitter and loss of data, we propose a dual regulator scheme for the AFDX system. The purpose of the additional regulator is to additionally regulate aggregated traffics from a number of per virtual link regulators. Using NS-2 simulator, we show that the proposed scheme provides a better performance than the single regulator one. It is worthwhile note that the proposed AFDX with Dual Regulator scheme can be employed to not only aircraft networks but other QoS sensitive networks for robot and industrial control systems.

Transceiver for Human Body Communication Using Frequency Selective Digital Transmission

  • Hyoung, Chang-Hee;Kang, Sung-Weon;Park, Seong-Ook;Kim, Youn-Tae
    • ETRI Journal
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    • v.34 no.2
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    • pp.216-225
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    • 2012
  • This paper presents a transceiver module for human body communications whereby a spread signal with a group of 64 Walsh codes is directly transferred through a human body at a chip rate of 32 Mcps. Frequency selective digital transmission moves the signal spectrum over 5 MHz without continuous frequency modulation and increases the immunity to induced interference by the processing gain. A simple receiver structure with no additional analog circuitry for the transmitter has been developed and has a sensitivity of 250 ${\mu}V_{pp}$. The high sensitivity of the receiver makes it possible to communicate between mobile devices using a human body as the transmission medium. It enables half-duplex communication of 2 Mbps within an operating range of up to 170 cm between the ultra-mobile PCs held between fingertips of each hand with a packet error rate of lower than $10^{-6}$. The transceiver module consumes 59 mA with a 3.3 V power supply.

Real-Time H/W Implementation of RPE-LTP Speech Coder for Digital Mobile Communications (디지틀 이동 통신용 RPE-LTP 음성 부호화기의 실시간 H/W 구현)

  • 김선영;김재공
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.16 no.1
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    • pp.85-100
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    • 1991
  • In the discussion of digital mobile communication systems the speech coder based on the high quality low bit rate is an essential part of topics to overcome the limited availability of radio spectrum, which will enhance the communication services. In this paper we present the implementation and performance evaluation of 13kbps RPE LTP speech coder. An implementation of a real time full duplex coder with 75% of DSP loading rate using a single DSP chip has been shown, and also the fixed point simulations for H/W implementation has been performed. Finally, analysis result for relative bit importance of each transmitting parameter has been shown for channel coding.

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Implementation of TDD LTE-Advanced Testbed adopted Dynamic Pre-coding for MU-MIMO (MU-MIMO를 위한 동적 Pre-coding을 적용한 TDD LTE-Advanced 테스트베드의 구현)

  • Han, Sangwook;Lee, Jeonghyeok;Choi, Seungwon
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.18 no.2
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    • pp.27-37
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    • 2022
  • In this paper, we presents a Multiple User Multiple Input Multiple Output (MU-MIMO) test-bed system for Time Division Duplex (TDD) Long Term Evolution-Advanced (LTE-A). Using two parameters, the condition number of the channel matrix and the path gain, the MU-MIMO system could switch pre-coder to maintain target Bit Error Rate (BER) level. This paper also introduces a calibration procedure for compensating error of Radio Frequency (RF) paths of the antennas and RF transceivers. From experimental measurements, dynamic pre-coding scheme could maintain target BER, set to 10-3, with the pre-coder set configured with Zero Forcing (ZF), Tomlinson Harashima Pre-coding (THP), Lattice Reduction (LR). The simplest pre-coder ZF is adopted in stable channel, and when path gain become less than 0.25, LR is adopted. Lastly, when condition number of channel matrix become larger than 7, THP is adopted.

An Echo Canceller Using the Parallel Adaptation NLMS Algorithm (병렬 적응 NLMS 알고리즘을 이용한 Echo Canceller)

  • Jeong, Ki-Seog
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.35S no.11
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    • pp.37-43
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    • 1998
  • This paper proposes a new echo canceller that can be used in a full-duplex digital subscriber loop modem. The proposed echo canceller uses a NLMS-based parallel adaptation NLMS (PA-NLMS) algorithm. The PA-NLMS algorithm that an estimate of the nonstationarity to additive noise ratio (NNR) gained from two distinct NLMS processes is used to select the value of NLMS convergence-controlling parameter has been developed. Numerical results based on computer simulation show that the proposed algorithm has a convergence rate approaching that of the fastest possible NLMS process while improving on its MAC performance considerably.

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