• Title/Summary/Keyword: back-to-back channels

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A TDMA-based MAC protocol in hybrid-vehicular communication systems for preventing a chain-reaction collision on a highway (하이브리드 차량 통신 시스템에서 연쇄 추돌 사고 방지를 위한 TDMA 기반 MAC 프로토콜)

  • Oh, Sang-Yeob
    • Journal of Digital Convergence
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    • v.10 no.8
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    • pp.179-184
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    • 2012
  • A car accident on a highway occurs a chain-reaction collision because of a vehicle's fast velocity. In order to prevent it, the accident vehicle should broadcast a safe message to its neighbors. If there are many neighbor nodes, a frame collision probability is high. To solve this, it was proposed for a system as a previous study to send a safe message without frame-collision using separating channels. However, the separation of multiple channels make feasibility low because of increasing hardware's development cost and complexity. In this paper, we proposes a TDMA-based MAC protocol using a single channel. As a result, we show the frame reception success rate of our protocol was almost the same as the previous protocol.

Turbo MIMO-OFDM Receiver in Time-Varying Channels

  • Chang, Yu-Kuan;Ueng, Fang-Biau;Jhang, Yi-Wei
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.8
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    • pp.3704-3724
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    • 2018
  • This paper proposes an advanced turbo receiver with joint inter-carrier interference (ICI) self cancellation and channel equalization for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems over rapidly time-varying channel environment. The ICI caused by impairment of local oscillators and carrier frequency offset (CFO) is the major problem for MIMO-OFDM communication systems. The existing schemes (conjugate cancellation (CC) and phase rotated conjugate cancellation (PRCC)) that deal with the ICI cancellation and channel equalization can't provide satisfactory performance over time-varying channels. In term of error rate performance and low computational complexity, ICI self cancellation is the best choice. So, this paper proposes a turbo receiver to deal with the problem of joint ICI self cancellation and channel equalization. We employ the adaptive phase rotations in the receiver to effectively track the CFO variations without feeding back the CFO estimate to the transmitter as required in traditional existing scheme. We also give some simulations to verify the proposed scheme. The proposed schene outperforms the existing schemes.

Backoff-based random access algorithm for offering differentiated QoS services in the random access channels of OFDMA systems (OFDMA 시스템 상향 링크에서, 임의 접근 채널의 차별화된 서비스 품질 제공을 위한 Backoff 기반 임의 접근 알고리즘 및 그 성능 분석)

  • Lee, Young-Du;Koo, In-Soo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.2
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    • pp.360-368
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    • 2008
  • In this paper, in order that the various QoS(Qualify of Service)s that are required by different traffic class are guaranteed in the random access channels in multi-service multi-user OFDMA systems, the backoff-based random access algorithm is proposed and corresponding performance is analyzed in terms of the access success probability, the throughput, the average delay and the blocking probability. Through the numerical analysis, it is shown that the proposed backoff-based random access algorithm can provide the differentiated QoSs to random access attempts according to their service class.

Plastic Deformation of Die due to Friction during Equal Channel Angular Pressing (Pure-Zr의 ECAP 공정에서 마찰에 따른 금형의 소성 변형)

  • 배강호;권기환;채수원;권숙인;김명호;황성근
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.804-807
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    • 1997
  • Recently equal-channel angular pressing (ECAP) has been employed to produce ultra-fine grain size materials. In this paper pure-Zirconium is considered due to its applicability to nuclear reactors. Among many process parameters of ECAP frictional effect on the plastic deformation of die has been investigated. The back pressure effect due to friction increases the stress level of die especially at the crossing area of channels, which may result in plastic deformation of die. The finite element method has been employed to investigate this issue.

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Cooperative Synchronization and Channel Estimation in Wireless Sensor Networks

  • Oh Mi-Kyung;Ma Xiaoli;Giannakis Georgios B;Park Dong-Jo
    • Journal of Communications and Networks
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    • v.7 no.3
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    • pp.284-293
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    • 2005
  • A critical issue in applications involving networks of wireless sensors is their ability to synchronize, and mitigate the fading propagation channel effects. Especially when distributed 'slave' sensors (nodes) reach-back to communicate with the 'master' sensor (gateway), low power cooperative schemes are well motivated. Viewing each node as an antenna element in a multi-input multi-output (MIMO) multi-antenna system, we design pilot patterns to estimate the multiple carrier frequency offsets (CFO), and the multiple channels corresponding to each node-gateway link. Our novel pilot scheme consists of non-zero pilot symbols along with zeros, which separate nodes in a time division multiple access (TDMA) fashion, and lead to low complexity schemes because CFO and channel estimators per node are decoupled. The resulting training algorithm is not only suitable for wireless sensor networks, but also for synchronization and channel estimation of single- and multi-carrier MIMO systems. We investigate the performance of our estimators analytically, and with simulations.

Detection of epileptiform activities in the EEG using wavelet and neural network (웨이브렛과 신경 회로망을 이용한 EEG의 간질 파형 검출)

  • 박현석;이두수;김선일
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.35S no.2
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    • pp.70-78
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    • 1998
  • Spike detection in long-term EEG monitoring forepilepsy by wavelet transform(WT), artificial neural network(ANN) and the expert system is presented. First, a small set of wavelet coefficients is used to represent the characteristics of a singlechannel epileptic spikes and normal activities. In this stage, two parameters are also extracted from the relation between EEG activities before the spike event and EEG activities with the spike. then, three-layer feed-forward network employing the error back propagation algorithm is trained and tested using parameters obtained from the first stage. Spikes are identified in individual EEG channels by 16 identical neural networks. Finally, 16-channel expert system based on the context information of adjacent channels is introducedto yield more reliable results and reject artifacts. In this study, epileptic spikes and normal activities are selected from 32 patient's EEG in consensus among experts. The result showed that the WT reduced data input size and the preprocessed ANN had more accuracy than that of ANN with the same input size of raw data. Ina clinical test, our expert rule system was capable of rejecting artifacts commonly found in EEG recodings.

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Reference Research of Bao(胞) (포(胞)에 대(對)한 문헌연구(文獻硏究))

  • Cha, Eun-yea;Kang, Jung-soo
    • Journal of Haehwa Medicine
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    • v.8 no.2
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    • pp.123-132
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    • 2000
  • The following results were obtained through studies related to bao(胞). 1 Bao(胞) is also called as uterus, zizang(子臟), baogong(胞宮), xieshi(血室), dantian(丹田), mingmen(命門), baomen(胞門), and guanyuan(關元). It is one of the extraordinary organs. Both of man and woman have it. 2 Man controls qi(氣), so dantian(丹田) which is considered xieshi(血室) for man doesn't have it's own shape and woman controls blood so xieshi(血室) has it's own shape. 3 Bao(胞) is in front of rectum, back of bladder, between guanyuan(關元) and 氣海. shape of 女子胞 is up side down triangle, the lower one branch is neck of uterus and the upper two branches are oviduct. Inside of Bao(胞) is vacant. 4 Bao(胞) is the origin of making essence and blood, and the place of completing essence, energy, and spirit(精氣神). Bao(胞) controls menstruation and also conceives and brings up embryo in woman. 5 Bao(胞) is related with channels of Du, Ren, Chong, and Dai directly and also related with twelve main meridians. Especially channels of Ren, and Chong control Bao(胞) the most importantly. 6 Bao(胞) is related with kidney, liver, and spleen very intimately.

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A Study on a Multichannel(128) Ultrasound Pulsed Doppler System with Serial Data Processing for Sensing the Blood Flow (혈류 진단을 위하여 직렬데이터 처리를 하는 다중(128) 채널 초음파 펄스 도플러 시스템에 관한 연구)

  • Kim, Young-Kil
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.23 no.3
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    • pp.389-396
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    • 1986
  • A pulsed ultrasonic doppler flowmeter for mesurements of velocity profils in man is described. The device projects a beam of ultrasound in burst of 570 ns duration at 3.5 MHz. The back-scattered signals are processed to produce a signal oxrresponding to the mean velocity over a small region of the flowing stream. The observation range of 112mm is divided into 128 depth channels. The size of this sample volume determines the flowmeter sensitivity and accuracy. The device uses a quadrature detector to detect the direction of the moving target(hemoglobin). The main feature of the novel instrumnet is its simple hardware structure due to sequential signal processing.

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Speed-Sensitive Handover Scheme over IEEE 802.16 Multi-Relay Networks

  • Kim, Dong-Ho;Kim, Soon-Seok;Lee, Yong-Hee
    • Journal of Information Processing Systems
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    • v.6 no.3
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    • pp.403-412
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    • 2010
  • Multi-Relay Networks should accommodate mobile users of various speeds. The cellular system should meet the minimum residency time requirements for handover calls while considering an efficient use of available channels. In this paper, we design speed-sensitive handover under dynamic hierarchical cellular systems, in which mobile users are classified according to the mean speed of mobile users and each class has its cellular layer. In order to meet the minimum residency time, the cell size of each cellular layer is dynamically determined depending on the distributions of mean speeds of mobile users. Since the speed-dependent non-preferred cell can provide a secondary resource, overflow and take-back schemes are adopted in the system. We develop analytical models to study the performance of the proposed system, and show that the optimal cell size improves the blocking probability.

LVDS I/O Cells with Rail-to-Rail Input Receiver

  • Lim, Byong-Chan;Lee, Sung-Ryong;Kwon, Oh-Kyong
    • 한국정보디스플레이학회:학술대회논문집
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    • 2002.08a
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    • pp.567-570
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    • 2002
  • The LVDS (Low Voltage Differential Signaling) I/O cells, fully compatible with ANSI TIA/ EIA-644 LVDS standard, are designed using a 0.35${\mu}m$ standard CMOS technology. With a single 3V supply, the core cells operate at 1.34Gbps and power consumption of the output driver and the input receiver is 10. 5mW and 4.2mW, respectively. In the output driver, we employ the DCMFB (Dynamic Common-Mode FeedBack) circuit which can control the DC offset voltage of differential output signals. The SPICE simulation result of the proposed output driver shows that the variation of the DC offset voltage is 15.6% within a permissible range. In the input receiver, the proposed dual input stage with a positive feedback latch covers rail-to-rail input common-mode range and enables a high-speed, low-power operation. 5-channels of the proposed LVDS I/O pair can handle display data up to 8-bit gray scale and UXGA resolution.

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