• Title/Summary/Keyword: Maximum transmission length

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A Turbo-coded OFDM Transmission System Using Orthogonal Code Multiplexing (직교코드 다중화를 이용한 터보부호화된 OFDM 전송 시스템)

  • 정방철;오성근;선우명훈
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.5A
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    • pp.333-340
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    • 2003
  • In this paper, we propose a new turbo-coded orthogonal frequency division multiplexing (OFDM) transmission scheme that can improve greatly the performance by making all the turbo-coded symbols have the same reliability for OFDM transmission over a frequency selective fading channel. The same reliability, that is, the same fading can be accomplished through multiplexing of turbo-coded symbols using distinct orthogonal codes and spreading over the whole effective subcarriers (hereafter, called as the orthogonal code multiplexing (OCM)). As for the orthogonal code selection, we choose the set of the discrete Fourier transform (DFT) basis sequences, since the code set holds the orthogonality irrespective of the length and also has the equal energy property. We perform computer simulations using the Log-maximum-a-posteriori (Log-MAP) algorithm for iterative decoding in order to assess the performance of the proposed transmission scheme.

Speech Intelligibility Analysis on the Vibration Sound of the Glass Window of a Conference Room (회의실 유리창 진동음의 음성 명료도 분석)

  • Kim, Hee-Dong;Kim, Yoon-Ho;Kim, Seock-Hyun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.4 s.121
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    • pp.363-369
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    • 2007
  • The purpose of the study is to obtain acoustical information to prevent eavesdropping of the glass window. Speech intelligibility was investigated on the vibration sound detected from the glass window of a conference room. Objective test using speech transmission index(STI) was performed to estimate quantitatively the speech intelligibility. STI was determined based on tile modulation transfer function(MTF) of the room-glass window system. Using Maximum Length Sequency(MLS) signal as a sound source, impulse responses of the glass window and MTF were determined by signals from accelerometers and laser doppler vibrometer. Finally, speech intelligibility of the interior sound and window vibration were compared under different sound pressure levels and amplifier gains to confirm the effect of measurement condition on the speech intelligibility.

Performance Estimation of a Window Shaker (유리창 도청방지 장치의 성능평가)

  • Kim, Seock-Hyun;Kim, Hee-Dong;Heo, Wook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.649-654
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    • 2007
  • Eavesdropping prevention performance is evaluated on a commercial window shaker, which is used to prevent a glass window from eavesdropping. Speech transmission index (STI) is introduced in order to estimate quantitatively the speech intelligibility of the sound detected on the glass window. Objective test by IEC standard using modulation transfer function (MTF) is performed to determine STI. Using Maximum Length Sequency (MLS) signal as a sound source, MTF is measured by accelerometers and laser doppler vibrometer. STI under different level of disturbing wave are compared to confirm the disturbing effect on the speech intelligibility.

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Eavesdropping of the Glass Window Using a Laser Sensor and Performance Estimation of a Window Shaker (레이저센서를 이용한 유리창 도청 및 도청방지기의 성능 평가)

  • Kim, Seock-Hyun;Heo, Wook;Kim, Hee-Dong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.551-556
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    • 2008
  • Possibility of the remote eavesdropping through window glass is investigated using a laser sensor. Various thicknesses and types of glass windows are excited by maximum length sequency (MLS) signal and the vibration sound is detected by a laser doppler vibrometer. Intelligibility of the detected sound is evaluated using the speech transmission index (STI), which is based on the modulation transfer function (MTF). In order to identify the disturbing effect, different level of disturbing wave is generated by an outside speaker and a window shaker attached on the glass window. On the different thickness of glass windows, decrease effect of the speech intelligibility is analysed.

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Calculations of Load Current of Multi-Stage Cascaded Transmission Lines Excited by a Small Loop in the Near-Field Region (작은 루우프 안테나의 근거리장 영역내에 있는 다단 연쇄 접속 전송선로에 유기되는 부하 전류 계산)

  • 박영태;이상설
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.6
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    • pp.836-842
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    • 1990
  • The noise currents in the load of cascaded transmission lines excited by a nearly small loop are analyzed and the effective approxiamte method by which we can calculate these currents easily and the computation time can be significantly reduced is developed. Numerical results for n=3 are well agreed with those of Smith by the maximum difference of 3-4dB and show that the length of a segment of line regarded to be illuminated by uniform electric fields should be 1.3 times the distance from the loop to the point midway between the conductors.

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Theoretical analysis of optimum refractive index profile and maximum transmission length of a GIPOF (GIPOF의 최적 굴절률 분포와 최대 전송거리에 대한 연구)

  • Jeong Hun;Kim Seung Taek;Gang Seong Bok;Lee Gyeong Gyun;Gang Hui Seok;Jo Yeong Jun
    • Proceedings of the Optical Society of Korea Conference
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    • 2003.07a
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    • pp.14-15
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    • 2003
  • Polymer optical fibers (POFs) are being considered as important high-speed communication media in the area of local area networks, datalinks and optical sensors. Large core diameter (500~1000 $\mu$m) and large numerical aperture (0.2~0.9) in a POF allow easy processing and connectorization, low cost high efficiency of beam coupling from LDs or LEDs, and complete immunity to EMI/EMR. There are many reports about 2.5 Gbps transmission the polymethylmethacrylate (PMMA) graded index (GI) POF over a distance of 100 m. (omitted)

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Intelligibility Analysis on the Eavesdropping Sound of Glass Windows Using MTF-STI (MTF-STI를 이용한 유리창 도청음의 명료도 분석)

  • Kim, Hee-Dong;Kim, Yoon-Ho;Kim, Seock-Hyun
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.1
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    • pp.8-15
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    • 2007
  • Speech intelligibility of the eavesdropping sound is investigated on a acoustic cavity - glass window coupled system. Using MLS (Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the glass window are measured by accelerometer and laser doppler vibrometer. MTF (Modulation Transfer Function) is used to identify tile speech transmission characteristics of the cavity and window system. STI (Speech Transmission Index) based upon MTF is calculated and speech intelligibility of the vibration sound of the glass window is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared. Finally, intelligibility of the conversation sound is confirmed by the subjective test.

New high-efficient universal code(BL-beta) proposal for com pressed data transferring of real-time IoT sensing or financia l transaction data (IoT 및 금융 거래 실시간 데이터 정보의 압축 전송을 위한 새로운 고효율 유니버설 코드(BL-beta) 제안)

  • Kim, Jung-Hoon
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.11 no.4
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    • pp.421-429
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    • 2018
  • While IoT device sensing data or financial transaction data is transmitted in real time, huge data traffic is generated in processing it. This huge data can be effectively compressed or transmitted using universal code, which is a real-time lossless compressor. In this paper, we propose our BL-beta code, which is newly developed universal code for compressing stock trading data, which the maximum range of measured values is difficult to predict and is generated within a relatively constant range over a very short period of time. For compressing real-time stock trading data, Compared with the fixed length bit transmission, the compression efficiency is at least 49.5% higher than that of the fixed length bit transmission, and the compression transmission performance is 16.6% better than the Exponential Golomb code.

Real-time Implementation of Variable Transmission Bit Rate Vocoder Improved Speech Quality in SOLA-B Algorithm & G.729A Vocoder Using on the TMS320C5416 (TMS320C5416을 이용한 SOLA-B 알고리즘과 G.729A 보코더의 음질 향상된 가변 전송률 보코더의 실시간 구현)

  • Ham, Myung-Kyu;Bae, Myung-Jin
    • Speech Sciences
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    • v.10 no.3
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    • pp.241-250
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    • 2003
  • In this paper, we implemented the vocoder of variable rate by applying the SOLA-B algorithm to the G.729A to the TMS320C5416 in real-time. This method using the SOLA-B algorithm is that it is reduced the duration of the speech in encoding and is played at the speed of normal by extending the duration of the speech in decoding. But the method applied to the existed G.729A and SOLA-B algorithm is caused the loss of speech quality in G.729A which is not reflected about length variation of speech. Therefore the proposed method is encoded according as it is modified the structure of LSP quantization table about the length of speech is reduced by using the SOLA-B algorithm. The vocoder of variable rate by applying the G.729A and SOLA-B algorithm is represented the maximum complexity of 10.2MIPS about encoder and 2.8MIPS about decoder in 8kbps transmission rate. Also it is evaluated 17.3MIPS about encoder, 9.9MIPS about decoder in 6kbps and 18.5MIPS about encoder, 11.1MIPS about decoder in 4kbps according to the transmission rate. The used memory is about program ROM 9.7kwords, table ROM 4.69kwords, RAM 5.2kwords. The waveform of output is showed by the result of C simulator and Bit Exact. Also, the result of MOS test for evaluation of speech quality of the vocoder of variable rate which is implemented in real-time, it is estimated about 3.68 in 4kbps.

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Adaptive Packet Scheduling Scheme to Support Real-time Traffic in WLAN Mesh Networks

  • Zhu, Rongb;Qin, Yingying;Lai, Chin-Feng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.5 no.9
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    • pp.1492-1512
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    • 2011
  • Due to multiple hops, mobility and time-varying channel, supporting delay sensitive real-time traffic in wireless local area network-based (WLAN) mesh networks is a challenging task. In particular for real-time traffic subject to medium access control (MAC) layer control overhead, such as preamble, carrier sense waiting time and the random backoff period, the performance of real-time flows will be degraded greatly. In order to support real-time traffic, an efficient adaptive packet scheduling (APS) scheme is proposed, which aims to improve the system performance by guaranteeing inter-class, intra-class service differentiation and adaptively adjusting the packet length. APS classifies incoming packets by the IEEE 802.11e access class and then queued into a suitable buffer queue. APS employs strict priority service discipline for resource allocation among different service classes to achieve inter-class fairness. By estimating the received signal to interference plus noise ratio (SINR) per bit and current link condition, APS is able to calculate the optimized packet length with bi-dimensional markov MAC model to improve system performance. To achieve the fairness of intra-class, APS also takes maximum tolerable packet delay, transmission requests, and average allocation transmission into consideration to allocate transmission opportunity to the corresponding traffic. Detailed simulation results and comparison with IEEE 802.11e enhanced distributed channel access (EDCA) scheme show that the proposed APS scheme is able to effectively provide inter-class and intra-class differentiate services and improve QoS for real-time traffic in terms of throughput, end-to-end delay, packet loss rate and fairness.