• Title/Summary/Keyword: bit loading

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Link Adaptive MAC protocol for Wi-Fi (Wi-Fi 네트워크를 위한 매체적응 MAC 프로토콜)

  • Kim, Byung-Seo;Han, Se-Won;Ahn, Hong-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.9 no.3
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    • pp.69-74
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    • 2009
  • A novel protocol is proposed to achieve sub-carner-based rate adaptation in OFDM-based wireless systems. The protocol requires the addition of one OFDM symbol to the Clear-to-Send (CTS) packet defined in the IEEE 802.11 standard_ When receiving a Ready-To-Send (RTS) packet, the receiver determines the number of bits to be allocated in each sub-carrier through channel estimation. This decision is delivered to the sender using an additional OFDM symbol. That is, bit-allocation over sub-carriers is achieved using only one additional OFDM symbol. The protocol also provides an error recovery process to synchronize the bit-allocation information between the sender and receiver. The protocol enhances the channel efficiency in spite of the overhead of one additional OFDM symbol.

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Production of High Loaded Paper by Dual Flow Addition of Fillers (II) - Effect of Location of Starch Addition - (충전제 투입 위치 이원화에 의한 고충전지 제조 (II) - 전분 투입 위치의 영향 -)

  • Choi, Do-Chim;Won, Jong Myoung;Cho, Byoung-Uk
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.47 no.1
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    • pp.84-92
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    • 2015
  • Fillers have been used to improve the optical and printing properties and to reduce the production cost while increasing the filler content in paper causes adverse effects on paper strength. In the previous study, it was shown that the thick stock addition of filler can increase the filler content without significantly sacrificing paper strength. This study was carried out to elucidate the effect of the location of starch addition (before or after the filler addition) on handsheet properties and a papermaking process as a part of developing the thick stock loading technology. In addition, effects of dual flow addition of cationic starch were evaluated. It was found that paper strength was superior when cationic starch was added after the filler addition. No adverse effects on optical properties, formation and filler retention were observed. Drainage was a bit slower when starch was added after the filler addition, which shall be resolved with regulating other factors. Dual flow addition of cationic starch before and after filler addition did not show any special advantage.

Hysteretic Behavior of Precast Concrete Large Panel Structures Subjected to Horizontal Cyclic Loading (반복 횡하중을 받는 프리캐스트 대형 콘크리트 판구조의 이력특성에 관한 실험적 연구)

  • Seo, Soo-Yeon;Yi, Waon-Ho;Lee, Li-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.3
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    • pp.253-260
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    • 1999
  • Main objective of this study is to examine the hysteretic behaviors and to evaluate the capacity of precast concrete (PC) large panel structures simulated from the prototype of 15-story building, Two 1/2 scaled precast concrete wall specimens and one monolithic reinforced concrete specimen were designed and tested under the cyclic loading conditions. The main parameter of test specimens in PC large panel structure is the type of details for vertical continuity of vertical steel in horizontal joint. Also the behaviors of PC large panel structures are compared with that of monolithic reinforcement concrete wall structure. From the results, the stiffness and energy dissipation ratio of the precast concrete specimens are shown little bit lower than those of monolithic reinforced concrete specimen. In the PC large panel structures, the specimen connected vertically by welding (strong connection) showed higher strength than that of the specimen connected vertically by joint box. However the failure pattern of the former showed more brittle than that of the latter due to the diagonal compressive failure of wall panels.

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A Study about Performance of Sum-Product Decoder Considering Adaptive Bit-Loading in LDPC Coded OFDM Systems (LDPC Coded OFDM 시스템에서 적응형 비트 로딩을 고려한 Sum-Product 복호기 성능에 관한 연구)

  • Oh, Hui-Myoung;Kim, Young-Sun;Lee, Jae-Jo
    • Proceedings of the KIEE Conference
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    • 2006.07d
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    • pp.2027-2028
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    • 2006
  • 추정된 채널 정보를 바탕으로 적용하는 적응형 비트 로딩 방식은, 전력선 통신 시스템의 고속화 및 대용량 데이터 전송을 위해 최근 대두되고 있는 LDPC(Low Density Parity Check) coded OFDM 시스템에 대해, 한정된 주파수 대역과 신호 전력의 효율적 사용을 제공한다. 그러나 적응형 비트로딩 방식은 한정된 수의 일정 SNR(신호대 잡음 전력비) 구간에 대한 mapping 방식으로 적용되기 때문에 송수신 과정에서 추정된 채널 정보를 이용하는 sum-product 복호기가 채널 변화에 민감하게 반응하지 못하는 상황이 발생하며, 결국 송신단에서 채널 추정 결과를 바탕으로 선택된 SNR 범위에 대해서는 실제 수신되는 신호에 대한 SNR과의 차이가 존재하고 시스템의 성능은 그 만큼의 성능 열하로 나타나게 된다. 본 논문에서는 이러한 성능 열하 정도를 시뮬레이션을 통해 확인하였다.

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Vibration Analysis of Network Communication Equipment (네트워크 통신장비의 진동 해석)

  • Lee Jae-Hwan;Kim Jin-Sup;Kim Young-Jung
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.467-472
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    • 2006
  • The purpose of this paper is to check the structural safety of the network equipments by performing the static and dynamic finite element analysis. The stress and displacement of structures under static loading condition are evaluated to check whether satisfying the design requirement conditions. Since the computed natural frequencies are similar to the results of experiment. the model could be used for the response spectrum analysis where experimental acceleration value at each frequency are used as seismic input excitation. It is shown that the analysis results are a little bit larger than that of the experimental values. Also sensitivity analysis and optimization for the natural frequency are performed and it is found that the first natural frequency is very sensitive to the stiffness of the equipment.

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Performance Analysis of Synchronous Downlink MC-CDMA with Precoding and Frequency Offset

  • Jang, Won-Mee;Lee, Moon-Woo
    • Journal of Communications and Networks
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    • v.9 no.2
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    • pp.192-197
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    • 2007
  • We analyze the performance of code division multiple access (CDMA) system with multicarrier (MC) that employs precoding in synchronous downlink channels. Even though considerable efforts are undergoing for frequency offset estimation and correction, it is inevitable for the system to bear the remaining frequency offset. Therefore it is important to predict accurately the system performance in the presence of the residual frequency offset. We obtain the bit error rate (BER) performance in terms of the number of users, the spreading factor, the number of sub-carriers, and frequency offset. We assume that the spreading factor is equal to the number of sub-carriers, although we can generalize the case. The simulation results show that the BER of MC-CDMA with precoding shows a performance that varies with frequency offset as well as system loading.

Realization of the Transmitter of Communication Modem for Control Systems using Power-Distribution Circuit (전력선 버스를 이용한 제어 시스템의 통신모뎀 송신기 구현에 관한 연구)

  • Chung, Chang-Kyung;Park, Young-Chull;Sohn, Dong-Sup
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.3
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    • pp.330-335
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    • 1999
  • Recently, there a lot of activities on the researches that implement many kinds of control system using power lines. To implement that, it is desirable to use hybrid PSK model because it takes advantage of PSK and DPSK which has a low-bit-error rate. In this parer, we implement the transmitter of this model. Because the power line is not designed for the data communication, we separated the signal generator circuit and the signal loading circuit so that minimized noises from outside. Also, to make it easy on the experiments, most of process are performed by software. As a result, transmitting a high frequency signal on the power line made no effects on the electrical devices.

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Seismic Performance of Precast Concrete Large Panel Structures Subjected to Horizontal Cyclic Loading (반복 횡하중을 받는 프리캐스트 대형 판구조의 내진성능에 관한 연구)

  • Seo, Soo-Yeon;Lee, Li-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.3
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    • pp.261-268
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    • 1999
  • The seismic performance of precast concrete panel structures tested previously has been evaluated in this paper. Hysteretic curves of test specimens are idealized to elasto-plastic curves to get reliable yielding and ultimate displacements. For the idealized curves, ductility and energy dissipation capacity of specimens have been evaluated using a few guide lines. In addition, the strength capacity of specimens is checked for the strength demand caused by the design earthquake load including overturning moment effects. The result shows while the strength of specimen with joint box for vertical continuity is little bit lower than that of specimen connected by welding, the ductility of the former is higher than that of the latter. The energy dissipation ratios of PC specimens are ranged from 83% to 96% of that of Re specimen and the average of those are shown 90%.

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Performance analysis of SNR and BER for radiation pattern reconfigurable antenna (인체 부착용 방사패턴 재구성 안테나의 SNR 및 BER 성능 분석)

  • Lee, Chang Min;Jung, Chang Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.6
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    • pp.4125-4130
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    • 2015
  • This paper presents the communication performance for the radiation pattern reconfigurable antenna in the wearable device measuring bio signal (temperature, blood pressure, pulse etc.) of human body. The operational frequency is 2.4 - 2.5 GHz, which covers Bluetooth communication bandwidth. The maximum gain of the antennas is 1.96 dBi. The proposed antenna is efficiently transmitting and receiving signal by generating two opposite beam directions using two RF switches (PIN diode). Also, we investigated how radiation pattern changes according to three angles ($30^{\circ}$, $90^{\circ}$, $150^{\circ}$) of Top Loading. In this paper, we measured and compared the SNR (Signal-to-Noise Ratio) and BER (Bit Error Rate) performances of the proposed antennas in the condition between an ideal environment of anechoic chamber and smart house existing practical electromagnetic interferences (Universal Software Radio Peripheral, USRP). Throughout the comparing the results of the measurement of two cases, we found that the SNR is degraded over 5dB in average and BER is increased over ten times in maximum, therefore, it is confirmed that the error rate of receiving signal is increased. The measured results of SNR and BER value in this paper able to expect the performance degrading by the interference from the electromagnetic devices.

Evaluation of Structural Performance the Hollow PC Column Joint Subjected to Cyclic Lateral Load (반복 횡하중을 받는 유공 PC 기둥 접합부의 구조성능 평가)

  • Seo, Soo-Yeon;Yoon, Seong-Joe;Lee, Woo-Jin
    • Journal of the Korea Concrete Institute
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    • v.20 no.3
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    • pp.335-343
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    • 2008
  • In order to improve the workability in erecting Precast Concrete (PC) members and enhance the seismic resistance capacity of the joints in PC moment frames, a new PC column and its construction process are introduced in this paper. This column is manufactured by centrifugal force in keeping the hollow tube inside; the hollow is little bit wide and the grout can be poured from top to bottom after erection at site so that more compact grouting is possible in horizontal joint. The repeated cyclic loading test for four full scaled specimens was conducted to evaluate the seismic resistance capacity of the joint designed by the proposed system. For the continuity of main reinforcements in column, two connecting methods are used in designing specimens; one is to use mechanical connector and other is lab splice. From the cyclic lateral loading test, it was found that the seismic capacity of the developed PC column joint is comparable to that of monolithic joint.