• Title/Summary/Keyword: Spreading Length

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A Study on Hybrid Interference Cacellation for Multirate DS-CDMA (Multirate DS/CDMA 시스템을 위한 하이브리드 간섭제거기법에 관한 연구.)

  • 유종엽;이승호;우대호;변윤식
    • Proceedings of the IEEK Conference
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    • 2000.09a
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    • pp.47-50
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    • 2000
  • In the Multirate DS/CDMA system based on VSL(Variable Spreading Length), the problem of the multiple access interference and effect similar to near-far effects in current system is generated. This problem can degrade performance of the system badly. Therefore, In this paper we proposed Hybrid Interference Cancellation to overcome this problems, Simulation result presents that the proposed Hybrid Interference Cancellation has the better performance than the conventional decorrelator, Parallel Interference Cancellation.

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Response Analysis of Buried Pipelines Considering Longitudinal Permanent Ground Deformation (종방향 영구지반변형에 의한 매설관로의 거동 특성 해석)

  • 김태욱
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.10a
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    • pp.184-191
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    • 2000
  • In this research, a numerical model is developed for analysis of buried pipelines considering longitudinal permanent ground deformation(PGD) due to liquefaction induced lateral spreading. Buried pipelines and surrounding soil are medeled as continuous pipelines using the beam elements and a series of elasto-plastic springs uniformly distributed along the pipelines, respectively. Idealized various PGD patte군 based on the observation of PGD are used as a loading configuration and the length of the lateral spread zone is considered as a loading parameter. Numerical results are verified with other research results and efficient applicability of developed procedure is shown. Analyses are performed by varying different parameters such as PGD pattern, pipe diameter and pipe thickness. Results show that response of buried pipelines are more affected by pipe thickness than pipe diameter. Finally, the critical length of the lateral spread zone and the critical magnitude of PGD which cause yielding, local buckling or tension failure are proposed for the steel pipe which are normally used in Korea.

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Performance Evaluation of Access Channel Slot Acquisition in Cellular DS/CDMA Reverse Link

  • Kang, Bub-Joo;Han, Young-Nam
    • ETRI Journal
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    • v.20 no.1
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    • pp.16-27
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    • 1998
  • In this paper, we consider the acquisition performance of an IS-95 reverse link access channel slot as a function of system design parameters such as postdetection integration length and the number of access channel message block repetitons. The uncertainty region of the reverse link spreading codes compared to that of forward link is very small, since the uncertainty region of the reverse link is determined by a cell radius. Thus, the parallel acquisiton technique in the reverse link is more efficient than a serial acquisition technique in terms of implementation and of acquisition time. The parallel acquisition is achieved by a bank of N parallel I/Q noncoherent correlator are analyzed for band-limited noise and the Rayleigh fast fading channel. The detection probability is derived for multiple correct code-phase offsets and multipath fading. The probability of no message error is derived when rake combining, access channel message block combining, and Viterbi decoding are applied. Numerical results provide the acquisition performance for system design parameters such as postdetection integration length and number of access channel message block repetitions in case of a random access on a mobile station.

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Complexity Reduced Blind Subspace Channel Estimation for DS/CDMA DMB Downlink (DS/CDMA DMB 하향 링크에서 복잡도가 감소된 블라인드 부분 공간 채널 추정)

  • Yang Wan-Chul;Lee Byung-Seub
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.9
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    • pp.863-871
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    • 2004
  • In this paper, we propose a subspace channel estimation technique for DS/CDMA DMB down link system, which can obtain reduction in numerical complexity by using of matched filtering outputs. The complexity reduction is considerable when the channel length is small and the system is moderately loaded. Previously proposed subspace-based blind channel estimation algorithm suffer from high numerical complexity for systems with large spreading gains. Although the proposed algerian suffers a slight performance loss, it becomes negligible for large observation length. Performance is evaluated through simulations and the derivation of the analytical MSE.

The Direct Sequence Spread Spectrum Signal Detection Using The Triple Correlation Estimator Value (3차 상관 추정치를 이용한 직접 시퀀스 확산대역 신호의 검출)

  • 임연주;조영하;박상규;임정석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.8C
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    • pp.1025-1033
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    • 2004
  • This paper covers the detection of covert direct sequence spread spectrum signal without the PN(Pseudo Noise) code information. Due to its low probability of interception, the difficulty of spectrum surveillance increases. Detection parameters are the signal existence of given bandwidth, the length of spreading sequence used by transmitter, and the identification of spreading code for detected chip length. The triple correlation function(TCF) value which is one of the higher order statistical signal processing techniques can be used to detect spread spectrum signal without a prior knowledge, but, it has weakness that TCF results depend on the spread data sequence in actual application. This paper proposes the new scheme that not only overcomes the weakness but also presents better performance than the traditional TCF scheme. The performance comparison of conventional TCF with proposed technique shows that the triple correlation estimator(TCE) has better detection capability.

A New Cultivar of Gypsophila paniculata 'Double Shine' with Bright Colored Flower and Strong Stem (줄기가 강하고 밝은 화색의 절화용 안개꽃 '더블샤인' 육성)

  • Cheong, Dong-Chun;Choi, Chang-Hak;Song, Young-Ju;Lim, Hoi-Chun;Kim, Jeong-Man;Lee, Jin-Je;Lee, Jung-Soo
    • Horticultural Science & Technology
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    • v.30 no.1
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    • pp.93-96
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    • 2012
  • 'Double Shine', a cultivar of Gypsophila paniculata was newly developed for the cut flowers by Jeollabuk-do Agricultural Research & Extension Services. It has morphological characteristics of the spreading plant type, double florets of many petals and two pistils, emarginate petal tip and cup shaped calyx. Also 'Double Shine' has several traits such as strong flower stalk, bright colored flower, narrow branching angle and more or less resistance to powdery mildew and pest injury. Furthermore, 'Double Shine' produced higher primary branches, and longer flower stalk length with internodal length and than did a check variety 'Bristol Fairy' during summer cultivation in subalpine areas. Blooming of 'Double Shine' was delayed by 16 days, its floret had broader width, compared to 'Bristol Fairy'. Moreover, 'Double Shine' produced normal flowers with two pistils and 8.5 stamens, with little production of malformed flowers in the high temperature condition.

Performance Analysis of DS/CDMA with Diversity and Channel Coding in a Land-Mobile Satellite Channel (육상이동 위성채널에서 다이버시티와 채널 부호를 적용한 DS / CDMA 성능 분석)

  • Kim, Hong-Chil;Kim, Nam
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.8 no.1
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    • pp.42-51
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    • 1997
  • The satellite channel with a line-of-sight signal component is modeled by a shadowed Rician fading channel. We adopt a direct-sequence / code division multiple access (DS / CDMA), which has the advantage to suppress the multipath effect and increase the user capacity. The performance which is evaluated by bit error probability is subjected to the influence of branch number, multi-user number, and spreading code-length. As the result of the analysis, performance advance is achieved with multi-user number decreasing, number of brnaches increasing, and spreading code-length increasing as chip duration is constant. To use both of diversity combining scheme and channel coding is more efficient for performance improvement than the case using diversity combining scheme only. The use of BCH coding and convolutional coding shows better consequence than Hamming coding. Totally, the performance degradation for heavy shadowing is much larger than that for light and average shadowing as heavy shadowing decreases LOS signal.

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Model Test to Predict the Runout Distance of Landslide according to Hourly Rainfall (강우강도에 따른 산사태 확산범위 예측을 위한 모형실험)

  • Song, Young-Suk;Chae, Byung-Gon;Kim, Won-Young;Seo, Yong-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.12-19
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    • 2006
  • Landslide model experiments considering hourly rainfall were performed to investigate and predict the run out distance induced by landslides. The model flume and the rainfall simulator were designed and produced. The model flume was designed in consideration of the landslide characteristics of Korea. The landslides in Korea were mainly occurred in the interface between soil layer and rock layer. The rainfall simulator was produced for controlling hourly rainfall ranged from 100mm/hr to 1,000mm/hr. Jumnunjin standard sand as slope soils was placed on the model flume. The model experiments were performed with changing the hourly rainfall ranged from 150mm/hr to 250mm/hr. In this experiments, the inclination of slope was 25o and the relative density of slope soils was 35%. As a result of experiments, the pore water pressure is rapidly increased at landslide occurring time, and the scale of landslide is increased with increasing in hourly rainfall. The spreading range of run out distance is occurred with pan type, and the spreading width and length are rapidly increased in its early stage and slowly increased after early stage. Also, The increasing velocity of run out distance of debris is influenced by hourly rainfall.

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Numerical and Experimental Simulation of Directional Waves in Towing Tank (예인수조에서 방향스펙트럼파의 수치적 및 실험적 재현)

  • Y.K. Chung;J.H. Lee;H.H. Chun;D.D. Ha
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.2
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    • pp.1-9
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    • 2001
  • Based on the linear potential theory with the side wall reflection. the directional spectrum waves are numerically simulated by a source distribution method and these together with long-crested irregular waves are also generated at the towing tank of Pusan National University by considering the transfer function of the wave maker obtained from the regular waves. In the numerical simulation, the characteristics of the directional spreading function are investigated by changing the breadth of the wave-maker unit. the width of the towing tank and the wave period. In the experimental generation, the statistical properties and the power spectrums of the long-crested irregular and directional waves are compared along the towing tank length. The directional spreading functions are also investigated at various positions in the tank.

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