• Title/Summary/Keyword: Ds

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Blind MOE-PIC Multiuser Detector for Multicarrier DS-CDMA Systems (다중 반송파 DS-CDMA 시스템을 위한 블라인드 MOE-PIC 다중사용자 검출기)

  • Woo Dae ho;Lee Seung yong;Byun Youn shik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.3C
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    • pp.153-157
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    • 2005
  • Frequency selective fading occurs due to the Doppler Effect in mobile communication systems. The performances of the systems are rapidly reduced due to effect of multiuser interference under frequency selective channels at DS-CDMA systems. To overcome these problems, we adopted the multi-carrier modulation techniques, and it is able to solve the frequency selective channel effects by means of these modulation techniques, and interference problems due to multiuser access are solved by means of multiuser detection techniques. In this paper, we proposed the blind MOE/PIC multiuser detection method which is composed of both the blind multiuser detection technique and parallel interference canceller. Thus, simulation results show that the proposed method performs better than conventional methods.

Dispersion Behavior and Size Analysis of Thermally Purified High Pressure-high Temperature Synthesized Nanodiamond Particles

  • Kwon, Hansang;Park, Jehong;Leparoux, Marc
    • Journal of Powder Materials
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    • v.24 no.3
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    • pp.216-222
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    • 2017
  • Synthesized monocrystalline nanodiamond (nD) particles are heat-treated at various temperatures to produce highly structured diamond crystals. The heat-treated nDs show different weight loss ratios during thermogravimetric analysis. The crystallinities of the heat-treated nDs are analyzed using Raman spectroscopy. The average particle sizes of the heat-treated nDs are measured by a dynamic light scattering (DLS) system and direct imaging observation methods. Moreover, individual dispersion behaviors of the heat-treated nD particles are investigated based on ultrasonic dispersion methods. The average particle sizes of the dispersed nDs according to the two different measurement methods show very similar size distributions. Thus, it is possible to produce highly crystallized nD powder particles by a heat-treatment process, and the nD particles are relatively easy to disperse individually without any dispersant. The heat-treated nDs can lead to potential applications such as in nanocomposites, quantum dots, and biomedical materials.

Fast code synchronization method of the DS-SS/TDMA control channel for satellite communication (직접대역확산 방식의 시분할 다중접속 위성통신 제어채널 고속 부호동기 방법)

  • Ryu, Young-Jae
    • Journal of Satellite, Information and Communications
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    • v.4 no.1
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    • pp.14-20
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    • 2009
  • This paper describes synchronization concept and algorithm of the reverse DS-SS/TDMA control channel to handle satellite terminals which are distributed through the mission area. Military satellite control channel should have ECCM capabilities and handle more than several hundreds satcom terminals simultaneously. DS-SS/TDMA control channel can satisfy these demand but it spend much synchronization time. Proposed algorithm insert the preamble which is divided with several short sub bins prior to control data and use the parallel matched filtering searcher for each sub bin. As a result of the test, proposed algorithm can acquire most of control channel packet successfully within several milliseconds in severe jamming environment.

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Implementation of DS-SS Modem-based Communication System for Long Distance Wireless-Transmission (원거리 무선전송을 위한 DS-SS 모뎀 기반의 통신시스템 구현)

  • Ju, Won-Ki;Kim, Yoon-Ho;Lee, Joo-Shin
    • Journal of Advanced Navigation Technology
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    • v.15 no.6
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    • pp.1075-1081
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    • 2011
  • In this paper, we proposed the DS-SS modem-based communication system for long distance wireless-transmission. The module we designed in this approach contained both convolution encoder and gold-code generator, which aimed at error correcting, T-DES encryption algorithm and spread-spectrum as well. It embodied PC-based GUI program in order to control the such command signal as data transceiver. This program also used to control the specific FPGA/MCU which is able to verify and interface to the modem. We demonstrated the communication system to verify its proper operation by using GUI program and designed hardware. A set of experiments are conducted and as a result, proposed communication system is well operated as the design specification.

Performance of a Modified Multicarrier Direct Sequence CDMA System

  • Lee, Dong-Wook;Lee, Hun;Kim, Jin-Su
    • ETRI Journal
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    • v.19 no.1
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    • pp.1-12
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    • 1997
  • In this paper, we present an improved multicarrier direct sequence (DS) code division multiple access (CDMA) scheme by modifying the system originally proposed by Kondo and Milstein [13]. In this modified system, different spreading sequences multiplied by a data sequence modulate different carriers. This is to prevent the multiple access capability from reducing when the fading characteristics of different carrier frequencies are highly correlated. We have derived a formula which determines the mean values of the relative received signal strength in a single carrier DS CDMA rake system and in a multicarrier DS-CDMA system. We present results on the comparison of the bit error rate (BER) performance of the two systems including the effect of correlation between fading characteristics of different frequencies under various multipath fading conditions. The results indicate that with 50 users the modified multicarrier DS CDMA system can achieve an uncoded irreducible BER of $1.7{\times}10^{-3}$ with an average received signal-to-noise ratio per bit of 10dB, which is better that $3.0{\times}10^{-3}$ achieved by the single carrier DS CDMA rake system, and also show that if multicarrier CDMA system is used with respect to single carrier CDMA system, the SNR gain is up to 4.5 dB for the uncode BER of $10^{-3}$ being achieved.

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Performance Analysis of DS-CDMA System using Space-Time Beamforming Technique (시공간 빔 형성 기술을 이용한 DS-CDMA 시스템의 성능 분석)

  • 김성곤;김영민
    • Journal of the Korea Society of Computer and Information
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    • v.9 no.2
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    • pp.97-104
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    • 2004
  • As a channel of a DS-CDMA system is shared among several users, the receivers face the problem of MAI. Also the bandlimited channel leads to ISI. Both components are undesired, but unlike the additive noise process, which is usually completely unpredictable, their space-time structure helps to estimate and remove them. This paper investigates a DS-CDMA system with a fading multipath channel. The investigations have been separated into a channel estimation part and a reception part. In the estimation part of seperated two parts, the multipath parameters such as DOA and TOA are evaluated in this paper. In the part of receiver. we used these parameters and tested the performance of this receiver about space-time beamformers. To assess many different estimation techniques and beamformers, the simulation compared with theoretical values is performed.

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Adaptive CM Array Antenna employing RAKE Receiver in Asynchronous DS-CDMA systems (비동기 DS-CDMA시스템에서 RAKE 수신기를 채용한 적응형 CM 배열 안테나)

  • 김용석;서성진;황금찬
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.5C
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    • pp.601-610
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    • 2004
  • In this paper, the performance of an adaptive array antenna using Constant Modulus Algorithm (CMA) based on the signal structure for the IMT-2000 3GPP specification reverse link of an asynchronous direct sequence code division multiple access (DS-CDMA) system are evaluated. In addition, the performance is compared with the array antenna using Least Mean Square (LMS) based on the training signal. The simulation parameters such as the number of multipath, mu10pa1h intensity profiles between path, spreading gain and multiuser etc., are considered in the Monte Carlo simulation. Simulation results demonstrate an adaptive array antenna using CMA may give more capacity gain than the amy antenna using LMS in the case of multipath fading channel.

Implementation and miniaturization of High Order Derivative Gaussian Pulse Generator for DS-UWB (DS-UWB를 위한 고차 미분 가우시안 펄스 생성기의 소형화와 구현)

  • Kim, Dong-Ho;Bang, Gyeong-Nam;Park, Chong-Dae
    • Journal of IKEEE
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    • v.10 no.2 s.19
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    • pp.109-115
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    • 2006
  • In this paper, High order derivative Gaussian pulse generator for DS-UWB communication satisfying the regulation of FCC was proposed and fabricated. In order to transform rectangular signal of 100Mbps to a Gaussian pulse, the fabricated Gaussian pulse generator consists of only two SRD. The output pulse had the widths of 330 psec and amplitudes of 920 mV. In addition, the designed and fabricated dual bandpass filter shows high order derivate characteristics by using micro-strip line and parallel stub to remove WLAN band. We generated the 13th Gaussian pulse restricted frequency spectrum of WLAN band more than -25dB. The pulse had pulse width of 1 nsec and amplitude of 25 mV.

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Formation of Teleomorph of the White Root Rot Fungus, Rosellinia necatrix, and the Potential Role of its Ascospores as Inocula

  • Lee, J.S.;Han, K.S.;Park, J.H.;Park, Y.M.;Naoyuki, Matsumoto
    • The Plant Pathology Journal
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    • v.19 no.3
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    • pp.152-158
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    • 2003
  • Stromata of the white root rot fungus, Rosellinia necatrix, were produced on diseased roots although they were reported to develop rarely in nature. Forty-two (42) out of 47 samples produced synnemata while 23 developed stromata. Forty-seven (47) isolates obtained from diseased root samples were divided into 24 mycelium compatibility groups (MCGs). Sixteen (16) out of 24 MCGs produced stromata. Single ascospore isolates from 10 stroma samples produced dsRNA-containing isolates from diseased tissue beneath stromata. The frequency of synnema production on axenic culture varied among isolates with different origin. The dsRNA was not transmitted vertically to the ascospore offspring despite the infection of various dsRNA in the parental isolates. The dsRNA was absent in 35 ascospore isolates in two stroma samples that originated from the isolates, in which dsRNA was not eliminated by hyphal tip isolation. Consequently, sexual reproduction in the white root rot fungus was suggested to produce propagules as a new infection source and to have the function to eliminate infectious factors such as mycoviruses.

Blind Signal Subspace-Based Channel Identification for DS/CDMA DM Downlink (DS/CDMA DMB 하향 링크에서의 신호 공간에 기초한 블라인드 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.848-855
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    • 2004
  • In this paper, we propose a new channel identification technique for long code DS/CDMA DMB down link system which estimate the channel response based on the signal space vector only, unlike the most conventional subspace method relying on the orthogonal property of noise space vectors to the signal space vector. Because of this property of the proposed method, it is optimum and practical in manipulation of the covariance matrix to be analyzed. In the paper, we derive the mathematical expression necessary to clarify the proposed method and show the relevant simulation and numerical results to verify the validity of the proposed algorithm.