• Title/Summary/Keyword: direct sequence code division multiple access (DS-CDMA)

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Extended OVSF for MIMO-CDMA System (HIMO-CDMA 시스템을 위한 확장 OVSF)

  • Lee, Kwank-Jae;Hou, Jia;Lee, Moon-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.9 s.100
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    • pp.855-861
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    • 2005
  • Two-dimensional orthogonal variable spreading codes are presented far multiplexing of forward link in direct sequence code division multiple access(DS-CDMA) multiple antennas system. The bit error rate(BER) performance under a multi-user environment fur the additive white Gaussian noise(AWGN) channel and Rayleigh fading MIMO channel are evaluated. The results demonstrate that the proposed scheme could provide flexible rates and lower peak correlation values.

Performance analysis of MC-CDMA Mobile Communication Systems with Smart Antennas (스마트 안테나를 적용한 MC-CDMA 시스템의 성능 분석)

  • 이종길
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.7 no.4
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    • pp.667-672
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    • 2003
  • Smart antennas will be used mon widely for the higher data rate and the larger number of users as the demand of wireless multimedia service is increased. Therefore, the BER performance is analyzed in this paper for DS-CDMA and MC-CDMA systems using smart antennas. A reverse link channel is simulated assuming the frequency selective Rayleigh fading. The simulation results are presented based on the characteristics of DS-CDMA and MC-CDMA systems according to the signal spectrum bandwidth and the method of adaptive beamforming. The BER performances of both systems are improved as the beam width of smart antennas is decreased. Also, it is shown that the performance of MC-CDMA system is much better than that of DS-CDMA system as the number of users is increased.

Review on RF Performance of Ultra Wide Band Device

  • Lee, Il-Kyoo;Kang, Bub-Joo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.21 no.2
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    • pp.34-39
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    • 2007
  • UWB(Ultra Wide Band) system for high speed and high accurate location has been studying actively. This paper presents the design and implementation of RF transceiver for DS-CDMA(Direct Sequence-Code Division Multiple Access) UWB device. Major components of RF transceiver such as Low Noise Amplifier(LNA) and Band Pass Filter(BPF) are designed and then fabricated to meet wideband characteristics. The RF transceiver was implemented by the use of the fabricated components and commercial devices after carrying out performance simulation. Through the performance evaluation of the UWB RF transceiver with W-CDMA signal, the approach of design, implementation and evaluation of RF transceiver which is available to DS-CDMA UWB system is verified.

Enhancement of acquisition performance using interference suppression filter in a microcellular environment (마이크로셀 환경에서 간섭억압여파기를 이용한 포착성능의 향상)

  • 김진영;이재홍
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.8
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    • pp.10-19
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    • 1997
  • In this paper, perfodrmance of matched-filter (MF) acquisition scheme is analyzed for a direct-sequence/code-division-multiple-access (DS/CDMA) system in a microcellular environment. Mean acquistion time is used as a performance measure. It is demonstrated that acquisition performance is enhanced using interference suppression filter in a Rician fading channel. To apply for multiuser environments, multiple access interference is considered in the performance analysis. From the numerical results, it is shown that mean acquistion time decreases with the increasing SNR/chip, and acquisition performance is improved as the number of taps of interference suppression filter. It is also shown that mean acquisition time increases with the number of users in the system, and acquistion performance is degraded as the icrease of narrowband interference bandwidth. The analysis in this paper can be applied to a DS/CDMA overlay environment.

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Interference Suppression Based on Code Grouping and Groupwise Decorrelation in W-CDMA Downlink (코드그룹화와 그룹단위 역상관을 이용한 W-CDMA 하향링크에서의 다중사용자 간섭억압기법)

  • Ha, Won;Bae, Jung-Hwa;Lim, Byun-Chun;Park, Jin-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.6A
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    • pp.631-639
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    • 2004
  • In this paper, we presented a new interference suppression method based on code grouping and groupwise decorrelation for multirate DS-CDMA downlink. The code grouping is accomplished according to the correlation property between the mother code and the child codes in OVSF code tree. Using groupwise decorrelation, the proposed receiver has relatively low computational complexity and does not require any information about interference users, such as code, data, and amplitude. From the simulation results in multipath channels, the proposed receiver is to provide significant performance enhancement.

Design and Implementation of Modulator Channel Card and VLSI Chip for a Wideband CDMA Wireless Local Loop System (광대역 CDMA WLL 시스템을 위한 변조기 채널 카드 및 VLSI 칩 설계 및 구현)

  • 이재호;강석봉;조경록
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.10A
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    • pp.1571-1578
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    • 1999
  • In this paper, we present the Modulator Channel Card and VLSI chip for the Radio Transceiver Unit (RTU) of direct sequence code division multiple access (DS-CDMA) Wireless Local Loop (WLL) System. The Modulator Channel Card is designed and implemented using ASIC's, FPGA's and DSP's. The ASIC, compliance with Common Air Interface specification proposed by ETRI, has 40K gates which is designed to operate at 32MHz, and is fabricated using $0.6\mu\textrm{m}$ CMOS process. The ASIC carries out for I- or Q- phase data channel signal processing at a time, where each data channel processing consists of channel coding, block interleaving, scrambling, Walsh modulation, Pseudo-Noise (PN) spreading, and baseband filtering. The Modulator Channel Card has been integrated as a part of RTU of WLL system and is confirmed that it meets all functional and performance requirements.

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Performance analysis of asynchronous DS-CDMA system with MRC diversity in fading channels

  • Seo, Seok;Lee, Chan-kil
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.11A
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    • pp.1237-1243
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    • 2004
  • This paper presents and analyses the closed-form expression of the average bit error rate (BER) for an asynchronous direct-sequence code division multiple access (DS-CDMA) system with coherent binary phase shift keying (BPSK) modulation scheme using a maximal ratio combining (MRC) diversity over a Rician fading channel. In addition to the average BER, outage probability, and user capacity of system are estimated as performance measures. The results are general enough so that it includes Rayleigh fading and nonfading channel with zero and infinite Rician factor, respectively, as special cases. The effects of various channel models, processing gains, and diversity orders on the system performances are also considered for the typical multipath delay profiles characterized by Rician fading channel.

DS-CDMA Ultra Wide Band RF 트랜시버 구현 및 성능 평가

  • Lee, Il-Gyu;Han, Sang-Cheol
    • 한국정보통신설비학회:학술대회논문집
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    • 2005.08a
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    • pp.422-426
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    • 2005
  • 초고속통신, 고 정밀 위치정보 시스템 등을 구현하기 위해 광 대역 특성을 요구하는 UWB(Ultra Wideband) 시스템에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 DS-CDMA(Direct Sequence - Code Division Multiple Access)를 근간으로 하는 3 GHz $\sim$ 5GHz의 주파수 대역을 갖는 UWB 시스템에서 아날로그 QPSK(Quadrature Phase Shift Keying) 변복조, 주파수 변환 및 전력 증폭 기능을 수행하는 RF 트랜시버 설계 방안을 제시하였고, 광 대역 특성을 만족하는 주요 구성 성분들의 설계 방법 및 성능 특성을 분석하였다. 상용 부품 및 제작된 부품 들을 이용하여 구현된 RF 트랜시버에 대한 성능평가를 통해 DS-CDMA 방식의 UWB 시스템을 위한 RF 트랜시버 설계 및 구현 접근 방법을 검증하였다.

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Performance Analysis of an Adaptive Hybrid Search Code Acquisition Algorithm for DS-CDMA Systems (DS-CDMA 시스템을 위한 적응 혼합 검색형 동기획득 알고리즘의 성능 분석)

  • Park Hyung rae;Yang Yeon sil
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.3C
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    • pp.83-91
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    • 2005
  • We analyze the performance of an adaptive hybrid search code acquisition algorithm for direct-sequence code division multiple access (DS-CDMA) systems under slowly-moving mobile environments. The code acquisition algorithm is designed to provide the desired feature of constant false alarm rate (CFAR) to cope with nonstationarity of the interference in CDMA forward links. An analytical expression for the mean acquisition time is first derived and the probabilities of detection, miss, and false alarm are then obtained for frequency-selective Rayleigh fading environments. The fading envelope of a received signal is assumed to be constant over the duration of post-detection integration (PDI), considering slow fading environments. Finally, the performance of the designed code acquisition algorithm shall be evaluated numerically to examine the effect of some design parameters such as the sub-window size, size of the PDI, decision threshold, and so on, considering cdma2000 environments.

Performance of Pilot Channel-Aided Channel Estimation for Multicarrier DS-CDMA (멀티캐리어 DS-CDMA시스템에서 파일롯 채널을 이용한 채널추정의 성능분석)

  • Park, Hyung-Kun
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • v.9 no.1
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    • pp.1109-1112
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    • 2005
  • In this paper, we evaluate the performance of pilot channel-aided channel estimation for multicarrier direct-sequence (DS) code division multiple access (CDMA) communication system as proposed by Kondo and Milstein [1]. We investigate the optimum number of pilot channels for various coherence bandwidths and different number of subchannels. Keeping the total transmit bandwidth fixed, an optimum number of total subchannels and pilot channels exists under specific channel and transmitted energy. We show that there is a tradeoff between the number of pilot channels and data subchannels, thereby requiring differing numbers of optimum pilot channels according to channel conditions.

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