• Title, Summary, Keyword: CDMA

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Performance Analysis of Multicarrier Code Select CDMA System for PAPR Reduction in Multipath Channels

  • Ryu, Kwan-Woong;Jin, Jiyu;Park, Yong-Wan;Choi, Jeong-Hee
    • Journal of Communications and Networks
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    • v.11 no.1
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    • pp.11-19
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    • 2009
  • Multicarrier direct sequence code division multiple access (MC DS-CDMA) is an attractive technique for achieving high data rate transmission. This is valid regardless of whether or not the potentially large peak-to-average power ratio (PAPR) is an important factor for its application. On the other hand, code select CDMA (CS-CDMA) is an attractive technique with constant amplitude transmission of multicode signal regardless of subchannels. This is achieved by introducing a code select method. In this paper, we propose a new multiple access scheme based on the combination of MC DS-CDMA and CS-CDMA. The proposed scheme, which we call MC CS-CDMA, includes as special cases the subclasses of MC DS-CDMA and CS-CDMA. This paper investigates the performance of these systems over a multipath frequency selective fading channel using a RAKE receiver with maximal ratio combiner. In addition, the PAPR of the proposed system is compared with that of both MC DS-CDMA and CS-CDMA. Simulation results demonstrate that the proposed system provides better PAPR reduction than MC DS-CDMA, at the expense of the complexity of the receiver and the number of available users. The numerical result demonstrates that the proposed system has better performance than MC DS-CDMA due to the increased processing gain and time diversity gain.

Performance Analysis of MFSK-MDPSK/DS-CDMa System Employing Diversity Techniquies and Error Coding Technique in Nakagami Fading Environment (나카가미 페이딩 환경하에서 다이버시티기법과 에러 정정부호화 기법을 채용한 MFSK-MDPSK/DS-CDMA 시스템의 성능 분석)

  • 양원일;강희조
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.4
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    • pp.553-564
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    • 2000
  • In this thesis, mobile communication channel with multi-path fading which is major factor of performance degradation of DS-CDMA system has been considered. An MRC diversity and error correcting coding technique have been used to improve performance of MFSK-MDPSK/DS-CDMA system. The MFSK-MDPSK/DS-CDMA system performance has been obtained quantitatively by the numerical analysis. the modulations under consideration are noncoherent M-ary frequency shift keying(MFSK) and an MFSK based joint frequency phase modulation utilizing MFSK/DS-CDMA and MDPSK-DS-CDMA systems the MFSK-MDPSK/DS-CDMA system obtain a better performance . Also, the error performance of MFSK-MDPSK/DS-CDMA system in Nakagami fading environments is improved by increasing the number of diversity branch and coding gain.

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Comparison and Analysis of the MC DS-CDMA/MPSK and DS-CDMA/MPSK Systems in Nakagami Fading (나카가미 감쇄에서 MC DS-CDMA/MPSK와 DS-CDMA/MPSK 시스템 비교 분석)

  • 이정도;강희조
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.10 no.6
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    • pp.951-958
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    • 1999
  • Multicarrier modulation or orthogonal frequency division multiplexing(OFDM) is a promising technique for mobile communications systems, since it has a strong immunity to multipath fading without employing complicated adaptive equalization. In this paper, performance of MC DS-CDMA/MPSK(multi-carrier direct sequence-code division multiple access/mary phase shift keying) and DS-CDMA/MPSK(direct sequence-code division multiple access/mary phase shift keying) with coherent detection for a CDMA system over Nakagami fading channel analysis. For a given bandwidth, it is shown that MC DS-CDMA/MPSK eventually outperforms DS-CDMA MPSK with random sequences.

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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.

Design and Fabrication of Dielectric Duplexers and Bandpass Filters for CDMA and W-CDMA Dualband Using the Notch and Isolation (너치와 아이솔레이션을 활용한 CDMA와 W-CDMA 듀얼밴드용 유전체 듀플렉셔와 밴드패스 필터의 설계 및 제작)

  • Choi, U-Sung;Yang, Sung-Hyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.6
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    • pp.1227-1232
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    • 2011
  • Using the notch and isolation, we investigated the insertion loss and isolation characterics of the fabricated dielectric duplexers and bandpass filters for CDMA and W-CDMA dualband. Insertion loss(Tx band) and isolation(between Tx and Rx) of duplxer were about -2.1708dB and 45dB at CDMA band, respectively. Also, in the case of W-CDMA, the insertion loss(Tx band) and isolation(between Tx and Rx) showed about -2.6946 and 100dB, respectively. Summering the aboved results, fabricated the dielectric duplexers and bandpass filters will be contributed the increase of atttenuation and the decrease of interference at CDMA and W-CDMA dualband.

Throughput Analysis of Multi-Carrier DS-CDMA System in Rayleigh Fading Channels (레일리 페이딩 채널에서 Multi-Carrier DS-CDMA 시스템의 Throughput 해석)

  • 김영철;노재성;강희조;조성준
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.675-679
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    • 2001
  • In this paper, throughput is derived for slotted ALOHA wideband DS-CDMA and slotted ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.

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Throughput Analysis of Multi-Carrier DS-CDMA System in Rayleigh Fading Channels (레일리 페이딩 채널에서 Multi-Carrier DS-CDMA 시스템의 Throughput 해석)

  • 김영철;노재성;강희조;조성준
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.6
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    • pp.1066-1072
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    • 2001
  • ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading, and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.

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A Uplink Performance Analysis of GAS-CP-CDMA Communication System (GAS-CP-CDMA 통신 시스템의 상향링크 성능분석)

  • Lee, Seong-Min;Kim, Whan-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.11A
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    • pp.1079-1086
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    • 2008
  • In this paper, we propose a Cyclic-Prefix Code Division Multiple Access system that uses Sequences with Good Autocorrelation property(GAS-CP-CDMA) and analyze the uplink signal-to-noise ratio performance of that system. Phase-shifted sequences are used for differentiating users. The signals of the GAS-CP-CDMA system experience no (or very little) interferences from co-cell signals because of the good autocorrelation property, but user signals of adjacent cells may yield interferences. The frequency reuse factor in the ordinary CDMA system is around 0.6 and the interference from adjacent cells is about 40 percent of the total interference in the conventional CDMA system. Our numerical analysis shows that the frequency reuse factor and user capacity versus signal-to-noise ratio of the GAS-CP-CDMA system are improved comparing to the conventional CDMA system. The uplink user capacity of the proposed system can be increased up to about twice of that of the conventional CDMA system.

Multiple-Symbol Differential Detection Scheme of Differentially Encoded MultiPhase Clipped MultiCode CDMA System (차동 부호화된 MultiPhase Clipped MultiCode CDMA 시스템의 수신 성능 개선을 위한 다중 심볼 차동 검출 방식 연구)

  • 이병하;안철용;김동구;조진웅
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.10A
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    • pp.807-815
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    • 2003
  • MultiCode-CDMA (MC-CDMA) system of chip level MPSK incorporating with clipper (MP-CDMA)[l] shows constant envelope signal which can mitigate the performance degradation due to nonlinear transmit amplifier. In this paper, modulation is modified to carry out differential encoded MPSK rather than MPSK. The modified system is called DMP-CDMA. DMP-CDMA using differential detection has advantages on receiver complexity and pilot overhead. However, it is inferior to coherent detection by about 4.0dB due to inherent power inefficiency of noncoherent detection and the error propagation. Multiple symbol differential detection is employed in order to improve DMP-CDMA using differential detection. As the result, the performance of DMP-CDMA system is improved about 3.6dB compared to differential detection.