• Title/Summary/Keyword: Multicode

Search Result 38, Processing Time 0.022 seconds

A Performance Comparison of Multicode and Multicarrier CDMA System (다중부호와 다중반송파 CDMA 방식의 성능 비교)

  • 김관옥;최승규
    • Journal of the Institute of Electronics Engineers of Korea TE
    • /
    • v.37 no.2
    • /
    • pp.75-82
    • /
    • 2000
  • In this paper, described is the comparison of performances based on the computer simulation under IMT-2000 environment between multicode and multicarrier CDMA system for the design of wireless systems using wideband CDMA technology. From simulation results, it can be concluded that both multicode and multicarrier CDMA scheme show comparable performances. Diversity scheme of RAKE receiver is indispensible for both multicode and multicarrier CDMA systems under IMT-2000 outdoor B and vehicular B channel environment. Either Hadamard matrix or PN sequence can be used as the orthogonal code as far as the orthogonality is kept. Finally, with increasing chip rate and less users, performance is getting better.

  • PDF

Performance Analysis of Multicode DS/CDMA-BPSK Signal in Nakagami Fading Channel (Nakagami 페이딩 채널에서 멀티코드 DS/CDMA-BPSK 신호의 성능 분석)

  • 조성언
    • Journal of the Korea Institute of Information and Communication Engineering
    • /
    • v.4 no.1
    • /
    • pp.201-209
    • /
    • 2000
  • In this paper, the bit error rate (BER) performance of Multicode DS/CDMA-BPSK communication system is investigated in the presence of multi user interference and Nakagami fading channel environments. The DS/CDMA-BPSK communication system adopts multicode technique to enhance the data transmission rate. Using the calculated BER performance, BER figures of Multicode DS/CDMA-BPSK communication system are shown to discuss the effect of the number of multi user interference, Nakagami fading index, and data transmission rate. From the results, the transmission rate of DS/CDMA-BPSK signal improve by adopting Multicode technique. And we know that the major parameter of BER performance degradation in Multicode DS/CDMA system is the effect of multi user interference than the fading depth.

  • PDF

Constant-Amplitude Multicode-Biorthogonal Modulation using Product Code (격자부호를 이용한 정진폭 다중부호 이진직교 변조방식)

  • Hong, Dae-Ki
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.8 no.3
    • /
    • pp.522-527
    • /
    • 2007
  • In this paper, we propose an error control coding scheme for constant-amplitude multicode-biorthogonal modulation. The product code is appropriate to the constant-amplitude multicode-biorthogonal modulation for the bit error rate performance improvement. In the constant-amplitude multicode-biorthogonal modulation, the vertical redundant bits are used for the constant amplitude coding. The proposed product code can be constructed by using the additional horizontal redundant bits. The hardware complexity of the encoder/decoder pair is very low. The simulation results show that the bit error rate performance of the proposed coding scheme is improve

  • PDF

Performance of a Multicode DS/CDMA Packet Radio Network with Adaptive Antenna Array

  • Kim, Jin-Young;Lee, Sang-Yun
    • Proceedings of the IEEK Conference
    • /
    • 2000.07a
    • /
    • pp.109-112
    • /
    • 2000
  • In this paper, performance of multicode DS/CDMA packet radio network with adaptive antenna array is analyzed and simulated in a multipath Rayleigh fading channel. The network performance is evaluated in terms of packet throughput. From the simulation results, it is confirmed that the adaptive antenna array is very effective in improving the packet throughput performance of the multicode DS/CDMA packet radio network. The results of this paper can be applied to design of IMT-2000 or future-generation mobile communication systems.

  • PDF

Online SNR Estimation for Turbo Coded Multicode DS/SS Systems

  • Takizawa, Ken-ichi;Shigenobu Sasaki;Jie Zhou;Shogo Muramatsu;Hisakazu Kikuchi
    • Proceedings of the IEEK Conference
    • /
    • 2002.07b
    • /
    • pp.1316-1319
    • /
    • 2002
  • In this paper, an online SNR estimator is derived for turbo coded multicode DS/SS systems in Nakagami fading channels. The multicode DS/SS approach is one of promising solutions to obtain higher-rate data transmission in DS/SS technologies. Turbo coding has paid much attention because of the significant improvements on error rate performances in various communication systems including multicode DS/SS systems. However, in the turbo decoding, channel state information, especially signal-to-noise ratio (SNR) at the correlator outputs, is desired in order to obtain such improvements. We evaluate the accuracy of the derived SNR estimation. It is shown that the bit error rate performance using our SNR estimation is close to the performance with perfect knowledge of channel state information.

  • PDF

Frequency Domain Turbo Equalization for Multicode DS-CDMA in Frequency Selective Fading Channel (다중 확산 부호를 사용한 DS-CDMA에 대한 주파수 선택적 페이딩 채널에서 주파수 영역 터보 등화 기법)

  • Lee, Jun-Kyoung;Lee, Taek-Ju;Chae, Hyuk-Jin;Kim, Dong-Ku
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.33 no.1C
    • /
    • pp.102-109
    • /
    • 2008
  • The higher data rate of mobile communications has been required for various multimedia services. In DS-CDMA system, one of the solutions to increase the throughput is to use multicode. However, multipath channel destorys the orthogonality of spreading codes, which causes the intercede interference(ICI). ICI gives severe effect on multicode DS-CDMA for BER performance. Conventionally, multicode DS-CDMA system uses the Rake receiver with turbo code, which cannot overcome error floor caused by ICI. In this paper, we propose frequency domain turbo equalization based on minimum mean squared error(FDTE-MMSE) for multicode DS-CDMA in frequency selective channel and evaluate its BER performance by computer simulation. The simulation results show that FDTE-MMSE gives much better performance in high Eb/N0 than the Rake receiver with turbo code in multipath length L>1.

An Improvement on Multicode CDMA Systems Using a Convolutional Code and a Bi-Orthogonal Code (길쌈 부호와 이원 직교 부호에 의한 다중부호 부호분할 다원접속 시스템의 개선)

  • 김기범;신요안
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.23 no.7
    • /
    • pp.1659-1666
    • /
    • 1998
  • The multicode CDMA systems that are widely studied as an effective transmission methodology in the IMT-2000 systems, employ orthogonal codes to transform high rate data into parallel, low rate data for simultaneous transmission. In this paper, we propose a new multicode CDMA system which achieves the same data rate and processing gain of the conventional systems, while significantly improves bit error rate performance by exploiting a convolutional code with code rate r=1/2 and a bi-orthogonal code. The simulation results for synchronous systems using maximal ratio combining Rake receivers under additive white Gaussian noise and multi-path fading channels, show significant improviements by the proposed system.

  • PDF

Performance Analysis and Comparison of Different Data Rates in Wideband CDMA Using Three Different Transmission Schemes

  • Pahadee, Sangita;Ahmed, Kazi M.;Rajatheva, R.M.A.P.;Sigdel, S.
    • Proceedings of the IEEK Conference
    • /
    • 2002.07a
    • /
    • pp.552-555
    • /
    • 2002
  • Wideband CDMA is one of the radio access technologies for the third generation in which voice is the basic service. There has been lot of research work in order to find out the suitable transmission scheme to meet the requirement of accommodating variable type of services in Wideband-CDMA. This paper studies the behavior of different services using different transmission schemes in Wideband CDU and compares their performance in terms of BER. Different transmission schemes are found to be suitable for different services. Transmission schemes used are- fixed processing gain scheme also called as variable bandwidth scheme, single code transmission and multicode transmission. It is found that fixed processing gain scheme is suitable fur high data rates. Single code transmission is suitable fer low data rates where as multicode transmission is suitable for low and medium data rates.

  • PDF

On the Code Selection of a Multicode DS/CDMA System for a High Data Rate Transmission

  • Kim, Jin-Young
    • Proceedings of the IEEK Conference
    • /
    • 2000.11a
    • /
    • pp.457-460
    • /
    • 2000
  • The effect of code selection for a multicode DS/CDMA system is evaluated for a high deta rate transmission, The performance is evaluated in terms of bit error and outage probabilities. The multipath fading channel is modeled as a Nakagami-m distribution which has been known to be appropriate to model the multipath fading in urban as well as indoor channels. From simulation results, it is shown that the concatenated sequence of Walsh code and Gold sequence is most promising among many code selections. The considerations in this paper can be applied to the next-generation mobile communication systems such as IMT-2000 which requires high bit rate transmissions.

  • PDF

A New Multicarrier Multicode DS-CDMA Scheme for Time and Frequency Selective Fading Channels

  • Cao Yewen;Tjhung Tjeng Thiang;Ko Chi Chung
    • Journal of Communications and Networks
    • /
    • v.7 no.1
    • /
    • pp.13-20
    • /
    • 2005
  • In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.