• Title/Summary/Keyword: Frequency-Selective Rayleigh fading

Search Result 66, Processing Time 0.024 seconds

Comparative Performance of Differential Space-Time Block Codes Over Time-Selective Fading Channels (시변 페이딩 채널에서 검파방식에 따른 차분 공간-시간 블록 부호의 성능 비교)

  • Kang, Sung-Ho;Kim, Young-Ju;Lee, In-Sung
    • The Journal of the Acoustical Society of Korea
    • /
    • v.25 no.8
    • /
    • pp.356-361
    • /
    • 2006
  • We present the performance of differential space-time block decoders. which does not require the channel state information. We suggest the structure of the multiple blocks differential space time decoders. which does not require the channel state information, and analyze the Performances. In quasi-static flat fading channels. the Performance of multiple blocks differential detection (MD-STC) outperforms that of 2 blocks(D-STC) by 1.5dB. But in the time-selective fading channels due to Doppler frequency $(f_d)$, the performance of MD-STC degrades as the vehicular speed is greater than 200km/hr in 802.16e systems, where the data transmission rate is 144kbps.

Mixture Filtering Approaches to Blind Equalization Based on Estimation of Time-Varying and Multi-Path Channels

  • Lim, Jaechan
    • Journal of Communications and Networks
    • /
    • v.18 no.1
    • /
    • pp.8-18
    • /
    • 2016
  • In this paper, we propose a number of blind equalization approaches for time-varying andmulti-path channels. The approaches employ cost reference particle filter (CRPF) as the symbol estimator, and additionally employ either least mean squares algorithm, recursive least squares algorithm, or $H{\infty}$ filter (HF) as a channel estimator such that they are jointly employed for the strategy of "Rao-Blackwellization," or equally called "mixture filtering." The novel feature of the proposed approaches is that the blind equalization is performed based on direct channel estimation with unknown noise statistics of the received signals and channel state system while the channel is not directly estimated in the conventional method, and the noise information if known in similar Kalman mixture filtering approach. Simulation results show that the proposed approaches estimate the transmitted symbols and time-varying channel very effectively, and outperform the previously proposed approach which requires the noise information in its application.

Performance Analysis of Maximum-Likelihood Code Acquisition Technique for Preamble Search in CDMA Reverse Link (CDMA 역방향 링크에서의 프리앰블 탐색을 위한 최대우도 동기획득 방식의 성능 분석)

  • 박형래;강법주
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.21 no.1
    • /
    • pp.161-174
    • /
    • 1996
  • Addressed in this paper is performance analysis of the maximum-likelihood code acquisition technique for slotted-mode preamble search in the CDMA reverse link. The probabilities of detection, miss, and false alarm are derived analytically for a multiple $H_{1}$ cell case in a frequency-selective Rayleigh fading channel, based on the statics of the CDMA noncoherent demodulator output. the probability density function of the decision variable consisting of successive demodulator outputs is also derived by considering the fading characteristics of the received signal for both single and dual antenna cases. The performance of the code acquisition technique is evaluated numerically with an emphasis on investigating the effects of post-detection integration, fading rate, and antenna diversity on the detection performance.

  • PDF

Performance of SFBC OFDM Transmission Systems Using PSAM Technique (PSAM 방식의 SFBC OFDM 전송 시스템의 성능)

  • Choi, Seung-Kuk
    • Journal of the Korea Institute of Information and Communication Engineering
    • /
    • v.15 no.5
    • /
    • pp.1031-1037
    • /
    • 2011
  • Pilot symbol assisted modulation (PSAM) can be used for the channel estimation in orthogonal frequency division multiplexing (OFDM) transmission systems. However, imperfect channel estimates in PSAM systems degrade the bit error rate (BER) performance. I derive the BER of PSAM OFDM systems over time dispersive fading channels. The BER performance of OFDM systems with SFBC antenna diversity are analyzed, where data is transmitted over time and frequency selective Rayleigh fading channel. The performance of this PSAM SFBC OFDM systems, gauged by the average bit error rate, is analyzed considering the channel estimation error.

Application of Turbo Code for Digital Audio Broadcasting (DAB) System (디지털 오디오 방송을 위한 터보부호의 응용)

  • 김한종
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.13 no.2
    • /
    • pp.176-187
    • /
    • 2002
  • The digital Audio Broadcasting (DAB) system adopts Coded OFDM(COFDM) for channel coding. The COFDM is a combined technique of multicarrier transmission(OFDM) and punctured convolutional coding with viterbi error correction. Because the channel coding is an important topic for OFDM systems, this paper proposes a new turbo coded OFDM system that replaces the existing RCPC codec by a turbo codec without modifying the puncturing procedure and puncturing vectors defined in the standard DAB system for compatibility. The performance of a new system is compared to that of the conventional system under the frequency selective Rician fading channel and the frequency selective Rayleigh fading channel in conjunction with DAB transmission mode I suitable for the terrestrial single frequency network(SFN) broadcasting. The standard system's performance was improved with the aid of turbo codec.

Capacity of synchronous DS-CDMA system on frequency selective multipath fading channels with imperfect power control (주파수 선택적 다중 경로 페이딩 채널에서 불완전 전력 제어를 고려한 동기식 DS-CDMA 시스템의 수용 용량)

  • 황승훈;김용석;김동희;황금찬
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.25 no.3A
    • /
    • pp.342-350
    • /
    • 2000
  • In this paper, the bit error performance for the reverse link of a synchronous direct sequence code division multiple access (DS-CDMA) system employing an imperfect power control scheme over a frequency selective Rayleigh fading channel is analyzed. The system capacity degradation due to power control error (PCE), which is approximated by a log-normally distributed random variable, is estimate as a function of a standard deviation of the PCE. In addition, the impact of the multipath intensity profile (MIP) shape and the number of resolvable paths on the performance of the synchronous transmission is investigated. To estimate the system capacity, the coded bit error performance is evaluated and compared with the conventional CDMA. It is found tat synchronous transmission has less sensitivity to imperfect power control and eases the power control requirements. In particular, as the decay constant $\delta$ of MIP increases, the synchronous transmission in the DS-CDMA reverse link results in a significant BER improvement over the asynchronous transmission even in the presence of imperfect power control. We further conclude that the capacity can be improved by employing the synchronous transmission.

  • PDF

On the error rate of multicode-CDMA system in frequency selective fading channel (주파수 선택적 페이딩 채널에서 멀티코드 CDMA 시스템의 성능 분석)

  • 김연진;김남수;김민택
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.23 no.4
    • /
    • pp.932-939
    • /
    • 1998
  • In this paper, we analyze the performance of a multicode-CDMA system which have been proposed for the multimedia communications. The performance of a multicode-CDMA system, providing good spectrum efficiency as well as serving various bit rates, is analyzed with multipath, frequency selective, slowly fading Rayleigh channel. Also the proposed scheme adopting RAKE receiver with MRC(Maximal Ratio Combine) is advantageous to multipath channel. For a practical channel modeling, the JTC(Joint Technical Committee) recommended channel model(JTC(AIR) 23-065R6) is applied to simulation. The proposed schemehas serial-to-parallel convertor which splits input data stream of 2 Mits/s into 20 branches o 100 kbits/s. From the result of simulation, the case of RAKE receiver with 3 fingers to reduce the system complexity required the relatively large $E_{b}/N_O$ of 0 dB~1.5 dB, compared to the case of RAKE receiver with the number of path finger to keep the average error rate to be $1{\times}10^{-3}$ in channel A.

  • PDF

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
    • /
    • v.7 no.4
    • /
    • pp.667-672
    • /
    • 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.

Performance improvement of the DS-CDMA/DPSK cellular mobile communication system with CCI canceller and RAKE receiver (DS-CDMA/DPSK 셀룰라 이동통신 시스템에서 간섭 제거기와 RAKE 수신기에 의한 성능 개선)

  • 이경준;오창헌;조성준;채수환
    • Journal of the Korean Institute of Telematics and Electronics A
    • /
    • v.33A no.4
    • /
    • pp.37-46
    • /
    • 1996
  • In this paper, we analyzed the performance improvement of the DS-CDMA/dPSK cellular mobile communication system with CCI canceller and RAKE receiver techniques in mobile radio channel which is characterized by AWGN, Multi-user interference (mUI) and frequency-selective rayleigh fading. System capacity i.e., number of user per cell has been derived and the evaluated results are shown in figuraes as a function of PN code sequence length, number of RAKE receiver tap, BER and E$_{b}$/N$_{o}$. The voice activity factor is assumed to be 3/8 the number of sectors in a cell 3 and MUI is modeled as gaussian process. From the results, the capacity of the DS-CDMA/DPSK cellular mobile communication system is improved by adopting CCI canceller. When we adopt the RAKE receiver to mitigate the multipath fading, the error performance is improved and the amount of improvement is proportional ot the number of taps L in the case that each tap contains a signal component and the better of improvement can be obtained, the smaller of the SNR difference in each tap. The system capacity is more increased when the CCI canceller and the RAKE receiver is used in cascade.

  • PDF

Reduced-state sequence estimation for TC 8PSK/OFDM with 2-stage IDFT/DFTs (두단계 IDFT/DFT를 갖는 TC 8PSK/OFDM를 위한 RSSE 방식)

  • Kang Hoon-Chul;Ko Sang-Bo;Jwa Jeong-Woo
    • Proceedings of the IEEK Conference
    • /
    • 2004.06a
    • /
    • pp.147-150
    • /
    • 2004
  • In this paper, we propose a reduced-state sequence estimation (RSSE) for trellis coded modulation (TCM) in OFDM with two-stage IDFT/ DFTs, MMSE-LE, and interleaving on frequency selective Rayleigh fading channels. The Viterbi algorithm (VA) is used to search for the best path through the reduced-state trellis combined with equalization and TCM decoding. Computer simulations confirm the bit error probability of the proposed scheme.

  • PDF