• Title/Summary/Keyword: SNR Degradation

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Viterbi-based Decoding Algorithm for DBO-CSS

  • Yoon, Sang-Hun;Jung, Jun-Mo
    • Journal of information and communication convergence engineering
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    • v.9 no.6
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    • pp.657-660
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    • 2011
  • Differential detection algorithm for DBO-CSS based on maximum signal energy detection (MSED) using viterbi algorithm is proposed. In order to mitigate SNR degradation caused by differential decoding, a modified viterbi algorithm with so called correlation metric (CM) in every state is proposed. It is shown that the performance gain of the proposed algorithm when compared with that of the conventional differential detection with the block decoding algorithm is about 2.5dB at BER = $10^{-5}$.

A Study on Adaptive Interference Suppressor for Multicarrier DS-CDMA (멀티캐리어 DS-CDMA를 위한 적응 간섭 억제기에 관한 연구)

  • 우대호;장병건;변윤식
    • Proceedings of the IEEK Conference
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    • 2000.09a
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    • pp.25-28
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    • 2000
  • In this paper, we choice multicarrier direct-sequence code division multiple access using bandwidth effectively in communication system. Because this system is based on DS-CDMA the same problem is raised. That is, the degradation of the performance is due to multiple access interference. To solve this problem, we proposed the blind adaptive receiver for MC DS-CDMA system. Simulation results show that the proposed blind receiver has more about 0.5(dB) value of SNR than conventional receiver.

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Binary ASK way for 1Giga bit MODEM (1Giga bit MODEM을 위한 Binary ASK방식)

  • ;;;Sosuke Onodera;Yoichi Sato
    • Proceedings of the IEEK Conference
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    • 2003.07a
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    • pp.194-197
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    • 2003
  • We proposed Binary ASK system for 1Giga bit Modem. The Binary ASK system has a high speed shutter transmitter and no IF receiver only by symbol synchronization. The advantage of proposed system is that circuitry is very simple without IF process. The disadvantage of proposed system are that line spectrum occurs unordinary interference to other channels, and enhancement to 4-level system is impossible due to its large SNR degradation.

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AN ALGORITHM TO REDUCE THE PITCH SEARCHING TIME USING MODIFIED DELTA SEARCH IN CELP VOCODER (개선된 델타검색기법을 이용한 피치검색시간의 단축)

  • 이주헌
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1994.06c
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    • pp.214-217
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    • 1994
  • The major drawback in the Code Excited Linear Prediction type vocoders is their large computational requirements. In this paper, a simple method is proposed to reduce the pitch searching time in the pitch filter almost without degradation of quality. On the basis of the observational regularity of the correlation function of speech, only the limited numbers of pitch lags are considered to be an optimum pitch. This is done by skipping the negative envelope side of the correlation function and limiting the maximum number of lags to be considered preliminarily. By doing so, we can reduce the computational time of pitch searching more than 51% with negligible quality degradation. In addition to that, by combining that method with the conventional delta search technique, we can reduce the computational time requirements more than 60% without serious lowering the speech quality in segmental SNR measure compared to the conventional full search method.

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Partially Coherent MC-CDMA Downlink Performance in Rayleigh Fading Channels

  • Kim, Nam-Soo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.3
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    • pp.470-477
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    • 2001
  • Multucarrier code-division multiple access(MC-CDMA) is one of the promising technique for high capacity wireless communication. Hower the carrier phase error and frequency offest cause the performance degradation of MC-CDMA due to the inter-carrier interference. In this work, downlink performance of the partially coherent MC-CDMA is analytically derived in Rayleigh fading channels. The bit error rate sensitivity by combining method, Maxiaml ratio combining (MRC)and Equal gain combining(EGC), is compared as functions of phase errors. multi-user interference, and received signal-to-noise ratio. The results show that the susceptibility for the performance degradation of EGc and MRC is negligible for loop SNR's of above 15 dB and above 10 dB, respectivtely.

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Performance Degradation due to Phase Jitter in IEEE 802.16 Downlink Signals

  • Kim, Youngsun;Kim, Seung-Geun;Kim, Kiseon
    • Proceedings of the IEEK Conference
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    • 2002.07c
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    • pp.1681-1684
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    • 2002
  • A multilevel modulation with selectable constellations is adopted in the downlink subframe modulation of the IEEE 802.16 standard to increase the total throughput. One of the decision factors of the modulation is the location of SS(Subscriber Station) . Also, for the 802.16, low phase noise of local oscillator is needed due to high operating frequency and severe loss in the propagation channel. We investigate the BER of down-link subframe with the phase jitter under the standard's specified LOS(line of sight) and multipath environment with randomly generated SS locations. Simulation results show BER performance degradation for the modulation corresponding to selected constellations and additionally required SNR to achieve 10$\^$-3/ BER under various phase jitter.

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Implementation of Stopping Criterion Algorithm using Variance Values of LLR in Turbo Code (터보부호에서 LLR 분산값을 이용한 반복중단 알고리즘 구현)

  • Jeong Dae-Ho;Kim Hwan-Yong
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.9 s.351
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    • pp.149-157
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    • 2006
  • Turbo code, a kind of error correction coding technique, has been used in the field of digital mobile communication system. As the number of iterations increases, it can achieves remarkable BER performance over AWGN channel environment. However, if the number of iterations is increased in the several channel environments, any further iteration results in very little improvement, and requires much delay and computation in proportion to the number of iterations. To solve this problems, it is necessary to device an efficient criterion to stop the iteration process and prevent unnecessary delay and computation. In this paper, it proposes an efficient and simple criterion for stopping the iteration process in turbo decoding. By using variance values of LLR in turbo decoder, the proposed algerian can largely reduce the average number of iterations without BER performance degradation in all SNR regions. As a result of simulation, the average number of iterations in the upper SNR region is reduced by about $34.66%{\sim}41.33%$ compared to method using variance values of extrinsic information. the average number of iterations in the lower SNR region is reduced by about $13.93%{\sim}14.45%$ compared to CE algorithm and about $13.23%{\sim}14.26%$ compared to SDR algorithm.

A Comparison of an Improvement Performance of S/N ratio with the Method of Weighting in DMTI System using a Uniform Pulse Train (일정한 펄스 예을 사용한 DMTI 시스템에서 Weighting 방법에 따른 S/N 북 개선 특성에 관한 비교)

  • Go, Seong-Seon;Lee, Jae-Gyun;Yun, Hyeon-Bo
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.22 no.1
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    • pp.41-45
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    • 1985
  • A degradation of the signal-to-noise ratio (SNR) in a digital moving target indicator system (DMTI System) can be Improved by weighting of the DMTI output pulses before the integration process. and it Is shown that the signal-to-noise ratio Is unproved as the nunlber of delay line cancellers. It is Known that signal-to-noise ratio obtained with optimum weighting is greater than that obtained with binomial weighting. An improvement performance of the signal-to-noise ratio for each case is presented through the results or a computter simulation.

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Outage Performance of Cooperative Cognitive Wireless Relay Networks with Delayed CSI (CSI 지연이 있는 상황 인지 무선 협동 릴레이 네트워크의 오수신율)

  • Kim, Nam-Soo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.6
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    • pp.19-25
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    • 2009
  • The performance of a cognitive radio system with cooperative diversity which includes the direct and indirect path is analysed. The selection relay cooperation which selects the best relay, the relay with the best received signal-to-noise ratio(SNR) in destination node, is considered and derived the performance degradation caused by the CSI(Channel State Information) delay analytically. Numerical examples show that the cooperative diversity which have the direct and the indirect paths effectively improves the system performance in Rayleigh fading; the performance improves 4.4 dB with 1/10 of SNR of the indirect path. And the system performance is more degraded with the less frequency acquisition probability and with the high CSI delay.

Semi-Analytical BER Evaluation Based on Error-Events at Relay Nodes for Decoded-and-Forward Relay Systems (복호 후 전달 릴레이 시스템의 평균 오류율에 대한 릴레이 노드에서의 오류 사건 기반의 의사-분석 기법)

  • Ko, Kyun-Byoung;Seo, Jeong-Tae
    • Journal of IKEEE
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    • v.15 no.1
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    • pp.64-69
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    • 2011
  • In this paper, a semi-analytical approach is proposed for decode-and-forward(DF) relay systems over rayleigh fading channels. At first, we derive the general form of the averaged bit error rate(BER) based on error-events at relay nodes in which a selection scheme is not used. It is confirmed that an erroneous detection and transmission at relay nodes can cause the degradation of the received signal-to-noise ratio (SNR) and the averaged BER performance. Furthermore, the proposed method can be extended to selective-DF(SDF) relay schemes so that it is verified to be another general solution for DF relay systems. Also, proposed semi-analytical expressions have been verified by comparing with simulations.