• Title/Summary/Keyword: symbol

Search Result 2,854, Processing Time 0.039 seconds

Blind Equalization Selectively Using Coarse Symbol Constellation and Dense Symbol Constellation (저밀도 심볼점과 고밀도 심볼점을 선택적으로 이용하는 블라인드 등화)

  • Oh, Kil Nam
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.39A no.11
    • /
    • pp.645-651
    • /
    • 2014
  • For blind equalization, we propose a method of updating an equalizer, which generates an error from selectively applying a transmitted symbol constellation and that of induced equivalently from the transmitted symbol constellation and updates the equalizer by using this error. The proposed method, by selectively using the symbol constellation effective for improvement of symbol estimation accuracy and that of effective for improvement of error performance, showed that it is possible to improve the error performance at the same time to open the eye diagram of equalizer output quickly. As a criterion applying the symbol constellation, we used the dispersion of symbol points of equalizer output. In addition, to increase the accuracy of updating an equalizer the error was controlled by using current and previous dispersions. By simulation, under multipath channel with additive noise, we verified the equalization performance of the proposed method for 64-QAM.

격자코드 변조 시스템에서 DFE의 심볼판정 알고리즘 제안 (Symbol Detection Methods for DFEs in Trellis Coded Modulation Systems)

  • Chung, Won-Zoo
    • Journal of IKEEE
    • /
    • v.10 no.1 s.18
    • /
    • pp.69-74
    • /
    • 2006
  • In this paper, we present symbol detection methods for decision feedback equalizers (DFE) in trellis coded modulation systems. The proposed symbol detectors improve symbol error rate (SER) by exploiting the coding structure of trellis coded modulation (TCM). For example, for 8-PAM signals the achieved SER with the proposed detection scheme is improved to $2{\times}10^{-5}$ from $2.5{\times}10^{-2}$ of the conventional symbol-by-symbol detector under AWGN channel at 20dB SNR. This SER improvements mitigate error propagation of DFE.and produces significant over-all SER improvement for under multipath channels (for example, from 0.26 to 0.01 and 0.005 under a severe multipath channel 20dB SNR as shown in the simulation result of this paper).

  • PDF

Closed-form Expression for the Symbol Error Probability of Orthogonal Space-Time Block Codes with Quadrature Amplitude Modulation (QAM 변조방식을 갖는 직교 시공간 블록 부호의 심볼 오율)

  • 김상효;강익선;노종선
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.28 no.6C
    • /
    • pp.561-569
    • /
    • 2003
  • In this paper, for my linear orthogonal space-time block including the orthogonal space-time codes introduced by Alamouti[1], Tarokh[14], and Xia[11], the exact expression for the pairwise error probability in the slow Rayleigh fading channel is derived in terms of the message symbol distance between two message vectors rather than the codeword symbol distance between two transmitted codeword matrices. Using the one-dimensional component symbol error probability, the exact closed form expressions for the symbol error probability of linear orthogonal space-time codes are derived for QPSK, 16-QAM, 64-QAM, and 256-QAM.

An Efficient symbol Synchronization Scheme with an Interpolator for Receiving in OFDM (OFDM 방식의 수신기를 위한 보간기의 효율적인 심볼 동기방법의 성능분석)

  • 김동옥;윤종호
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2002.05a
    • /
    • pp.574-577
    • /
    • 2002
  • In this paper, we propose a new symbol time synchronization scheme suitable for the OFDM system with an interpolator. The proposed performs the following three steps. In the first step, the coarse symbol time synchronization is achieved by continuously measuring the average power of the received envelope signal. Based on this average power, the detection possibility for the symbol time synchronization is determined. If the signal is sufficient for synchronization, we next perform a relatively accurate symbol time synchronization by measuring the correlation a short training signal and the received envelope signal. Finally, an additional frequency synchronization is performed with a long training signal to correct symbol synchronization errors caused by the phase rotation. From the simulation results, one can see that the proposed synchronization scheme provides a good synchronization performance over frequency selective channels.

  • PDF

Timing Recovery Algorithm with Slop Compensated for Multi-level PAM Signals (Multi-level PAM신호에 적용 가능한 기울기 보상 심볼타이밍 알고리즘)

  • 전광호;임명섭
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.26 no.11A
    • /
    • pp.1864-1871
    • /
    • 2001
  • In this paper, new symbol timing recovery algorithm is proposed, which is suitable for the digital communication system with Multi-level PAM signals. In the newly proposed symbol timing recovery algorithm, the timing error function is derived by compensating the several difference values between sampled symbol and neighboring symbol every symbol period with mid samples and decided symbol values. Conventional symbol timing recovery methods did not work well in Multi-level PAM signals, but the newly proposed method can be applied to Multi-level PAM signals as well as QPSK. For the performance analysis, the derived variance of the timing error function and the timing error characteristics of S-curve show that the proposed method has better performance than Gardner method and the modified Gardner method.

  • PDF

Pilot Symbol Assisted High Speed Packet Transmission System based on Adaptive OFDM in Broadband Mobile Channel

  • Ahn, Chang-Jun;Sasase, Iwao
    • Journal of Communications and Networks
    • /
    • v.5 no.1
    • /
    • pp.25-32
    • /
    • 2003
  • 4G mobile communication system requires the throughput of 10-100Mbps. Adaptive modulated OFDM system is promising technique for increasing the throughput. In the pilot symbol assisted high-speed packet transmission system, the data symbol duration is generally considered to be small compared to the coherence time. However, OFDM symbol duration is longer than the symbol duration of a single carrier system, so that the packet duration of the pilot symbol assisted high speed packet transmission system is long. In this case, the change of channel conditions is too fast to be accurately estimated by channel estimator at the receiver in high Doppler frequency, so that many errors occur during demodulation, especially with the data symbols at the end of each packet. In this paper, we consider the BER at various instantaneous $E_b/N_o$ that includes the demodulation errors in high Doppler frequency. When the coherence time is ten times longer than the duration of a single packet, the channel can be closely approximated as an AWGN channel. Otherwise, the approximation breaks down and the above-mentioned errors that occur during demodulation must be taken into consideration. In this paper, we propose the pilot symbol assisted high speed packet transmission system based on adaptive OFDM using a novel lookup table to consider the demodulated errors and evaluate the throughput performance.

A Study on the Meaning Function of Symbol Design based on The Comic Dual Forces and The Five Elements (음양오행(陰陽五行) 사상에 의한 심볼디자인의 의미적용 가능성 연구)

  • 장은석;김재희
    • Archives of design research
    • /
    • v.12 no.2
    • /
    • pp.53-62
    • /
    • 1999
  • The modern is image age, and The visually expressed symbols have much influence on individuals or enterprises and have an effect on the variety of individual and the innovation of management. Espacially, the symbols carry on the axis composing total image. According to the reason of positive & negative five elements, this paper analysised and studied the meaning of symbol design which analysis the thoughtful, abstract and formal meaning. This is the most fundmental elements and principals and means the good symbol composed harmoniously the positive & negative five elements give good image. Namely, the symbols of the Eum & Yan which applied the philosophical reason of the Orient thought became good image. The lively elements of design composed the reason of Eum & Yang have effect on auspicious and upgrade one step to the dimension of symbol design. The purpose of this paper analysises and understands the meaning of symbol was composed the positive & negative five elements. In the point of view of modern design. the overlOOking elements of the symbol(line, form, space etc) reminded and established the new model which the new idea approached by the thought of the positive & negative five elements.

  • PDF

Turbo Trellis Coded Modulation with Multiple Symbol Detection (다중심벌 검파를 사용한 터보 트렐리스 부호화 변조)

  • Kim Chong Il
    • Journal of the Institute of Convergence Signal Processing
    • /
    • v.1 no.2
    • /
    • pp.105-114
    • /
    • 2000
  • In this paper, we propose a bandwidth-efficient channel coding scheme using the turbo trellis-coded modulation with multiple symbol detection. The turbo code can achieve good bit error rates (BER) at low SNR. That comprises two binary component codes and an interleaver. TCM codes combine modulation and coding by optimizing the euclidean distance between codewords. This can be decoded with the Viterbi or the symbol-by- symbol MAP algorithm. But we present the MAP algorithm with branch metrics of the Euclidean distance of the first phase difference as well as the Lth phase difference. The study shows that the turbo trellis-coded modulation with multiple symbol detection can improve the BER performance at the same SNR.

  • PDF

Window based Symbol Timing Recovery (윈도우 기반 심벌 타이밍 복원)

  • Lee, Chul-Soo;Jang, Seung-Hyun;Jung, Eui-Suk;Kim, Byoung-Whi
    • Proceedings of the KIEE Conference
    • /
    • 2005.10b
    • /
    • pp.487-489
    • /
    • 2005
  • This paper proposes a symbol timing recovery method that is simple in structure and can provide high speed symbol synchronization. Transmitter and receiver are not synchronized in communication systems using digital modulation. Receiver should search the timing variation of transmitter continuously. The proposed timing recovery method searches sample position by comparing previous sample value with next sample value. This method can be applied to digital and optical transceivers with high data rate.

  • PDF

Design of Low-Complexity MIMO-OFDM Symbol Detector for High Speed WLAN Systems (고속 무선 LAN 시스템을 위한 저복잡도 MIMO-OFDM 심볼 검출기 설계)

  • Im, Jun-Ha;Kim, Jae-Seok
    • Proceedings of the IEEK Conference
    • /
    • 2008.06a
    • /
    • pp.447-448
    • /
    • 2008
  • This paper presents a low-complexity design and implementation results of a multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) symbol detector for high speed wireless LAN (WLAN) systems. The proposed spatial division multiplexing (SDM) symbol detector is designed by HDL and synthesized to gate-level circuits using 0.18um CMOS library. The total gate count for the symbol detector is 238K.

  • PDF