• Title/Summary/Keyword: Symbol Recovery

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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
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    • 2005.10b
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    • pp.487-489
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    • 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.

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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
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    • v.26 no.11A
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    • pp.1864-1871
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    • 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.

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Design of burst receiver with symbol timing and carrier synchronization (심벌동기와 반송파동기를 가진 버스트 수신기의 설계)

  • 남옥우
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2001.11a
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    • pp.44-48
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    • 2001
  • In this paper we describe the design of symbol timing and carrier synchronization algorithms for burst receiver. The demodulator consists of digital down converter, matched filter and synchronization circuits. For symbol timing recovery we use modified Gardner algorithm. And we use decision directed method for carrier phase recovery. For the sake of performance analysis, we compare simulation results with the board implemented by FPGA which is APEX20KE series chip for Alter. The performance results show it works quite well up to the condition that a frequency offset equal to 0.1% of symbol rate.

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A Timing Recovery Scheme for Variable Symbol Rate Digital M-ary QASK Receiver (가변 심볼율 MQASK(M-ary Quadrature Amplitude Keying) 디지털 수신기를 위한 타이밍 복원 방안)

  • Baek, Daesung;Lim, Wongyu;Kim, Chong-Hoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.7
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    • pp.545-551
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    • 2013
  • Timing recovery loop composed of the Timing Error Detector(TED), loop filter and resampler is widely used for the timing synchronization in MQASK receivers. Since TED is sensitive to the delay between the symbol period of the signal and sampling period, the output is averaged out when the symbol rate and sampling rate are quite different the recovery loop cannot work at all. This paper presents a sampling frequency discriminator (SRD), which detects the frequency offset of the sampling clock to the symbol clock of the MQASK data transmitted. Employing the SRD, the closed loop timing recovery scheme performs the frequency-aided timing acquisition and achieve the synchronization at extremely high sampling frequency offset, which can be used in variable symbol rate MQASK receivers.

A Rotational Decision-Directed Joint Algorithm of Blind Equalization Coupled with Carrier Recovery for 32-QAM Demodulation (회전결정 경계를 이용한 32-QAM 목조용 반송파 복구와 채널등화의 Joint 알고리즘)

  • Song, Jin-Ho;Hwang, Hu-Mor
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.51 no.2
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    • pp.78-85
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    • 2002
  • We introduce a rotational decision-directed joint algorithm of blind equalization coupled with carrier recovery for 32-QAM demodulation with high symbol rate. The proposed carrier recovery, which we call a rotational decision-directed carrier recovery(RDDCR), removes the residual phase difference by rotating the decision boundary for the kth received symbol by the frequency detector output of the (k-1)th received symbol. Since the RDDCR includes the function of PLL loop filter by rotating the decision boundary, it gives a simpler demodulator structure. The rotational decision-directed blind equalization(RDDBE) with the rotated decision boundary based on the Stop-and-Go Algorithm(SGA) operated during tracking the frequency offset by the RDDCR and removes intersymbol interference due to multipaths and channel noise. Test results show that symbol error rate of $10^{-3}$ is obtained before the forward error correction when SNR equals 15dB with 150KHz of carrier frequency offset and two multipaths, which is the channel condition for 32-QAM receiver.

Burst Mode Symbol Timing Recovery for VDL Mode-2 (VDL Mode-2에 적용 가능한 버스트 모드 심벌 타이밍 복원기)

  • Gim, Jong-Man;Choi, Seung-Duk;Eun, Chang-Soo
    • Journal of Advanced Navigation Technology
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    • v.13 no.3
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    • pp.337-343
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    • 2009
  • In this paper, we proposed a burst mode symbol timing recovery unit that is applicable to the VDL Mode-2 using D8PSK modulation. A method that IIR loop filter is used to minimize symbol timing error is hard to apply to burst mode because its convergence time is long. That is, the fast convergence property is important. In this paper, the proposed method takes one sample which has maximum symbol power after the initial synchronization has been achieved by using preambles. The main principle of operation is that the unit moves one sample clock to advance or retard according to symbol power. We verify that the proposed method is operated well in ${\pm}100$ ppm or greater through the test results between Australia ADS Corp. transmitter and the designed receiver.

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Design of a Symbol Timing Recovery of QAM Using the Interpolation in AWGN channel (AWGN 채널에서 보간기를 이용한 QAM 방식에 대한 심볼동기회로 설계)

  • 박범대;오동진;김철성
    • Proceedings of the IEEK Conference
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    • 1999.06a
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    • pp.77-80
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    • 1999
  • This paper deals with a design of a symbol timing recovery circuit of QAM using the interpolation in AWGN channel. To reduce timing jitter and the amount of processing data, we employ MGA (Modified Gardner Algorithm) as a symbol timing error detector which is called NDA(Nondecision Directed Algorithm). We show the characteristics (S-curve and the variance) of timing error detector with the roll-off factor of a shaping filter, which are compared with GA. Also, we compare the BER curve of interpolation method with that of ideal case. The performance of the STR is shown to be close to that of ideal case. This result shows that this method can be useful to implement symbol timing recovery circuit for multi-level modulation.

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Performance Analysis of Symbol Timing Recovery for 16QAM System in Rayleigh Fading (레일리 페이딩 환경에서 16QAM 시스템에서 심볼 타이밍 복원의 성능분석)

  • 문재경;김영수;김창주
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.7 no.3
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    • pp.201-210
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    • 1996
  • In this paper, we analyzed performance of a symbol timing recovery scheme for 16QAM Radio system. As a symbol timing recovery scheme, both maximum amplitude method(MAM) and wave difference method(WDM) are analyzed employing a pulse shaping filter, such as raised cosine filter(RCF) and nonlinear filter(NLF). Simulation result shows that the jitter performance of MAM or WDM using NLF is better than that using square root RCF. In order to estimate and compensate for the Rayleigh fading PSAM(Pilot Symbol Assisted Modulation) and space diversity are also employed. Consequently, BER performance of about $10^{-4}$ is obtained for $E_b/N_o$= 20 dB.

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A Recovery Method of External Symbol Information in Statically-Linked ELF Files (정적 링크된 ELF 파일에서의 외부 심볼 정보 복구 기법)

  • Kim, Jung-In
    • Journal of Korea Multimedia Society
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    • v.13 no.2
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    • pp.161-170
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    • 2010
  • ELF, an abbreviation for Executable and Linkable Format, is the basic file format for shared libraries and executable files used in the Linux system, whereas 'Linker' copies the symbol information of static shared libraries into the symbol table in the target file generated by way of static linking. At this time, the symbol table keeps various pieces of debugging-related information including function names provided by the shared libraries, and it can be deleted to avoid debugging for security reasons by utilizing the fact that it does not directly affect the program execution. This paper proposes a method for restoring the symbol information of static shared libraries from the ELF object file in which the symbol table is deleted, and confirms that the symbol information is restored by conducting practical experiments.

Design of a High Speed QPSK/16-QAM Receiver Chip (고속 QPSK/16-QAM 수신기 칩 설계)

  • Park, Ki-Hyuk;Sunwoo, Myung-Hoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.4B
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    • pp.237-244
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    • 2003
  • This paper presents the design of a QPSK/16-QAM downstreams receiver chip. The proposed chip consists of a blind equalizer, a timing recovery block and a carrier recovery block. The blind equalizer uses a DFE sturucture using CMA(Constant Module Algorithm). The symbol timing recovery uses the modified parabolic interpolator. The decision-directed carrier recovery is used to remove the carrier frequency offset, phase offset and phase jitter. The implemented LMDS receiver can support four data rates, 10, 20, 30 and 40 Mbps and can accommodate the symbol rate up to 10 Mbaud. This symbol rate is faster than existing QAM receivers.