• Title/Summary/Keyword: Carrier-Frequency Synchronization

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Hybrid Synchronization Scheme for Multi-Carrier Communication Systems

  • Kim, Eung-Sun;Park, Sang-Kyu
    • Journal of electromagnetic engineering and science
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    • v.12 no.3
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    • pp.223-225
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    • 2012
  • In this paper, we develop a symbol/frame time and carrier frequency synchronization scheme for multi-carrier signaling in wireless mobile channels. The proposed scheme achieves simultaneous time synchronization and carrier frequency offset estimation. Simulation results show that the frequency offset of multiple sub-carrier spacings can be estimated and that performance is improved with robustness regardless of the cyclic prefix length.

A synchronization algorithm for OFDM signals (OFDM 신호의 동기 알고리듬)

  • 허영식;김기호김용훈
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.187-190
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    • 1998
  • In this paper, a synchronization method of OFDM signals are introduced and its performance is estimated. A proposed method can perform a frame/symbol timing, carrier frequency synchronizations. Reference symbols consist of two duplicate OFDM symbols carrying signals on every sub-carriers. Performances of synchronization under 60GHz millimeter-wave indoor channels are evaluated, which were measured with frequency-sweeping method in common office buildings. A proposed method has improved performances owing to long averaging durations of synchronization metrics in frame/symbol timing, carrier frequency synchronization procedures.

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An Improved Joint Detection of Frame, Integer Frequency Offset, and Spectral Inversion for Digital Radio Mondiale Plus

  • Kim, Seong-Jun;Park, Kyung-Won;Lee, Kyung-Taek;Choi, Hyung-Jin
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.2
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    • pp.601-617
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    • 2014
  • In digital radio broadcasting systems, long delays are incurred in service start time when tuning to a particular frequency because several synchronization steps, such as symbol timing synchronization, frame synchronization, and carrier frequency offset and sampling frequency offset compensation are necessary. Therefore, the operation of the synchronization blocks causes delays ranging from several hundred milliseconds to a few seconds until the start of the radio service after frequency tuning. Furthermore, if spectrum inversed signals are transmitted in digital radio broadcasting systems, the receivers are unable to decode them, even though most receivers can demodulate the spectral inversed signals in analog radio broadcasting systems. Accordingly, fast synchronization techniques and a method for spectral inversion detection are required in digital radio broadcasting systems that are to replace the analog radio systems. This paper presents a joint detection method of frame, integer carrier frequency offset, and spectrum inversion for DRM Plus digital broadcasting systems. The proposed scheme can detect the frame and determine whether the signal is normal or spectral inversed without any carrier frequency offset and sampling frequency offset compensation, enabling fast frame synchronization. The proposed method shows outstanding performance in environments where symbol timing offsets and sampling frequency offsets exist.

Fast Carrier Frequency Synchronization for CMMB Robust to Time Offset and Fading (시간 오프셋 및 페이딩 환경에 강인한 CMMB 고속 주파수 동기 알고리듬)

  • Kang, Eun-Su;Han, Dong-Seog
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.6C
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    • pp.516-522
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    • 2010
  • In this paper, the carrier frequency offset estimator is proposed for the China multimedia mobile broadcasting (CMMB). The fractional carrier frequency offset is estimated by utilizing the cyclic prefix in each CMMB symbol. In addition, the integer carrier frequency offset can be estimated with the synchronization signal in every CMMB frame. The proposed estimator is the most suitable for the frame structure of CMMB. It shows a prominent performance even in timing offset and multipath conditions.

A Study on a New Carrier Recovery Algorithm for Coherent Burst-mode Communication Systems (동기식 버스트 통신시스템 적용을 위한 새로운 반송파 동기 기법에 관한 연구)

  • Park, Sung-Bok
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.6
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    • pp.1043-1048
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    • 2011
  • In this paper, a newsynchronization technique applied to burst-mode communication is proposed. A synchronization technique is to estimate carrier frequency and phase offsets in a noisy channel environment. A fundamental problem for estimating the parameters(carrier phase and frequency offsets) in burst-mode transmission is that the ways of pursuing estimation accuracy and transmission efficiency are always trade-off. To solve this problem, a new carrier recovery technique is proposed to improve the transmission efficiency with reliable performance especially at low S/N. In the proposed technique, the synchronization parameters are first estimated based on a data-aided feed-forward estimation scheme. Then, a phase tracker using decision-directed DPLL estimates the phase offset for the data portion of the burst data. From simulation results, it shows fast synchronization with shorter preamble maintaining reasonable BER performance at low S/N.

A Distributed Frequency Synchronization Technique for OFDMA-Based Mesh Networks Using Bio-Inspired Algorithm (Bio-inspired 알고리즘을 이용한 OFDMA 기반 메쉬 네트워크의 분산 주파수 동기화 기법)

  • Yoo, Hyun-Jong;Lee, Mi-Na;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37B no.11
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    • pp.1022-1032
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    • 2012
  • In OFDMA-based wireless mesh networks, synchronization of carrier frequencies among adjacent nodes is known to be difficult. In this paper, a distributed synchronization technique is proposed to solve the synchronization problem in OFDMA-based wireless mesh networks by using the bio-inspired algorithm. In the proposed approach, carrier frequencies of all nodes in a mesh network are converged into one frequency by locally synchronizing the frequencies of adjacent nodes. It may take a long time to be converged in some topologies since the convergence characteristic of carrier frequencies in a mesh network may vary depending on the size of the network and deployment of nodes. It is shown that fast frequency synchronization, not heavily depending on the topology, can be achieved through the proposed algorithm with an adjustable weight.

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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System Performance with Synchronization Errors in Distributed Beamforming Systems (분산 빔포밍을 이용한 시스템에서 동기에러에 의한 시스템 성능 영향 분석)

  • Kim, Haesoo;Kwon, Seong-Geun
    • Journal of Korea Multimedia Society
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    • v.18 no.4
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    • pp.452-459
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    • 2015
  • Three synchronization issues, i.e., phase, frequency, and symbol time, have to be properly controlled to achieve distributed beamforming gain. In this paper, the impacts of synchronization errors in distributed beamforming are analyzed for both single-carrier and OFDM systems. When the channel is constant over a symbol duration, the performance degradation due to phase offset is the same for both single-carrier and OFDM systems. For symbol timing offset in OFDM systems, high frequency subcarriers are more susceptible as compared to low frequency ones. Frequency offset is critical in OFDM systems since it leads to interference from the other subcarriers as well as power loss in the desired signal.

Non-Data-Aided Spectral-Line Method for Fine Carrier Frequency Synchronization in OFDM Receivers

  • Roh, Heejin;Cheun, Kyungwhoon
    • Journal of Communications and Networks
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    • v.6 no.2
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    • pp.112-122
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    • 2004
  • A nonlinear spectral-line method utilizing the fourth absolute moment of the receiver discrete Fourier transform output is proposed as a non-data-aided fine carrier frequency synchronization algorithm for OFDM receivers. A simple modification of the algorithm resulting in low implementation complexity is also developed. Analytic expressions are derived for the steady-state frequency error variances of the algorithms and verified to be very accurate via computer simulations over AWGN and frequency selective multipath channels. Numerical results show that the proposed algorithms provide reliable and excellent steady-state performance, especially with PSK modulation. Also, the proposed algorithms are insensitive to symbol timing offsets, only requiring a coarse symbol timing recovery.

A Multiple-Symbol Interval Estimation Algorithm for Precision Improvement of Initial Carrier-Frequency Synchronization in Multiband-OFDM UWB System (MB-OFDM UWB 시스템에서 초기 반송파 주파수 동기의 정확도 향상을 위한 다중 심볼 간격 추정 알고리즘)

  • Jin, Yong-Sun;Park, Kye-Wan
    • 전자공학회논문지 IE
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    • v.47 no.3
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    • pp.35-40
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    • 2010
  • In this paper, we propose an algorithm to improve the precision of initial carrier-frequency offset estimation for multiband-OFDM (MB-OFDM) UWB system which is considering the quantization-noise effect. In the general OFDM system, the two adjacent and repeated preamble symbols are used for the initial carrier-frequency synchronization while the performance of the frequency-offset estimation is bounded by quantization effect generated from analog-to-digital conversion at the receiver. This paper proposes a method in which one-symbol interval between two adjacent preamble symbols for the initial frequency synchronization is extended to multiple-symbol interval between non-adjacent symbols in an extent that phase ambiguity does not occur. In this paper, we also present '6' as optimal multiple symbol interval for the MB-OFDM system with 30 preamble symbols on 3-band hopping and with 4-bit A/D conversion at the receiver. Under the channel environments for the MB-OFDM UWB system, the simulation results show that the proposed estimation algorithm can achieve the initial estimation in offset precision less than 5 ppm.