• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.613-616
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• 2008

In this paper, a fine residual frequency offset estimation scheme is proposed for multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) systems. The basic idea of our approach is based on the fact that two adjacent OFDM symbols carry the identical information in the MB-OFDM UWB system, thus removing the need of pilot symbols. The mean square error of the synchronization scheme is evaluated and simulation results are used to verify the effectiveness of the proposed estimator. When compared to the pilot-aided conventional estimator, the proposed estimator has a lower estimation error.

• Journal of information and communication convergence engineering
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• v.2 no.1
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• pp.1-4
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• 2004

In this paper, We analyzes how a synchronization error affects receiving system when using OFDM(Orthogonal Frequency Division Multiplexing) transmission method in wireless LAN channel environment in which we can efficiently transmit wide-band information data. As a performance improvement method, performance distortion can be improved by applying convolution coding. As a result, in OFDM system, we could see that the higher a frequency offset is, the worse performance will be, and we could see that there was performance improvement by applying convolution coding in OFDM system in order to reach (BER=$10^{-3}$). However, when we use 64QAM (64Quadrature Amplitude Modulation), there was a huge influence between carriers by frequency offset at 0.05, 0.1.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.101-102
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• 2006

Similar to Orthogonal Frequency Division Multiplexing (OFDM), a Single Carrier with Frequency Domain Equalization (SC-FDE) system is computationally efficient since equalization is performed on a block of data in the frequency domain. In coherent QAM schemes, the mean phase rotation error caused by the residual carrier frequency offset may lead to serious degradation. When the frequency equalizer is combined with the mean phase error tracking algorithm, its performance can be enhanced noticeably.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.16-24
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• 1997

In order to prevent the presence of the residual phase difference at the discriminator output by the existing AFC techniques, we propose a new automatic frequency control(AFC) tracking algorithm for QPSK demodulation at the digital direct broadcasting satellite(DBS) receiver, which we call a rotational decision-directed AFC(RDDAFC). The RDDAFC rotates the decision boundary for the kth received symbol by the frequency deterctor output of the (k-1)th received symbol. Tracking performances of carrier frequency offset by the proposed RDDAFC algorithm are evaluated through computer simulations under the practical DBS channel conditions with a carrier frequency offset of 2.3MHz when S/N equals 2dB. Test results show that the total pull-in time of the RDDAFC is 1.697msec for 10$^{-3}$ SER before forwared error correction at the receiver.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.357-365
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• 2009

In an OFDM system, the sampling frequency offset between the transmitter and receiver is known to cause the inter-channel interference (ICI), resulting in performance degradation. Sampling frequency offset can be generally estimated by correlation of the pilot signal within contiguous OFDM symbol. In this paper, we propose sampling frequency offset estimation schemes using various mixture of consecutive symbols. We conduct a simulation in DVB-T(2K mode) system, which shows that the proposed schemes can improve the performance of sampling frequency offset estimation by decreasing noise effect within consecutive symbols in AWGN channel model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.906-911
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• 2008

This paper designed Simulik Model to cancel the carrier frequency offset in OFDM using CORDIC Algorithm and evaluated its performance. And Simulink Model compared with Xilinx System Generator Model for FPGA implementation. As a result of simulation, we confirmed that both model is error free by CORDIC when offset frequency is lower than $10^5MHz$. Also, we verified the performance through Hardware Co-simulation with Xilinx Spartan3 xc3s1000 fg676-4 Target Device, and timing analysis and resource estimation.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.182-191
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• 2010

In this paper, a simple Carrier Frequency Recovery(CFR) scheme is introduced. In relating the use of consumer-grade equipment and satellite transmission environments, carrier frequency recovery have to recovery a large initial Carrier Frequency Offset(CFO), which is 20% normalized CFO, for DVB-S2 receivers. For these reasons, conventional CFR schemes for DVB-S2 systems need significant hardware complexity. Introduced CFR scheme employs Fitz algorithm for coarse CFR and recovers a coarse CFO accurately, and a simple pilot block correlation algorithm is employed for fine CFR. Introduced scheme reduce the number of multiplication operations by 80% and does not need any additional memory without degrading the achievable performance.

• ETRI Journal
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• v.36 no.5
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• pp.783-790
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• 2014

In this paper, we first analyze carrier-to-interference ratio performance of the space-frequency block coded orthogonal frequency-division multiplexing (SFBC-OFDM) system in the presence of phase noise (PHN) and residual carrier frequency offset (RCFO). From the analysis, we observe that conventional SFBC-OFDM systems suffer severely in the presence of PHN and RCFO. Therefore, we propose a new inter-carrier interference (ICI) self-cancellation method - namely, ISC - for SFBC-OFDM systems to reduce the ICI caused by PHN and RCFO. Through the simulation results, we show that the proposed scheme compensates the ICI caused by PHN and RCFO in Alamouti SFBC-OFDM systems and has a better performance than conventional schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.610-628
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• 2012

Dual carrier frequency offsets (CFOs) occur in multiple-input single-output (MISO)-mode DVB-T2 systems, where signals are transmitted simultaneously from two distributed transmitters in a single frequency network (SFN). In this paper, we first derive an optimal compensation frequency for dual CFOs. We also propose an algorithm that optimizes the compensation frequency for the MISO-mode DVB-T2 application. Its performance is compared with the conventional scheme by using a full DVB-T2 simulator.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1074-1080
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• 2013

The low phase noise and wideband frequency synthesizer has been designed by using YTO. Offset PLL structure is used for reducing a division ratio of feedback loop. The phase noise modeling is applied to optimize loop filter of PLL and YTO module. And DDS is used as reference signal of frequency synthesizer for fine resolution. The fabricated wideband frequency synthesizer has the output frequency of 3.2 GHz to 6.8 GHz, phase noise of -107 dBc/Hz at 10 kHz offset from the carrier and frequency resolution of 1 Hz. The measured phase noise is well agreed with the simulated one.