• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.951-962
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• 2002

A DMT transceiver recovers the sampling time from reserved sub-carriers, the pilots. Since the pilots are available after the FFT, the symbol synchronization must be done before sample synchronization. In DMT VDSL system, symbol synchronization is handled separately from sample synchronization, although the two processes are intimately related. The DMT symbol itself contains sufficient information, the cyclic extension, for symbol synchronization. Using only the sign bit of received signal, the Maximum Likelihood Estimation solution is derived. The Tx windowing in the transmitter of DMT VDSL system results in the blurring of MLE peaks. We propose the weighted summing MLE method using the sign bit which produces the clearly sharp top of MLE peaks. The stability of symbol synchronization is improved significantly by averaging over a few symbols. This paper presents the study of the original MLE and the weighted summing MLE using sign bit. A clock difference between transmitter and receiver destroys the oahogonality of the carriers. Therefore, a receiver using asynchronous sampling must perform timing correction in the discrete-time domain. We introduce an efficient digital sample synchronization method which is based on temporal and frequency domain digital signal processing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.980-987
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• 2009

A timing synchronization method is presented for IEEE 802.11a wireless OFDM system. First the signal detection is achieved by measuring the moving energy of the received OFDM signal in two consecutive windows. By measuring the correlation between the short training signal and received envelope signal, fine OFDM symbol synchronization can be acquired. The variance and average value of the correlation value is acquired. And the theoretical values are compared with computer simulation results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.583-586
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• 2004

In this paper, we have analyzed the performance of synchronization of CCK(Complementary Code Keying) modulation scheme used for IEEE 802.11g wireless LAM system supporting 54 Mbps of high speed data rate over 2.4 GHz. At receiver, the clock frequency offset is caused by noise or fading. This frequency error occurs the offset of clock timing and causes ISI. Therefore the tracking is required to reduce the clock timing offset. The DLL(Delay Lock Loop), asychronization mode, performing tacking the clock is used for the simulation. The simulation result shows jitter variance and BER performance in the AWGN and multipath fading channel environment.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.287-289
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• 2012

This paper proposes an alternate time-switched space-frequency block coding transmission technique for orthogonal frequency division modulation systems. There are two antennas in the transmitter but it still has only a baseband and RF and a switch that alternates between the antennas at every symbol timing. Alternating transmit symbols result in zeros that make maximal ratio receive combining possible in the receiver. Simulation results show that it provides better performance than the traditional algorithm at the expense of one additional antenna.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.225-226
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• 2013

본 논문은 OFDM (Orthogonal Frequency Division Multiplexing)기반의 LTE (Long Term Evolution)하향링크 시스템에서 PS (Primary Synchronization)신호를 이용한 잔여 시간동기 오차를 검출 기법을 제안한다. 제안된 잔여 시간동기 오차 검출 기법은 기존의 잔여 시간동기 오차 검출 기법과 달리, 수신된 PS 신호간의 상호상관 값을 이용하여 잔여 시간동기오차를 검출한다. 제안된 기법은 기존의 기법보다 낮은 복잡도를 가지며, 비슷한 성능을 보여주며 이는 컴퓨터 모의실험을 비교하였다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.239-239
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• 2006

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.1-11
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• 1996

In this paper, we evaluate the performance of DD-bardner (decision-directed gardner) algorithm. We derive an analytic gain of the thiming detector that is a function of SNR and an excess bandwidth, and verify the result by simulation. We also compare the DD-gardner algorithm with the bardner algorithm with respect to tracking performance and jitter performance under low SNR and a residual frequency component.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.210-210
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• 2004

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11B
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• pp.965-971
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• 2003

This paper suggests a low-complexity frame timing synchronization system for IEEE802.11a wireless LAN systems. The proposed timing synchronization scheme has been implemented by correlating the received OFDM preamble with quantized coefficients composed of ｛0, ${\pm}$2$^{0}$ , ${\pm}$2$^1$‥‥‥ ${\pm}$2$^{i}$ ), where i is an integer number. The 2$^{i}$ -valued coefficients enable the multipliers in the correlation system to be simplified to i-bit shifters. So we can design the correlation system using shifters instead of multipliers. We estimate the performance of the proposed scheme in comparison with conventional systems under the AWGN and Rayleigh fading channels. In this paper we show that the complexity can be reduced by 90% while still maintaining a performance comparable to that of the conventional system.