• Journal of information and communication convergence engineering
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• v.8 no.3
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• pp.289-294
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• 2010

In the vehicle communication system, transferred information is needed to be detected as possible as fast in order to inform car status located in front and rear side. Through the moving vehicle information, we can avoid the crash caused by sudden break of front one or acquire to real time traffic data to check the detour road. To be connecting the wireless communication between the vehicles, fast timing synchronization can be a key factor. Finding out the sync point fast is able to have more marginal time to compensate the distorted signals caused by channel variance. Thus, we introduce the combination method which helps find out the start of frame quickly. It is executed by auto-correlation and cross-correlation simultaneously using only short preambles. With taking the absolute value at the implemented synch block output, the proposed method shows much better system performance to us.

• 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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• 2008.10a
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• pp.689-692
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• 2008

WAVE based on OFDM is made for vehicle to vehicle wireless communication. Its performance is decreased by continual timing delay in multipath fading channels after starting initial timing synchronization. In this paper, the tracking algorithm that synchronizes symbol timing is proposed to continually compensate additional timing delay. Computer simulation of the proposed algorithm is performed in the worst communication environment that applies to maximum timing delay. Computer simulation shows that the proposed algorithm can improve the system performance in various channel conditions.

• 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.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.857-860
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• 1999

It is made possible a removal of the preamble for carrier recovery and symbol-timing recovery by storing a burst in memory with low overhead QPSK demodulation and this demodulation method also effects frame efficiency improved by processed synchronization performance. In this paper, we have proposed that new algorithm for arc-tangent look-up table which transform the input I, Q data by phase. This I, Q data plays an important role in demodulation and makes demodulator with low-overhead by storing a burst in memory. To evaluate proposed new algorithm and symbol-timing recovery method, function simulation and timing verification have been done by using synopsys VHDL tool.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.659-665
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• 2008

If ranging processes are not frequent in an uplink OFDMA system, the timing synchronization between base and mobile stations may not be maintained. Especially in the case of infrequent random accesses in a large cell, timing offsets can be considerable and the destroyed orthogonality of OFDMA signals may result in the degraded performance. This paper proposes a novel random access scheme for uplink OFDMA systems, which support the orthogonality of OFDMA signals with timing offsets by allowing a random access OFDMA symbol shorter than a normal one. In order to make uplink OFDMA systems robust to timing offsets, the proposed scheme inserts a zero-padding region in an OFDMA symbol.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.336-340
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• 2003

The frame synchronization should be acquired before performing other data-aided receiving algorithms, such as data-aided channel equalizing, beam-forming and phase, symbol timing, and frequency synchronizing, since all of them are using preamble or training sequence to estimate the amount of error from the received signal. In this paper, we present a new frame synchronization scheme for underwater ultrasonic image burst transmission system, which computes the correlation between received symbol sequence and one CAZAC sequence, composed of the latter half of the first CAZAC sequence of preamble and the first half of the second CAZAC sequence of preamble and then compares a threshold value. If the correlation value is bigger than the threshold value, the frame detector determines that the frame synchronization is achieved at that sample.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.11a
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• pp.56-59
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• 2001

OFDM 시스템은 부반송파의 직교성을 이용하는 특징으로 인하여 신호치 시간동기 및 주파수동기가 맞지 않은 경우 수신신호를 정확히 복조하기가 거의 불가능하다. 보호구간(Guard Interval)은 신호의 데이터 구간 일부분을 복사하여 심볼의 앞에 추가하는 CP(Cyolic Prefix)방식을 사용하고 있으며, 채널에서 발생하는 ISI(InterSymbol Interference)를 흡수하는 중요한 역할을 한다. 본 논문에서는 시간동기에 사용되어지는 보호구간을 여러 부구간으로 나눈 후, 이를 이용하여 심볼 타이밍 동기를 추정하고자 한다. 제안된 방법은 기존의 방법에 비해 성능의 손실없이 많은 계산량을 줄이는 방법으로서 수신기의 구조를 단순화시킬 수 있다. 여러 채널 환경에서의 모의 실험을 통해 제안한 방법과 기존의 방법을 비교하였다.

• ETRI Journal
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• v.30 no.4
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• pp.495-505
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• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.687-694
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• 1999

In this paper, to draw out the parameter of synchronization for ADSL(Asymmetric Digital Subscriber Line) chip design, we analyze the performance of STR(Symbol Timing Recovery) and frame synchronization with computer simulation. We analyze and design PLL(Phase Lock Loop) loop for ADSL. As a result, we obtained the optimum parameter of STR to design ADSL chip. Also, when performed frame synchronization with several algorithm, we analyzed the performance of FER(Frame Error Rate) and the effect of frame offset with computer simulation.