• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.232-239
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• 2006

In this paper, we analyze the preamble model for Wireless PAN(WPAN) in proposed Ultra WideBand(UWB) Multi-Band OFDM(MB-OFDM) system of IEEE 802.15.3a standard. Besides, we propose effective Carrier Frequency Offset and Symbol Timing Offset Estimation algorithm which offers enhanced performance, and analyze its performance using Detection Probability, False Alarm Probability, Missing Probability, Mean Acquisition Time and MSE(Mean Square Error) through simulation in AWGN and UWB channel environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.367-374
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• 2012

In this paper, we propose a novel cancellation scheme of correlation side-peaks for binary offset carrier (BOC) signals. The proposed scheme is based on a combination of the sub-correlation functions composing the BOC autocorrelation and applicable to both sine- and cosine-phased BOC signals without requiring any auxiliary signal in the receiver. From numerical results, it is confirmed that the proposed scheme provides a better tracking accuracy than the conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5A
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• pp.441-449
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• 2011

Sample timing offset (STO) and carrier frequency offset (CFO) are caused by inter-symbol interference (ISI), inter-carrier interference (ICI) and phase error in orthogonal frequency division multiplexing (OFDM) system. OFDM characteristic is sensitive about STO and CFO. So when ICI occurs, compensation is hard and complex equalizer is needed. In this paper, we propose an effective correction method using feedback process with pilot and synchronization symbol. After feedback with estimated value in frequency domain, STO and CFO are corrected by control sample & and holder and oscillator. As a result of simulation, we confirm that STO and CFO can be corrected without equalizer through feedback.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2A
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• pp.169-178
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• 2007

In this paper, we propose a signal structure and its optimum receiver to improve performance of SC-FDE(Single Carrier with Frequency Domain Equalization) system. Conventional SC-FDE systems have a drawback of power unbalance in frequency domain due to generation of pilot signals in time domain. The unbalanced power in frequency domain induces a channel estimation error and the performance of the receiver is degraded significantly. To overcome the drawback we apply CAZAC sequence which has constant power distribution in time and frequency domain. We design the signal structure to improve the performance with the repeated CAZAC sequence, and we design a receiver to optimize the proposed structure. Computer simulation results show that the proposed structure is superior to the conventional structure considering frame synchronization, frequency synchronization and channel equalization on typical wireless mobile channel environment.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.290-297
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• 2014

The synchronization of OFDM receiver is consisted of symbol timing offset(STO) estimation in time domain and carrier frequency offset(CFO) estimation in frequency domain. This paper proposes new algorithm for correcting the integer CFO after we have done correcting the STO and partial CFO. ICFO must be corrected, since the ICFO lead to degrade bit error rate(BER) of demodulation performance. The PN sequence has information which is subcarrier order since the modified PN sequence, length is same subcarrier, is used in this paper and is modulated each subcarrier by each chip. Thus the receiver track phase of PN sequence after FFTin order to find the subcarrier frequency offset. The proposed algorithm is faster and more simple than convenient methode as measuring carrier energy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.807-813
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• 2009

A Satellite transponder is the Communication system to process signal with up-link signal recovery, and transmit to ground station through down-link. The orbit flight in the deep space causes high doppler shift in the received signals from the ground station so that the Carrier recovery and fast synchronization system are essential for the transponder system. The conventional analog transponder is employing the system's carrier recovery along with the PLL (Phase Locked Loop) designed for satellite's operation. This paper presents a digital carrier recovery scheme which can provide more reliable and software reconfigurable implementation technique for satellite transponder system without verifying scheme along with transponder designed for short distance or deep space satellite.

• Journal of Navigation and Port Research
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• v.31 no.9
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• pp.763-769
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• 2007

A narrow loop noise bandwidth method is desirable to reduce the error of raw measurements due to the thermal noise. However, it degrades the performance of GPS initial synchronization such as mean acquisition time. And it restricts the loop noise bandwidth to a fixed value determined by the lower bound of the allowable range of carrier-to-noise power ratio, so that it is difficult to optimally track GPS signal. In order to make up for the weak points of the fixed-type narrow loop noise bandwidth method and simultaneously minimize the error of code and carrier measurements, this paper proposes a stepwise-type adaptive bandwidth algorithm for DGPS reference receivers. In this paper, it is shown that the proposed adaptive bandwidth algorithm can provide more accurate measurements than those of the fixed-type narrow loop noise bandwidth method, in view of analyzing the simulation results between two signal tracking algorithms. This paper also carries out sensitivity analysis of the proposed adaptive bandwidth algorithm due to the estimation uncertainty of carrier-to-noise power ratio. Finally the analysis results are verified by the experiment using GPS simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4A
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• pp.402-411
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• 2006

In OFDMA system, multiple users transmit signal through the subcarriers assigned to the user. Capabilities of high data-rate transmission in OFDMA system come from the ability to compensate the ICI (Inter Carrier Interference) using a single-tap equalizer and to implement transmitter and receiver by employing high speed FFT circuitry. Issues of time and frequency synchronization in OFDM system is quite essential to preserve the orthogonality among subcarriers not to produce ICI. In this paper, we Int analyze the preamble used in 802.16 d/e and WiBro system. Then we propose an effective timing synchronization algorithm, which is more accurate than the conventional one in the sense of timing position, and integral frequency offset estimation scheme for the simultaneouse estimation of the fractional and integral frequency offset. Through the simulation utilizing the proposed synchronization algorithm and structure, we show that the performance degradation due to the adjacent channel interference can be mitigated for the than conventional ones.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3428-3434
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• 2010

In this paper, we proposed and implemented a quality measurement algorithm for IS-95 reverse-link signal. To measure the quality of the received signal, equalization, carrier frequency/phase offset estimation, and timing synchronization are essential. And, all signal processing are carried out with baseband signal. The equalizer works with 4-oversampled samples to remove ICI(InterChip Interference). The frequency/phase offset estimator is followed by timing synchronizer since it can work without aid of data and timing information. As the number of interpolation in timing synchronization increases, the measurement accuracy improves, but computation load increases simultaneously. Therefore, one need to choose adequately the number of interpolation regarding to the platform performance to be used for the proposed algorithm.

• 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.