• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.3-9
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• 2015

In this paper, we propose an initial timing and frequency synchronization scheme for low probability detection (LPD) systems with cyclic code shift keying (CCSK). The performance of the LPD system with CCSK highly depend on initial timing and frequency offset. On the other hand, the operating SNR (Signal-to-Noise Ratio) of LPD systems is usually very low. Hence, to guarantee a reliable performance of the LPD system, it is crucial to develop suitable initial synchronization algorithms. In this paper, we propose an initial timing and frequency synchronization scheme suitable for CCSK based LPD system using a repeated preamble pattern.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.1
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• pp.1-13
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• 2024

In this paper, we investigate the signal design of six (USA, EU, Russia, China, Japan, and India) countries for Global Navigation Satellite Systems (GNSS). Recently, a navigation satellite system that is capable of high-precision and reliable Positioning, Navigation, Timing (PNT) services has been developed. Prior to system design, a survey of the signal design for other GNSS systems should precede to ensure compatibility and interoperability with other GNSS. The signal design includes carrier frequency, Pseudorandom Noise (PRN) code, modulation, navigation service, etc. Specifically, GNSS is allocated L1, L2, and L5 bands, with recent additions of the L6 and S bands. GNSS uses PRN code (such as Gold, Weil, etc) to distinguish satellites that transmit signals simultaneously on the same frequency band. For modulation, both Binary Phase Shift Keying (BPSK) and Binary Offset Carrier (BOC) have been widely used to avoid collision in the frequency spectrum, and alternating BOCs are adopted to distinguish pilot and data components. Through the survey of other GNSS' signal designs, we provide insights for guiding the design of new satellite navigation systems.

• 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.

• Journal of Biomedical Engineering Research
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• v.2 no.1
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• pp.55-64
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• 1981

The important parameters of DC amplifier, which is widely use4 for the medical and engineering fields, are input offset voltage and temperature drift. Chopping amplifier reduces approximately 10% the parameters changing than monolithic operational amplifier. In this study, a chopping amplifier with semiconductor chopper is designed and tested, this chopper is realized by CMOS analog switch and timing circuits. The test results approve that designed amplifier is suitable for precision instrument DC amplifier.

• ETRI Journal
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• v.24 no.3
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• pp.247-250
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• 2002

In this paper, we propose three symbol syn-chronization schemes for Orthogonal Frequency Division Multiplex (OFDM) systems. The cyclic extension preceding OFDM symbols is of decisive importance for these schemes. The first scheme uses the phase-differential coding of the received OFDM signal. The second and the third schemes use the length of the received OFDM signal. All three schemes make symbol synchronization possible, even though there is a frequency off-set in the system. Simulation results show that these schemes can be used to synchronize an OFDM system over AWGN and multi-path fading channels.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.10
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• pp.979-984
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• 2010

The users who use a combined GPS/Galileo receiver will benefit from an improved availability of the combined system and a reduced dependence on one particular positioning system. However, these users must solve the problem of an offset between the time scales of GPS and Galileo (GGTO). GGTO must be analyzed for not only a navigation system but also a timing system requesting precise time service. This paper analyzes the interoperability problem in a combined GPS/Galileo timing receiver and estimates the timing performance under various assumptions. The GPS real measurements were collected by using the commercial timing receiver from Ashtech Ltd. and the Galileo measurements were generated by a simulation software. A suitable test scenario set-up and the performance in a point of timing stability was evaluated.

• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.319-324
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• 2022

If radio interference occurs or there is no navigation device, radio navigation of high-speed moving object becomes impossible. Nevertheless, if there are multiple ground stations and precise range measurement between the high-speed moving object and the ground station can be secured, it is possible to estimate the position of moving object. This paper proposes a position estimation method using high-precision TDOA measurement generated using TLM signal. In the proposed method, a common error of moving object is removed using the TDOA measurements. The measurements is generated based on TLM signal including SOQPSK PN symbol capable of precise timing synchronization. Therefore, since precise timing synchronization of the system has been performed, the timing error between ground stations has a very small value. This improved the position estimation performance by increasing the accuracy of the measured values. The proposed method is verified through software-based simulation, and the performance of estimated position satisfies the target performance.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.64-72
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• 2012

Synchronization including timing recovery, frequency offset compensation, and frame synchronization is most important signal processing block in all wireless/wired communication systems. In most communication systems, synchronization schemes based on training sequences or preambles are used. WLAN standards of 802.11a/g/n released by IEEE are based on OFDM systems. OFDM systems are known to be much more sensitive to frequency and timing synchronization errors than single carrier systems. A loss of orthogonality between the multiplexed subcarriers can result in severe performance degradations. The starting position of the frame and the beginning of the symbol and training symbol can be estimated using correlation methods. Correlation processing functionality is usually complex because of large number of multipliers in implementation especially when the reference signal is non-binary. In this paper, a simple correlation based synchronization scheme is proposed for IEEE 802.11a/g/n systems. Existing property of a periodicity in the training symbols are exploited. Simulation and implementation results show that the proposed method has much smaller complexity without any performance degradation than the existing schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.733-742
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• 2008

In 3GPP LTE downlink system, initial cell search is essential for mobile station to connect to base station. In order to obtain information of the base station, the mobile station detects frame timing, frequency offset, and cell identification using primary synchronization channel(PSC) and secondary synchronization channel(SSC), which are defined in downlink OFDMA specification. In this paper, we analyze various detection algorithms in practical environment of inter-cell-interference, frequency offset, and multi-path fading channel and propose the optimal algorithm. Simulation results show that partial correlation method (for PSC acquisition) and interference cancellation method (for SSC detection) are the most superior algorithms among the applicable algorithms. Employ these two algorithms for receiver design, initial cell search is performed with 99% probability within 70ms in the channel environment considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.429-438
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• 2004

In this paper, a decision-feedback coherent code tracking loop is designed for WCDMA systems and its performance is analyzed in terms of jitter variance considering the effect of phase and symbol estimation errors for both AWGN and fading environments. An analytical closed-form formula for jitter variance is Int derived for AWGN environments as a function of a pulse-shaping filter, timing offset, signal-to-interference ratio, and loop bandwidth while involving the phase estimation error and bit error rate, and the upper bound of jitter variance is derived for fading environments. Finally a second-order coherent code tracking loop is designed with the DPCH frame format #13 of the WCDHA forward link selected as a target system, and its performance is evaluated by the closed-form formula and compared with the simulation results for both AWGN and Rayleigh fading environments.