• Journal of Positioning, Navigation, and Timing
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• v.3 no.4
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• pp.163-170
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• 2014

A pseudolite is used as a GPS backup system, and is also used for the purpose of indoor navigation and correction information transmission. It is installed on the ground, and transmits signals that are similar to those of a GPS satellite. In addition, in recent years, studies on the improvement of positioning accuracy using the pseudorange measurement of a pseudolite have been performed. As for the effect of the time synchronization error between a pseudolite and a GPS satellite, a time synchronization error of 1 us generally induces a pseudorange error of 300 m; and to achieve meter-level positioning, ns-level time synchronization between a pseudolite and a GPS satellite is required. Therefore, for the operation of a pseudolite, a time synchronization algorithm between a GPS satellite and a pseudolite is essential. In this study, for the time synchronization of a pseudolite, "a pseudolite time synchronization method using the time source of UTC (KRIS)" and "a time synchronization method using a GPS timing receiver" were introduced; and the time synchronization performance depending on the pseudolite time source and reference time source was evaluated by designing a software-based pseudolite time synchronization performance evaluation simulation platform.

• Journal of Advanced Navigation Technology
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• v.18 no.5
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• pp.429-436
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• 2014

This paper proposes three methods of the time synchronization for Pseudolite and GPS and analyzes pseudolite time synchronization error factors for software based performance evaluation on proposed time synchronization methods. Proposed three time synchronization methods are pseudolite time synchronization station construction method, method by using UTC(KRIS) clock source and GPS timing receiver based time synchronization method. Also, we analyze pseudolite time synchronization error factors such as errors of pseudolite clock and reference clock, time delay as clock transmission line, measurement error of time interval counter and error as clock synchronization algorithm to design simulation platform for performance evaluation of pseudolite time synchronization.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.3
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• pp.67-78
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• 2013

In this paper, We proposed an development method of application framework for using the precision time protocol(PTP) based on physical layer devices to synchronize clocks across a network with IEEE1588 capable devices. The algorithm was not designed as a complete solution across all conditions, but is intended to show the feasibility of such a for the PTP(Precision Time Protocol) based on time synchronization of heterogeneous network between devices that support in IEEE 1588 Standard application framework. With synchronization messages per second, the system was able to accurately synchronize across a single heavily loaded switch. we describes a method of synchronization that provides much more accurate synchronization in systems with larger networks. In this paper, using the IEEE 1588 PTP support for object-oriented modeling techniques through the 'application framework development Development(AFDM)' is proposed. The method described attempts to detect minimum delays, or precision packet probe and packet metrics. The method also takes advantage of the Tablet PC(Primary to Secondary) clock control mechanism to separately control clock rate and time corrections, minimizing overshoot or wild swings in the accuracy of the clock. We verifying the performance of PTP Systems through experiments that proposed method.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.1
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• pp.17-23
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• 2020

We propose a system time synchronization method between embedded Linux-based distributed control devices by using Transmission Control Protocol (TCP) communication and General Purpose Input Output (GPIO) device. The GPIO signal is used as the trigger signal for synchronization and the TCP communication is used to transfer the system time of master Linux, which serves as the reference clock, to slave Linux. Precise synchronization performance is achieved by measuring and compensating for the propagation delay of GPIO signal and the acquisition and setting latency of Linux system time. We build an experimental setup consisting of two embedded Linux systems, and perform extensive experiments to verify the performance of the proposed synchronization method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1860-1875
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• 2013

In this paper, we present a comparative performance evaluation of the sampling frequency synchronization method that eliminates the initial sampling frequency offset (SFO) to reduce the overall synchronization time in Digital Radio Mondiale (DRM) receivers. To satisfy the advanced synchronization performance requirements of DRM receivers, we introduce the conventional DRM synchronization method (Method 1) and another method (Method 2), which does not perform the initial sampling frequency synchronization in the conventional synchronization method (both methods are mentioned later in this paper). To demonstrate the effectiveness of the performance evaluation, analytical expressions for frame detection are derived and simulations are provided. Based on the simulations and numerical analysis, our result shows that Method 2, with a negligible performance loss, is robust to the effects of the initial sampling frequency synchronization even if SFO is present in the DRM signal. In addition, we verify that the inter-cell differential correlation used between reference cells is robust to the effect of the initial SFO.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.141-154
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• 2013

The technology of precise time-synchronization between signal receive devices for separation distance operation can be a key point for the technology with TDoA-based system. We propose a new method for the higher accuracy of system's time-synchronization in this paper, which uses OCXO and DPLL with high accuracy to achieve phase synchronization at 1 pps (pulse per second) of signal. And the method receive time value from a GPS satellite. Essentially, the performance of GPS with high accuracy refers to long-term frequency stability for its reliability. As per the characteristic, as the GPS timing signals are synchronized continuously, the accuracy of time-synchronization gets improved proportionally. Therefore, if the time synchronization is accomplished, the accuracy of the synchronization can be up to 0.001 ppb (part per billion). Through the improved accuracy of the time-synchronization, the measurement error of TDOA-based location detection technology is evaluated. Consequently, we verify that TDoA-based location measurement error can be greatly improved via using the improved method for time-synchronization error.

• Journal of Korea Multimedia Society
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• v.19 no.10
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• pp.1808-1815
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• 2016

TPSN(Timing-sync Protocol for Sensor Networks), the representative of time synchronization protocol, has been already developed to provide time synchronization among nodes in wireless sensor networks. Even though the TPSN's method has been referenced by so many other time synchronization schemes for resource-constrained networks like wireless sensor networks or low power personal area networks, it has some inefficiency in terms of power consumption and network-wide synchronization time (or called convergence time). The main reason is that each node in TPSN needs waiting delay to solve the collision problem due to simultaneous transmission among competing nodes, which causes more power consumption and longer network convergence time for a network-wide synchronization. In this paper an improved scheme is proposed by changing message exchange method among nodes. The proposed scheme not only shortens network-wide synchronization time, but also reduce collision traffic which lead to needless power consumption. The proposed scheme's performance has been evaluated and compared with an original scheme by simulation. The results are shown to be better than the original algorithm used in TPSN.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.1-10
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• 1994

In the real-time delivery of multimedia data streams over networks, the interruption of continuity in a single media stream and the mismatching of the data within the same time interval in multimedia data streams transfered in paralled on different channels are considered as the most serious synchronization problems. There are several mechanisms proposed to handle these problems. In this paper, these mechanisms are analyzed and compared in various point of view by the computer simulation. According to the simulation results, it has been shown that the method which uses the segmentation and the method which uses the seperate synchronization channel are superior to the method which uses the synchronization marks in view of the real-time transmission and quality of sevice. On the other hand, it can be seen that the method which uses the segmentation is superior to the method which uses the seperate synchronization channel from a channel utilization's point of view.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.701-704
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• 2004

In this paper, we proposed that the synchronization method for build small world. In order to build a small world, we used Chua's oscillator which well represent the chaos dynamics and composed several stage with Chua's oscillator by using coupled synchronization method. This paper shows a synchronization result in the small world network using coupled synchronization method. Not only time series and phase plane are implemented but also degree of synchronization in the small world network is presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.506-515
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• 2015

In this paper, we propose a group playback synchronization method using adaptive synchronization delay time by the bit rate of media to synchronize a play position of streaming media between mobile smart devices. This method consists of streaming server-side and client-side synchronization algorithms based on synchronization delay time which includes connection time, control packet transmission time, streaming data buffering time, and synchronization processing time. We implement the Android media player application with synchronization support using the proposed algorithms and present the result of performance evaluation.