• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.391-398
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• 2018

There are many problems caused by data sharing between general heterogeneous digital devices due to various interfaces. To solve this problem, this paper proposes heterogeneous data sharing with cloud service and mobile through D2D communication that supports communication between different devices. The proposed technique is used to reduce the load on the server to perform data synchronization. Also, in order to minimize data latency caused by data replication between different devices, a technique to enhance the speed of data writing with copying only the modified parts in the chunk list is adopted and cloud service model integrated with mobile environment is realized in order to minimize the network bandwidth consumed for synchronization for data sharing. Therefore, it is possible to share data in different spaces efficiently with maintaining data integrity and minimizing latency in data.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.715-718
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• 2000

Although shared memory parallel programs are designed to be deterministic both in their final results and intermediate states, the races that occur when different processes access a common memory location in an order not guaranteed by synchronization could result in unintended non-deterministic executions of the program. So, Detecting races, particularly first data races, is important for debugging explicit shared memory parallel programs. It is possible that all data races reported by other on-the-fly algorithms would disappear once the first races were removed. To detect races parallel programs with nested loops and inter-thread coordination, it must guarantee the order of synchronization operations in an execution instance. In this paper, we propose an improved restructuring method that guarantee ordering execution instance and preserve the semantics of original program. This method requires O(np) time and (s + up) space, where n is the number of total operations, s is the number of synchronization operations and p is the number of parallelism in the execution. Also, this method makes on-the-fly detection of parallel program with nested loops and inter-thread coordination more easily in space and time complexity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.896-905
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• 2010

The sensor networks can be used attractively for various application areas. Time synchronization is important for any Ubiquitous Sensor Networks (USN) systems. USN makes extensive use of synchronized time in many contexts for data fusion. However existing time synchronization protocols are available only for homogeneous sensor nodes of USN. It needs to be extended or redesigned in order to apply to the USN with heterogeneous sensor nodes. Because heterogeneous sensor nodes have different clock sources with the SinkNode of USN, it is impossible to be synchronized global time. In addition, energy efficiency is one of the most significant factors to influence the design of sensor networks, as sensor nodes are limited in power, computational capacity, and memory. In this paper, we propose specific time synchronization based on master-slave topology for the global time synchronization of USN with heterogeneous sensor nodes. The time synchronization master nodes are always able to be synchronized with the SinkNode. Then time synchronization master nodes enable time synchronization slave nodes to be synchronized sleep periods. The proposed master-slave time synchronization for heterogeneous sensor nodes of USN is also helpful for power saving by maintaining maximum sleep time.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.13-21
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• 2012

Mobile data caching is usually used as an effective way to improve the speed of local transaction processing and reduce server load. In mobile database environment, due to its characters - low bandwidth, excessive latency and intermittent network, caching is especially crucial. A lot of mobile data caching strategies have been proposed to handle these problems over the last few years. However, with smart phone widely application these approaches cannot support vast data requirements efficiently. In this paper, to make full use of cache data, lower wireless transmission quantity and raise transaction success rate, we design a new mobile data caching synchronization strategy based on in-demand and replacement priority. We experimentally verify that our techniques significantly reduce quantity of wireless transmission and improve transaction success rate, especially when mobile client request a large amount of data.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.61-65
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• 2015

For effective distribution planning and operation, we need a reliable estimation of operation capacity. But it is difficult to ensure reliability due to the low accuracy of section load data, which is used as a basis in estimating the operation capacity. This paper discusses how to improve the accuracy of section load data by analyzing the existing method of estimating the section load, using statistical techniques to adjust the acquired data, and using the section load estimation algorithm to estimate the section load based on the adjusted data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1503-1510
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• 2007

To implement a high-precision lightning tracking system utilizing TDOA measurements, high-speed data acquisition and precise timing synchronization between ground sensors should be achieved. At the same time, considering the size of digitizer's memory, the data memory needs to be managed so that only the sampled data around the occurrence of stepped leader pulse is stored. This paper presents a detection-and-acquisition system for lightning signals that is the main equipment of ground sensor in lightning tracking system. GPS clock module is used to get precise timing synchronization and the 500MHz high speed digitizer is employed. In order to detect the leading edge of the lightning pulse and save the sampled data and its timing, lightning detection module is implemented and multi-record method is employed in the proposed system. Field experiment results show that the proposed system can detect and save the lightning signal efficiently.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.815-821
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• 2021

This study addresses on the design of performance monitoring system for the time synchronization service of the enhanced long-range navigation (eLoran) system, which has a representative ground-wave radio broadcast system capable of providing positioning, navigation, timing and data (PNT&D) services. The limitations of time-synchronized systems due to the signal vulnerabilities of the global navigation satellite system (GNSS) are explained, and the performance monitoring system for the eLoran timing service as a backup to the GNSS is proposed. The time synchronization service using eLoran system as well as system configurations and the user requirements in the differential Loran (dLoran) system are described to monitor the time synchronization performance. The results of the designed system are presented for long-term operation in the eLoran testbed environment. As the results of time performance monitoring, we were able to verify the time synchronization precision within 43.71 ns without corrections, 22.52 ns with corrections. Based on these results, the eLoran system can be utilized as a precise time synchronization source for GPS timing backup.

• The KIPS Transactions:PartB
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• v.9B no.1
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• pp.47-56
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• 2002

In the distributed multimedia document system, media objects distributed over a computer network are retrieved from their sources and presented to users according to specified temporal relations. For effective presentation, synchronization has to be supported. Furthermore, since the presentation in the distributed environment is influenced by the network bandwidth and delay, they should be considered for synchronization. This paper proposes a distributed multimedia presentation system that performs presentation effectively in the distributed environment. And it also suggests a method to supports synchronization, in which, network situation and resources are monitored when media objects are transferred from servers to a client. Then a feedback message for the change of them is sent to the server so that the server might adjust the data sending rate to control synchronization. To monitor the situation of network, we use two methods together. One is to manage the level of the buffer by setting thresholds on a buffer and the other is to check the difference between the sending time of a packet from the server and the arrival time of the packet to the client.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.3-9
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• 2013

This paper proposes a selective-weighted energy detection (S-WED) and a synchronization algorithm appropriate for it in IR-UWB system. Energy detectors that are practical in terms of implementation are employed widely for noncoherent reception in IR-UWB systems. However, they show low performance due to using the energy samples captured at symbol rate. For this reason, weighted energy detectors are developed to improve the performance of EDs. Hence, for WED, not only synchronization but also the weight coefficients are needed to be obtained prior to data detection. Meanwhile, the optimal weighting coefficients of WEDs are known to be energy values. Therefore, synchronization and the weighting coefficients can be obtained simultaneously. This paper proposes an S-WED and a simple synchronization algorithm for it in which sub-intervals having energies under a certain level are excluded in energy accumulation resulting in a simpler WED with a bit performance increase in low SNR region. The proposed algorithm is verified through simulations using the preamble symbol and channel models defined in the IEEE 802.15.4a.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.124-131
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• 2014

This paper describes a design of an adaptive baseband modem based on TDMA(time division multiple access) with a relay protocol function for wireless personal area networks. The designed baseband modem is controlled by a master synchronization signal and can be configured a relay network up to 14 hops. For efficient data relay communications, the internal buffer design is optimized by implementing a priority memory bus controller to a single port memory. And the priority memory bus controller is also designed to minimize the number of synthesized logic gates. To implement the synchronization function of the narrowband TDMA relay communication, the number of gates has been reduced by dividing the frame synchronization circuits and the network slot synchronization circuits. By using these methods, the number of gates are used about 37%(34,000 gates) on Xilinx FPGA XC6SLX9 which has 90,000 gates. For the 1024-bit frame size with a 32-bit synchronization word, the communication reception rate is 96.4%. The measured maximum transmission delay of the designed baseband modem is 230.4 msec for the 14-hop relay communication.