• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.801-805
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• 2009

The importance of high-speed networking is ever increasing to better support multimedia application such as video conferencing. It is crucial to synchronize the network so that the delay between computers on the network is minimized. In high-speed LAN, for example, most computers use clocks with almost same frequency to minimize the delay for data transmission. However, because of the deviation of transmitter's and receiver's clock frequency and phase difference there can be a metastability problem. Elasticity buffer is to provide a solution for this situation and this paper presents an implementation is a high-speed elasticity buffer.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.7-13
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• 2008

본 연구에서 개발한 노변 영상(roadside image) 취득 시스템은 효율적으로 도로 시설물들을 관리하기 위함이다. 복잡하고 긴 구간의 도로에 존재하는 도로 시설물을 인력을 사용하여 조사하기에는 많은 시간과 비용이 소요된다. 도로를 따라 움직이는 차량을 이용하는 경우에는 적은 인원과, 단시간에 노변에 설치된 시설물 등의 현황과 상태를 조사 할 수 있으며 도로 주변의 다양한 정보를 알 수가 있다. 또한, 차량에 장착된 GPS/INS 통합시스템을 사용하여 해당 영상의 정확한 위치 정보를 획득 할 수 있다. 그러나 선명한 영상을 취득하기 위해서 야외의 다양한 조건을 만족시키는 카메라와 렌즈의 선정이 중요하며, 이에 따른 동기화 장치(synchronization device)와 영상 획득 프로그램의 개발이 필요하다. 본 논문에서는 경기도 고양시를 대상으로 시험을 실시하였으며, 현재 시판되고 있는 최신의 다양한 종류의 카메라와 렌즈를 차량에 장착한 후 영상을 취득하여 연구에 적합한 하드웨어를 선정하였다. 또한 동기화 장치를 사용하여 DMI(Distance Measuring Instrument)에서 발생되는 트리거 신호를 입력받아 일정한 거리마다 영상을 취득하는 S/W와 동기화 장치의 성능을 테스트하였다. 취득된 노변 영상의 위치 정확도를 테스트하기 위해 DGPS 방법을 이용하여 후처리 하였으며, 레벨 2수준의 교통주제도에 차량의 이동궤적과 도로의 선형을 중첩하여 육안으로 비교 분석하였다. 취득된 노변 영상을 분석하여 지상 모니터링 분야에서 도로 주변 시설물의 변화 탐지에 이용이 가능한 대상 시설물 목록을 선정하였으며 매우 효율적으로 도로의 유지관리에 활용이 가능할 것으로 기대된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.9
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• pp.4609-4623
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• 2017

The commercialization of LTE/SAE technologies has begun a new era in which data can be transmitted at remarkably high rates. The security of the LTE/SAE network, however, remains problematic. The forward security in LTE/SAE X2 handover key management can be threatened by key compromise and de-synchronization attacks as base station in public spaces can be compromised. This study was conducted to address the lack of forward key security in X2 handover key management in scenarios in which an adversary controls a legal base station. We developed the proposed X2 handover key management by changing the parameter in the renewing step and adding a verification step. We compare the security and performance of our proposal with other similar schemes. Our enhancement scheme ensures forward separation security accompanied by favorable signal and computation load performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.10
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• pp.4042-4059
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• 2020

The development of new multimedia techniques such as 3D printing is increasingly attracting the public's attention towards 3D objects. An optimized robust and imperceptible watermarking method based on Ant Colony Optimization (ACO) and Weber Law is proposed for 3D polygonal models. The proposed approach partitions the host model into smaller sub meshes and generates a secret watermark from the sub meshes using Weber Law. ACO based optimized strength factor is identified for embedding the watermark. The secret watermark is embedded and extracted on the wavelet domain. The proposed scheme is robust against geometric and photometric attacks that overcomes the synchronization problem and authenticates the secret watermark from the distorted models. The primary characteristic of the proposed system is the flexibility achieved in data embedding capacity due to the optimized strength factor. Extensive simulation results shows enhanced performance of the recommended framework and robustness towards the most common attacks like geometric transformations, noise, cropping, mesh smoothening, and the combination of such attacks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1640-1645
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• 2010

There exists an inconvenience that players of each instrument pass musical score in orchestra recital. In this paper, we implement the electronic musical score transmitting system that possible to hand sheet music automatically, using Mini - ITX and LCD Panel. We made them unite with a sheet music pair, and it was made and a message and data transmission were embodied using reliable TCP/IP socket communication. In this paper, the client hands sheet music automatic, and server implemented the manual function to manage each clients individually. Because one band can be managed by one Access file all together, it is easy to manage each band. Along with this, this system selects TCP/IP as the reliable transfer protocol that protect loss and errors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4271-4294
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• 2018

Communication cost is the most important factor in Wireless Sensor Networks (WSNs), as exchanging control keying messages consumes a large amount of energy from the constituent sensor nodes. Time-based Dynamic Keying and En-Route Filtering (TICK) can reduce the communication costs by utilizing local time values of the en-route nodes to generate one-time dynamic keys that are used to encrypt reports in a manner that further avoids the regular keying or re-keying of messages. Although TICK is more energy efficient, it employs no re-encryption operation strategy that cannot determine whether a healthy report might be considered as malicious if the clock drift between the source node and the forwarding node is too large. Secure SOurce-BAsed Loose Synchronization (SOBAS) employs a selective encryption en-route in which fixed nodes are selected to re-encrypt the data. Therefore, the selection of encryption nodes is non-adaptive, and the dynamic network conditions (i.e., The residual energy of en-route nodes, hop count, and false positive rate) are also not focused in SOBAS. We propose an energy efficient selection of re-encryption nodes based on fuzzy logic. Simulation results indicate that the proposed method achieves better energy conservation at the en-route nodes along the path when compared to TICK and SOBAS.

• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.45-53
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• 2011

This paper is technical review about Direct Sequence Spread Spectrum(DSSS) to apply in launch vehicle system. First, we introduce communication protocol(carrier frequency, code length, process gain, data rate, chip rate etc) about several application system using DSSS. And then, we survey and summarize the effect of doppler shift to the DSSS. The doppler shift is important error factor for PN code tracking in the fast moving system like launch vehicle. So, spread spectrum code acquisition technique for a direct sequence system in the presence of doppler effect must be investigated.

• Journal of the Korean Society of Systems Engineering
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• v.2 no.2
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• pp.45-50
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• 2006

Tilting technology is to tilt the train on the curve in order to minimize centrifugal force to passengers and to improve the speed within the limits of passenger's comfort and safety. According to reports from other countries, there is 15~30% speed improvement compared to the conventional trains. Recently, the advent of World-Wide-Web(WWW) and the explosive popularity of the Internet gave birth to collaborative applications which were enabled by computers and networks as their primary media. The progress of 3D computer graphics enabled collaborative applications with 3D virtual environments or distributed virtual environments. In this paper, we explain our implementation of the Share collaboration engine which is for collaboration applications based on a distributed virtual environment. The Share collaboration engine proposes a new Share network architecture for management of participants, and it provides some synchronization methods for 3D objects in virtual collaboration. TTX_PDM is an experimental application that tries to prevent wastes of human, material and time resources in networked virtual collaboration.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.321-334
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• 2003

Globally-Asynchronous Locally-Synchronous (GALS) systems are worthy of notice as an adequate architecture for a large scaled chip design with guaranteeing easy designs and functional confidence. In this paper, we suggest an advanced structure of the interface unit which is indispensable for GALS systems by using stoppable clocks. The proposed interface unit is composed of a sender module and a receiver module. The sender module can carry out data transmission partially without the relation to an internal clock. We have designed it with 0.25${\mu}{\textrm}{m}$ standard cell library at the gate level and simulated its operation to show performance improvement. Finally, we constructed all example circuit with the interface unit and proved the correct operation of it.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.88-96
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• 2009

Interoperation between heterogeneous simulators employs definition of standard protocols for data exchange and time synchronization among simulators. The High Level Architecture(HLA) is a specification of common services for such interoperation, which is approved as IEEE standard 1516. This paper presents the design and implementation of an interoperable adaptor which supports development of interoperable simulators under the IEEE 1516 HLA/RTI environment. The adaptor, KHLAAdaptor1516, is implemented as a library form which is linked to HLA-compliant simulators. Design of the adaptor employs a protocol conversion method, the model of which is finite state machine. KHLAAdaptor1516 allows developers to separate interoperable adaptors from stand-alone simulators. The interoperable adaptor manages mapping between HLA services and simulation messages for simulator, This separation increases robustness of a federation and reusability of simulators as well as alleviates much effort and time for maintenance.