• ETRI Journal
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• 제35권4호
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• pp.578-586
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• 2013

Using a sub-terahertz (sub-THz) wave generated using a photonics-based technology, a high-speed wireless link operating at up to 10 Gbps is designed and demonstrated for realization of seamless connectivity between wireless and wired networks. The sub-THz region is focused upon because of the possibility to obtain sufficient bandwidth without interference with the allocated RF bands. To verify the high-speed wireless link, such dynamic characteristics as the eye diagrams and bit error rate (BER) are measured at up to 10 Gbps for non-return-to-zero pseudorandom binary sequence $2^{31}-1$ data. From the measurement results, a receiver sensitivity of -23.5 dBm at $BER=10^{-12}$ is observed without any error corrections when the link distance between the transmitter and receiver is 3 m. Consequently, we hope that our design and experiment results will be helpful in implementing a high-speed wireless link using a sub-THz wave.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권7호
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• pp.3393-3412
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• 2017

As a main challenge in network virtualization, virtual network embedding problem is increasingly important and heuristic algorithms are of great interest. Aiming at the problems of poor correlation in node embedding and link embedding, long distance between adjacent virtual nodes and imbalance resource consumption of network components during embedding, we herein propose a two-stage virtual network embedding algorithm NA-PVNM. In node embedding stage, resource requirement and breadth first search algorithm are introduced to sort virtual nodes, and a node fitness function is developed to find the best substrate node. In link embedding stage, a path fitness function is developed to find the best path in which available bandwidth, CPU and path length are considered. Simulation results showed that the proposed algorithm could shorten link embedding distance, increase the acceptance ratio and revenue to cost ratio compared to previously reported algorithms. We also analyzed the impact of position constraint and substrate network attribute on algorithm performance, as well as the utilization of the substrate network resources during embedding via simulation. The results showed that, under the constraint of substrate resource distribution and virtual network requests, the critical factor of improving success ratio is to reduce resource consumption during embedding.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.98-106
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• 2009

This paper proposes an optical wireless transfer agent method which realizes the continuous and swift data transfer of optical wireless terminals in optical wireless networks. The unguided wireless channel generally shows frequent link disconnections and propagation delays due to weak wireless links. Specially speaking, optical wireless channels have more vulnerable links and roaming propagation delays relative to the weakness of the previous RF channels due to their low signal connectivity and small geographic coverage. Conventional optical wireless network protocols did not consider any fault models about physical link faults. Consequently, they have shown data transfer inefficiency for both data link control and physical wireless link control. To overcome these optical wireless environmental problems, this paper suggests a new wireless access point (or base station) agent system, which provides wireless or mobile clients with previous link layer protocols compensated.

• 디지털산업정보학회논문지
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• 제8권1호
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• pp.47-53
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• 2012

Sensor networks and car networks that have different structure from that of conventional TCP/IP network require extreme network environment due to frequent change of connectivity. Because such extreme network environment has characteristics like unreliable link connectivity, long delay time, asymmetrical data transfer rate, and high error rate, etc., it is difficult to perform normally with the conventional TCP/P-based routing. DTNs (delay and disruption tolerant network) was designed to support data transfer in extreme network environment with long delay time and no guarantee for continuous connectivity between terminals. This study suggests an algorithm that limits the maximum number of copying transferred message to L by improving the spray and wait routing protocol, which is one of the conventional DTNs routing protocols, and using the azimuth and density data of the mobile nods. The suggested algorithm was examined by using ONE, a DTNs simulator. As a result, it could reduce the delay time and overhead of unnecessary packets compared to the conventional spray and wait routing protocol.

• 한국IT서비스학회지
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• 제18권4호
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• pp.97-113
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• 2019

With the development of sensor, communication and intelligent software technology, expectation of IoT-based service which can receive desired service automatically and anytime, anywhere is getting higher. In addition, IoT-based services have begun to anticipate the development of a hyper-connected society. Despite these expectations and anticipations, few studies have empirically identified ways to improve the intentions of prospective customers to use IoT-based services. Therefore, the purpose of this paper is to propose a theoretical model that can explain the factors that determine the intention of using IoT-based services. In addition, this study investigates what factors affect the intention to use IoT-based services focusing on the connectedness. Especially, perceived connectivity with the (virtual) community, unlike the connectivity with the machines, is newly proposed, to understand the IoT technology adoption behavior. The empirical results suggest that social relationship is one of the critical factors to affect the use of services running on interconnected technology such as IoT. When IoT-based service is recognized as a link to other communities, it has been found to have a positive effect on intention to use via perceived belongingness.

• 한국지능시스템학회논문지
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• 제23권3호
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• pp.191-195
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• 2013

본 논문에서는 방대한 웹 자원의 연결성을 더욱 증가시키기 위해 영어 위키피디아 문서로부터 한국어 위키피디아 문서로의 교차언어 링크를 자동으로 탐색하는 방법을 제안한다. 어구의 링크확률을 대략 추정하여 사용하던 기존의 방법에 비해, 본 연구에서는 위키피디아 문서 집합으로부터 추출한 제목 목록과 링크 확률과 같은 다양한 정보들과 개체명 인식 결과를 함께 사용하여 링크가 걸릴 앵커 후보를 선택한다. 앵커 후보를 한국어 대역어로 번역한 후, 대역어에 가장 적합한 한국어 웹문서를 찾아 교차언어 링크로 설정하게 된다. 실험한 결과 MAP 수치로 0.375를 얻었다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.127-130
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• 2017

최근 발전되고 있는 정보통신 IT기술은 자동차 시장에도 큰 영향을 미치며 발전하고 있다. 근래에는 운전자의 안전성과 편의성을 위해 IT 기술이 접목된 장치들이 장착 되고 있고 Smartphone의 확산과 더불어 더욱 발전하고 있다. 이러한 변화에 맞춰 Smartphone과 차량이 연동 가능한 System 개발이 필요하다. 본 논문에서는 자동차 회사가 제공하는 자동차 연결 service를 분석하고 사용자의 요구에 따라 차량 내 대부분의 Smart Device 응용 Program을 지원하고 제어 할 수 있는 향상 된 System을 구현했다. 또한 운전 규정을 만족시키지 못하는 응용 Program을 제한 할 수 있는 Program을 구현하고 향후 회사의 연결 System에 적용 할 수 있는 Scenario를 제안하고자 한다.

• International journal of advanced smart convergence
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• 제13권3호
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• pp.48-58
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• 2024

Fiber to the Home (FTTH) technology is among the most advanced broadband services, delivering voice, data, and television through a single optical fiber directly to customer premises, ensuring high-speed and reliable connectivity. The study conducted on Nepal Telecom's FTTH networks involved direct measurements from the optical line terminal to the fiber access point and optical network unit, providing detailed insights into network performance. Using the OptiSystem software, the analysis revealed a link loss of 24.99 dB, a Q-factor of 12.98, and a minimum Bit Error Rate (BER) of 7.31E-39, all within standard limits, which underscores the robustness of the network. The study also identified that the highest contributors to signal loss were connector loss, fiber attenuation, and fusion splices, emphasizing the importance of minimizing these factors to maintain optimal network performance. Overall, these findings highlight the critical aspects of FTTH network design and maintenance, ensuring that service providers can deliver high-quality broadband services to customers.

• Industrial Engineering and Management Systems
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• 제15권3호
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• pp.259-267
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• 2016

In Wireless Sensor Network, various routing protocols were employed by our Research and Development community to improve the energy efficiency of a network as well as to control the traffic by considering the terms, i.e. Packet delivery rate, the average end-to-end delay, network routing load, average throughput, and total energy consumption. While maintaining network connectivity for a long-term duration, it's necessary that routing protocol must perform in an efficient way. As we discussed Optimized Link State Routing protocol between all of them, we find out that this protocol performs well in the large and dense networks, but with the decrease in network size then scalability of the network decreases. Whenever a link breakage is encountered, OLSR is not able to periodically update its routing table which may create a redundancy problem. To resolve this issue in the OLSR problem of redundancy and predict link breakage, an enhanced protocol, i.e. S-OLSR (More Scalable OLSR) protocol has been proposed. At the end, a comparison among different existing protocols, i.e. DSR, AODV, OLSR with the proposed protocol, i.e. S-OLSR is drawn by using the NS-2 simulator.

• 한국통신학회논문지
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• 제39C권11호
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• pp.1159-1166
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• 2014

본 논문에서는 무선 USB 시스템에서 신뢰성과 연결성을 향상하기 위한 기법을 제안하였다. 무선USB 프로토콜은 고속의 전송속도를 지원하기 때문에, 실시간 멀티미디어 서비스 제공과 같은 응용분야에 적합하다. 하지만, 디바이스의 이동은 네트워크 토폴로지와 디바이스간 링크 상태의 급격한 변화를 야기하며, 네트워크의 성능 저하의 원인이 되기도 한다. 특히 사람의 이동이 빈번한 선박 네트워크 환경에서는 디바이스의 이동성이 더 심해진다. 본 논문에서는 기존의 무선 USB 표준에서 무선 채널의 상태 변화를 적절하게 대처하지 못하여 발생하는 네트워크 성능 저하 문제를 해결하는 릴레이 통신을 위한 자원 관리 기법을 제안하여 성능을 분석하였다.