• 전기학회논문지
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• 제65권12호
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• pp.2218-2224
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• 2016

Opportunistic routing is designed for an environment where there is no stable end-to-end routing path between source node and destination node, and messages are forwarded via intermittent contacts between nodes and routed using a store-carry-forward mechanism. In this paper, we consider PRoPHET(Probabilistic Routing Protocol using History of Encounters and Transitivity) protocol as a base opportunistic routing protocol and propose an efficient context-aware opportunistic routing protocol by using the context information of delivery predictability and node type, e.g., pedestrian, car, and tram. In the proposed protocol, the node types of sending node and receiving node are checked. Then, if either sending node or receiving node is tram, messages are forwarded by comparing the delivery predictability of receiving node with predefined delivery predictability thresholds depending on the combination of sending node and receiving node types. Otherwise, messages are forwarded if the delivery predictability of receiving node is higher than that of sending node, as defined in PRoPHET protocol. Finally, we analyze the performance of the proposed protocol from the aspect of delivery ratio, overhead ratio, and delivery latency. Simulation results show that the proposed protocol has better delivery ratio, overhead ratio, and delivery latency than PRoPHET protocol in most of the considered simulation environments.

• 한국통신학회논문지
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• 제33권8B호
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• pp.636-645
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• 2008

센서 네트워크에 있어서 정보 전송 노드인 근원지의 위치를 악의적 추적자로부터 보호하기 위해 길이가 긴 경로를 통해 단일 메시지를 전송하는 라우팅에서는 전달 지연이 길어지는 단점이 있다. 본 논문에서는 전송 메시지가 사전에 주어진 경우, 근원지 위치를 보호하면서 최소 비용의 단일 경로를 이용하여 이들을 목적지로 전달하는 문제는 NP-complete 임을 보인다. 이러한 양 극단의 절충 방안이라 할 수 있는 경로 당 $\omega$개의 메시지들을 전송하도록 하여 근원지의 위치 보호 능력을 높이면서도 전달 지연을 저감시키는 라우팅 프로토콜 GSLP-$\omega$ (GPSR-based Source Location Privacy with crew size $\omega$)를 제안한다. 평가 기준으로는 목적지와의 최단 경로의 홉 수를 기준으로 정규 안전 기간(NSP: Normalized Safety Period)과 정규 전달 지연(NDL; Normalized Delivery Latency)을 고려한다. 평균 차수(degree)가 8인 노드 50,000개로 구성되는 네트워크 토폴로지 100개를 생성하여 측정한 결과 제안된 GSLP-$\omega$는 GSLP-$\omega$의 초기 버전인 GSLP와 기존의 대표적인 근원지 위치 보호 라우팅 프로토콜인 PR-SP(Phantom Routing - Single Path)보다 더 높은 안전 기간을 보였다. 전달 지연에서는 GSLP-$\omega$가 PR-SP보다 높으나 GSLP 보다는 낮은 것으로 나타났다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.2143-2159
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• 2011

The hybrid architecture of content delivery networks (CDN) and peer-to-peer overlay networks (P2P) is a promising technology enables effective real-time streaming services. It complements the advantages of quality control and reliability in a CDN, and the scalability of a P2P system. With real-time streaming services, however, high connection setup and media delivery latency are becoming the critical issues in deploying the CDN-P2P system. These issues result from biased peer selection without location awareness or content awareness, and can lead to significant service disruption. To reduce service disruption latency, we propose a group-based CDN-P2P hybrid architecture (iCDN-P2P) with a location/content-aware selection of peers. Specifically, a SuperPeer network makes a location-aware peer selection by employing a content addressable network (CAN) to distribute channel information. It also manages peers with content awareness, forming a group of peers with the same channel as the sub-overlay. Through a performance evaluation, we show that the proposed architecture outperforms the original CDN-P2P hybrid architecture in terms of connection setup delay and media delivery time.

• 인터넷정보학회논문지
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• 제20권5호
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• pp.113-119
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• 2019

최근 상용화된 5G 이동통신의 주요한 특징은 High Data Rate와 Connection Density 그리고 Low Latency로 대표할 수 있는데, 이중 기존 4G와 가장 차별되는 특징은 Low Latency로 다양한 새로운 서비스 제공의 기반이 될 것이다. 이러한 특징을 활용한 서비스로는 AR, 자율주행 등이 검토되고 있으며 관련표준에서도 5G Network Latency 논의를 진행하고 있다. 그러나 서비스 관점의 E2E Latency 논의는 많이 부족한 것이 사실이다. 5G에서 Low Latency를 달성을 위한 최종목표는 RTD 기준 Air Interface 1ms 달성으로 이는 '20년 초 Rel-16을 통한 URLLC(Ultra-reliable Low Latency Communications)를 통해 가능하며, 추가적으로 MEC(Moble Edge Computing)를 통한 Network latency 감소도 연구 중이다. 전체 5G E2E Latency는 5G Network 관련 외에도 다양한 요인이 존재하는데, 주요 요인으로는 5G Network과 서비스 제공을 위한 IDC Server 사이의 경로에 놓인 선로/장비 Latency, 단말 App과 Server 내 서비스 처리를 위한 Processing Latency 등이 존재한다. 한편, 서비스 초기 Setup을 위한 Latency와 서비스가 지속 중인 경우의 Latency를 구분하여 세부 서비스 요구사항에 대하여 연구하는것도 필요한데, 이를 위해 본 논문에서는 서비스 초기 Setup과 관련하여 다음과 같은 세가지 요인에 대하여 검토를 진행하였다. 첫째로 (1) Data호 Setup시에 발생 가능한 Latency, 둘째 전력 효율화를 위한 (2) CRDX On/Off에 따른 영향, 마지막으로 (3) H/O가 발생되는 경우에 Latency에 대하여 Latency에 미치는 영향을 실험과 분석을 제시했다. 이를 통해 우리는 Low Latency가 필요한 서비스의 초기 Setup시에 Latency와 관련된 서비스 요구사항 및 기획에 기여할 수 있을 것으로 기대한다.

• 한국정보컨버전스학회:학술대회논문집
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• 한국정보컨버전스학회 2008년도 International conference on information convergence
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• pp.199-204
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• 2008

Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad-hoc method of deployment. Considerable research has been focused at overcoming these deficiencies through faster media accessing, more energy efficient routing, localization algorithms and system design. Our research attempts to provide a method of improvement MAC performance in these issues. We show that traditional carrier-sense multiple access(CSMA) protocols like IEEE 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size, We present more efficient method of a medium access for real-time wireless sensor networks. Proposed MAC protocol is a randomized CSMA protocol, but unlike previous legacy protocols, does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, it carefully decides a fixed-size contention window, non-uniform probability distribution of transmitting in each slot within the window. We show that it can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely used simulator ns-2. We, finally show that proposed MAC scheme comes close to meeting bounds on the best latency achievable by a decentralized CSMA-based MAC protocol for real-time wireless sensor networks which is sensitive to latency.

• 정보처리학회논문지D
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• 제12D권2호
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• pp.303-308
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• 2005

중앙집중 구조의 멀티미디어 디지털콘텐트 서비스에서는 서버의 과부하 문제와 네트워크 트래픽의 급격한 증가 문제가 발생한다. 최근에는 이러한 문제점을 해결하기 위한 디지털콘텐트 전송기술로 CDN에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 디지털콘텐트의 전송 및 관리 시스템에서, 보안성능과 처리지연시간을 개선한 시스템인 SDCDS(Secure Digital Content Delivery System)을 설계하였다. SDCDS에서는 CDN에서의 보안성과 이에 따른 처리 지연시간 개선을 목적으로 하고 있다. 이를 위해서는 보안방식과 캐싱 방식을 CDN의 구조적 특성을 고려하여 설계하여야 한다. SDCDS에서는 공개키 기반 보안 방식을 CDN의 구조적 특성을 반영하도록 설계하였고, 암호화된 DC와 일반 DC의 그룹별 캐싱 방식의 향상된 캐싱 성능을 통해 처리 지연시간을 개선하였다. 또한 실험을 통해 제안 시스템의 성능을 평가하였다.

• The Journal of Korean Physical Therapy
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• 제15권2호
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• pp.182-195
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• 2003

This study investigated the effects of triamcinolone acetonide by iontophoretic transdermal drug delivery on anti-inflammatory action into the rats and which had carrageenan-induced hyperalgesia and edema in the feet, trauma-induced tissue damage in the thigh. Each group was treated under the fellowing conditions. 1. Group I : Control group 2. Group II : Application of direct current 3. Group III : Application of 0.1$\%$ triamcinolone acetonide solution 4. Group IV : Iontophoresis of 0.1$\%$ triamcinolone acetonide solution The degree of anti-inflammation was evaluated by the paw withdrawal latency, the change in volume of foot the change of paw edema, histological change in rats. 1. In paw withdrawal latency, group IV showed the most significant therapeutic effect than the other groups at 0, 3, 6 and 9 hours(p < 0.001). 2. In paw edema experiment in the foot, group IV showed the most significant effect than group I at 0, 3, 6 and 9 hours. It meant that there was effective anti-inflammatory reaction in group I (p < 0.001). 3. In the light microscopic observation, group IV showed the most significant reduction of haemorrhage, hyperemia and infiltrative inflammation. From the results, the iontophoresis with triamcinolone acetonide is more effective than using each groups. It is one of the effective physical agent which delivered large molecular weight drug into the body. The continuous study is needed for many interesting issues of iontophoretic transdermal drug delivery in new future.

• 한국통신학회논문지
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• 제34권8A호
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• pp.600-609
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• 2009

기존의 IEEE 802.11 DCF(Distributed Coordination Function)와 같은 전통적인 CSMA(carrier sense multiple access) 프로토콜은 네트워크 규모가 커짐에 따라서 성능의 급격한 감쇠와 전송 지연 증가를 초래한다. 이러한 문제를 효과적으로 해결하기 위하여 본 논문에서는 무선 센서 네트워크에 적합한 MAC(medium access control) 프로토콜을 제안한다. 기존의 DCF 프로토콜은 데이터 전송을 위한 슬롯(slot)을 선택할 때 패킷 충돌로 인한 재전송이 반복될 때 마다 크기가 커지는 경쟁 윈도우(contention window) 내에서 일반 확률 분포(uniform probability distribution)를 이용한 랜덤(random) 선택 기법을 사용하지만 제안한 프로토콜에서는 전송 지연을 최대한 감소시키기 위하여 경쟁 윈도우의 크기를 고정시키고, 전송 슬롯을 보다 효율적으로 선택하도록 비 균등(non-uniform)확률 분포를 사용하여 전송 슬롯을 랜덤하게 선정한다. 시뮬레이션을 통하여 제안한 프로토콜이 802.11 MAC 표준에 비하여 전송 지연이 감소함을 보여 전송 지연에 민감한 실시간 무선 센서 네트워크의 최적 지연 한계점(best latency bound)을 충족시키는 프로토콜임을 입증한다.

• Journal of Ginseng Research
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• 제39권2호
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• pp.116-124
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• 2015

Background: Ginseng, the root of Panax ginseng (PG), is used widely as a herbal medicine to prevent and treat various diseases. Panax ginseng has pharmacological effects on neurodegenerative diseases such as Alzheimer's disease (AD). The present study evaluated the neuroprotective effects of PG and its possible neuroprotective mechanisms in advanced glycation end product (AGE)-induced AD in a rat model. Methods: Advanced glycation end products were injected bilaterally into the CA3 region of the rats' brains. The Morris water maze test and step-down type passive avoidance test were performed to evaluate their memory and cognitive abilities. The oxidation indexes in the hippocampus were detected. Immunohistochemistry was conducted to visualize the receptors for advanced glycation end products (RAGEs) and nuclear factor-kappa-light-chain-enhancer of activated B cell (NF-${\kappa}B$). Results: Behavioral results showed that PG (1 g/kg, 0.5 g/kg, and 0.25 g/kg) significantly shortened the escape latency, remarkably increased the number of crossing times, significantly decreased the number of errors, and prolonged the latency in rats with AGE-induced AD. Panax ginseng also significantly reduced the malondialdehyde level, increased the glutathione content, and increased superoxide dismutase activity in the hippocampus. Panax ginseng significantly decreased the expression of RAGE and NF-${\kappa}B$. The blockade of anti-RAGE antibody could significantly reduce AGE-induced impairments and regulate these expressions. Conclusion: Our results demonstrated that PG significantly inhibits AGE-induced memory impairment and attenuates Alzheimer-like pathophysiological changes. These neuroprotective effects of PG may be associated with the RAGE/NF-${\kappa}B$ pathway. Our results provided the experimental basis for applying PG in preventing and treating AD.

• Journal of Communications and Networks
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• 제17권3호
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• pp.306-320
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• 2015

Due to an explosive growth in services running in different datacenters, there is need for service selection and routing to deliver user requests to the best service instance. In current solutions, it is generally the client that must first select a datacenter to forward the request to before an internal load-balancer of the selected datacenter can select the optimal instance. An optimal selection requires knowledge of both network and server characteristics, making clients less suitable to make this decision. Information-Centric Networking (ICN) research solved a similar selection problem for static data retrieval by integrating content delivery as a native network feature. We address the selection problem for services by extending the ICN-principles for services. In this paper we present Queue and Latency, a network-driven service selection algorithm which maps user demand to service instances, taking into account both network and server metrics. To reduce the size of service router forwarding tables, we present a statistical method to approximate an optimal load distribution with minimized router state required. Simulation results show that our statistical routing approach approximates the average system response time of source-based routing with minimized state in forwarding tables.