• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.12
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• pp.1723-1728
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• 2021

C-ITS is an intelligent transportation system that can improve transportation convenience and traffic safety by collecting, managing, and providing traffic information between components such as vehicles, road infrastructure, drivers, and pedestrians. In Korea, road infrastructure is being built across the country through the C-ITS project, and various services such as real-time traffic information provision and bus operation management are provided. However, the current state-of-the-art road infrastructure and information linkage system are insufficient to build C-ITS. In this paper, considering the continuity of time in various spatial aspects, we proposed a group-type network-based traffic situation recognition system that can recognize traffic flows and unexpected accidents through information linkage between traffic infrastructures. It is expected that the proposed system can primarily respond to accident detection and warning in the field, and can be utilized as more diverse traffic information services through information linkage with other systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2321-2328
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• 2006

Today, SIP standard (The signalling protocol for the Internet phone service) raises to be the standard technique because the expandability is high and complexity is low. It is widely investigated and actively advocated to use Si81a1 ring protocol for SIP in VoIP service. SIP service can be applied even outside the Internet phone service; instance messaging and various multimedia technology are just an example. This paper proposed an embodiment proxy server for rambling support to use JAIN SIP API. It provides standard interface for testing the Proxy server for SIP and embodiment of user agent that transfer instant massaging and voice communication.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1052-1059
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• 2016

Video-on-Demand(VoD) is one of the most popular media streaming which attracted many researchers' attention. VMesh is one of the most cited works in the field of the VoD system. VMesh is proposed to solve the problem of random seeking functionality. However, a large number of the DHT(Distributed Hash Table) searches in VMesh is sill the main problem which needs to be solved. In order to reduce the number of the DHT searches, the clustered segment index(CSI) scheme is proposed. In this scheme, the video segments are divided into clusters. The segment information of the video segments, which are clustered into the same cluster, are stored in the same clustered segment index that can be searched by using the hash key. Each peer also can request the required segments by using this clustered segment index. The experiment results show that the number of the DHT searches in the proposed scheme is less than that of VMesh even in case of peers leave and join the network or peers perform the fast forward/backward operations.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.95-103
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• 2012

In this paper, we propose an efficient mobile P2P streaming architecture to minimize playback jitters in P2P overlay networks based on wired/wireless networks even though mobile peers experience the handover. In this architecture, mobile peers receive data in a push manner to maximize the data receiving speed before and after the handover. In addition, they can maintain the buffering above a specific level through handover prediction and re-selection of neighbor peers. By simulation experiments, we show that our proposed architecture can improve the performance significantly when the handover occurs compared to the existing mesh structure.

• Journal of Digital Contents Society
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• v.15 no.2
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• pp.251-261
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• 2014

In the typical P2P VOD system, it is very important to develop the fast and efficient peer searching scheme since the peers frequently join and leave to/from P2P system. This paper proposes a new peer searching scheme for P2P VOD system based on DHT network environment. The proposed scheme constructs DHT network by managing the peers having close playback starting times and close network locations into a peer all together. The peer information is mapped onto DHT nodes by hashing the key values each of which consists of the starting time and network location of the peer. From the simulation results, the number of messages required to search the partner peers are decreased, and the number of buffer maps exchanging among the peers are also decreased. The proposed scheme can reduce the average network distances among the partner peers. As a result, the proposed scheme makes routing more efficient and it saves the network resources by decreasing communication traffic overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1483-1490
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• 2009

Orthogonal frequency division multiplexing (OFDM) has been investigated as an enabling technology for future wireless communications such as ad hoc, mesh and sensor networks. However, prior works on bit-loading lack consideration of the constraints on energy and computing facility in sensor networks. In this paper, we suggest an adaptive bit allocation algorithm for a frequency selective fading channel environment which exploits channel state information obtained through a feedback channel. The proposed algorithm significantly reduces computational complexity and satisfies the power budget. Also, its throughput is comparable to the optimum solution. Simulation results support the claim stated.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11a
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• pp.115-118
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• 2003

최근 MOM 기술은 비즈니스 로직을 수행하는 애플리케이션 서버의 필수적인 구성요소로서 자리잡고 있으며, 보통 수백에서 수천의 클라이언트 요청을 처리할 수 있는 능력을 제공한다. MOM 은 이러한 대용량의 클라이언트 요청을 효과적으로 처리하기 위해서 효율적이고 확장성있는(스케일러블) 네트워크 모듈이 필요하며, 다양한 네트워크 프로토콜을 지원해야 한다. MOM이 기본적으로 지원하는 메시징 기능은 PTP(Point-To-Point)와 publish/subscribe 메시징 도메인으로 나뉘는데 이 논문에서는 두 가지 메시징 도메인과 그룹통신 메시징 서비스 기능을 동시에 지원하는 MoIM-Message 시스템의 하부 통신 모듈의 설계에 대해 기술한다. PTP와 publish/subscribe 메시징을 지원하기 위해 세가지 프리미티브 메시징 오퍼레이션인 "synchronous send", "synchronous receive", "asynchronous receive"를 정의하였으며 하부 통신 모듈 역할을 하는 메시지 트랜스포트 관리 계층내의 트랜스포트 관리자 내에 구현되었다. 트랜스포트 관리자는 다양한 트랜스포트 프로토콜을 적용할 수 있도록 하기 위해 트랜스포트 어댑터로 설계되었으며, 대량의 통신 요청을 효과적으로 처리하기 위해 "polling with multiple service thread model" 기법을 적용하여 구현되었다. 또한, 모바일 클라이언트 환경을 지원하기 위해 클라이언트 측 통신 모듈을 IPaq PDA 상에 포팅하였다. 본 논문에서 제안하는 세 가지 프리미티브 메시징 오퍼레이션을 제공하는 통신 모듈은 MOM이 기본적으로 지원해야 할 메시징 도메인과 대용량의 클라이언트 요청을 효율적으로 처리할 수 있는 구조를 가진다.es}8$ 모드를 모두 사용한 경우와 $8{\times}8$ 단일모드를 사용한 경우보다 계산 시간이 감소하였음을 확인하였다.행중인 MoIM-Messge서버의 네트워크 모듈로 다중 쓰레드 소켓폴링 모델을 적용하였다.n rate compared with conventional face recognition algorithms. 아니라 실내에서도 발생하고 있었다. 정량한 8개 화합물 각각과 총 휘발성 유기화합물의 스피어만 상관계수는 벤젠을 제외하고는 모두 유의하였다. 이중 톨루엔과 크실렌은 총 휘발성 유기화합물과 좋은 상관성 (톨루엔 0.76, 크실렌, 0.87)을 나타내었다. 이 연구는 톨루엔과 크실렌이 총 휘발성 유기화합물의 좋은 지표를 사용될 있고, 톨루엔, 에틸벤젠, 크실렌 등 많은 휘발성 유기화합물의 발생원은 실외뿐 아니라 실내에도 있음을 나타내고 있다.>10)의 $[^{18}F]F_2$를 얻었다. 결론: $^{18}O(p,n)^{18}F$ 핵반응을 이용하여 친전자성 방사성동위원소 $[^{18}F]F_2$를 생산하였다. 표적 챔버는 알루미늄으로 제작하였으며 본 연구에서 연구된 $[^{18}F]F_2$가스는 친핵성 치환반응으로 방사성동위원소를 도입하기 어려운 다양한 방사성의 약품개발에 유용하게 이용될 수 있을 것이다.었으나 움직임 보정 후 영상을 이용하여 비교한 경우, 결합능 변화가 선조체 영역에서 국한되어 나타나며 그 유의성이 움직임 보정 전에 비하여 낮음을 알 수 있었다. 결론: 뇌활성화 과제 수행시에 동반되는 피험자의 머리 움직임에 의하여 도파민 유리가 과대평가되었으며 이는 이 연구에서 제안한 영상정합을 이용한 움직임 보정기법에

• Journal of Digital Convergence
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• v.10 no.6
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• pp.259-267
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• 2012

Internet telephony is an Internet service which supports voice telephone using VoIP technology on the IP-based Internet. It has some advantages in that voice telephone services can be accompanied with multimedia services such as video communication and messaging services. Recently, the introduction of smart phones has led to a growth in social networking services and thus, the research and development of Internet telephony has been actively progressed and has the potential to become a replacement for the telephone service that is currently being used. In this paper we designed and implemented an Internet telephony network system which is developed by using Asterisk and open source softwares. It is developed on the linux system and has some features such as VoIP telephony service between SIP phones, voice mail, and call recording. It also supports web-based functions such as SIP users and server system management that is implemented by Apache web server and PHP programs. Afterwards, this system will be applied as VoIP network base technology for small sized companies and organizations. It will paly a role for encouraging companies to use open source softwares.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.49-55
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• 2007

Recently, with the IPTV services, e-learning, real-time broadcasting and e-contents, many application services need the multicasting routing protocol. In this paper, the performance of the algorithm to assign the rendezvous router (RP: rendezvous point) in the center-based multicasting mesh network is analyzed. The estimated distance to select RP in the candidate nodes is calculated, and the node minimizing the distance is selected as the optimal RP. We estimate the distance by using the maximum distance, average distance, and mean of the maximum and average distance between the RP and members. The performance of the algorithm is compared with the optimal algorithm of all enumeration. With the assumptions of mesh network and randomly positioned for sources and members, the simulations for different parameters are studied. From the simulation results, the performance deviation between the algorithm with minimum cost and optimal method is evaluated as 6.2% average.

• Journal of Digital Convergence
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• v.18 no.5
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• pp.249-256
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• 2020

The session initiation protocol (SIP) is a signaling protocol, which is used to controlling communication session creation, manage and finish over Internet protocol. Based on it, we can implement various services like voice based electronic commerce or instant messaging. Recently, Qiu et al. proposed an enhanced password authentication scheme for SIP. However, this paper withdraws that Qiu et al.'s scheme is weak against the off-line password guessing attack and has denial of service problem. Addition to this, we propose an improved password authentication scheme as a remedy scheme of Qiu et al.'s scheme. For this, the proposed scheme does not use server's verifier and is based on elliptic curve cryptography. Security validation is provided based on a formal validation tool ProVerif. Security analysis shows that the improved authentication scheme is strong against various attacks over SIP.