• Journal of KIISE:Computer Systems and Theory
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• v.33 no.6
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• pp.326-336
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• 2006

Due to the evolution of wired and wireless communication technologies and the Internet, multimedia services such as Internet broadcast and VOD have been prevalent recently. RTP is designed to be suitable for transmission of real-time multimedia data on the Internet by IETF While a variety of applications have utilized different RTPs implemented as a library, embeddedRTP is RTP-based kernel-level protocol that resolved performance issues of this kind of RTPs. This paper proposes the ExtendedERTP protocol based on existing embeddedRTP. This new protocol resolves a couple of issues such as packet processing overhead and buffer requirement and combines its APIs with BSD socket APIs which have been widely utilized in network applications. This paper demonstrates that this integration makes it possible to transmit real-time multimedia data through the accustomed interface of BSD socket APIs with nominal extra overhead. This paper also proposes a scheme for improving packet processing time by 15$\sim$20% and another scheme for reducing memory requirement for packet processing to about 3.5%, comparing with those of embeddedRTP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1173-1181
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• 2007

A number of routing algorithms have been studied for wireless mobile ad-hoc network. Among them, the AODV routing algorithm with on-demand method periodically transmits hello message and monitors link state during data transmission in order to maintain routing paths. When a path is disconnected, a node that senses it transmits a RERR packet to the transmitting node or transmits a RREQ locally so that the path could be repaired. With that, the control packet such as a RREQ is broadcast, which causes the consumption of bandwidth and incurs data latency. This paper proposes a LRRLBP algorithm that locally repairs a path by predicting link state before disconnecting the path based on the AODV routing protocol for solving such problems. Intensive simulations with the results using NS-2 simulator are shown for verifying the proposed protocol.

• The KIPS Transactions:PartD
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• v.8D no.3
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• pp.221-232
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• 2001

Due to rapid advance of wireless communication technology, demand on data services in mobile environment is gradually increasing. Caching at a mobile client could reduce bandwidth consumption and query response time, and yet a mobile client must maintain cache consistency. It could be efficient for the server to broadcast a periodic cache invalidation report for cache consistency in a cell. In case that long period of disconnection prevents a mobile client from checking validity of its cache based solely on the invalidation report received, the mobile client could request the server to check cache validity. In doing so, some schemes may be more efficient than others depending on the number of available channels and the mobile clients involved. In this paper, we propose new cache consistency schemes, effects, efficient especially (1) when channel capacity is enough to deal with the mobile clients involved or (2) when that is not the case, and evaluate their performance.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.75-82
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• 2009

In this parer, we propose a new way of improving DGNSS service using combination of multiple SBAS information. Because SBAS uses Geostationary Earth Orbit (GEO) satellites, it has very large coverage but it can be unavailable in urban canyon because of visibility problem. R. Chen solved this problem by creating Virtual Reference Stations (VRS) using the SBAS signal [1]. VRS converts SBAS signal to RTCM signals corresponding its location, and broadcast the converted RTCM signals over the wireless internet. This method can solve the visibility problem cost effectively. Furthermore it can solve DGNSS coverage problem by creating just a transmitter instead of a reference station. Developing above method, this paper proposes the methods that integrate two or more SEAS signals into one RTCM signal and broadcast it. In Korea, MSAS signal is available even though it is not officially certified for Korean users. As a Korean own SBAS-like system, there is the internet-based KWTB (Korean WADGPS Test Bed) which we developed and released at ION GNSS 2006. As a result, virtually two different SBAS corrections are available in Korea. In this paper, we propose the integration methods for these two independent SBAS corrections and present the test results using the actual measurements from the two systems. We present the detailed algorithm for these two methods and analyze the features and performances of them. To verify the proposed methods, we conduct the experiment using the logged SBAS corrections from the two systems and the RINEX data logged at Dokdo monitoring station in Korea. The preliminary test results showed the improved performance compared to the results from two independent systems, which shows the potential of our proposed methods. In the future, the newly developed SBASs will be available and the places which can access the multiple SBAS signals will increase. At that time, the integration or combination methods of two or more SBASs will become more important. Our proposed methods can be one of the useful solutions for that. As an additional research, we need to extend this research to the system level integration such as the concept of the decentralized W ADGPS.

• The KIPS Transactions:PartD
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• v.9D no.6
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• pp.1017-1024
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• 2002

According as mobile computing environment is generalized by development of wireless networking technology and communication device, mobile host uses local cache for extensibility and early response time. and reduction of limited bandwidth. This time, between mobile host and mobile support station cache need consistency interested person of done data accordingly much techniqueses propose. Existent consistency techniques because detection based techniqueses are used mainly and broadcast periodic invalid message considering frequent disconnection. However, these techniqueses increase abort step through increase or delay of transmission message number by accuracy examination of data. Therefore, because mobile host deletes cached data, and extensity are decreased. Techniques that is proposed in this paper did to perform refering update frequency about object that page request or when complete update operation happens to solve these problem. Therefore, have advantage that response is fast because could run write intention declaration or update by update frequency electively asynchronously when update operation consists and abort step decreases. Also, improved extensity running delete or propagation electively according to update frequency about periodic invalid message gone since disconnection.

• Broadcasting and Media Magazine
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• v.11 no.4
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• pp.104-117
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• 2006

In this Paper, we analyze the application of Interactive Data Broadcasting in DMB(Digital Multimedia Broadcasting) in the accordance with convergence of service and technology. With the acceleration of digital convergence in the Ubiquitous period substantial development of digital media technology and convergence of broadcasting and telecommunication industry are being witnessed. Consequently these results gave rise to newly combined-products such as DMB(Digital Multimedia Broadcasting), WCDMA(Wide-band code division multiple access), Wibro(Wireless Broadband Internet), IP-TV (Internet protocol TV) and HSDPA(High speed downlink packet access). The preparatory stage for the implementation of Interactive Data Broadcasting Service will be reached by the end of December, 2006. DMB is the first result of a successful convergence service between Broadcasting and Telecommunication in new media era. Multimedia technology and services are the core elements of DMB. The Data Broadcasting will not only offer various services of interactive information such News, Weather, Broadcasting Program etc, but also be linked with characteristic function of mobile phone such as calling and SMS(Short Message Service) via Return Channel.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.136-138
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• 2005

무선 브로드캐스트 환경에서는 모바일 클라이언트의 제한된 배터리와 클라이언트에서 서버로의 제한된 상향 대역폭 등의 문제로 기존의 동시성 제어 기법을 그대로 사용할 수 없다. 이런 문제를 해결하고자 많은 동시성 제어 기법들이 연구되어 왔는데, 지금까지 제안된 기법들은 편향된 데이터의 접근 패턴을 반영한 브로드캐스트 환경을 고려하지 못하고 있다. 무선 브로드캐스트 환경에서 서버는 일반적으로 모바일 클라이언트의 접근 패턴을 고려하여 편향된 접근 빈도를 갖는 데이터 아이템을 브로드캐스트 한다. 본 논문에서는 무선 브로드캐스트 환경에서 편향된 데이터 접근 패턴을 고려한 동시성 제어 기법을 제안한다. 제안하는 기법은 브로드캐스트 디스크 모델에서 전체 메이저 브로드캐스트 주기마다. 모바일 트랜잭션을 위한 제어 정보를 보내는 것이 아니라 일정한 마이너 브로드캐스트 주기마다. 제어 정보를 전송한다. 이는 접근 빈도가 놓은 데이터가 갱신된 경우 갱신된 내용을 마이너 그룹마다 반영하므로 읽기 전용 트랜잭션이 접근하는 데이터가 최신 정보임을 보장할 뿐만 아니라 갱신 트랜잭션이 최종 검증을 위해서 상향 통신 대역폭을 이용하는 횟수를 줄이고, 보다. 빠른 재실행을 통해 모바일 트랜잭션의 평균 응답시간을 줄여줄 수 있다. 또한 모바일 트랜잭션의 요청이 편향된 경우, 반복적인 트랜잭션의 중단, 재실행으로 인한 성능 저하를 개선하고자 정적 백오프 기법을 이용하여 모바일 트랜잭션 간 충돌 가능성을 줄여준다. 마지막으로 시뮬레이션을 통해 기존의 기법들에 비해 평균 접근 시간, 상향 통신 대역폭 등의 사용량이 현저히 줄어드는 것을 보임으로써 제안하는 기법의 성능을 검증한다.한 평균 access time을 최소화하는 동시에 클라이언트들의 제한된 에너지 소비를 최소화하는데 목적이 있다. 제안기법에 대한 평가는 수학적 분석을 통해 HIDAF 기법과 기존의 브로드캐스트 기법의 성능을 비교 분석한다.하였으나 사료효율은 증진시켰으며, 후자(사양, 사료)와의 상호작용은 나타나지 않았다. 이상의 결과는 거세비육돈에서 1) androgen과 estrogen은 공히 자발적인 사료섭취와 등지방 침적을 억제하고 IGF-I 분비를 증가시키며, 2) 성선스테로이드호르몬의 이 같은 성장에 미치는 효과의 일부는 IGF-I을 통해 매개될 수도 있을을 시사한다. 약 $70 {\~} 90\%$의 phenoxyethanol이 유상에 존재하였다. 또한, 미생물에 대한 항균력도 phenoxyethanol이 수상에 많이 존재할수록 증가하는 경향을 나타내었다. 따라서, 제형 내 oil tomposition을 변화시킴으로써 phenoxyethanol의 사용량을 줄일 수 있을 뿐만 아니라, 피부 투과를 감소시켜 보다 피부 자극이 적은 저자극 방부시스템 개발이 가능하리라 보여 진다. 첨가하여 제조한 curd yoghurt는 저장성과 관능적인 면에서 우수한 상품적 가치가 인정되는 새로운 기능성 신제품의 개발에 기여할 수 있을 것으로 사료되었다. 여자의 경우 0.8이상이 되어서 심혈관계 질환의 위험 범위에 속하는 수준이었다. 삼두근의 두겹 두께는 남녀 각각 $20.2\pm8.58cm,\;22.2\pm4.40mm$으로 남녀간에 유의한 차이는 없었다. 조사대상자의 식습관 상태는 전체 대상자의 $84.4\%$가 대부분

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.133-143
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• 2023

As drones (also known as UAV) become popular with advanced information and communication technology (ICT), they have been utilized for various fields (agriculture, architecture, and so on). However, malicious attackers with advanced drones may pose a threat to critical national infrastructures. Thus, anti-drone systems have been developed to respond to drone threats. In particular, remote identification data (R-ID)-based UAV detection and identification systems that detect and identify illegal drones with R-ID broadcasted by drones have been developed, and are widely employed worldwide. However, this R-ID-based UAV detection/identification system is vulnerable to security due to wireless broadcast characteristics. In this paper, we analyze the security vulnerabilities of DJI Aeroscope, a representative example of the R-ID-based UAV detection and identification system, and propose a replay-attack-based neutralization method using the analyzed vulnerabilities. To validate the proposed method, it is implemented as a software program, and verified against four types of attacks in real test environments. The results demonstrate that the proposed neutralization method is an effective neutralization method for R-ID-based UAV detection and identification systems.