• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.1
• /
• pp.80-84
• /
• 2010

Data multicasting from a source to multiple sinks in wireless sensor networks is used to achieve both reducing communication costs and energy efficiency. Almost all existing schemes for the multicasting might be effectively performed by optimal construction of a multicasting tree between a source and multiple stationary sinks. However, in practical sensor applications, sinks could move around on the wireless sensor networks for own missions, such as scouting of soldiers and saving lives of victims by firefighters. Unfortunately, the sink mobility causes frequent entire reconstruction of the multicasting tree and thus it leads to exhaustion of battery power of sensors. Hence, we propose an energy-efficient multicast protocol to support multiple mobile sinks by the local multicast tree reconstruction, called Local Update-based geographic Multicasting for Mobile sinks (LUMM) for wireless sensor networks. Our simulation results show that our scheme for mobile sinks is more efficient in terms of energy resource management than other exist works.

• Journal of KIISE:Computing Practices and Letters
• /
• v.11 no.2
• /
• pp.124-132
• /
• 2005

We propose a method using a transformation of an object and a scene tree in order to author MPEG-4 contents for mobile devices in this paper. The method transforms media objects in the scene into geometry objects in order to reduce initial loading time of the contents, and reduces an external form of each object in a scene of the content for presenting it efficiently on the small interface of mobile devices. Therefore, the contents for mobile devices are reconstructed by the method. An original object in the scene is presented on a mobile device when a user clicks a related geometry object. The method was applied to a conventional authoring tool, so we could find that the method showed an efficient presentation of MPEG-4 contents on mobile devices.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.7A
• /
• pp.1028-1036
• /
• 2000

In this paper, an error-resilient image compression technique using wavelet transform is proposed. The zerotree technique that uses properties of statistics, energy and directions of wavelet coefficients in the space-frequency domain shows effective compression results. Since it is highly sensitive to the propagation of channel errors, evena single bit error degrades the whole image quality severely. In the proposed algorithm, the image is encoded by the SPIHT(Set Partitioning in Hierarchical Trees) algorithm using the zerotree coding technique. Encoded bitstreams are partitioned into some blocks using the subband correlations and then fixed-length blocks are made by using the effective bit reorganization algorithm. finally, an effective bit allocation technique is used to limit error propagation in each block. Therefore, in low BER the proposed algorithm shows similar compression performance to the zerotree compression technique and in high BER it shows better performance in terms of PSNR than the conventional methods.

• The Journal of Information Technology
• /
• v.3 no.2
• /
• pp.63-72
• /
• 2000

The peformance and quality of Web sites are often being estimated by the frequency that the users approach its site. This paper suggest how a link-editing method can automatically fix a poor organization by calculating each page's relative popularity, and how improve fix poor pages. Page's relative popularity depended on only cases where the objective Is to make it easier for a user to find the requested data; the faster the access, the better the organization of the Web sites according to tree depth.

• The KIPS Transactions:PartB
• /
• v.13B no.2 s.105
• /
• pp.115-120
• /
• 2006

In This Paper, We Propose The Method To Reconstruct And Estimate Partially Occluded Elliptical Objects In Images From Overlapping And Cutting. We Present The Robust Method For Recognizing Partially Occluded Objects Based On Symmetry Properties, Which Is Based On The Contours Of Elliptical Objects. A Proposed Method Provides Simple Techniques To Reconstruct Occluded Regions Via A Region Copy Using The Symmetry Axis Within An Object. Based On The Estimated Parameters For Partially Occluded Objects, We Perform Object Recognition On The Classifier. Since A Proposed Method Relies On Reconstruction Of The Object Based On The Symmetry Properties Rather Than Statistical Estimates, It Has Proven To Be Remarkably Robust In Recognizing Partially Occluded Objects In The Presence Of Scale Changes, Object Pose, And Rotated Objects With Occlusion, Even Though h Proposed Method Has Minor Limitations Of Object Poses.

• Journal of KIISE:Computer Systems and Theory
• /
• v.35 no.9_10
• /
• pp.476-484
• /
• 2008

Most string problems and their solutions are relevant to diverse applications such as pattern matching, data compression, recently bioinformatics, and so on. However, there have been few works on the relations between string problems and cryptographic problems. In this paper, we consider the following string reconstruction problems and show how these problems can be applied to cryptography. Given a string x of length n over a constant-sized alphabet ${\sum}$ and a set W of strings of lengths at most an integer $k({\leq}n)$, the first problem is to find the sequence of strings in W that reconstruct x by the minimum number of concatenations. We propose an O(kn+L)-time algorithm for this problem, where L is the sum of all lengths of strings in a given set, using suffix trees and a shortest path algorithm for directed acyclic graphs. The other is a dynamic version of the first problem and we propose an $O(k^3n+L)$-time algorithm. Finally, we show that exponentiation problems that arise in cryptography can be successfully reduced to these problems and propose a new solution for exponentiation.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.04b
• /
• pp.517-519
• /
• 2002

MPEG-4 시스템에서는 씬 디스크립션 언어로 BIFS와 XMT를 정의하고 있다. 씬 디스크립션은 MPEG-4 씬을 구성하는 객체들의 시공간적 구성관계를 기술하는 것이다. 본 논문에서는 MPEG-4에 정의된 다양한 데이터 포맷과 3차원 MPEG-4 객체의 효율적인 재생 지원을 위해 XMT에 노드를 기술하고 재생하는 시스템을 제안한다. 제안하는 시스템은 XHT 파일을 XMT 파서를 이용하여 파싱하고, 그 결과로 생성되는 DOM 트리에 DOM APIs를 이용하여 재생에 필요한 노드 정보를 얻는다. 사용자 인터페이스상에서는 DOM 트리에서 얻은 노드를 기준으로 그래픽 라이브러리를 호출하여 화면상에 재생하는 구조를 가진다. 또한 재생이 진행되는 도중에 발생하는 사용자 이벤트도 감지 및 처리하며, 필요한 정보에 따라서 화면과중간 자료구조를 재구성한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2001.10c
• /
• pp.433-435
• /
• 2001

IETF Mobile IP는 이동 컴퓨팅 환경에서 IP 멀티캐스트를 지원하기 위한 메커니즘으로 HA 기반 라우팅과 FA 기반 라우팅을 간략히 언급하고 있다. FA 기반 라우팅의 경우, 단말기 이동 시 멀티캐스트 트리를 재구성하는 오버헤드가 존재하는 단점이 있다. 반면. HA 기반 라우팅의 경우, 단말기 이동시 경로 최적화가 이루어지지 않는 단점에도 불구하고. 멀티캐스트 트리 수정에 대한 오버헤드가 존재하지 않은 장점이 있다. 이러한 장점은 망의 안정성을 놓일 수 있기 때문에 많은 연구에서 HA 기반 라우팅을 채택하고 있다. 하지만, 기존의 HA 기반 라우팅 방법에서 가장 큰 장애 요소는 터널링 집중화 현상이며, 이를 해결하기 위해 Mobile Multicast (MOM) 등에서 정성적인 방법을 제안하고 있지만, 구체적인 프로토콜이 없으며 모든 HA들이 관여하는 복잡도로 인해 실제로 망에 배치되는 데 한계성을 가진다. 본 논문에서는 현재의 Mobile IP 메시지의 간단한 확장과 FA메 멀티캐스팅을 위한 기능을 첨가하여. 터널링 집중화 현상을 해결하는 프로토콜을 제안하고자 한다. 제안되는 프로토콜은 현재의 모든 IP 멀티캐스트를 수용하고, Mobile IP와의 호환성을 유지한다.

• Journal of KIISE:Information Networking
• /
• v.28 no.4
• /
• pp.498-507
• /
• 2001

For the Internet multicast routing, there are some protocols researched. This paper presents a new protocol called DPIM (Delay-bounded PIM) to support QoS of delay in multicast routing. This protocol is based on PIM-SM. When the specified delay bound is not satisfied by dynamic membership, the RP (Rendezvous Point) of shared tree is changed and the shared tree is reconstructed. Therefore, the QoS of delay is always supported in this protocol. Through performance analysis and comparison with other protocol, we certify that this protocol is pertinent.

• Journal of Advanced Navigation Technology
• /
• v.20 no.6
• /
• pp.625-630
• /
• 2016

Recently, various types of image contents are being produced, and interest in copyright protection technology is increasing. In this paper, we propose an image encryption technology for color images. This technique divides the image into RGB color components and then performs quad-tree decomposition based on the edge of image. After the quad-tree partitioning, encryption is performed on the selected blocks. Encryption is performed on color components to measure encryption efficiency, and encryption efficiency is measured even after reconstitution into a color image. The encryption efficiency uses a visual measurement method and an objective image quality evaluation method. The PSNR values were measured as 7~10 dB for color difference components and 16~19 dB for color images. The proposed image encryption technology will be used to protect copyright of various digital image contents in the future.