• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1214-1221
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• 2006

Header compression scheme is suggested as a solution to reduce the inefficient overhead of general packet stream data. Especially, it is shown that there are more overhead rate for real-time media stream links such as voice because of its short payload size, and it is possible to get higher bandwidth efficiency using the header compression scheme. There are two kinds of error recovery in header compression such as Periodic Header Refresh(PHR) and Header Request(HR) schemes. In this paper, we analyze the performance of these two compression recovery schemes, and some results such as the overhead rate, bandwidth gain and bandwidth efficiency(BE) are presented.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.311-314
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• 2002

This paper deals with an improved method of utilizing end-to-end bandwidth in the All-IP environment. The proposed method includes compression of UDP/RTP headers, and multiplexing of the RTP stream packets over the end-to-and media transfer. Although the conventional method of using TCRTP(Tunneling Multiplexed Compressed RTP) is an efficient mettled of maximizing tile network throughput, it is inadequate for the All-IP based end-to-end communication. The method is a link-layer independent solution that can be easily implemented in the NGN(Next Generation Network).

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.539-542
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• 2011

TAR와 같은 아카이브 포맷에는 파일 중복을 제거하는 기능이 포함되어 있지 않아서 리눅스 배포 미러와 같이 버전단위로 저장되는 시스템에서 디스크 공간의 낭비가 발생하였다. 본 연구에서는 파일 중복 제거 기능을 추가한 TAR형태의 압축 포맷인 DTAR와 이를 제어하는 DTM 유틸리티를 제안하였다. 주요 아이디어는 클라이언트에서 DTAR 생성 시, 헤더에 SHA1 해시 정보를 추가하여 DTM 유틸리티를 통해 SHA1 해시를 노드로 하는 R-B Tree를 생성하고 이를 서버에 저장된 해시 정보와 비교하여 DTAR내에서 중복이 없는 파일을 선택적으로 파일을 압축하고 서버로 백업하고 관리하는 것이다. 실험 결과 DTM을 통한 백업은 중복 데이터가 누적될수록 DTAR가 tar.gz보다 공간적인 측면이나 백업을 위한 데이터 패킷 전송 시간에서 크게 향상된 성능을 보였다.

• Journal of Korea Multimedia Society
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• v.12 no.2
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• pp.257-271
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• 2009

In this paper, we propose a protocol compression scheme for enhancing the performance of call processing of PTT(Push-to-Talk) which is one of the important services in IMS(IP Multimedia Subsystem), a next generation integrated wired/wireless packet communication network. To service the PTT on an IMS network, it should use the same call setup procedure as legacy Mobile and TRS(Trunked Radio System) networks and have a fast call setup time and enough communication bandwidth because a number of terminals should be able to exchange same data in real time. The proposed A+SigComp scheme reduces the initial call setup delay of SIP by about 10%, which is used by PTT service for call setup. In addition, the A+ROHC scheme is proposed to compress the header of RTP packets transferred during PTT voice transmission and, as a result, about 5% of increase in communication efficiency is observed.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.685-687
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• 1999

인터넷의 발달과 이동단말기 서비스의 확대는 이동단말기를 이용한 인터넷 서비스의 요구를 증대시키고 있다. 이동 환경에서의 인터넷 서비스를 지원하기 위해서는 기존 유선망에서 널리 사용되고 있는 TCP 프로토콜의 개선이 반드시 필요하다. TCP 프로토콜의 개선은 이동단말기의 여러 제약점들을 극복하는 문제에 집중되어 있다. 첫째, 무선링크(wireless line)에서 나타나는 패킷손실의 원인에서 혼잡에 의한 원인과 링크자체의 전송에러(transmission error)에 의한 원인을 구별해 내는 능력을 부가하여야 한다. 둘째로, 이동단말기의 협소한 대역폭으로 인한 TCP 프로토콜의 헤더 압축에 대한 개선이 필요하다. 셋째로, 이동단말기의 위치정보를 실시간으로 관리할 수 있는 기능과 하위계층의 프로토콜과의 상호연동 기능도 추가되어야 할 것이다. 본 논문에서는 이러한 여러 가지 개선 방안들 중에서 무선링크의 사용으로 인한 패킷 손실의 원인을 구별해 내고 그 개별적 원인에 따라 적절하게 제어하는 기법들을 소개하고 비교분석한다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.128-130
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• 2011

디지털 미디어의 발전과 네트워크의 발전에 따라 영상 콘텐츠에 대한 사용이 늘어나고 있다. 이에 따라 저작물의 불법적 사용이 증가되고 이를 막기 위한 기법의 일환인 스크램블링 방법이 사용되고 있다. 스크램블링은 계산 비용과 에너지 소모를 줄이고 디지털 저작권 관리의 사용제어에 대한 요구사항을 만족시키기 위해 사용된다. 스크램블링은 일반적으로 동영상 압축의 변환 계수에 대한 헤더부분만을 암호화하거나 블록으로 나누고 변경과 회전을 통하여 난독화를 발생시킴으로 저작물을 대한 보호한다. 본 논문은 영상을 프레임 단위로 적출하여 영상 프레임이 가지는 색상정보 값에 난독화를 한 후 블럭 암호화 알고리즘을 적용한 스크램블링 기법을 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.14 no.10
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• pp.101-110
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• 2009

The 6LoWPAN(IPv6 Low-power Wireless Personal Area Network) performs IPv6 header compression, TCP/UDP/IGMP header compression, packet fragmentation and re-assemble to transmit IPv6 packet over IEEE 802,15.4 MAC/PHY. However, from the point of view of security. It has the existing security threats issued by IP packet fragmenting and reassembling, and new security threats issued by 6LoWPAN packet fragmenting and reassembling would be introduced additionally. If fragmented packets are retransmitted by replay attacks frequently, sensor nodes will be confronted with the communication disruption. This paper analysis security threats introduced by 6LoWPAN fragmenting and reassembling, and proposes a re-transmission mechanism that could minimize re-transmission to be issued by replay attacks. Re-transmission procedure and fragmented packet structure based on the 6LoWPAN standard(RFC4944) are designed. We estimate also re-transmission delay of the proposed mechanism. The mechanism utilizes timestamp, nonce, and checksum to protect replay attacks. It could minimize reassemble buffer overflow, waste of computing resource, node rebooting etc., by removing packet fragmentation and reassemble unnecessary.

• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.571-578
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• 2002

In this paper, we propose a video sequence coding scheme called AMV (Auxiliary Motion Vector) to minimize error propagation caused by transmission errors over the Internet. Unlike the conventional coding schemes the AMY coder, for a macroblock in a frame, selects two best matching blocks among several preceding frames. The best matching block, called a primary block, is used for motion compensation of the destination macroblock. The other block, called an auxiliary block, replaces the primary block in case of its loss at the decoder. When a primary block is corrupted or lost during transmission, the decoder can efficiently and simply suppress error propagation to the subsequent frames by replacing the block with an auxiliary block. This scheme has an advantage of reducing both the number and the impact of error propagations. We implemented the proposed coder by modifying H.263 standard coding and evaluated the performance of our proposed scheme in the simulation. The simulation results show that AMV coder is more efficient than the H.263 baseline coder at the high packet loss rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1721-1730
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• 1999

In this thesis, an error resilient video coding algorithm, under the error-prone environment such as wireless communication, is suggested. The suggested algorithm adapts the Classified VQ method for intra imagers that reduces some load by searching similar vectors. The Duplicate Vector Position Code is proposed for the higher compression efficiency and the robust decoding in error environment. As a result, the bitstream encoded by the proposed method is in a CBR(Constant Bit Rate) preventing from error propagation. The experiment that adds practical error to the encoded bitsrteam shows the error-robustness superior to H.263.

• Journal of Korea Multimedia Society
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• v.8 no.8
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• pp.1042-1050
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• 2005

This paper proposed a novel low-power video decoding scheme for mobile multimedia communication. In general, there are quite a large number of non-coded blocks in the encoded bitstream where all quantized DCT coefficients are truncated into zero. When the number of the non-coded blocks are known at the start of frame decoding, the amount of computation reduction can be precisely estimated for frame decoding. When the computation reduces, the operation speed and the corresponding supply voltage of VLSI circuits in the decoder also reduce, thus thus power consumption also reduces. In the proposed scheme, the number of the non-coded blocks is stored in the frame header of the encoded bitstream, and the decoder efficiently reduces the power consumption exploiting this information. Simulation results show that the proposed scheme reduces the power consumption to about 1/20.