• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.213-220
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• 2009

Cooperative diversity is a promising technique for range extension and diversity increase without the use of multiple transmit antennas at the user equipment. In this paper, we propose a cooperative hybrid automatic repeat request relay method with adaptive retransmission to increase the throughput when the SNR of a source user is low. In the proposed method, the source user transmits the first segment of a codeword to relay users and a base station. If the base station fails to recover the information from the received packet, it requests the source or some relay users to retransmit the packet previously sent. In addition, the retransmission type of a selected user is chosen from repetition or incremental redundancy according to the quality of systematic bits in a turbo codeword. Simulation results show that the proposed method improves the throughput compared to conventional methods, and the improvement is significant when the source user has a low SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.610-617
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• 2009

This paper proposes a cross-layer design combining adaptive modulation and coding (AMC) with truncated hybrid automatic repeat request (HARQ) for wireless multicast transmission, in order to increase the spectral efficiency while meeting the target quality-of-service (QoS). In the design, we provide the selection criterion of AMC so as to satisfy the target packet error rate (PER) of all users when the multicast data is received through the common channel and the number of retransmission is limited by the delay constraint of the service. The analytically derived results show that the cross-layer design using HARQ provides a better spectral efficiency than the AMC without HARQ by allowing retransmission and code combining. It is also observed that the design for multicast outperforms that for unicast in the mid to high signal-to-noise ratio region.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.3
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• pp.336-341
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• 2014

When using a higher-order modulation scheme, there are variations in bit-reliability depending on the bit position in a modulation symbol. Variations of bit-reliability in the codeword block lower the decoding performance. Also, the decoding performance increases as the sum of the bit-reliabilities in the codeword block increases. This paper presents a novel hybrid automatic repeat request scheme that increases the sum of the reliabilities of the transmitted bits by lowering the modulation order, and decreases the variations of bit-reliability in the codeword block by preferentially retransmitting bits with low reliability. The proposed scheme outperforms the constellation rearrangement scheme. Furthermore, the proposed scheme also provides a good solution in cases where the size of the retransmission block is smaller than the size of the initial transmission block.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.205-207
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• 2006

이동 애드 혹 네트워크는 인프라가 구축된 일반 통신 네트워크와는 달리 특정 인프라 없이 구성 노드들 간 통신이 가능하며, 노드의 이동 특성으로 네트워크의 변화가 심하다. 애드 혹 네트워크 환경에 따른 적합한 경로 설정 알고리즘을 선택하고 소스 노드에서 목적지 노드로의 패킷 전송 전송 중 에러 발생 시 기존 프로토콜의 경로 재설정 방법 보다 경로 재설정 시간을 최소한으로 줄여 사라진 경로 복구를 위한 최소 지연 경로 재설정 방법 및 효율적 전송 방법을 제안한다. 일정 규모 이상의 이동 노드로 구성된 애드 혹 네트워크에서 효율적인 DSR 라우팅 프로토콜을 이용하고, 에러 발생으로 인한 경로 재설정 시 빠른 경로 복구를 위하여 소규모 네트워크 환경에서 빠른 전송 성능을 가진 AODV 라우팅 프로토콜을 이용하여 패킷 전송 지연을 최소화 하는 최소 지연 경로 재설정 및 재전송 방법을 제안한다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1995.06a
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• pp.563-567
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• 1995

• Journal of KIISE:Information Networking
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• v.33 no.4
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• pp.333-342
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• 2006

The cdma2000 lxEV - DO mobile communication system provides broadcast and multicast services (BCMCS) to meet an increasing demand from multimedia data services. The servicing of video streams over a BCMCS network must, however, face a challenge from the unreliable and error-prone nature of the radio channel. The BCMCS network uses Reed-Solomon coding integrated with the MAC protocol for error recovery. We analyze this coding technique and show that it is not effective in the case of slowly moving mobiles. To improve the playback quality of an MPEG-4 FGS video stream, we propose the Hybrid error recovery scheme, which combines Reed-Solomon with ARQ, using slots which are saved by reducing the Reed-Solomon coding overhead. The target packets to be retransmitted are prioritized by a utility function to reduce the packet error rate in the application layer within a fixed retransmission budget. This is achieved by considering of the map of the error control block at each mobile node. The proposed Hybrid error recovery scheme also uses the characteristics of MPEG-4 FGS (fine granularity scalability) to improve the video quality even when conditions are adverse: slow-moving nodes and a high error rate in the physical channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.9-12
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• 2007

In this paper, we propose and analyze a scheme for wireless channels, which is a combination of a type I hybrid-automatic repeat request (H-ARQ) scheme and a power ramping. The power ramping is considered for more reliable downlink data transmission, in which the transmission power is gradually changed from a small level to a large level when the number of retransmissions increases. The simulation results demonstrate that, when the power ramping step size is 0.5dB, the average throughput gain may be as high as 2% to 5% with properly selected parameters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.24-29
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• 2011

Comparing conventional one-way relaying, two-way relaying scheme with network coding can achieve high throughput by reducing the transmission time. Coded cooperation protocol, which is a algorithm that uses coding on physical layer, can achieve high reliability. In this paper, we propose coded cooperation protocol over two-way relay network. Simulation results show proposed protocol has better performance in terms of reliability and throughput compare with conventional amplify and forward protocol. Also, with same throughput, proposed protocol has better performance in terms of reliability compare with the conventional hybrid decoded and forward protocol.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.7
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• pp.12-21
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• 2002

In this paper, we propose a new hybrid ARQ scheme to consider real-time and non real-time services in a wireless ATM network. Real-time and non-real-time services require different error control schemes according to each service characteristics. Therefore, in the next generation mobile communication environments where these service scenarios should be deployed, hybrid ARQ scheme using RCPC code with variable coding rate becomes one of the most suitable solutions. Because the variable coding rate is applied according to traits of transmitted frame and channel status, hybrid ARQ scheme using RCPC code can expect UEP effect. The UEP scheme does not apply equal error protection level to all information, but does high error protection level to more important information. In Our scheme, UEP of high error protection level is applied to real-time service, and UEP of low error protection and retransmission techniques are applied to non real-time service. We show that the proposed hybrid ARQ scheme improves channel utilization efficiency and yields high error correction behaviors.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1555-1558
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• 2011

본 논문에서는 멀티미디어 데이터에 대한 내용기반 인식 기법을 이용하여 인터넷에 불법으로 배포되어 있는 콘텐츠를 추적하는 기법을 소개한다. 내용기반 인식 기법은 콘텐츠의 원신호에서 내용기반 해쉬나 혹은 축약된 형태의 특징벡터를 추출하여 콘텐츠를 인식하는 기술로 저작권보호 분야에서 불법 저작물을 필터링하는데 많이 활용되고 있다. 불법 콘텐츠 추적시스템은 인터넷에서 광범위하게 유포되어 있는 저작물을 검색하여 그 내용을 기반으로 인식하여 불법 여부를 판단한 후 삭제메일이나 재전송 중지 등의 후속 조치를 자동으로 수행하는 저작권보호 시스템이다. 본 논문에서는 오디오, 비디오, 어문, 게임 콘텐츠에 대해 내용을 기반으로 인식을 수행하고 불법 여부를 판단하여 재전송 중지 조치를 취하는 능동적 저작물 추적 시스템을 제안한다. 제안된 시스템에서는 검색모듈에 의해 수집된 다양한 저작물에 대해 저작물별 독립적으로 인식 기능을 수행하는 기능을 제공한다.