• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.271-273
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• 2003

무선 네트워크에서는 전송오류에 의한 패킷손실이 많이 발생한다. 이러한 전송오류를 복구하기 위해 ARQ방식이나 FEC방식이 사용된다. 그러나 채널의 에러율이 증가하면 ARQ와 같은 재전송 방식의 효율은 급격히 저하된다. 이와는 달리 정정코드를 덧붙이는 FEC방식은 ARQ 방식에 비해서 채널의 에러율이 높은 환경에서 효율적인 에러 복구가 가능하다. 그러나 이러한 FEC방식도 항상 일정한 크기를 가지는 정적인 FEC방식일 경우 변화하는 무선 채널의 상태에 알맞은 정정 코드를 채택하지 못해 FEC방식의 단정인 대역폭 낭비를 초래하게 된다. 본 논문에서는 이러한 정적인 FEC방식의 단점을 개선하기 위해, 무선 채널의 전송 오류율에 따라 FEC의 정정도를 동적으로 변화시키는 동적 FEC(dynamic FEC) 알고리즘을 Mote라고 불리는 노드로 구성된 실제 센서 네트워크에 구현했다. 동적 FEC 알고리즘은 무선 채널을 모델링해서 시뮬레이션 결과에서는 성능이 향상되었고, 실제 센서 네트워크에서 실험한 결과 에러율이 낮은 환경에서는 비슷한 성능음 가지게 된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.1248-1250
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• 2007

IEEE 802.11 WLAN(Wireless LAN)은 그 편리함과 효율성으로 인해 급격히 시장에 보급되었다. 이에 따라 다양한 멀티미디어 서비스를 위해 QoS(Quality of Service)의 지원이 필요하게 되었다. 본 논문에서는 IEEE 802.11 WLAN 에서의 기존의 Backoff 방식을 분석하고, 여기에 기존의 재전송 기법에 ARQ 방식을 도입한 새로운 알고리즘을 제시하여 에너지 효율 (Energy Efficiency)의 향상을 도모한다. 또한, 기존의 Backoff 방식과 제안한 알고리즘의 처리율을 비교하여 기존의 방식 보다 제안된 알고리즘이 에너지 효율(Energy Efficiency)를 향상시키는 것을 확인하였다.

• Journal of KIISE:Information Networking
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• v.36 no.1
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• pp.34-42
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• 2009

In this paper, we propose a practical hybrid transport error control scheme to provide SVC video streaming service over error-prone IP networks. Many error control mechanisms for various video coding standards have been proposed in the literature. However, there is little research result which can be practically applicable to the multilayered coding structure of SVC(the scalable extension of H.264/AVC). We present a new hybrid transport error control scheme that efficiently combines layered Forward Error Correction(FEC) and Automatic Repeat Request(ARQ) for better packet-loss resilience. In the proposed hybrid error control, we adopt ACK-based ARQ instead of NACK-based ARQ to maximize throughput which is the amount of effective data packets delivered over a physical link per time unit. In order to prove the effectiveness of the proposed hybrid error control scheme, we adopt NIST-Net network emulator which is a general-purpose tool for emulating performance dynamics in IP networks. It is shown by simulations over the NIST-Net that the proposed hybrid error control scheme shows improved packet-loss resilience even with much less number of overhead packets compared to various conventional error control schemes.

• Journal of Broadcast Engineering
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• v.23 no.5
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• pp.682-692
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• 2018

In this paper, we propose an ARQ packet error control scheme using multiple threads in delivering massive capacity of multimedia based on MMT(MPEG Media Transport) protocol. On the sending side, each frame that constitutes an image is packetized into MMT packets based on MMT protocol. The header of the packet stores the sequence number of the frames contained in the packet and the time of presentation information. The payload of the packet stores the direct information that comprises the frame. The generated MMT packet is transmitted to the IP network. The receiving side checks if any error has occurred in the received packet. For any identified error, it controls the error through ARQ error control scheme and reconfigure the frame according to the information stored in the header of the received packet. At this point, a multi-threading based transport design is constructed so that each thread takes over a single frame, which increases the transmission efficiency of massive capacity multimedia. The efficiency of the multi-threading transport method is verified by solving the problems that might arise when using a single-thread approach if packets with errors are retransmitted.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.501-501
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• 2006

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.63-67
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• 2001

본 논문에서는 블루투스 Scattenet 환경에서 임펄스 잡음의 영향을 분석하였다. 임펄스 잡음은 Middleton의 A급 임펄스 환경을 가정하였고, Scatternet에 의한 동일채널 간섭과 라이시안 페이딩을 고려하였다. 임펄스 잡음이 존재하는 블루투스 Scatternet에서 PER (Packet Error Rate)과 ARQ 기법을 적용한 처리율 (Throghput) 향상을 임펄스 파라미터 A와 I'에 따라서 알아 보았다. 시뮬레이션 결과 임펄스 파라미터 A와 I'에 따라 PER 성능에 미치는 영향이 큰 것을 알 수 있었고 SAW-ARQ 방법을 사용하여 성능이 향상됨을 알 수 있었다.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.45-53
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• 2005

In this paper, we present a cross-layer analysis of wireless TCP systems over correlated channels. The effects of error correlation on the behavior of link retransmission strategy and the end-to-end throughput of TCP layer are investigated. Based on the cross-layer analysis, an efficient refinement of link layer protocol is proposed by consciously utilizing the information of channel correlations, which leads to the performance improvement of wireless TCP systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.1
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• pp.45-52
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• 2015

Since the broadcast message in satellite signals the security of the data is extremely poor compared to other communication technologies such as the broadcast signal. Thus, encryption of the communication satellite has become a very important issue, an analysis of the communication performance of a general service is always required. In this paper, In order to analyze the encrypted communication the turbo code in an IP-based satellite communication applies the code rate compatible punctured and The wireless channel in consideration of the actual satellite communication was constructed by placing a weight on the Rayleigh fading and the Rician fading two channels. Retransmission-based error control scheme were constructed in the best performance of H-ARQ Type-II, III scheme of a number of ways that are recently considered. we analyzed the effects of normal service against a satellite communication network The security services were configured with encryption algorithms AES, ARIA (CTR, CBC mode).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.941-950
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• 2011

In this paper, we analysis the end-to-end performance of the incremental cooperative communication with relay selection. In the conventional cooperative scheme, the source(S) broadcasts the signal to the relay(R) and the destination(D) at 1st phase, and the R forwards the signal to the D at 2nd phase. Although this scheme can improve performance and provide diversity gain, it suffers from decreasing spectrum efficiency. In order to overcome this problem, the incremental cooperative model can be used. In this paper, we study two incremental cooperative method : the first uses ARQ with threshold SNR and the second uses HARQ with channel coding. we also evaluated performance of the incremental cooperative communication based on the R arrangement by using both methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.1
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• pp.62-77
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• 2010

Emerging applications with high data rates will need to transport bulk data reliably in wireless sensor networks. ARQ (Automatic Repeat request) or Forward Error Correction (FEC) code schemes can be used to provide reliable transmission in a sensor network. However, the naive ARQ approach drops the whole frame, even though there is a bit error in the frame and the FEC at the bit level scheme may require a highly complex method to adjust the amount of FEC redundancy. We propose a bulk data transmission scheme based on erasure-resilient code in this paper to overcome these inefficiencies. The sender fragments bulk data into many small blocks, encodes the blocks with LT codes and packages several such blocks into a frame. The receiver only drops the corrupted blocks (compared to the entire frame) and the original data can be reconstructed if sufficient error-free blocks are received. An incidental benefit is that the frame error rate (FER) becomes irrelevant to frame size (error recovery). A frame can therefore be sufficiently large to provide high utilization of the wireless channel bandwidth without sacrificing the effectiveness of error recovery. The scheme has been implemented as a new data link layer in TinyOS, and evaluated through experiments in a testbed of Zigbex motes. Results show single hop transmission throughput can be improved by at least 20% under typical wireless channel conditions. It also reduces the transmission time of a reasonable range of size files by more than 30%, compared to a frame ARQ scheme. The total number of bytes sent by all nodes in the multi-hop communication is reduced by more than 60% compared to the frame ARQ scheme.