• TTA Journal
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• s.128
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• pp.73-76
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• 2010

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2813-2819
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• 2015

In this paper, we investigate the physical layer network coding (PNC) technique in a two-way relay channel (TWRC) where two source nodes send and receive data with each other via a relay node. In particular, we consider the communication scenario where packet length from the two sources is different from each other. We analyze the bit error rate (BER) of the received packet at the relay node according to degree of overlapping between two packets. The BER of the short packet remains unchanged regardless of the degree of overlapping since the entire packet is overlapped with the longer packet, while the BER of the longer packet becomes improved as the degree of overlapping decreases. Thus, we need a novel transmission scheme to enhance BER performance of the PNC technique in TWRC environments since the overall BER performance of the PNC technique at the relay node depends on the worse BER between two ovelapping packets' BERs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.645-654
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• 2012

In this paper, we consider a two-way relay (TWR) system, where two user nodes exchange their information within two transmission phases, by the help of a relay node adopting physical layer network coding. In the system, two users transmit their binary phase shift keying symbols simultaneously in the first phase, and the relay node decodes the XORed version of two user data and broadcasts it back to two users in the second phase. The performance of the system is analyzed in terms of the average end-to-end symbol error probability in Nakagami-m fading channels, for which a tight upper bound is derived in a closed form to provide an accurate and handy estimate on the performance. The results show that our upper bounds are almost indistinguishable from simulation results for various channel and system configurations. In addition, the optimal relay location and power allocation for various conditions can be obtained quickly with our analysis.

• Journal of KIISE
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• v.44 no.11
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• pp.1219-1230
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• 2017

Real-time streaming services over the Internet have increased with the explosive growth of the various mobile platforms, with a focus on smart phones, and the demand for them is growing. In addition, the bandwidth occupied by the streaming services over the Internet had already surpassed 50% in 2010. Because of the shortage of network bandwidth for multimedia services traffic, restrictions on quality and capacity will become more and more serious. CCN is a future Internet architecture that improves how existing host-based Internet architecture handles content-oriented structure, but it is designed for the transmission of general contents and is not suitable for transmitting real-time streaming contents. In this paper, we focus on the inefficient aspects of CCN and propose a hierarchical grade-based scheme for real-time service for a more efficient environment in real-time streaming services. Experiments have shown better performance in terms of bandwidth, network load, and reliability.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.5
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• pp.539-547
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• 2001

Cluster systems employ high speed interconnection networks and use efficient communication layers to gain high performance and scalability. But the diversity in implementation mechanism among these communication layers causes lack of portability. A solution is to provide communication standard APIs such as MPI. This paper introduces MPI-VMMC: an MPI implementation on VMMC. Though the direct deposit transfer mechanism used in VMMC is not suitable for Send/Recv mechanism used in MPI, the proposed sub-layer laid between MPI and VMMC efficiently translates from one mechanism to the other. We also use the lazy pointer and selective zero-copy transfer technique to gain high performance. The peak performance of MPI-VMMC is 90.7Mbytes/sec, which is about 95% of the base communication layer\`s.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.141-150
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• 2011

In this paper, we propose a Cross-Layer Cooperative Routing(CLCR) architecture to support transmission efficiency in mobile wireless sensor networks. The main features and contributions of the proposed architecture and method are as follows. First, the clustering which uses the location information of nodes is utilized as infrastructure. Second, a cross-layer strategy which uses the technologies of network layer, MAC layer, physical layer together to support transmission efficiency and channel efficiency for cooperative-aided routing and transmission. Third, we consider realistic approach in the view points of the mobile ad-hoc wireless sensor networks while conventional methods just consider fixed sensor network environments. The performance evaluation of the proposed method is performed via simulation using OPNET and theoretical analysis. The results of performance evaluation of the proposed CLCR show improvement of transmission efficiency by the proposed CLCR.

• Journal of Broadcast Engineering
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• v.27 no.3
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• pp.283-294
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• 2022

The feature map used in the network for deep learning generally has larger data than the image and a higher compression rate than the image compression rate is required to transmit the feature map. This paper proposes a method for transmitting a pyramid feature map with high compression rate, which is used in a network with an FPN structure that has robustness to object size in deep learning-based image processing. In order to efficiently compress the pyramid feature map, this paper proposes a structure that predicts a pyramid feature map of a level that is not transmitted with pyramid feature map of some levels that transmitted through the proposed prediction network to efficiently compress the pyramid feature map and restores compression damage through the proposed reconstruction network. Suggested mAP, the performance of object detection for the COCO data set 2017 Train images of the proposed method, showed a performance improvement of 31.25% in BD-rate compared to the result of compressing the feature map through VTM12.0 in the rate-precision graph, and compared to the method of performing compression through PCA and DeepCABAC, the BD-rate improved by 57.79%.

• Information and Communications Magazine
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• v.24 no.6
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• pp.50-57
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• 2007

오늘날 인프라 무선 랜은 많은 사용자들이 사용하는 중요한 인터넷 접속 기술이다. 따라서, IEEE 802.11 MAC의 성능분석은 지난 몇 년간 무선 랜 연구의 중요한 테마 중의 하나였다. 본고에서는 프로토콜 계층 사이에 존재하는 상호 의존성의 중요성에 주목하며, IEEE 802.11 기반의 무선 랜이 갖는 성능 특성에 관하여 알아본다. 먼저, 무선 노드의 개수가 많아짐에 따라 무선 랜 시스템의 처리율이 감소한다는 IEEE 802.11 MAC DCF 분석 결과를 설명한다. 여기에 MAC 계층과 다른 계층 사이의 상호 작용에 주목하여, 무선 랜의 성능이 어떤 특성을 갖는지 알아본다. 물리 계층에 존재하는 무선 노드들 사이의 불평등성에 대해서 설명하고, 그로 인하여 노드들 간의 혼잡 수준이 떨어지고 경쟁 기반의 DCF 처리율이 혼잡 상태에서도 서서히 감소하게 되는 것을 설명한다. 또한, 전송 계층 프로토콜로서 TCP를 사용하는 경우의 무선 랜 성능에 관하여 알아본다. TCP는 실제로 무선 채널의 경쟁에 참여하는 노드를 $2{\sim}3$개 정도로 제한하는 효과가 있어서, TCP를 사용하는 무선 랜의 성능은 무선 노드의 개수에 상관없이 안정적인 것을 설명한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1377-1380
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• 2003

계층적 모바일 IPv6는 이동 노드의 지역적인 이동시 보다 빠르고 효과적으로 서비스를 제공하기 위하여 네트워치를 계층적으로 구성한 프로토콜로써, 모바일 IPv6의 단점인 핸드오프시의 긴 지연시간을 단축시켜 손실되는 패킷을 줄이며, 외부로 전송되는 트래픽의 양을 감소시키는 장점이 있다. 따라서 많은 양의 데이타 처리가 필요한 멀티미디어 통신이나, 신속한 서비스를 필요로 하는 실시간 통신에 적용이 가능하다. 본 논문에서는 기존의 모바일 IPv6와 계층적 모바일 IPv6를 구현하여 핸드오프 지연시간과 패킷 손실량을 측정하고 성능 비교를 통하여 계층적 모바일 IPv6의 성능 향상을 확인하였다.

• Journal of Broadcast Engineering
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• v.20 no.2
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• pp.310-339
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• 2015

In this paper, the possibility of a terrestrial fixed 4K UHD (Ultra High Definition) and mobile HD (High Definition) convergence broadcasting service through a single channel employing the FEF (Future Extension Frame) multiplexing technique in DVB (Digital Video Broadcasting)-T2 (Second Generation Terrestrial) systems is examined. The performance of such a service is also investigated. FEF multiplexing technology can be used to adjust the FFT (fast Fourier transform) and CP (cyclic prefix) size for each layer, whereas M-PLP (Multiple-Physical Layer Pipe) multiplexing technology in DVB-T2 systems cannot. The convergence broadcasting service scenario, which can provide fixed 4K UHD and mobile HD broadcasting through a single terrestrial channel, is described, and transmission requirements of the SHVC (Scalable High Efficiency Video Coding) technique are predicted. A convergence broadcasting transmission system structure is described by employing FEF and transmission technologies in DVB-T2 systems. Optimized transmission parameters are drawn to transmit 4K UHD and HD convergence broadcasting by employing a convergence broadcasting transmission structure, and the reception performance of the optimized transmission parameters under AWGN (additive white Gaussian noise), static Brazil-D, and time-varying TU (Typical Urban)-6 channels is examined using computer simulations to find the TOV (threshold of visibility). From the results, for the 6 and 8 MHz bandwidths, reliable reception of both fixed 4K UHD and mobile HD layer data can be achieved under a static fixed and very fast fading multipath channel.