• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.1025-1033
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• 2003

The CDN is proposed as a solution of network bottleneck problem resulting from the rapid growth of Internet user and multimedia contents on the Internet. This paper suggests MDC and path diversity between CDN Edge server and end-user, and multicast transmission among CDN servers based on CDN infrastructure. It may be a solution for reliable and fast transmission of rich multimedia contents. These research will support to solve the unreliable transmission problem of multicasting and to create the new business models in the field of web contents.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.9
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• pp.2213-2231
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• 2013

Compressed sensing is a novel technology used in the field of wireless communication and sensor networks for channel estimation, signal detection, data gathering, network monitoring, and other applications. It plays a significant role in highly secure, real-time, well organized, and cost-effective data communication in smart-grid (SG) systems, which consist of multi-tier network standards that make it challenging to synchronize in power management communication. In this paper, we present a multi-layer communication model for SG systems and propose compressed-sensing based data transmission at every layer of the SG system to improve data transmission performance. Our approach is to utilize the compressed-sensing procedure at every layer in a controlled manner. Simulation results demonstrate that the proposed monitoring devices need less transmission power than conventional systems. Additionally, secure, reliable, and real-time data transmission is possible with the compressed-sensing technique.

• ETRI Journal
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• v.34 no.2
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• pp.168-174
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• 2012

In Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) systems, additional very low-rate data can be transmitted by modulating the amplitude and polarity of the transmitter identification (TxID) signal. Although the additional data transmission scheme offers reliable transmission and has a very large coverage area, it has a limitation on the data rate. In this paper, we propose a novel additional data transmission scheme based on the TxID sequences of the ATSC DTV system and Walsh modulation. The proposed scheme not only increases the data rate significantly, but also offers a virtually identical coverage area compared to a conventional scheme.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.348-350
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• 2003

In recent years, with the continuous development of modem power system, the need for high performance protection to meet the customers' requests for more stable and reliable power supply has become increasingly emphasized. So, there is urgent need for a proper testing platform about not only existing digital protection relay but also new digital protection relay on the transmission line. It is also dynamic-state test which can test the performance of digital relay. This paper suggests basic system model for testing transmission line protection using PSCAD/EMTDC, and presents the process of the component modeling in the basic system.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.19-26
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• 2016

In this paper, the performance of dual-hop multi-relay maximum ratio transmission (MRT) over Rayleigh flat fading channels is studied with both conventional (all relays participate the transmission) and opportunistic (best relay is selected to maximize the received signal-to-noise ratio (SNR)) relaying. Performance analysis starts with the derivation of the probability density function, cumulative distribution function and moment generating function of the SNR. Then, both approximate and asymptotic expressions of symbol error rate (SER) and outage probability are derived for arbitrary numbers of antennas and relays. With the help of asymptotic SER and outage probability, diversity and array gains are obtained. In addition, impact of imperfect channel estimations is investigated and optimum power allocation factors for source and relay are calculated. Our analytical findings are validated by numerical examples which indicate that multi-relay MRT can be a low complexity and reliable option in cooperative networks.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.571-585
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• 2022

As a vital component of power grids, long-span transmission tower-line systems are vulnerable to wind load excitation due to their high flexibility and low structural damping. Therefore, it is essential to reduce wind-induced responses of tower-line coupling systems to ensure their safe and reliable operation. To this end, a shape memory alloy-bidirectional tuned mass damper (SMA-BTMD) is proposed in this study to reduce wind-induced vibrations of long-span transmission tower-line systems. A 1220 m Songhua River long-span transmission system is selected as the primary structure and modeled using ANSYS software. The vibration suppression performance of an optimized SMA-BTMD attached to the transmission tower is evaluated and compared with the effects of a conventional bidirectional tuned mass damper. Furthermore, the impacts of frequency ratios and SMA composition on the vibration reduction performance of the SMA-BTMD are evaluated. The results show that the SMA-BTMD provides superior vibration control of the long-span transmission tower-line system. In addition, changes in frequency ratios and SMA composition have a substantial impact on the vibration suppression effects of the SMA-BTMD. This research can provide a reference for the practical engineering application of the SMA-BTMD developed in this study.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.605-609
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• 2002

Reliable multicast data transmission in a 1:N environment needs more sophisticated error control mechanism than that of in 1:1 environment due to ACK implosion and duplicated retransmission. Although there have been many related research on error control in reliable multicast, real implemented protocols are rare. As one of the reliable multicast transport protocols, ECTP is selected as an international standard reliable multicast protocol by ITU-T and ISO and implemented on RedHat 7.2 machine by us. In this paper, we evaluate the performance of the error control mechanism in the respect of throughput and generated control packet numbers with a real implementation code. From the results, it is concluded that the suitable values of error control parameters can be obtained from the local group size and network environments.

• The KIPS Transactions:PartC
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• v.10C no.2
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• pp.163-170
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• 2003

In this paper we propose a robust clustered croup Multicast in Ad-hoc network. The proposed scheme applies to weighted clustered Algorithm. Ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized administration or reliable support services such as wired network and base station. In ad hoc network routing protocol because of limited bandwidth and high mobility robust, simple and energy consume minimal. WCGM method uses a base structure founded on combination weighted value and applies combination weight value to cluster header keeping data transmission by scoped flooding, which is the advantage of the exiting FGMP method. Because this method has safe and reliable data transmission, it shows the effect to decrease both overhead to preserve transmission structure and overhead for data transmission.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.3
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• pp.509-516
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• 2018

TCP is a well-known communication protocol which is widely used for reliable message transmissions. The urgent mechanism of TCP plays a key role to transmit messages with a high priority. If a high priority message occurs at the transmitting node, the urgent mechanism informs the receiving node about the presence of a high priority message prior to its transmission so that the receiving node can be prepared for handling this message in advance. This implies that the existing urgent mechanism of TCP does not guarantee an immediate or faster delivery of the high priority message itself. Therefore, the ability of priority-based transmission is required on TCP not only to ensure reliable transmissions of normal messages but also to offer a differentiated service according to the priority of message. This paper presents a priority-based transmission algorithm over TCP using a priority queue in a multi-threaded environment. The effectiveness of the proposed algorithm is explored using an experimental setup in which various messages with different priority levels are transmitted.

• Journal of IKEEE
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• v.6 no.1 s.10
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• pp.65-71
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• 2002

In this study, we evaluate the reliability of using bluetooth wireless communication method, the industrial, scientific, and medical standards for local wireless communications, in the medical environment. For the study, an ECG measurement system using bluetooth is developed and used in various conditions of medical environment. It is found that the bluetooth communication method has shown a reliable data transmission capability when both transmitter and receiver are positioned in the same room. However, the increase of transmission distance and the existence of a wall prevent the retailable data transmission. Therefore, it is necessary to make sure if reliable data transmission is achieved for individual environments, before we use this technology.