• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.157-159
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• 2004

기존의 수위 제어기는 단 방향 무선 통신을 이용함으로써 오류가 발생한 정보의 수신 시에 정정 능력이 없었다. 그리고 대부분의 관정이 산간 오지에 설치됨으로써 태양전지와 보조 배터리를 전원으로 사용하기 때문에 소모 전력의 절감이 큰 과제였다 또한 송신기와 수신기의 채널 변경 시에는 전문가의 도움을 받아야만 가능하였다. 본 연구에서는 수위 제어기에 마이크로 컨트롤러를 채용하고 양방향 통신 방식을 이용함으로써 잘못 수신된 정보를 정정할 수 있도록 하고, 전력 소모가 많은 송신기의 전원을 관리하며, 일반 사용자도 DIP 스위치를 이용하여 채널을 변경할 수 있는 수위제어 시스템을 구현하고자 하였다.

• Journal of the Korea Society of Computer and Information
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• v.8 no.1
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• pp.84-89
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• 2003

In this Paper, an improved protocol is proposed by supplementing a control station for transmission cycle management. This protocol is proposed to complement the shortcomings of the conventional L-Expressnet protocol which is used for round robin process in bus topology. We analyzed the improved protocol in channel utilization viewpoint and compared the result with that of the conventional protocol. From this result, we showed that the channel utilization of the improved protocol is superior to that of the conventional protocol when a maximum normalized propagation delay is increased.

• Journal of the Korea Society of Computer and Information
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• v.8 no.2
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• pp.106-111
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• 2003

In this Paper, an improved protocol is proposed by supplementing a control station for transmission cycle management and slot-extension function. This protocol is proposed to complement the shortcomings of the conventional L-Expressnet protocol which is used for round robin process in bus topology. We analyzed the improved protocol in channel utilization viewpoint and compared the result with that of the conventional Protocol. From this result, we showed that the channel utilization of the improved protocol is superior to that of the conventional protocol when a maximum normalized propagation delay is increased.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.31-36
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• 2015

The demand for multi-functionality, high density, high performance, and miniaturization of IC devices has caused the technology paradigm shift for electronic packaging. So, thermal management of new packaged chips becomes a bottleneck for the performance of next generation devices. Among various thermal solutions such as heat sink, heat spreader, TIM, thermoelectric cooler, etc. on-chip liquid cooling module was investigated in this study. Micro-channel was fabricated on Si wafer using a deep reactive ion etching, and 3 different micro-channel designs (straight MC, serpentine MC, zigzag MC) were formed to evalute the effectiveness of liquid cooling. At the heating temperature of $200^{\circ}C$ and coolant flow rate of 150ml/min, straight MC showed the high temperature differential of ${\sim}44^{\circ}C$ after liquid cooling. The shape of liquid flowing through micro-channel was observed by fluorescence microscope, and the temperarue differential of liquid cooling module was measuremd by IR microscope.

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.97-104
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• 2001

In this paper, we present a new hierarchical model for performance analysis of channel allocation and packet service protocol in wireless n network. The proposed hierarchical model consists of two parts : upper and lower layer models. The upper layer model is the structure state model representing the state of the channel allocation and call service. The lower layer model, which captures the performance of the system within a given structure state, is the wireless packet retransmission protocol model. These models are developed using SRN which is an modeling tool. SRN, an extension of stochastic Petri net, provides compact modeling facilities for system analysis. To get the performance index, appropriate reward rates are assigned to its SRN. Fixed point iteration is used to determine the model parameters that are not available directly as input. That is, the call service time of the upper model can be obtained by packet delay in the lower model, and the packet generation rates of the lower model come from call generation rates of the upper model.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.998-1002
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• 2009

In IPTV multicast architecture, the IGMP(Internet Group Management Protocol) is used for access networks. This protocol supports the functionality of join or leave for a specific multicast channel group. But, malicious attackers can disturb legitimate users being served appropriately. By using spoofed IGMP messages, attackers can hi-jack the premium channel, wasting bandwidth and exhausting the IGMP router's resources. To prevent the message spoofing, we can introduce the packet-level authentication methods. But, it causes the additional processing overhead to an IGMP processing router, so that the router is more susceptible to the flooding attacks. In this paper, we propose the two-level authentication scheme in order to mitigate the IGMP flooding attack.

• Journal of the military operations research society of Korea
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• v.34 no.2
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• pp.63-77
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• 2008

With the limited frequency spectrum and an increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. However, finding a conflict free channel assignment with the minimum channel span is NP hard. The innovations are cellular concept, dynamic channel assignment and hierarchical network design. We consider the frequency assignment problem and the base station placement simultaneously. Our model takes the candidate locations emanating from this process and the cost of assigning a frequency, operating and maintaining equipment as an input. Hierarchical network design using genetic algorithm is the first three-tier (Macro, Micro, Pico) model. We increase the reality through applying to Electromagnetic Compatibility Constraints. Computational experiments on 72 problem instances which have $15{\sim}40$ candidate locations demonstrate the computational viability of our procedure. The result of experiments increases the reality and covers 90% of the demand.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.664-674
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• 1996

In high speed multi-wavelength networks, retransmission overhead due to desination conflict or control packet collision is one factor of performance degration because signal prpagation delay is much larger than the transmission time of data packet. In this paper, an efficient WDMA protocol with a collision avoidance mechanism is proposed for high speed WDM single-hop network with a passive star topology. In proposed protocol, each node has cource queues and routing table to store souting informatio. This architecture makes is possible to avoid any kind of collision when a node reserves the channel to transmit a data packet. High system thoughput and channel utilization can be achieved by proposed protocol since there are no discarded packets caused by any collision at transmission time. The performance of proposed protocol is evaluated in term of throughput and delay with variations in offered load. Simulation results show that the proposed protocol has superior performance to convertional protocols under nonuniform traffic as well as uniform traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.569-580
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• 2003

One of the important advantages of multichannel switches is the incorporation of inherent fault tolerance into the switching fabric. For example, if a link which belongs to the multichannel group fails, the remaining links can assume responsibility for some of the traffic on the failed link. On the other hand, if faults occur in the switching elements, it can lead to erroneous routing and sequencing in the multichannel switch. We investigate several fault localization algorithms in multichannel crossbar ATM switches with a view to early fault recovery, The optimal algorithm gives the best performance in terms of time to localization but is computationally complex which makes it difficult to implement. We develop an on-line algorithm which is computationally mote efficient than the optimal algorithm. We evaluate its performance through simulation. The simulation results show that performance of the on line algorithm is only slightly sub-optimal for both random and bursty traffic. Finally a fault recovery algorithm is described which utilizes the information provided by the fault localization algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.5
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• pp.694-702
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• 2022

This paper shows a small and low-powered wireless communication system based on the ATSC broadcasting system using the ISM frequency band that can be used as a PBS(Personal Broadcasting System). It is designed to demonstrate a channel-adaptive CR(Cognitive Radio) system to provide a better service quality in the unlicensed band where co-channel interference exists. And it achieved very reliable communications by a closed-loop active phased array antenna. This ATSC-based personal broadcasting platform can be modified easily with given flexibility by using GNU Radio as an open-source signal processing platform based on USRP and implementing additional functions in FPGA. In addition, the chosen communication frequency resource can be managed and controlled by the return channel that transmits the channel status and communication parameters between transmission and reception in real-time.