• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.201-206
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• 2011

This paper presents a miniaturized epsilon negative (ENG) zeroth-order resonance (ZOR) patch antenna with an improved bandwidth. The miniaturization and the broad bandwidth of the ENG ZOR patch antenna are achieved by using a meandered via and a high permeability substrate instead of a straight via and a dielectric substrate. The use of a meandered via allows miniaturization of the ENG ZOR patch antenna without narrowing the bandwidth. The use of a high permeability substrate allows further miniaturization of the ENG ZOR patch antenna and improvement of the bandwidth. A high permeability substrate consisting of a multi-layered substrate is designed to have a small material loss. The antenna (kr=0.32) has a 10 dB fractional bandwidth of ~1 %, which is 1.74 times as broad as that of an antenna with a dielectric substrate.

• Journal of the Korea Society of Computer and Information
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• v.24 no.8
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• pp.1-8
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• 2019

Modern computers provide tremendous computing capability and a large memory system. Hybrid memories consist of next generation memory devices and are adopted in high performance systems. However, the increased complexity of the microprocessor makes it difficult to operate the system effectively. In this paper, we propose a simple data migration method called Bandwidth-aware Data Migration (BDM) to efficiently use memory systems for high performance processors with hybrid memory. BDM monitors the status of applications running on the system using hardware performance monitoring tools and migrates the appropriate pages of selected applications to High Bandwidth Memory (HBM). BDM selects applications whose bandwidth usages are high and also evenly distributed among the threads. Experimental results show that BDM improves execution time by an average of 20% over baseline execution.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.344-354
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• 2014

Transmission control protocol friendly rate control (TFRC) is designed to mainly provide optimal service for unicast applications, such as multimedia streaming in the best-effort Internet environment. However, high bandwidth networks with large delays present an environment where TFRC may have a problem in utilizing the full bandwidth. TFRC inherits the slow-start mechanism of TCP Reno, but this is a time-consuming process that may require many round-trip-times (RTTs), until an appropriate sending rate is reached. Another disadvantage inherited from TCP Reno is the RTT-unfairness problem, which severely affects the performance of long-RTT flows. In this paper, we suggest enhanced TFRC for high quality video streaming over high bandwidth delay product networks. First, we propose a fast startup scheme that increases the data rate more aggressively than the slow-start, while mitigating the overshooting problem. Second, we propose a bandwidth estimation method to achieve more equitable bandwidth allocations among streaming flows that compete for the same narrow link with different RTTs. Finally, we improve the responsiveness of TFRC in the presence of severe congestion. Simulation results have shown that our proposal can achieve a fast startup and provide fairness with competing flows compared to the original TFRC.

• Journal of electromagnetic engineering and science
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• v.18 no.2
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• pp.101-107
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• 2018

The impedance bandwidth and radiation characteristics of an aperture-coupled microstrip line-fed patch antenna (ACMPA) with a high permittivity (${\varepsilon}_r=10$) feed substrate suitable for integration with a monolithic microwave integrated circuit (MMIC) are investigated for various feed substrate thicknesses through an experiment and computer simulation. The impedance bandwidth of an ACMPA with a high permittivity feed substrate increases as the feed substrate thickness decreases. Furthermore, the front-to-back ratio of an ACMPA with a high permittivity feed substrate increases and the cross-polarization level decreases as the feed substrate thickness decreases. As the impedance bandwidth of an ACMPA with a high permittivity feed substrate increases and its radiation characteristics improve as the feed substrate thickness decreases, the ACMPA configuration becomes suitable for integration with an MMIC.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.10a
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• pp.361-364
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• 2005

As increasing the Internet traffic, many researches on access network are reported for end-to-end high-speed broadband network, where E-PON(Ethernet-Passive Active Network) is one of reasonable candidate fur the network with respect to cost and bandwidth utilization. For the high-speed access network, E-PON need an efficient bandwidth allocation method. This paper suggests a WFA(Water-Filling Allocation) algorithm for the efficient bandwidth allocation with various simulation test.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.842-849
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• 2011

The transponder simulator designed to simulate the transponder of military satellite communication systems in the geostationary orbit is required to have time delay function, because of 250 ms delay time, when a radio wave transmits the distance of 36,000 km in free space. But, it is very difficult to develop 250 ms time delay device in the transponder simulator of 100 MHz bandwidth, due to unstable operation of FPGA, loss of memory data for the high speed rate signal processing. Up to date, bandwidth of the time delay device is limited to 45 MHz bandwidth. To solve this problem, we propose the new time delay techniques up to 100 MHz bandwidth without data loss. Proposed techniques are the low speed down scaling and high speed up scaling methods to read and write the external memory, and the matrix structure design of FPGA memory to treat data as high speed rate. We developed the satellite link simulator in 100 MHz bandwidth using the proposed new time delay techniques, implemented to the transponder simulator and verified the function of 265 ms time delay device in 100 MHz bandwidth.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.6
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• pp.39-49
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• 2013

In recent, many countries and research institutes have been studying how to construct the high-speed subscriber access network. Task Force team of IEEE 802.3ah has accomplished the standardization of EPON which is the next generation subscriber access network. EPON doesn't still have the bandwidth enough to support the new service(e.g various multimedia service) which demands the high bandwidth. For these new multimedia services,10G EPON is the next generation subscriber access network which expanded the up-down bandwidth range of 1G EPON 10 times in order to support demanding high bandwidth. We have proposed the model which can accommodate IEEE 802.1 AVB traffics smoothly in 10G EPON and suggesting the Intra-ONU scheduling model which makes this model operate effectively.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.423-442
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• 2015

This study examines the wavelet transform for output-only system identification of ambient excited engineering structures with emphasis on its utilization for modal parameter estimation of high-order and closely-spaced modes. Sophisticated time-frequency resolution analysis has been carried out by employing the modified complex Morlet wavelet function for better adaption and flexibility of the time-frequency resolution to extract two closely-spaced frequencies. Furthermore, bandwidth refinement techniques such as a bandwidth resolution adaptation, a broadband filtering technique and a narrowband filtering one have been proposed in the study for the special treatments of high-order and closely-spaced modal parameter estimation. Ambient responses of a 5-story steel frame building have been used in the numerical example, using the proposed bandwidth refinement techniques, for estimating the modal parameters of the high-order and closely-spaced modes. The first five natural frequencies and damping ratios of the structure have been estimated; furthermore, the comparison among the various proposed bandwidth refinement techniques has also been examined.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.199-201
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• 2008

In this paper, We studied optimum service model of passenger car monitoring system at limited wireless bandwidth subway and railway. High bandwidth is better if we need more services. But, high bandwidth requires more cost at tunnel of subway. More bandwidth make receive sensitivity to bad. We deduced best bandwidth of subway wireless transmission system reflecting the cost of installation and efficiency of system. Consequently, we decide efficient service model of passenger car monitoring system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.4
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• pp.178-184
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• 2005

In this paper, using diplexer structure and varactor diode controlled by reverse bias voltage for diplexer switch gives possibilities to improve isolation and current characteristics. 1 have newly designed switch with high isolation by application varactor diode corresponding to capacitor of diplexer. The low-pass filter for proposed tunable diplexer passes the microwave signal in the bandwidth for wireless cellular network systems and high-pass filter passes it in the bandwidth for wireless personal communication services (PCS) network systems. As the capacitance of the low-pass filter increases, the cut-off frequency can be moved to low frequency, so that the switch is on state in cellular bandwidth and off state in the PCS bandwidth, in contrast to, as the capacitance for attenuation characteristic of high-pass filter increases, it can be moved to high frequency, so that the switch is off state and on state in the cellular bandwidth. it is possible to improve isolation and current consumption characteristics by application diplexer design methods and varactor diode. 1 expect that the tunable diplexer circuit and design methods should be able to find applications on MMIC and low temperature copired ceramic (LTCC).