• 대한산업공학회지
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• 제23권4호
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• pp.687-698
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• 1997

In this paper, a Variation of Blast with Go-Back-N(V-BGBN) protocol is proposed, which differs from Blast with Go-Back-N(BGBN) and Blast with Full Retransmission on Error(BFRE) protocols in the retransmission strategy of packets. Performances of these three protocols under correlated packet errors are analyzed. Throughput efficiency of an arbitrary packet is obtained under the assumption that the round trip delay and the packet length are respectively constant. Recursive formula and difference equations are used as analytical tools. Correlation of packet errors is modelled by a two state Markov chain. The throughput efficiencies under these protocols are compared. V-BGBN protocol is shown to be superior to other two protocols in high speed network.

• 전자공학회논문지A
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• 제32A권1호
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• pp.26-35
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• 1995

Bo-Back-N ARQ is widely used in packet networks for error and flow control methanisms. This paper analyzes the network throughput under the go-back-N schem. Contrast to other analytic methods which assume independent frame losses or the first order Markov frame analytic methods which assume independent frame losses or the first order Markov frame losses concoptually, the proposed method takes into account the correlation between successive frame losses in a congested node. Computer simulation shows that our method generates more accurate performance results that independent assumption method. We apply the proposed method to analyze the performance of BWM in high speed networs. Our results show that BWM maintains the independence between traffic streams.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.73-76
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• 2000

In the basic continuous ARQ schemes (Go-Back-N or Selective Repeat ARQ), each block is continuously transmitted without interruptions. Only when the transmitter receives NAK from the receiver side, the transmitter stops sending current data block and retransmit the erroneous block (Naked block). When channel error rate increases and become sufficiently high, there exists a point at which each block of message is transmitted, on average, more than once. Under such conditions, it will be more efficient to send continuously two or more copies(generally $\ell$ copies) of each block from the first transmission over noisy channel. A request for repeat will be made again only when none of $\ell$ duplicates are received correctly. By this way, the proposed scheme yields a better throughput efficiency and holds nearly constant throughput as compared to others continuous A.R.Q schemes under wide error rate variations (0 < P < 0.3).

• 한국가시화정보학회지
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• 제13권3호
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• pp.15-19
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• 2015

We developed a high-throughput microscopy (HTM) method which enabled us to replace a conventional phase contrast microscopy (PCM) method that has been used as a standard analytical method for airborne asbestos. We could obtain the concentration of airborne asbestos fibers under detection limit by automated image processing and analysis using HTM method. Here we propose an improved image processing algorithm with variable parameters to enhance the accuracy of the HTM analysis. Since the variable parameters that compensate the difference of the brightness are applied to the individual images in our new image processing method, it is possible to enhance the accuracy of the automatic image analysis method for sample slides with low asbestos concentration that caused errors in binary image processing. We demonstrated that enumeration of fibers by improved image processing algorithm remarkably enhanced the accuracy of HTM analysis in comparison with PCM. The improved HTM method can be a potential alternative to conventional PCM.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권6호
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• pp.1828-1847
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• 2014

Coordinated multi-point (CoMP) transmission has been regarded as a potential technology for LTE-Advanced. In frequency division duplexing systems, channel quantization is applied for reporting channel state information (CSI). Considering the dynamic number of cooperation base stations (BSs), asymmetry feature of CoMP channels and high searching complexity, simply increasing the size of the codebook used in traditional multiple antenna systems to quantize the global CSI of CoMP systems directly is infeasible. Per-cell codebook based channel quantization to quantize local CSI for each BS separately is an effective method. In this paper, the theoretical upper bounds of system throughput are derived for two codeword selection schemes, independent codeword selection (ICS) and joint codeword selection (JCS), respectively. The feedback overhead and selection complexity of these two schemes are analyzed. In the simulation, the system throughput of ICS and JCS is compared. Both analysis and simulation results show that JCS has a better tradeoff between system throughput and feedback overhead. The ICS has obvious advantage in complexity, but it needs additional phase information (PI) feedback for obtaining the approximate system throughput with JCS. Under the same number of feedback bits constraint, allocating the number of bits for channel direction information (CDI) and PI quantization can increase the system throughput, but ICS is still inferior to JCS. Based on theoretical analysis and simulation results, some recommendations are given with regard to the application of each scheme respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.2977-2997
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• 2018

In big data era, fresh data grows rapidly every day. More than 30,000 gigabytes of data are created every second and the rate is accelerating. Many organizations rely heavily on real time streaming, while big data stream computing helps them spot opportunities and risks from real time big data. Storm, one of the most common online stream computing platforms, has been used for big data stream computing, with response time ranging from milliseconds to sub-seconds. The performance of Storm plays a crucial role in different application scenarios, however, few studies were conducted to evaluate the performance of Storm. In this paper, we investigate the performance of Storm under different application scenarios. Our experimental results show that throughput and latency of Storm are greatly affected by the number of instances of each vertex in task topology, and the number of available resources in data center. The fault-tolerant mechanism of Storm works well in most big data stream computing environments. As a result, it is suggested that a dynamic topology, an elastic scheduling framework, and a memory based fault-tolerant mechanism are necessary for providing high throughput and low latency services on Storm platform.

• 대한전자공학회논문지TC
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• 제45권6호
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• pp.20-26
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• 2008

현대에는 언제 어디서나 자신이 원하는 데이터를 빠르게 접할 수 있는 서비스가 요구되고 있고 이것을 반영하듯이 많은 시스템들이 개발되었다 특히 HSDPA (High Speed DATA Packet Access)의 경우 최대 14.4Mbps의 데이터 수율을 가져 3세대 이동통신으로 각광을 받고 있다. 하지만 HSDPA의 경우도 지상망 시스템인 관계로 LOS (Line of Sight)가 보장되지 못해 이것은 다중 페이딩에 의한 데이터 수율의 악화로 나타난다. 이러한 문제는 HAPS(High Altitude Platform Station)를 사용하게 되며 해결이 된다. HAPS는 비행선을 이용한 시스템으로 LOS의 보장뿐만 아니라 기존의 지상망 이동통신에 접목해 좀 더 높은 성능을 낼 수 있다. 이 논문에서는 HAPS 시스템을 HSDPA 시스템과 결합한 시스템 모델을 제안하고 시뮬레이션을 통해 그 성능을 분석하고 가능성을 살펴본다.

• 반도체디스플레이기술학회지
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• 제10권4호
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• pp.89-94
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• 2011

In recent years there have been considerable attentions on nanoimprint lithography (NIL) by the display device and semiconductor industry due to its potential abilities that enable cost-effective and high-throughput nanofabrication. A major disadvantage of thermal NIL is the thermal cycle, that is, heating over glass transition temperature and then cooling below it, which requires a significant amount of processing time and limits the throughput. One of the methods to overcome this disadvantage is to improve the cooling performance in NIL process. In this paper, a numerical analysis model of cooling system in thermal NIL was development by CAD/CAE program and the performance of the cooling system was analyzed by the model. The calculated temperatures of nanoimprint device were verified by the measurements. By using the analysis model, the case that the cooling material is replaced by liquid nitrogen is investigated.

• 한국콘텐츠학회논문지
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• 제10권4호
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• pp.19-27
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• 2010

최근에 고속 genome-wide RNA 간섭 스크리닝 기술은 복잡한 세포 기능을 이해하는 생명공학 연구의 핵심적인 도구로 자리 잡고 있다. 그러나 관련 연구에서 발생되는 수많은 영상을 수작업을 통해 분석하는 것은 많은 시간과 노력이 요구된다. 따라서 세포영상의 자동분석 기술은 매우 시급히 확보되어야 하는 기술이며, 그 중 영상 분할은 자동분석을 위한 첫 단계로서 가장 중요한 과정이라 할 수 있다. 세포영상의 자동분할에서는 영역의 겹침 현상과 영역별 모양의 다양성 및 영상 특성의 불균일성 등이 정확한 세포 분할을 어렵게 만드는 주원인으로 작용한다. 본 논문에서는 이러한 문제점을 극복하기 위해 영상 특징들의 국부적인 연속성과 특징 벡터 기반의 워터쉐드 알고리즘을 적용한 새로운 자동 세포 분할 알고리즘을 제안한다. 영상 특징들의 연속성을 국부적인 영역으로 제한함으로써 영역별 모양의 다양성 및 영상 특성의 불균일성에 따른 문제점을 극복할 수 있으며, 특징벡터의 사용을 통해 하나의 영상특징만을 고려한 경우 발생되는 겹침 영역에서의 분할 성능 저하를 개선할 수 있다. 세포영상 분석을 위한 소프트웨어 패키지인 Cellprofiler와의 비교/분석 실험을 통해 제안 알고리즘의 효율성을 입증하였다.

• Journal of Communications and Networks
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• 제9권3호
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• pp.265-273
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• 2007

This paper expands an analytical performance model of 802.11 to accurately estimate throughput and energy demand of 802.11-based wireless sensor network (WSN) when sensor nodes employ Reed-Solomon (RS) codes, one of block forward error correction (FEC) techniques. This model evaluates these two metrics as a function of the channel bit error rate (BER) and the RS symbol size. Since the basic recovery unit of RS codes is a symbol not a bit, the symbol size affects the WSN performance even if each packet carries the same amount of FEC check bits. The larger size is more effective to recover long-lasting error bursts although it increases the computational complexity of encoding and decoding RS codes. For applying the extended model to WSNs, this paper collects traffic traces from a WSN consisting of two TIP50CM sensor nodes and measures its energy consumption for processing RS codes. Based on traces, it approximates WSN channels with Gilbert models. The computational analyses confirm that the adoption of RS codes in 802.11 significantly improves its throughput and energy efficiency of WSNs with a high BER. They also predict that the choice of an appropriate RS symbol size causes a lot of difference in throughput and power waste over short-term durations while the symbol size rarely affects the long-term average of these metrics.