• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.6
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• pp.483-490
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• 2015

There are many software reliability models that are based on the times of occurrences of errors in the debugging of software. It is shown that it is possible to do likelihood inference for software reliability models based on finite failure model and non-homogeneous Poisson Processes (NHPP). For someone making a decision about when to market software, the conditional failure rate is an important variables. The infinite failure model are used in a wide variety of practical situations. Their use in characterization problems, detection of outlier, linear estimation, study of system reliability, life-testing, survival analysis, data compression and many other fields can be seen from the many study. Statistical process control (SPC) can monitor the forecasting of software failure and thereby contribute significantly to the improvement of software reliability. Control charts are widely used for software process control in the software industry. In this paper, proposed a control mechanism based on NHPP using mean value function of Musa-Okumo and Power law type property.

• The Transactions of the Korea Information Processing Society
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• v.4 no.3
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• pp.775-791
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• 1997

This paper describes Real-Time Trasport Protocol(RTTP) that procisdes for a ; user cmnnection-oriented sercices with performance fuarantee.Assuming that eral-time network services will be provided,RTTP solves provlems at end-hosts.RTTP has defined a new set of primitives for real-time communication servies based on the analysis of uwer requirements on various applications.Introducing the notion of Abstract Network Layer independent of real networks.RTTP's implementation scheme can be applied to various netwoeks.The study also intriduces an inplemenation strategy, provide prdeictability of protocol processing time,wich should be known a priori for performance guarantee.Intermally,RTTP has a set of QoS translation rules that change a user'w performance requirements to the equivalent network QoS paramenters.RTTP also introuduces a new apportunistic error control mehtod that can trade-off between overhead and error corredtion according to a uwer's requirement on reliability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.7A
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• pp.1152-1161
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• 2001

본 논문에서는 이동국 수신 신호의 SINR을 최대화하는 빔 성형 알고리듬을 이용하여, 폐쇄 루프 송신 빔 성형기술을 적용한 순방향 링크 CDMA 시스템에서의 안테나 수, 귀환 채널의 구조, 귀환 지연 등과 시스템 성능과의 상관관계를 연구하였다. 폐쇄 루프 전송 빔 성형에서는 이동국이 각 안테나가 겪는 채널을 추정하여 수신 SINR을 최대화시키는 가중치 벡터를 계산하고, 귀환채널을 통해 가중치 벡터의 양자화된 진폭과 위상정보를 전송한다. 컴퓨터 모의 실험 결과는 송신 안테나가 2개, 3개, 4개로 늘어남에 따라 빔 성형 이득은 단일 송신 안테나와 비교해 $10^{-5}$ BER 근방에서 4.2dB, 5.8dB, 7dB로 증가하지만 양자화 오류에 의한 성능 저하 또한 0.1dB, 0.6dB, 1.3dB로 커지는 것을 보여준다. 또한 순방향 채널의 최대 도플러 주파수가 100Hz일 때에는 귀환 채널을 통한 소신 가중치 벡터를 보다 빠르게 갱신하는 것이 가중치 벡터의 양자화 레벨의 수를 늘여주는 것보다 $10^{-5}$ BER 근방에서 0.6dB 더 좋은 성능을 보이며, 최대 도플러 주파수가 10Hz일 때에는 가중치 벡터의 갱신 속도를 늘이기 보다 양자화 레벨의 수를 늘여주어 정확한 가중치 벡터를 전송하는 편이 0.9dB의 성능 향상을 보인다. 두 전력제어 그룹 길이의 귀환지연으로 인한 성능저하는 채널의 최대 도플러 주파수가 50Hz인 경우가 채널의 최대 도플러 주파수가 100Hz인 경우보다 $10^{-5}$ BER 근방에서 0.3dB 정도 더 작다. 또한 AOS가 3$^{\circ}$인 경우가 AOS가 $10^{\circ}$인 경우보다 $10^{-5}$ BER 근방에서 1.9dB 정도, 주파수 선택적 페이딩 채널이 주파수 비선택적 페이딩 채널보다 $10^{-5}$ BER 근방에서 1dB 정도 귀환 지연으로 인한 성능의 저하가 작다.

• The KIPS Transactions:PartD
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• v.15D no.4
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• pp.531-540
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• 2008

An Adaptive Random Testing(ART) is one of test case generation algorithms, which was designed to get better performance in terms of fault-detection capability than that of Random Testing(RT) algorithm by locating test cases in evenly spreaded area. Two ART algorithms, such as Distance-based ART(D-ART) and Restricted Random Testing(RRT), had been indicated that they have significant drawbacks in computations, i.e., consuming quadratic order of runtime. To reduce the amount of computations of D-ART and RRT, iterative partitioning of input domain strategy was proposed. They achieved, to some extent, the moderate computation cost with relatively high performance of fault detection. Those algorithms, however, have yet the patterns of non-uniform distribution in test cases, which obstructs the scalability. In this paper we analyze the distribution of test cases in an iterative partitioning strategy, and propose a new method of input domain enlargement which makes the test cases get much evenly distributed. The simulation results show that the proposed one has about 3 percent of improvement in terms of mean relative F-measure for 2-dimension input domain, and shows 10 percent improvement for 3-dimension space.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.67-71
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• 2010

In this study, an algorithm for blind modulation detection in EDGE systems is presented. EDGE introduces an 8PSK modulation to provide high-speed data rates in addition to the existing GSM system. A transmitter may switch dynamically the modulation and coding schemes for transmission of data according to the channel quality. To decode the data correctly, the receiver has to detect using only training sequence which modulation is being used. Basically the property of one radio block composed of four bursts to detect effectively the modulation scheme even under severe conditions is used. More specifically, the reference value calculated for received burst is accumulated with previous reference value to minimize statistically the false detection probability in one radio block. Also each burst data having different modulation from the modulation of the fourth burst is set to zero to improve the decoding performance because the reference of the fourth burst has the highest reliability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10A
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• pp.809-815
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• 2011

In this paper, we have proposed and implemented a novel architecture which can be used to effectively design the modified Euclidean (ME) algorithm for key equation solver (KES) block in high-speed Reed-Solomon (RS) decoder. With polynomial expressions of newly-defined state variables for controlling each processing element (PE), the proposed architecture has simple input/output signals and requires less hardware complexity because no degree computation circuits are needed. In addition, since each PE circuit is independent of the error correcting capability t of RS codes, it has the advantage of linearly increase of the hardware complexity of KES block as t increases. For comparisons, KES block for RS(255,239,8) decoder is implemented using Verilog HDL and synthesized with 0.13um CMOS cell library. From the results, we can see that the proposed architecture can be used for a high-speed RS decoder with less gate count.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1078-1087
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• 2014

In the conventional centralized mobility management schemes, it can lead to single points of failure, occurrence of a bottleneck, since all data and control are concentrated on the mobility anchor which is located in home network. In the current research of distributed mobility management, it is doing research into distributed mobility management which is supported by distributed mobility anchors. Such schemes do not consider a failure of the mobility anchor. However, it could be an issue under tactical environment since it occur non-service problem due to anchor movement, maintenance, failure, etc. In this paper, we proposed new DMM scheme named T-DMM(Tactical-Distributed Mobility Management) which can support handover even if mobility anchor breaks down. From the numerical analysis, we evaluate signaling cost and handover latency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.235-243
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• 2009

In this paper, we investigate the cognitive and cooperative communication scheme to improve the spectral efficiency in multiuser OFDMA systems using wireless relays. First, we propose the frame structure in which the efficient frequency reuse scheme with the cognitive technique is performed to increase the system throughput. And in the case where the THP (Tomlinson-Harashima preceding) is used for the elimination of interference from the relay, we derive the effective signal to noise ratio of the link largely affected by the channel quantization error. From the system level simulation results, it is shown that the proposed cognitive and cooperative communication scheme increases the overall system performance including the feedback overhead.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.3
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• pp.181-186
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• 2012

PMU based power grid monitoring and control system, WAMAC (Wide Area Monitoring And Control) system is required system design for accurate power data without error and loss through a system-wide. In the paper, we propose system design that measured data from PMU transmitted without loss to PDC and DSM server. and we propose a method to verify the real-time "data has been transmitted accurately". Verification system has been designed to reflect the WAMAC system. Therefore the WAMAC can enhance the reliability of the analysis of the data, and it can monitor lossless real-time trend data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1719-1727
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• 2015

In this paper we have studied about the interconnection technology between tablet device and interactive white board(IWB) system. For this study we have implemented the board writing software for both tablet device and interactive white board system which has contents management, page turning and basic writing functions. Then we defined the data format to communicate the control information and board writing information between two devices, and implemented the communication module for the real-time bidirectional communication by using the Socket programming. The page turning or writing information on tablet device were transferred to the IWB system in real-time and vice versa. From the result of performance test based on the error rate, latency time and communication coverage we derived that our implementation software has good performance between tablet device and IWB system. Also from the result of field test we proved that our solution is well suitable to use in real education environment.