• Journal of Communications and Networks
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• v.7 no.3
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• pp.337-352
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• 2005

In this paper, a fuzzy logic implementation of the random early detection (RED) mechanism [1] is presented. The main objective of the proposed fuzzy controller is to reduce the loss probability of the RED mechanism without any change in channel utilization. Based on previous studies, it is clear that the performance of RED algorithm is extremely related to the traffic load as well as to its parameters setting. Using fuzzy logic capabilities, we try to dynamically tune the loss probability of the RED gateway. To achieve this goal, a two-input-single-output fuzzy controller is used. To achieve a low packet loss probability, the proposed fuzzy controller is responsible to control the $max_{p}$ parameter of the RED gateway. The inputs of the proposed fuzzy controller are 1) the difference between average queue size and a target point, and 2) the difference between the estimated value of incoming data rate and the target link capacity. To evaluate the performance of the proposed fuzzy mechanism, several trials with file transfer protocol (FTP) and burst traffic were performed. In this study, the ns-2 simulator [2] has been used to generate the experimental data. All simulation results indicate that the proposed fuzzy mechanism out performs remarkably both the traditional RED and Adaptive RED (ARED) mechanisms [3]-[5].

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.655-662
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• 2012

In this work, we propose an airborne cognitive radio system that searches a new spectrum band to avoid a communication interruption due to the interference from many radar signals. We develop a method of fast spectrum sensing based on an effective frequency by recognizing the interfering radar as well as geographical information. This effective frequency is calculated by the free-space path loss between a base station and a fighter with the speed parameter. From our analysis, it is verified that the maximum frequency searching time is reduced by half by using our method.

• Speech Sciences
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• v.15 no.2
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• pp.67-77
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• 2008

In this paper, we implemented a robust speech recognizer using the TMS320VC33 DSP. For this implementation, we had built speech and noise database suitable for the recognizer using spectral subtraction method for noise removal. The recognizer has an explicit structure in aspect that a speech signal is enhanced through spectral subtraction before endpoints detection and feature extraction. This helps make the operation of the recognizer clear and build HMM models which give minimum model-mismatch. Since the recognizer was developed for the purpose of controlling car facilities and voice dialing, it has two recognition engines, speaker independent one for controlling car facilities and speaker dependent one for voice dialing. We adopted a conventional DTW algorithm for the latter and a continuous HMM for the former. Though various off-line recognition test, we made a selection of optimal conditions of several recognition parameters for a resource-limited embedded recognizer, which led to HMM models of the three mixtures per state. The car noise added speech database is enhanced using spectral subtraction before HMM parameter estimation for reducing model-mismatch caused by nonlinear distortion from spectral subtraction. The hardware module developed includes a microcontroller for host interface which processes the protocol between the DSP and a host.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1077-1082
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• 2016

IDS can be used as a countermeasure for malicious attacks which cause degrade of network transmission performance by disturbing of MANET routing function. In this paper, effects of IDS for transmission performance on MANET under grayhole attacks which has intrusion objects for a part of transmissions packets, some suggestion for effective IDS will be considered. Computer simulation based on NS-2 is used for performance analysis, performance is measured with VoIP(: Voice over Internet Protocol) as an application service. MOS(: Mean Opinion Score), CCR(: Call Connection Rate) and end-to-end delay is used for performance parameter as standard transmission quality factor for voice transmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.854-857
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• 2008

Wireless sensor consists of an internal power source which has limited life time. Several MAC protocols have exploited scheduled sleep/listen cycles to conserve energy in sensor networks. Duty cycle is a user-adjustable parameter in low duty cycle MAC protocols, which determines the length of the sleep period in a frame. The sire of duty cycle has direct effect on the Performance of MAC Protocols. In this Paper, we simulated TEEM (A Traffic Aware, Energy Efficient MAC) and S-MAC in NS-2 with different duty cycle values and analyze how duty-cycle effects on the performance and energy consumption of both the protocols.

• Journal of Plant Biotechnology
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• v.33 no.4
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• pp.263-270
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• 2006

Pongamia pinnata Pierre is a tree legume, having potential in production of raw material for biodiesel. A protocol for in wk propagation of this plant was standardized using seedling explants. Growth regulators (GR) including gibberellic acid $(GA_3),\;N^6-benzylaminopurine(BA)$, thidiazuron (TDZ), and Adenine sulphate (Ads) were tested for optimum germination of seeds. Removal of seed coat prior to germination, controlled fungal growth partially but enhanced bacterial growth. Antibiotic cefotaxime was ineffective in controlling bacterial contamination. Seedling derived nodal explants and cotyledon nodes with attached cotyledons were excised and cultured for induction of shoots. Optimum sprouting and multiplication of shoot buds were obtained in MS medium supplemented with $8.88{\mu}M$ BA. These buds differentiated and rooted on medium devoid of GR. Optimum growth of Pongamia seedling was obtained in cotton plugged culture vessels. Reculturing of the cotyledon node explants produced more shoots from the same site. This process of removing shoots and reculturing of cotyledon node was followed for eight passages yielding 4 to 8 shoots in each cycle. The shoots (75%) rooted on half strength MS basal medium supplemented with 0.22% charcoal. All plants survived on transfer to soil. This is the first report on in vitro regeneration of Pongamia pinnata. This report demonstrates the possibility of coupling more than one parameter in single experiment to hasten the process of standardization. The process of cycling the nodal explant repeatedly for production of large number of shoots from single meristem may find application in genetic transformation experiments wherein meristems are used for transformation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2305-2312
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• 1998

This paper analyzed the delay characteristics of speech packets in virtual cellular network(VCN). The probability distribution of packet delay is obtained using the markov chain model when periodic speech packets are transmitted by slotted-ALOHA protocol. The effects of probility of capture and retransmission policy on the performance were also analyzed. At first, the probability cumulative function of packet delay is calculated from the probability of capture as a function of location of mobile terminal. In order to investigate the effects of backoff delay, we defined a parameter NPr, where N is the period (frame size) of the speech packets and Pr is the retransmission probability for each speech packet. We also obtained the 1% outage delay for various frame size N.

• Journal of Biomedical Engineering Research
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• v.18 no.4
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• pp.373-380
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• 1997

In this paper, we describe the intrabed network in a patient monitoring system we developed The intrabed network handles data communication between the main unit of a bedside patient monitor and parameter modules plugged in it. We designed the intrabed network based on RS-485 and HDLC protocol with 1 Mbps data rate. Message exchanges are implemented based on three data structures of packet frame. and stream. We present the specification and the performance of the data communication network for the developed patient monitor.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.151-156
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• 2017

Communication performance requirements are described as QoS parameters in multimedia communication Protocols including SCTP. One of the important QoS parameters is the reliability of the transfer. As a QoS parameter, the reliability defines error detection, report and correction mechanisms. Including SCTP, conventional error control mechanisms, however, do not consider the integrated viewpoint of multimedia data. In this paper, I have designed and proposed the multimedia oriented error control method based on multimedia characteristics. The proposed scheme should have the reduction effect of the communication resources such as frame buffer, procesing power and bandwidth as well as satisfy the requirements of users.

• Journal of the Korea Society of Computer and Information
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• v.13 no.2
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• pp.167-175
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• 2008

The current pre-distribution of secret keys uses a-composite random key and it randomly allocates keys. But there exists high probability not to be public-key among nodes and it is not efficient to find public-key because of the problem for time and energy consumption. We presents key establishment scheme designed to satisfy authentication and confidentiality, without the need of a key distribution center. Proposed scheme is scalable since every node only needs to hold a small number of keys independent of the network size, and it is resilient against node capture and replication due to the fact that keys are localized. In simulation result, we estimate process time of parameter used in proposed scheme and efficiency of Proposed scheme even if increase ECC key length.