• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2B
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• pp.120-129
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• 2012

Wireless mesh network (WMN) has recently emerged as a promising technology for tactical operation. If a platoon is organized with MPs, this system is suitable for tactical coverage is given for battle field where there is a shortage of wired infrastructure. However, MPs of typical WMN are generally fixed. This condition does not apply to diverse tactical scenarios. In this paper, it is considered that MPs have group mobility for flexible tactical networks. We propose cluster based multi-channel MAC scheme for mobilie WMN with single antenna condition. We have reduced the collision problems and message storming problems occur by mobility, so the reliability of WMN has been improved. Consequently, reliable communication is guaranteed by our framework in mobile WMN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.712-721
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• 2012

In this paper, we propose an Enhanced cross-layer Geographic Forwarding (EGF) protocol for wireless sensor networks (WSNs). EGF uses an optimal back-off time to make the packet forwarding decisions using only source and destination's location information and energy cost without information about neighbor nodes' location or the number of one hop neighbor nodes. EGF is also a cross-layer protocol by combining efficient asynchronous MAC and geographic routing protocol. The proposed protocol can find optimal next hop location quickly without broadcasting node's location update and with minimizing overhead. In our performance evaluation, EGF has better performance in terms of packet success ratio, energy efficiency and end-to-end delay in wireless sensor networks.

• Speech Sciences
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• v.15 no.2
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• pp.119-129
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• 2008

The purpose of this study were to develop short form versions of MacArthur-Bates Communicative Development Inventories - Korean and to discuss clinical implications. Two short versions were developed: one for $9\sim17$ month-olds(including 69 words and 17 object manipulation skills) and the other for $18\sim35$ month-olds (including 128 words and 5 grammatical items). Short versions seemed to be representative of full versions and showed developmental validity. Short versions showed concomitant validity with SELSI which is a standardized test for Korean children under 37 month-olds. Norm tables for words and criteria for object manipulation and grammaticality are also provided. M-B CDI-K short versions could be used as a preliminary screening tool to identify Korean children with language impairment economically and efficiently. Cautions using short versions of M-B CDI-K are discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.820-829
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• 2000

In this paper, DSPA(Dynamic Signalling Period Allocation) algorithm that has been proposed by the authors for MAC(Medium Access Control) protocols in W-ATM(Wireless Asynchronous Transfer Mode) is applied to mixed traffic conditions composed of various service classes. We investigate the bandwidth utilization efficiency and quality of service(QoS) fulfillment by the DSPA algorithm used in W-ATM MAC protocols. Simulation results indicate that the DSPA algorithm significantly increases the throughput of the system with the minimum control overhead. Moreover, QoS of each service class is well satisfied by proper and fair channel allocation to different service classes according to their requirements.

• Carbon letters
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• v.9 no.2
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• pp.108-114
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• 2008

We have demonstrated the feasibility of using electrospinning method to fabricate long and continuous composite nanofiber sheets of polyacrylonitrile (PAN) incorporated with zinc oxide (ZnO). Such PAN/ZnO composite nanofiber sheets represent an important step toward utilizing carbon nanofibers (CNFs) as materials to achieve remarkably enhanced physico-chemical properties. In an attempt to derive these advantages, we have used a variety of techniques such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution X-ray diffraction (HR-XRD) to obtain quantitative data on the materials. The CNFs produced are in the diameter range of 100 to 350 nm after carbonization at $1000^{\circ}C$. Electrical conductivity of the random CNFs was increased by increasing the concentration of ZnO. A dramatic improvement in porosity and specific surface area of the CNFs was a clear evidence of the novelty of the method used. This study indicated that the optimal ZnO concentration of 3 wt% is enough to produce CNFs having enhanced electrical and physico-chemical properties.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.704-712
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• 2010

Recently, the lack of the frequency have been emerged due to the use of various wireless terminals. To find solutions for obtaining new frequency resources and for avoiding an interference, a cognitive radio technology have focused on as the new technology that can use the whitespace in TV broadcasting band. In this paper, the Cognitive Radio terminal system for whitespace in TV band is first introduced. The purpose of the CR terminal platform is to evaluate the feasibility of the unlicensed wireless service in the TV band. Then, we design and develop the software for Sensing MAC applied the cognitive radio terminal system. The developed Sensing MAC software based on IEEE 802.22 specification can be aware of using the whitespace in TV band that operates on cognitive radio terminal system. Finally, we have tested for evaluating the sensing MAC module.

• The Journal of the Korean Society for Microbiology
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• v.34 no.5
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• pp.491-500
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• 1999

A recent study showed that comparative sequence analysis of rpoB DNAs could reveal natural relationships in genus Mycobacterium [J Clin Microbial. 37 (6). 1999]. rpoB DNAs showed interspecies variation and intraspecies conservation. Based on these data, we developed polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) protocols which enable species differentiation in genus Mycobacterium. When this assay was applied to 24 clinical isolates identified as M. avium complex (MAC) by biochemical test, these were successfully differentiated into M. avium and M. intracellulare. These results were concordant with those obtained by 16s rDNA analysis. It is the first report that PCR-SSCP analysis of rpoB DNA could be used for species differentiation of MAC strains.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11B
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• pp.985-998
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• 2003

본 논문에서는 IEEE 802.11 규격을 기반으로 다중 홉 Ad Hoc 모드에서 비 실시간 및 실시간 트래픽에 대한 통합 서비스를 지원하는 Wireless LAN을 구성할 때, 분산 방식으로 실시간 서비스의 우선권을 고려한 채널 액세스의 차별화를 제공할 수 있는 매체접근제어(Medium Access Control: MAC) 프로토콜의 구현 방안을 제안한다. 이를 위해 실시간과 비 실시간 트래픽의 Contention Window (CW)를 서로 분리하며, 실시간 서비스의 지연 바운드에 따라 정해진 잔여 수명(residual time)을 우선권 설정에 반영함으로써 실시간 트래픽의 지연 요구 사항을 보장할 수 있도록 한다. 또한 실시간 트래픽의 부하에 따라서 적응적으로 offset 값을 조정함으로써 offset에 의해 발생될 수 있는 수율의 저하를 최소화한다. 제안된 방식은 기존 IEEE 802.11 MAC 규격의DCF (Distributed Coordination function) 방식을 그대로 사용하면서 CSMA/CA 기반의 경쟁 방식을 통해서도 비 실시간 트래픽과의 차별화가 가능하고, 또한 잔여 수명 시간을 고려한 동적인 우선권 할당이 가능하도록 하였다. 시뮬레이션에 의한 분석 결과에 따르면 기존 DCF와 비교할 때 실시간 단말의 용량을 2배까지 향상시킬 수 있으며, 트래픽 부하에 따라 적응적 제어를 통해 추가적인 성능 개선 효과를 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.862-875
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• 2003

본 논문에서는 IEEE 802.11 규격을 기반으로 다중 홉 Ad Hoc 모드에서 비실시간 및 실시간 트래픽에 대한 통합 서비스를 지원하는 Wireless LAN을 구성할 때, 분산 방식으로 실시간 서비스의 우선권을 고려한 채널 액세스의 차별화를 제공할 수 있는 매체접근제어(Medium Access Control: MAC) 프로토콜의 구현 방안을 제안한다. 이를 위해 실시간과 비실시간 트래픽의 Contention Window (CW)를 서로 분리하며, 실시간 서비스의 지연 바운드에 따라 정해진 잔여 수명(residual time)을 우선권 설정에 반영함으로써 실시간 트래픽의 지연 요구 사항을 보장할 수 있도록 한다. 또한 실시간 트래픽의 부하에 따라서 적응적으로 offset 값을 조정함으로써 offset에 의해 발생될 수 있는 수율의 저하를 최소화한다. 제안된 방식은 기존 IEEE 802.11 MAC 규격의DCF (Distributed Coordination Function) 방식을 그대로 사용하면서 CSMA/CA 기반의 경쟁 방식을 통해서도 비실시간 트래픽과의 차별화가 가능하고, 또한 잔여 수명 시간을 고려한 동적인 우선권 할당이 가능하도록 하였다. 시뮬레이션에 의한 분석 결과에 따르면 기존 DCF와 비교할 때 실시간 단말의 용량을 2배까지 향상시킬 수 있으며, 트래픽 부하에 따라 적응적 제어를 통해 추가적인 성능 개선 효과를 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1200-1206
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• 2009

In this paper, we propose an energy-efficient MAC(Medium Access Control) protocol for processing context information in ubiquitous sensor network environments. CASMAC(Context Aware Sensor MAC) use context information for energy-efficient operation and its operation principle is as follows. First, we make scenarios with possible prediction for CASMAC. And then we save setted context information in server. When event occur at specific sensor node, and then it send three times sample data to server. According to context information, server process sample data. If server process sample data with event, it receive continuous data from event occur node by a transmission request signal. And then server send data transmission stop signal to event occur node when it do not need to data. If server process sample data with no event, it have not reply. Through we make energy consumption tables and an energy consumption model, we simulate analysis of CASMAC performance. In a result, we gains about 5.7 percents energy reduction compared to SMAC.