• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1843-1853
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• 1997

The channel throughput and packet delay of wireless media control (MAC) protocols with Rayleigh fading, log-normal shoadowing and near-far effects are analyzed. We consider CSMA/CA protocols as the wireless MAC protocols, since CSMA/CA protocols are based on the standard for wireless Local Area Networks (LANs) IEEE 802. 11. We have found that the performance of CSMA/CA in radion channel model is reduced above 50% than those of error free channel model in low traffic load. We also found that 4-Way Handshake CSMA/CA protocol is supterior to the other CSMA/CA protocols in high traffic load.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.2
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• pp.312-320
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• 2010

Most online monitoring systems of running currently based on the wired network and local area wireless network generate an increase of administrative costs such as synchronization of data protocol conversion, flexible operation of measurement devices and maintenance. To solve this problem, this paper proposes the SMS data transmission protocol which allows multiple data collecting device to manage effectively including implementation method of cdma-based environmental information monitoring system. Also this paper shows operational safety of the proposed protocol and analyzes efficiency of data transfer and operating using SMS.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.522-525
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• 2018

In this paper, we design a UWB / WAS microstrip antenna for wireless local high - speed communication. The substrate of the proposed antenna is FR-4 (er = 4.3) and its size is $30[mm]{\times}30[mm]$. It is designed to have characteristics that can be used in the frequency bands of 3.5 [GHz] and 5.2 [GHz], which are UWB / WAS frequency bands. The simulation was performed using CST Microwave Studio 2014. Simulation results show that the gain is 1.592 [dBi] at 3.5 [GHz] and 2.210 [dBi] at 5.2 [GHz]. The S-parameter also showed a result of less than -10 [dB] (WSWR 2: 1) in the desired frequency band. Microstrip antennas have been miniaturized, high performance, and light weight, and excellent and low cost systems are continuously being developed. In addition, many people use wireless local area network systems used in homes, companies, and public facilities. Since the UWB / WAS technology is proposed according to the development of the system and the demand increase, the antenna that satisfies the above conditions will be designed and the technology applicable to the system will be used more conveniently.

• Review of KIISC
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• v.14 no.1
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• pp.46-55
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• 2004

21세기에는 정보기술의 혁명적 발전과 함께 전쟁양상이 파격적으로 변화될 것으로 예측되며, 전력체계의 특성이 근본적으로 변화됨과 더불어 전쟁 패러다임이 획기적으로 변하고 있다. 특히, 정보과학기술을 이용한 정밀감시, 통제, 타격 복합체계의 구축이 군사력 발전의 근간이 되고 있으며, 앞으로 디지털, 인터넷, 생명공학, 나노기술 등을 복합적으로 활용하는 것이 전력체계의 중심 축이 될 것이다. 특히 전쟁 수행 방식 및 수단의 변혁과 군사패러다임의 보편적 변화추세에 능동적으로 대비하기 위하여 유선과 무선 그리고 근거리 무선 사이에 이음매 없는 통신망이 실현됨으로써 누구든지 어디서나 네트워크로부터 자신이 필요한 정보를 얻을 수 있는 유비쿼터스 컴퓨팅을 민간분야에 활용하여 스마트 흠과 물류에 적용한 사례를 살펴보았다. 유비쿼터스 컴퓨팅과 네트워크 기술은 21세기 변화될 형태의 전쟁을 수행하기 위해 국방 분야 적용이 필수적이며, 이를 통해 전술적인 감지$.$추적 능력의 차대 및 고도화된 전술 정보의 실시간 교환$.$공유, 전술부대의 커뮤니티 파워증대 효과를 가져 올 수 있다. 따라서 유비쿼터스 국방(u-Defense) 시대로 가기 위해 개발하여 적용 가능한 핵심 분야인 내장형 모바일 ad-hoc 네트워크 프로토콜, 무선 센서 네트워크, RFID(Radio Frequency Identification)를 활용한 유비쿼터스 군수지원 등을 제시하였다. 이러한 유비쿼터스 국방을 위하여 우선 비용 측면과 민간분야에 비해 훨씬 강화된 정보 보호 및 무기체계간 상호인증 환경을 고려해야 하며, 국방 정보화에 전력증강차원의 과감한 투자가 요구된다. 또한, 저 비용 고효율의 군사력을 구축해야할 것이며, 첨단 정보체계 건설을 주도할 수 있는 정보 인력을 양성하여, 장기적으로 종합적인 발전계획을 수립하고 국방 정보 체계를 효율적으로 구축하면 군 전력향상에 획기적으로 기여할 수 있을 것이다.

• Journal of KIISE:Information Networking
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• v.32 no.5
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• pp.633-640
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• 2005

This paper proposes and analyzes a message scheduling scheme and corresponding bandwidth allocation method for the hard real-time communication on dual standard 802.11 Wireless LANs. By making the superframeof one network precede that of the other by half, the dual network architecture can minimize the effect of deferred beacon and reduce the worst case waiting timeby half. The effect of deferred beacon is formalized and directly considered to decide the polling schedule of PCF phase. Simulation results executed via ns-2 show that the proposed scheme can improve the schedulability by 3$36\%$ for real-time messages and give $9\%$ more bandwidth to non-real-time messages for the given stream sets, compared with the network whose bandwidth is just doubled with the same MAC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1208-1220
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• 1996

In this paper, the performance of a Carrier Sense Multiple Access/Collision avoidance (CSMA/CA) protocol using stop-and-Wait automatic Repeat reQuest, which is adapted as a draft standard in IEEE 802.11, is analyzed using a mathematical method based on a renewal theory, and simulation checks are performed, which confirm the goodness of our anlysis. In order to anlayze of CSMA/CA, we model that network is composed of finite populationand channel is slotted. And, we consider the CSMA/CA protocol as a hybrid protocol of 1-persistent CSMA and p-persistent CSMA protocol. As resuls of analysis, we have found that the throughput is degraded and packet delay is increased as the number of stations, Acknowledgement (ACK) length and Distributed coordination function Inter Frame Space (DIFS) length are increased.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.1
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• pp.9-16
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• 2019

Smartphones are becoming a portable computer. As a result, even the most sensitive financial application services are now available anywhere on the smartphone. Compared to general PCs, smartphones communicate with external devices through various channels such as wireless internet, mobile communication network, Bluetooth, and NFC, and a wide variety of applications are provided. Therefore, if vulnerabilities exist, the possibility of attack damage increases. In this paper, we analyze the vulnerabilities of dynamic virtual keyboards used in login of banking apps of smartphones with various physical constraints and propose countermeasures.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.15-18
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• 2007

RoF 링크 시스템을 적용한 무선 근거리 통신망(IEEE 802.11b/g)의 중심 주파수 대역인 2.4 GHz에서 저가의 Febry-Perot 레이저 다이오드를 이용한 피드포워드 광송신기를 제작 및 측정 하였다. 제작된 피드포워드 광송신기의 측정 결과는 2.4 GHz에서 주신호의 간격이 10 MHz이고 크기가 -4 dBm인 입력 신호에서 피드포워드 보상기법을 적용하기 전보다 3차 상호 변조 왜곡 신호가 22.9 dB 개선되었다. 제작된 피드포워드 광송신기의 전자소자의 사양을 바탕으로 송신기 집적을 위한 RFIC회로(감쇄기, 증폭기)를 0.18 ${\mu}m$ 공정을 이용하여 설계하였다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.1
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• pp.1-8
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• 1994

In this paper, we have analyzed the performance of a BRAM (The Broadcasting Recognizing Access Method) protocol, as a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) scheme, which is widely used in wireles LAN systems. We have selected a Fair BRAM protocol among CSMA/CA schemes, considering the fairness of channel usage and the simplicity of the protocol. We have compared the performance of BRAM protocol to that of CSMA/CD. to research the characteristics of BRAM in wireless LAN system. In order to analyze the performance of this system, we have set up an imbedded Markov chain and calculated state transition probabilities. Then we have calculated steady state probabilities and finally derived the throughput of a Fair BRAM moder. To verify our analysis, we have simulated practical models. Then, we have found that analytic results are very close to simulation ones. Our analysis of the BRAM protocol will be expected to be very helpful to design and evaluate a MAC (Media Access Control) protocol in wireless LAN systems.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.188-192
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• 1997

The purpose of this study are changing wired medical instrument's terminal into wireless and implementing BSS of Wireless Local Area Network. the wireless terminal using frequency hopping spread spectrum in ISM band transfers patients medical information data such as ECG data, Patient Disease Indication Message to AP(or Server) and it also performs that as a response of transmission request in server. we made Clinet-Server network structure support only BSS service and patient's terminal controlled by polling in server. Wireless Terminal will guarantee mobility and give doctors real time monitoring capability in office.