• Title/Summary/Keyword: 네트워크 구간

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Partitioned Contention Access Mechanism to Enhance the Performance of IEEE 802.15.4 MAC Layer (IEEE 802.15.4 MAC 계층의 성능 향상을 위한 분할 경합 접근 방식)

  • Bae, Sueng-Jae;Ki, Hyung-Joo;Lee, Tae-Jin;Chung, Min-Young
    • Journal of KIISE:Computing Practices and Letters
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    • v.14 no.4
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    • pp.436-440
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    • 2008
  • In IEEE 802.15.4 beacon-enabled mode, performance decreases as the number of devices competing in the contention access period(CAP) increases. In this letter, we propose partitioned contention access mechanism(PCAM) to compensate performance degradation. In PCAM, the PAN coordinator divides CAP into two sub-periods and activity of devices is delimited in their assigned sub-periods. Since PCAM reduces the number of devices which compete at the same time by half, collision probability between transmitted frames can be reduced. In addition, devices can save their power consumption because PCAM shorten the duration that devices stay in active state into half. We perform simulations to compare the performance of PCAM with that of the IEEE 802.15.4 standard. From the result, PCAM yields better performance than IEEE 802.15.4 standard.

TCP Buffer Tuning based on MBT for High-Speed Transmissions in Wireless LAN (무선 랜 고속전송을 위한 최대버퍼한계 기반 TCP 버퍼튜닝)

  • Mun, Sung-Gon;Lee, Hong-Seok;Choo, Hyun-Seung;Kong, Won-Young
    • Journal of Internet Computing and Services
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    • v.8 no.1
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    • pp.15-23
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    • 2007
  • Wireless LAN (IEEE 802.11) uses traditional TCP for reliable data transmission, But it brings the unintentional packet loss which is not congestion loss caused by handoff, interference, and fading in wireless LAN. In wireless LAN, TCP experiences performance degradation because it consumes that the cause of packet loss is congestion, and it decrease the sending rate by activating congestion control algorithm. This paper analyzes that correlation of throughput and buffer size for wireless buffer tuning. We find MBT (Maximum Buffer Threshold) which does not increase the throughput through the analysis, For calculation of MBT, we experiment the throughput by using high volume music data which is creased by real-time performance of piano. The experiment results is shown that buffer tuing based on MBT shows 20.3%, 21.4%, and 45.4% throughput improvement under 5ms RTT, 10ms RTT, and 20ms RTT, respectively, comparing with the throughput of operation system default buffer size, In addition, we describe that The setting of TCP buffer size by exceeding MBT does not have an effect on the performance of TCP.

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An Optical Fiber Perimeter Guard System Using OTDRs (OTDR을 이용한 광섬유 외곽경비시스템에 관한 연구)

  • Chang, Jin-Hyeon;Lee, Yong-Cheol;Shin, Dong-Ho;Oh, Sang-Gun;Lee, Jong-Youn;Jung, Jin-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.12B
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    • pp.1236-1243
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    • 2010
  • The perimeter defense system was created and its characteristics were evaluated. It was designed to utilize the fiber sensing device, namely OTDR(Optical Time Domain Reflectometer) which has been used for the maintenance of the optical communication network. An OTDR was constituted by a pulse laser with the nature of 1310nm, +15dBm for the observation of 400 meter optical fence. The high-speed 32-bit processor(S3C2440) has applied to MPU(Main Processor Unit) which helps to improve the performance of OTDR algorithms. Consequently, the maximum error was 0.84 meter on the performance test of the 10km monitoring and the pass criteria of ${\pm}1m$ satisfied in all the sections. The alarm delay time was under 3 sec after detecting the disorder. For the case of secondary trespassing after primary trespassing, the optical switch was installed in OTDR to monitor the secondary trespassing and to measure the multi-point detection. Therefore, this paper shows that the detections of secondary trespassing and multi-point is possible by means of optical switch.

Hibernation Structure Design of Wireless USB over IEEE 802.15.6 Hierarchical MAC Protocol (WUSB over IEEE 802.15.6 통합 MAC 프로토콜의 Hibernation 구조 설계)

  • Hur, Kyeong
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.7
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    • pp.1610-1618
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    • 2014
  • Wearable computer systems can use the wireless universal serial bus (WUSB) that refers to USB technology that is merged with WiMedia PHY/MAC technical specifications. In this paper, we focus on an integrated system of the wireless USB over the IEEE 802.15.6 wireless body area networks (WBAN) for wireless wearable computer systems supporting U-health services. And a communication structure that performs the hibernation for low power consumption is proposed for WUSB over IEEE 802.15.6 hierarchical protocol. In the proposed hibernation mechanisms, WUSB communications are permitted at each m-periodic inactive periods of WBAN superframes by using the WBAN information of Wakeup Period and Wakeup Phase message fields. In our performance evaluations, performances according to amount of WUSB traffic and Wakeup Periods are analyzed respectively to evaluate the effectiveness of proposed hibernation structure in WUSB over IEEE 802.15.6.

이산화티타늄($TiO_2$)의 Anatase상에 따른 가스감응 특성의 영향

  • O, Sang-Jin;Heo, Jeung-Su;Lee, Han-Yong;Jo, Bong-Han
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2009.05a
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    • pp.30.2-30.2
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    • 2009
  • TiO2는 3가지의 결정구조를 가지고 있으며 결정 입자, 구조, 상의 형태에 따라서 성질 및 기능에 영향을 주고 있다. anatase상의 애너지 밴드갭과 전자와의 재결합 확률이 크기 때문에 Rutile상 보다 우수한 성질을 갖고 있어 산화물 반도체로 이용하는 것이 적합하다. 본 실험에서는 나노로드의 TiO2를 수열처리법에 의해 합성한 후 박막을 제조하여 감응특성을 조사하였다. X선 회절분석기(X-Ray Diffraction)로 분석결과 ph=1의 루타일상을 제외하고, pH=2~7의 더 넓은 구간에서 뚜렷한 회절피크의 anatase 상이 나타났으며 다른 비정질상이 발생되지 않는 결정성이 좋은 단결정임이 나타났다. NaOH solution 을 이용하여 수열처리후 $180^{\circ}C$이상의 특정 온도 구간에서 수십 나노 로드 형태로의 2차 성장된 모습을 TEM과 EDS로 결정구조와 화학조성을 분석하였다. 그리고 BET 측정을 통해 $180^{\circ}C$의 소성온도에서 TiO2 입자의 비표면적이 가장 우수한 것으로 나타났다. 나노로드의 수용액을 Al2O3기판의 감지막 위에 떨어뜨려 네트워크된 막을 형성한후에 센서를 제작하였다. 히터 전압이 $400^{\circ}C$에서 나노 파우더센서에서는 반응이 일어나지 않은 반면, 나노 로드센서는 CH3SH에서 28% 의 높은 감도를 얻었고, Toluene의 반응에서는 15%의 감도가 나타났다. 그 외 NO, CO, H2등의 측정에서 아무런 반응이 일어나지 않았다. 이는 비교적 기공이 큰분자(Size)를 가진 CH3SH=76nm, Toluene=60nm에서 반응이 일어난 반면, H2=28nm, CO=22nm에서 감도가 나타나지 않은 것을 보아 흡착분자크기에 의한 영향이 큰 것으로 나타났다.

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Travel Time Prediction Algorithm Based on Time-varying Average Segment Velocity using $Na{\ddot{i}}ve$ Bayesian Classification ($Na{\ddot{i}}ve$ Bayesian 분류화 기법을 이용한 시간대별 평균 구간 속도 기반 주행 시간 예측 알고리즘)

  • Um, Jung-Ho;Chowdhury, Nihad Karim;Lee, Hyun-Jo;Chang, Jae-Woo;Kim, Yeon-Jung
    • Journal of Korea Spatial Information System Society
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    • v.10 no.3
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    • pp.31-43
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    • 2008
  • Travel time prediction is an indispensable to many advanced traveler information systems(ATIS) and intelligent transportation systems(ITS). In this paper we propose a method to predict travel time using $Na{\ddot{i}}ve$ Bayesian classification method which has exhibited high accuracy and processing speed when applied to classily large amounts of data. Our proposed prediction algorithm is also scalable to road networks with arbitrary travel routes. For a given route, we consider time-varying average segment velocity to perform more accuracy of travel time prediction. We compare the proposed method with the existing prediction algorithms like link-based prediction algorithm [1] and Micro T* algorithm [2]. It is shown from the performance comparison that the proposed predictor can reduce MARE (mean absolute relative error) significantly, compared with the existing predictors.

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Data Modeling using Cluster Based Fuzzy Model Tree (클러스터 기반 퍼지 모델트리를 이용한 데이터 모델링)

  • Lee, Dae-Jong;Park, Jin-Il;Park, Sang-Young;Jung, Nahm-Chung;Chun, Meung-Geun
    • Journal of the Korean Institute of Intelligent Systems
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    • v.16 no.5
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    • pp.608-615
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    • 2006
  • This paper proposes a fuzzy model tree consisting of local linear models using fuzzy cluster for data modeling. First, cluster centers are calculated by fuzzy clustering method using all input and output attributes. And then, linear models are constructed at internal nodes with fuzzy membership values between centers and input attributes. The expansion of internal node is determined by comparing errors calculated in parent node with ones in child node, respectively. As a final step, data prediction is performed with a linear model having the highest fuzzy membership value between input attributes and cluster centers in leaf nodes. To show the effectiveness of the proposed method, we have applied our method to various dataset. Under various experiments, our proposed method shows better performance than conventional model tree and artificial neural networks.

A Robotcar-based Proof of Concept Model System for Dilemma Zone Decision Support Service (딜레마구간 의사결정 지원 서비스를 위한 로봇카 기반의 개념검증 모형 시스템)

  • Lee, Hyukjoon;Chung, Young-Uk;Lee, Hyungkeun
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.13 no.4
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    • pp.57-62
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    • 2014
  • Recently, research activities to develop services for providing safety information to the drivers in fast moving vehicles based on various wireless network technologies such as DSRC (Dedicated Short Range Communication), IEEE 802.11p WAVE (Wireless Access for Vehicular Environment) are widely being carried out. This paper presents a proof-of-concept model based on a robot-car for Dilemma Zone Decision Assistant Service using the wireless LAN technology. The proposed model system consists of a robot-car based on an embedded Linux OS equipped with a WiFi interface and an on-board unit emulator, an Android-based remote controller to model a human driver interface, a laptop computer to run a model traffic signal controller and signal lights, and a WiFi access point to model a road-side unit.

Web Monitoring based Encryption Web Traffic Attack Detection System (웹 모니터링 기반 암호화 웹트래픽 공격 탐지 시스템)

  • Lee, Seokwoo;Park, Soonmo;Jung, Hoekyung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.25 no.3
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    • pp.449-455
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    • 2021
  • This paper proposes an encryption web transaction attack detection system based on the existing web application monitoring system. Although there was difficulty in detecting attacks on the encrypted web traffic because the existing web traffic security systems detect and defend attacks based on encrypted packets in the network area of the encryption section between the client and server, by utilizing the technology of the web application monitoring system, it is possible to detect various intelligent cyber-attacks based on information that is already decrypted in the memory of the web application server. In addition, since user identification is possible through the application session ID, statistical detection of attacks such as IP tampering attacks, mass web transaction call users, and DDoS attacks are also possible. Thus, it can be considered that it is possible to respond to various intelligent cyber attacks hidden in the encrypted traffic by collecting and detecting information in the non-encrypted section of the encrypted web traffic.

Development and its APPLIcation of Computer Program for Slope Hazards Prediction using Decision Tree Model (의사결정나무모형을 이용한 급경사지재해 예측프로그램 개발 및 적용)

  • Song, Young-Suk;Cho, Yong-Chan;Seo, Yong-Seok;Ahn, Sang-Ro
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.2C
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    • pp.59-69
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    • 2009
  • Based on the data obtained from field investigation and soil testing to slope hazards occurrence section and non-occurrence section in crystalline rocks like gneiss, granite, and so on, a prediction model was developed by the use of a decision tree model. The classification standard of the selected prediction model is composed of the slope angle, the coefficient of permeability and the void ratio in the order. The computer program, SHAPP ver. 1.0 for prediction of slope hazards around an important national facilities using GIS technique and the developed model. To prove the developed prediction model and the computer program, the field data surveyed from Jumunjin, Gangneung city were compared with the prediction result in the same site. As the result of comparison, the real occurrence location of slope hazards was similar to the predicted section. Through the continuous study, the accuracy about prediction result of slope hazards will be upgraded and the computer program will be commonly used in practical.