• Title/Summary/Keyword: time-synchronization

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The Energy Performance Analysis Between Synchronous and Asynchronous Duty Cycle based MAC Protocols in Wireless Sensor Networks (무선 센서네트워크 환경에서 Duty Cycle 기반 동기식 및 비동기식 MAC 프로토콜의 에너지 성능과 지연시간에 대한 상호 분석)

  • Lee, Jae-Ho;Eom, Doo-Seop
    • Journal of Information Technology Services
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    • v.10 no.3
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    • pp.237-250
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    • 2011
  • Recently, Wireless Sensor Networks (WSN) require energy performance and guaranteed delivery delay time, contrarily with previous MAC protocols that aim to high throughput mostly. In order to satisfy the new significant requirements, many MAC protocols of WSN employ and try to enhance the duty cycle mechanism which is energy efficient technique in MAC layer. This duty cycle mechanism is oriented by toggling the transceiver conditions composed of wakeup and sleep states. The synchronous MAC protocols perform the period synchronization process. Hence, these are energy efficient in periodic monitoring environment, but are inefficient in where an event is incurred rarely and infrequently. Otherwise, the performance of asynchronous MAC protocols are contrarily with synchronous protocols. In this paper, we design two models consisting Always-busy and Always-idle ti simplify the general network congestion conditions. Through these models, moreover, we analyze two types MAC protocols in terms of energy efficiency and delay performance by analytical results. Additionally, we also evaluate two MAC protocols with two gongestion models that we designed. By the analytical and simulated results, we provide the general and efficient decision method in which protocols are more appropriate in a certain WSN environment.

Gait-Event Detection for FES Locomotion (FES 보행을 위한 보행 이벤트 검출)

  • Heo Ji-Un;Kim Chul-Seung;Eom Gwang-Moon
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.3 s.168
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    • pp.170-178
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    • 2005
  • The purpose of this study is to develop a gait-event detection system, which is necessary for the cycle-to-cycle FES control of locomotion. Proposed gait event detection system consists of a signal measurement part and gait event detection part. The signal measurement was composed of the sensors and the LabVIEW program for the data acquisition and synchronization of the sensor signals. We also used a video camera and a motion capture system to get the reference gait events. Machine learning technique with ANN (artificial neural network) was adopted for automatic detection of gait events. 2 cycles of reference gait events were used as the teacher signals for ANN training and the remnants ($2\sim5$ cycles) were used fur the evaluation of the performance in gait-event detection. 14 combinations of sensor signals were used in the training and evaluation of ANN to examine the relationship between the number of sensors and the gait-event detection performance. The best combinations with minimum errors of event-detection time were 1) goniometer, foot-switch and 2) goniometer, foot-switch, accelerometer x(anterior-posterior) component. It is expected that the result of this study will be useful in the design of cycle-to-cycle FES controller.

Signal Optimization Model Considering Traffic Flows in General Traffic Networks (일반적인 네트워크에서의 신호최적화모형 개발 연구)

  • 신언교;김영찬
    • Journal of Korean Society of Transportation
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    • v.17 no.2
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    • pp.127-135
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    • 1999
  • Most existing progression bandwidth models maximize the single or multi weighted sum of bandwidths in the both directions to improve traffic mobility on an arterial, but they cannot be applied to general networks. Even though a few models formulating a looped network problem cannot be applied to networks have not loops. Also they have some defects in optimizing phase sequences. Therefore, the objective of this study is to develope a mathematical formulation of the synchronization problem for a general traffic network. The goal is achieved successfully by introducing the signal phasing for each movement and expanding the mixed integer linear programming of MAXBAND. The experiments indicate that the proposed model can formulate the general traffic network problem mere efficiently than any other model. In conclusion, this model may optimize signal time to smooth progression in the general networks.

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Embedded One Chip Computer Design for Hardware Implementation of Genetic Algorithm (유전자 알고리즘 하드웨어 구현을 위한 전용 원칩 컴퓨터의 설계)

  • 박세현;이언학
    • Journal of Korea Multimedia Society
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    • v.4 no.1
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    • pp.82-90
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    • 2001
  • Genetic Algorithm(GA) has known as a method of solving NP problem in various applications. Since a major drawback of the GA is that it needs a long computation time, the hardware implementation of Genetic Algorithm is focused on in recent studies. This paper proposes a new type of embedded one chip computer fort Hardware Implementation of Genetic Algorithm. The proposed embedded one chip computer consists of 16 Bit CPU care and hardware of genetic algorithm. In contrast to conventional hardware oriented GA which is dependent on main computer in the process of GA, the proposed embedded one chip computer is independent on main computer. Conventional hardware GA uses the fixed length of chromosome but the proposed embedded one chip computer uses the variable length of chromosome by employing the efficient 16 bit Pipeline Unit. Experimental results show that the proposed one chip computer is applicable to the design of evolvable hardware for Random NRZ bit synchronization circuit.

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Optimal Trajectory Planning for Cooperative Control of Dual-arm Robot (양팔 로봇의 협조제어를 위한 최적 경로 설계)

  • Park, Chi-Sung;Ha, Hyun-Uk;Lee, Jang-Myung
    • Journal of Institute of Control, Robotics and Systems
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    • v.16 no.9
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    • pp.891-897
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    • 2010
  • This paper proposes a cooperative control algorithm for a dual-arms robot which is carrying an object to the desired location. When the dual-arms robot is carrying an object from the start to the goal point, the optimal path in terms of safety, energy, and time needs to be selected among the numerous possible paths. In order to quantify the carrying efficiency of dual-arms, DAMM (Dual Arm Manipulability Measure) has been defined and applied for the decision of the optimal path. The DAMM is defined as the intersection of the manipulability ellipsoids of the dual-arms, while the manipulability measure indicates a relationship between the joint velocity and the Cartesian velocity for each arm. The cost function for achieving the optimal path is defined as the summation of the distance to the goal and inverse of this DAMM, which aims to generate the efficient motion to the goal. It is confirmed that the optimal path planning keeps higher manipulability through the short distance path by using computer simulation. To show the effectiveness of this cooperative control algorithm experimentally, a 5-DOF dual-arm robot with distributed controllers for synchronization control has been developed and used for the experiments.

A Balanced Piggybacking Techniques with Minimizing Average Errors in Near-VOD Service Environment (Near-VOD 서비스 환경에서 평균 오류의 최소화를 고려한 Balanced piggybacking 기술)

  • Choi, Sung-Wook
    • Journal of the Korea Computer Industry Society
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    • v.5 no.9
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    • pp.911-920
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    • 2004
  • Intensive studies have been made in the area of VOD server. Multimedia files in the VOD sever are characterized with the large volume of data, the requirements of synchronization and real-time playback of streams. The basic goal of the study is to find an efficient mechanism to allow maximum number of users under the limited resources such as Bu11er size and disk bandwidth. we propose a efficient user-grouping policy for multi-casting services with dynamic monitoring and management of VOD sever resources. Simulation results show that the rate of buffer usage and QOS change of proposed scheme are about 23% performance improved than that of traditional methods. This implies that our method can allow much more users for given resources.

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Analysis of Global Oscillation via Sync Search in Power Systems (전력계통에서 동조탐색과 광역진동해석)

  • Shim, Kwan-Shik;Nam, Hae-Kon;Kim, Yong-Gu;Moon, Young-Hoan;Kim, Sang-Tae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.7
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    • pp.1255-1262
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    • 2009
  • The present study explained the phenomenon that low frequency oscillation is synchronized with discrete data obtained from a wide area system, and a sync search method. When a disturbance occurs in an power system, various controllers operate in order to maintain synchronization. If the system's damping is poor, low frequency oscillations continue for a long time and the oscillations are synchronized with one another at specific frequency. The present study estimated dominant modes, magnitude and phase of signals by applying parameter estimation methods to discrete signals obtained from an power system, and performed sync search among wide area signals by comparing the estimated data. Sync search was performed by selecting those with the same frequency and damping constant from dominant oscillation modes included in a large number of signals, and comparing their magnitude and phase. In addition, we defined sync indexes in order to indicate the degree of sync between areas in a wide area system. Furthermore, we proposed a wide area sync search method by normalizing mode magnitude in discrete data obtained from critical generator of the wide area. By applying the sync search method and sync indexes proposed in this study to two area systems, we demonstrated that sync scanning can be performed for discrete signals obtained from power systems.

An Analysis of Authentication and Key Agreement Protocols in UMTS (UMTS에서 인증 및 키 동의 프로토콜에 대한 분석)

  • Cui Yong-Gang;Kim Dae-Young;Kim Sang-Jin;Oh Hee-Kuck
    • Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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    • 2006.06a
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    • pp.457-462
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    • 2006
  • In UMTS (Universal Mobile Telecommunication System), a protocol called UMTS AKA is used to authenticate MSs (Mobile Stations). When an MS is in a foreign network, the serving network contacts the AuC (Authentication Center) located at the home network of the MS to authenticate it. To reduce this cost, AuC sends n AVs(Authentication Vectors) to the serving network. Although the use of AVs allows the serving network to authenticate an MS without contacting the AuC each time, there are also shortcomings such as synchronization problem. Subsequently, a set of protocols adopting the same or similar method have been proposed. In this paper, we analyze and compare authentication protocols for UMTS with respect to the use of AVs and its alternatives. We conclude that using Kerberos-like ticket key overcomes some of the drawbacks of using AVs, whereas AVs provide much better security.

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The Development of High Precision Laser Finder Ranger (고정밀 레이저 거리 계측기 개발에 관한 연구)

  • Bae, Young-Chul;Kim, Yi-Gon;Park, Jong-Bae;Kim, Chun-Suk;Cho, Eui-Joo;Seo, Jonh-Joo;Azimov, U.B.;Koo, Young-Duk
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.12
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    • pp.2296-2302
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    • 2006
  • In this paper, we propose a development technique of high precision laser finder ranger within instrument distance 1km, instrument error less than 1 m by using pulse time of flight method in the 5m unit instrument and heterodyne method in the within Am unit. These propose methods can be more advanced to measurement velocity and more highly precision distance instrument not affected the strength of light. We also validate this usefulness.

Design and Implementation of Automatic Installation System for Application Synchronization in PDA (개인 휴대단말에서 응용 프로그램 동기화를 위한 자동설치 시스템의 설계 및 구현)

  • Na, Seung-Won;Oh, Se-man
    • The KIPS Transactions:PartA
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    • v.10A no.6
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    • pp.685-690
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    • 2003
  • The application for PDA as a new wireless Internet device is variously developed to improve the function of PDA, and the application software must be installed to PDAs. In addition. when the power supply of PDA becomes fully discharged, all data stored in the RAM (Random Access Memory) could be vanished, and then the application programs should be reinstalled. This paper presents an automatic installation system of application program, PAIS (PDA Automatic Installation System). It is designed to solve the problem of PDA that PDA's users have to install the application programs on their PDA themselves. When this engine is applied, PDA users can save the time and effort for installation. It's convenient for the PDA users. The PDA and application software company can save the cost to create materials to explain the installation process.