• Title/Summary/Keyword: state-delay

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An Improvement Delay Efficient Scheduling Scheme for Data Aggregation in Duty-Cycle MWSNs (듀티 사이클 MWSN 에서 데이터 집계를위한 개선 지연 효율적인 스케줄링 체계)

  • Vo, Van-Vi;Kim, Moonseong;Choo, Hyunseung
    • Annual Conference of KIPS
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    • 2020.11a
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    • pp.175-177
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    • 2020
  • In multi-channel wireless sensor networks, optimizing data aggregation delay without any channels and timeslots conflicts has been concerned these days. The aggregation delay can be reduced by using different aggregation tree construction methods or scheduling in different methods in bottom-up or top-down manners. In this paper, we propose a new way of constructing aggregation tree purposing to decrease the total aggregation delay. The result shows that our proposed scheme can improve up to 64% comparing with state-of-the-art schemes.

Comparison of Delay Estimates for Signalized Intersection (신호교차로 지체 산정 비교)

  • Jo, Jun-Han;Jo, Yong-Chan;Kim, Seong-Ho
    • Journal of Korean Society of Transportation
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    • v.23 no.1
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    • pp.67-80
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    • 2005
  • In this paper, the primary objective of the research are to review the methods currently avaliable for estimating the delay incurred by vehicles at signalized intersections. The paper compares the delay estimates from a deterministic queueing model, a model based on shock wave theory , the steady-state Webster model, the queue-based models defined in the 1994 and 2001 version of the High way Capacity Manual, in addition to the delays estimated from the TRANSYT-7F macroscopic simulation and NETSIM microscopic simulation. More especially, this paper is to compare the delay estimates obtained using macroscopic and microscopic simulation tools against state-of-the practice analytical models that are derived from deterministic queueing and shock wave analysis theory. The results of the comparisons indicate that all delay models produce relatively similar results for signalized intersections with low traffic demand, but that increasing differences occur as the traffic demand approaches saturation. In particular, when the TRANSYT-7F and NETSIM are compared, it is highly differences as approach for traffic condition to over-saturation. Also, the NETSIM microscopic simulation is the lowest estimates among the various models.

Energy-efficient Low-delay TDMA Scheduling Algorithm for Industrial Wireless Mesh Networks

  • Zuo, Yun;Ling, Zhihao;Liu, Luming
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.10
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    • pp.2509-2528
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    • 2012
  • Time division multiple access (TDMA) is a widely used media access control (MAC) technique that can provide collision-free and reliable communications, save energy and bound the delay of packets. In TDMA, energy saving is usually achieved by switching the nodes' radio off when such nodes are not engaged. However, the frequent switching of the radio's state not only wastes energy, but also increases end-to-end delay. To achieve high energy efficiency and low delay, as well as to further minimize the number of time slots, a multi-objective TDMA scheduling problem for industrial wireless mesh networks is presented. A hybrid algorithm that combines genetic algorithm (GA) and simulated annealing (SA) algorithm is then proposed to solve the TDMA scheduling problem effectively. A number of critical techniques are also adopted to reduce energy consumption and to shorten end-to-end delay further. Simulation results with different kinds of networks demonstrate that the proposed algorithm outperforms traditional scheduling algorithms in terms of addressing the problems of energy consumption and end-to-end delay, thus satisfying the demands of industrial wireless mesh networks.

Measurement Scheme for One-Way Delay Variation with Detection and Removal of Clock Skew

  • Aoki, Makoto;Oki, Eiji;Rojas-Cessa, Roberto
    • ETRI Journal
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    • v.32 no.6
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    • pp.854-862
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    • 2010
  • One-way delay variation (OWDV) has become increasingly of interest to researchers as a way to evaluate network state and service quality, especially for real-time and streaming services such as voice-over-Internet-protocol (VoIP) and video. Many schemes for OWDV measurement require clock synchronization through the global-positioning system (GPS) or network time protocol. In clock-synchronized approaches, the accuracy of OWDV measurement depends on the accuracy of the clock synchronization. GPS provides highly accurate clock synchronization. However, the deployment of GPS on legacy network equipment might be slow and costly. This paper proposes a method for measuring OWDV that dispenses with clock synchronization. The clock synchronization problem is mainly caused by clock skew. The proposed approach is based on the measurement of inter-packet delay and accumulated OWDV. This paper shows the performance of the proposed scheme via simulations and through experiments in a VoIP network. The presented simulation and measurement results indicate that clock skew can be efficiently measured and removed and that OWDV can be measured without requiring clock synchronization.

Development of a variable resistance-capacitance model with time delay for urea-SCR system

  • Feng, Tan;Lu, Lin
    • Environmental Engineering Research
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    • v.20 no.2
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    • pp.155-161
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    • 2015
  • Experimental research shows that the nitric oxides (NOX) concentration track at the outlet of selective catalytic reduction (SCR) catalyst with a transient variation of Adblue dosage has a time delay and it features a characteristic of resistance-capacitance (RC). The phenomenon brings obstacles to get the simultaneously NOX expected to be reduced and equi-molar ammonia available to SCR reaction, which finally inhibits NOX conversion efficiency. Generally, engine loads change frequently, which triggers a rapid changing of Adblue dosage, and it aggravates the air quality that are caused by NOX emission and ammonia slip. In order to increase the conversion efficiency of NOX and avoid secondary pollution, the paper gives a comprehensive analysis of the SCR system and tells readers the key factors that affect time delay and RC characteristics. Accordingly, a map of time delay is established and a solution method for time constant and proportional constant is carried out. Finally, the paper accurately describes the input-output state relation of SCR system by using "variable RC model with time delay". The model can be used for a real-time correction of Adblue dosage, which can increase the conversion efficiency of NOX in SCR system and avoid secondary pollution forming. Obviously, the results of the work discover an avenue for the SCR control strategy.

The State Estimator Design for Servo system with Delayed Input (지연 입력을 가진 서보시스템의 상태 추정자 설계)

  • Shin, Doo-Jin;Kong, Jeong-Ja;Huh, Uk-Youl
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.5
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    • pp.607-614
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    • 1999
  • This paper deals with the design problem of the state estimator for servo system. The servo system has input time delay which depends on the computational time of control algorithm. The delayed input is a factor that brings out the state estimation error. So in order to reduce the state estimation error of the system, we propose a state estimator in which the delayed input of the system is considered. For this purpose, discrete time state space model is established accounting for the delayed input and a state estimator is designed based on this model. Kalman filter algorithm is employed in the design of the state estimator. The proposed estimator is used in the speed control of servo system with delayed input. Performance of the proposed state estimator is exemplified via simulations and experiments for servo system. Also, robustness of the proposed estimator to modeling error by variation of the system parameters is also shown in simulations.

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A Study on Robust Control of DC Servo Motor Using Time Delay Control and Observer/Controller Stabilization (시간지연 제어기법을 이용한 DC서보모터 강인제어 및 관측기/제어기 안정화에 관한 연구)

  • 이정완;장평훈;김승호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.5
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    • pp.1029-1040
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    • 1993
  • Recently the Time Delay Control (TDC) method has been proposed as a promising technique in the robust control area, where the plants have nonlinear dynamics with parameter variations and substantial disturbances are present. TDC method, however, requires the measurements of all the state variables, together with their derivatives. This requirement imposes a severe limitation on the applications to most real systems. In order to solve this measurement problem, we proposed an observer design method that can stably reconstruct the state variables and their derivatives. the stability of the overall system has been analyzed and proved. Then, for a simulation study, the controller/observer based on our design method has been applied to a nonlinear plant, the result of which confirmed that the controller/observer performs satisfactorily as predicted, Finally we made experimentations on a DC servo motor that is substantial amount of inertia variations and external disturbances. the results showed that the controller/observer performs quite robustly under those variations and disturbances, and is much less sensitive to sensor noise than the controller using numerical differentiations.

Extended Integral Control with the PID Controller (PID 제어기를 이용한 확장 적분 제어)

  • Moon, Young-Hyun;Jung, Ki-Young;Ryu, Heon-Su;Song, Kyung-Bin
    • Proceedings of the KIEE Conference
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    • 1999.07c
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    • pp.1063-1066
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    • 1999
  • This paper presents an extended integral control with the PID controller by introducing the delay and decaying factors. The convolution integral control scheme is developed by substituting proportional convolution integral controls for the proportional-integral control. So far, the integral part of the PI controller produces a signal that is proportional to the time integral of the input of the controller. The steady-state operation points are affected forever by the errors in the past due to the input signal containing the information of the errors in the past. These phenomina may cause some disturbances for other control purposes related to the given PI control. Introduction of forgetting factors of the error in the past can resolve the disturbance problems. Various forgetting factors are developed using the delay, the decaying factors, and the combination of the delay and the decaying factors. The proposed various extended integral control schemes can be applicable to corresponding PI control designs in which the error in the past may badly affect to the current steady-state operation points and may cause some disturbances for other control purposes.

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A Study on Hybrid(Position/Force) Control of Robot Using Time Delay Control (시간지연제어기법을 이용한 로봇의 혼합(위치/힘) 제어에 관한 연구)

  • 장평훈;박병석;박주이
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.10
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    • pp.2554-2566
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    • 1994
  • Robot position/force control has been a difficult task owing to the interaction between a robot and an environment with a rather high stiffness. In addition to the dynamic instability, the interaction causes the following problem : 1) chattering at steady-state, 2) dynamic coupling effect of robot, and 3) performance degradation due to a titled environment. To solve the problem, the Time Delay Control(TDC), which has been known to be quiet robust to plant uncertainties and disturbances, has been applied. In conjunction to TDC, the following three ideas were also used : 1) To reduce the amplitude of the chattering at the steady state, a novel scheme was adopted to enhance the resolution type solution of A/D conversion for the force sensor. 2) To reduce the dynamic coupling, a trajectory type position command was tried on a comparative basis to the step command, as well as a more accurate mass matrix was used instead of the constant mass matrix. 3) And finally to improve the performance in the tilted environment, force derivatives instead of position derivatives were used in the TDC law. Computer simulations and experiments resulted in obvious improvements on the quality of the hybrid control, thereby clearly demonstrating the effectiveness of TDC with the proposed ideas.

A Linear Precoding Technique for OFDM Systems with Cyclic Delay Diversity

  • Hui, Bing;Chang, Kyung-Hi
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.2 no.5
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    • pp.253-264
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    • 2008
  • Cyclic delay diversity (CDD) is considered a simple approach to exploit the frequency diversity, to improve the system performance in orthogonal frequency division multiplexing (OFDM) systems. Also, the linear precoding technique can significantly improve the performance of communication systems by exploiting the channel state information (CSI). In order to achieve enhanced performance, we propose applying linear precoding to the conventional CDD-OFDM transmit diversity schemes over Rayleigh fading channels. The proposed scheme works effectively with the accurate CSI in time-division-duplex (TDD) OFDM systems with CDD, where the reciprocity is assumed instead of channel state feedback. For a BER of 104 and the mobility of 3 km/h, simulation results show that a gain of 6 dB is achieved by the proposed scheme over both flat fading and Pedestrian A (Ped A) channels, compared to the conventional CDD-OFDM system. On the other hand, for a mobility of 120 km/h, a gain of 2.7 dB and 3.8 dB is achieved in flat fading and Vehicular A (Veh A) channels, respectively.