• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.684-693
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• 2011

Measurement time delay in the transfer alignment is very important. It has been well known that the time delay degrades the alignment performance and makes some navigation errors on the transfer alignment of slave INS(SINS). Therefore there are many schemes to eliminate that time delay but the compensation technique through the estimation by Kalman filter through modeling the time delay as a random constant is generally used. In the case of change over measurement time delay or the large measurement time delay, estimation performance in the existing compensation technique is degraded because model of time delay is not correct any more. In this paper, we propose the method to keep the time delay almost constant even though in the abnormal communication state and very small through feedback compensation using double buffer. Double buffer consists of two moving window to temporarily store measurements from master INS and slave INS in real time.

• International Journal of Computer Science & Network Security
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• v.23 no.1
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• pp.96-102
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• 2023

In this paper, we proposed Channel Transfer Function estimation based on Delay and Doppler Profile for underwater acoustic OFDM communication system. It improved the estimation accuracy of the channel transfer function by linear time interpolation the change of Scattered Pilot (SP) insertion frequency in the time direction and the time by Delay and Doppler profile that analyzes the multipath situation of the channel investigated the performance of interpolation by simulation and report it. Previous works is inserted SP every 4 OFDM. It was effective under the environment without multipath, but it has observed that the effect of CTF compensation has been lowered in multipath channel condition. In addition to be better when inserted SP every 2 OFDM. But the amount of sending data will be decrease. Therefore, we conducted research to improve 4 OFDM with new interpolator. A computer simulation was performed as a comparison of SP inserted every 4 OFDM, SP inserted every 2 OFDM, and 4 OFDM with new interpolator. the performance of the proposed system is overwhelmingly improved, and the performance is slightly improved even 64 QAM.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.40.1-40
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• 2001

In this paper, control theoretic approaches are proposed to guarantee QoS (Quality of Series) such as packet delay and packet loss of real-time traffic in high-speed communication network. Characteristics of variable rate real-time traÆc in communication networks are described. The mathematical model describing networks including source and destination nodes are suggested. By a traffic control mechanism, it is shown that worst-case end-to-end transfer delay of traffic can be controlled and packet loss can be prevented. The simulation shows results of delay control and buer level control to raise QoS in realtime traffic.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.355-364
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• 2010

A session transfer method, referred to as a Recipient Serving-call session control function (S-CSCF) Assured (RSA), is proposed in order to support both session mobility and consistency in IP multimedia subsystem (IMS) based next generation network (NGN). RSA session transfer simplifies a basic session transfer operation specified in [1] by using the user agent client (UAC) like characteristics of an S-CSCF. To show its efficiency, the session transfer delay and the traffic cost of RSA session transfer are investigated and compared with those of existing session transfer applications, including Assured and Consultative session transfers, by practically considering multiple session transfer failures. It is shown that RSA session transfer can further improve user experience by reducing session transfer delay as well as traffic cost than Assured and Consultative session transfers.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.219-227
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• 2014

Ethernet, ATM, and CAN are wide-utilized communication protocols for information transfer by internet. Many researches about Network Time-delay have been based on network modeling. But almost of them have not shown an optimal solution in various communication environments. So, asynchronous sample system modeling based internet is needed to be robust in various network environments. Also as closed loop system in internet has a different operational characteristics and noise characteristics comparing with conventional control system, new robust control method is needed in instruments which demand to be safe and precise for internet environments. In order to achieve the safe and precise real-time control in remote plant, this paper is aimed to analysis the transfer characteristics and time-delay of control system in cluster web server.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.1
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• pp.157-163
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• 2023

Recently, as businesses and data types become more complex and diverse, efficient data analysis using machine learning is required. However, since communication in the cloud environment is greatly affected by network latency, data analysis is not smooth if information delay occurs. In this paper, SPT (Safe Proper Time) was applied to the cluster-based machine learning data analysis agent proposed in previous studies to solve this delay problem. SPT is a method of remotely and directly accessing memory to a cluster that processes data between layers, effectively improving data transfer speed and ensuring timeliness and reliability of data transfer.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.2
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• pp.241-249
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• 1998

In this paper, we seek to find an optimal allocation of link capacity in a data communication network. The architecture of the data communication network considered in the study is an online-service network based on public switched telephone network(PSTN) and packet switched data network(PSDN). In designing the architecture of the network, we need to deal with various measures of quality of service(QoS). Two important service measures are the call blocking probability in PSTN and the data transfer delay time in PSDN. Considering the tradeoff between the call blocking probability and the data transfer delay time in the network, we have developed the optimal link capacity allocation model that minimizes the total link cost, while guarantees the call blocking probability and the data transfer delay time within an acceptable level of QoS. This problem can be formulated as a non-linear integer programming model. We have solved the problem with tabu search and simulated annealing methods. In addition, we have analyzed the sensitivity of the model and provided the insight of the model along with computational results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.8
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• pp.3542-3566
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• 2018

In this paper, we investigate a buffer-aided wireless powered cooperative communication network (WPCCN), in which the source and relay harvest the energy from a dedicated power beacon via wireless energy transfer, then the source transmits the data to the destination through the relay. Both the source and relay are equipped with an energy buffer to store the harvested energy in the energy transfer stage. In addition, the relay is equipped with a data buffer and can temporarily store the received information. Considering the buffer-aided WPCCN, we propose two buffer-aided relaying protocols, which named as the buffer-aided harvest-then-transmit (HtT) protocol and the buffer-aided joint mode selection and power allocation (JMSPA) protocol, respectively. For the buffer-aided HtT protocol, the time-averaged achievable rate is obtained in closed form. For the buffer-aided JMSPA protocol, the optimal adaptive mode selection scheme and power allocation scheme, which jointly maximize the time-averaged throughput of system, are obtained by employing the Lyapunov optimization theory. Furthermore, we drive the theoretical bounds on the time-averaged achievable rate and time-averaged delay, then present the throughput-delay tradeoff achieved by the joint JMSPA protocol. Simulation results validate the throughput performance gain of the proposed buffer-aided relaying protocols and verify the theoretical analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.262-269
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• 2005

Automatic landing of UAVs receives increasing interest these days, with increasing number of the developed UAV systems. In this paper, a glidepath tracking algorithm of the subscale UAV was proposed and the performance was analyzed. Flight data analysis shows that the existing autolanding flight control algorithm has a classical type glidepath control. This paper presents an alternative glidepath tracking strategy based on embedded flight control law. The performance of the proposed strategy was investigated through the TDP(Touch Down Point) error analysis with regard to various flight environment: steady headwind, atmospheric disturbance, communication transfer delay. It was verified that the proposed glidepath tracking strategy can be successfully applied to the practical autolanding of UAV systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2318-2324
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• 2017

Quantum cryptography, which is emerging as a next generation password, is being studied by quantum cryptographic transfer protocols and quantum secret communication. Quantum key transfer protocol can be used in combination with the modern password because of the inefficiency of the use of the password, or the use of OTP(one time password). In this paper an algorithm for direct communication by means of direct cryptographic communications rather than quantum keys. The method of implementing quantum secure direct community was adopted using 2-channel methods using Einstein gravity field. Two channels were designed to adopt a quantum secret communication protocol that applies time delay between 2-channels of channel to apply time difference between 2-channels. The proposed time delay effect reflects the time delay by reflecting the gravitational lensing phenomenon. Gravity generator with centrifugal acceleration is incorporated in the viscometer, and the time delay using this implies the correlation between the variance of the metametry.