• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.195-199
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• 2014

Various M2M applications have different quality-of-service(QoS) requirements to be implemented practically. QoS requirements are normally data rate and delay constraint. However, there are limited number of wireless communication chip solutions which cannot support QoS requirements for all M2M application. Hence, aggregated usage of plural wireless communication chip solutions should be needed to implement M2M applications. In this paper, we consider the case that two wireless communication chips using random access protocol work together to transmit data of an M2M application. In such case, data rate and delay performance are mathematically analyzed. In our results, practical data rate can be improved from 2.5 to 7 times while delay constraints are satisfied if we simply use two wireless communication chips together.

• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.1191-1205
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• 2008

We consider a delayed predator prey model. The local stability and Hopf bifurcation results are stated taking the time delay as a control parameter. We apply multiple scale analysis to analyze the effects of additive white noises near the Hopf bifurcation point at the positive interior equilibrium state. The governing equations for the amplitude of oscillations on a slow time scale are derived. We identify the process of amplitude of oscillations and derive its transient properties. We show that oscillations, which would decay in the deterministic system whenever time delay lies below its critical value, persists for long time under the validity of multiple scale analysis.

• Journal of Korean Society of Transportation
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• v.9 no.1
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• pp.47-56
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• 1991

With respect to stochastic delays at linked signals the solid quantitative information has not been available as yet. On the basis of field data the values of "I" (variance-mean ration of flow) were related with the rate of flow. The stochastic delays with specific "I" values were obtained from the distribution of overflow queue, which were calculated by the use of Markov chains. This examination of the results led to the derivation of a simple method for calculating stochastic dclays through the introduction of "I" into Miller's model. The good agreement was shown between the model and the field. The relationships between the cycle lengths and delays were examinated in a large number of conditions with regard to degree of saturation. signal split and link length. Within the practical range of cycle length uniform delays were dominant and no critical point was found in terms of minimum, delay. In highly saturated conditions however the weight of stochastic delay is noticeable.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.13-16
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• 2002

In this paper, we newly propose a predictor model which is a method to overcome the time-varying delay in a system and we verify that the predictor model is well suited for the time-delayed system and improves the stability a lot through the experiments. The proposed predict compensator compensates uncertain time delays and minimizes variance of system performance. Therefore it is suitable for the control of uncertain systems and nonlinear systems that are difficult to be modeled. The simulation conditions are set for the cases of various input time delays and simulations are applied for the 2-axis robot arms which are drawing a circle on the plane. Conclusively, the proposed predict compensator represents stable properties regardless of the time delay. As a future research, we suggest to develope a robust control algorithm to compensate the random time delay which occurs in the tole-operated systems.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.1
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• pp.15-22
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• 2013

In oceanic flight routes, HF radio and satellite data links have weather restrictions, long propagation delay and low data throughput. In this paper, we propose oceanic aeronautical communications scheme in the VHF band based on ad-hoc communication. The proposed scheme organizes autonomously a multi-hop network that is divided into multiple local network using aircraft to fly long-distance communication and supports a hybrid type of multiple access, which consists of random access and TDMA (Time Division Multiple Access) scheme. In addition, several algorithms to apply spatial reuse of transmission to multi-hop long range communication environments have been proposed. The proposed system proves performance improvement on delay time as an effective solution to communicate end-to-end on the oceanic flight routes and strengthens the reliability of oceanic aeronautical communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.10
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• pp.2620-2633
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• 1996

In this paper, a new high-speed local area network using a dual mode switching access (DMSA) protocol implemented on a dual unidirectional bus is described. By utilizing the implicit positionalordering of stations on a unidirectional bus, the proposed system switches between random access mode and the token access model withoug unnecessary delay. Therefore, unlike other hybrid systems such as Buzz-net and Z-net, DMSA does not show a rapid degradation in performance as the load increases. We obtain the average channel utilization and the average access delay by using a simplified analytic model. The numerical results obtained via analysis are compared to the simulation resuls for a partial validation of the approximate model. The performance characteristics of DMSA are superior delay-throughput characteristics at light and medium loads, compared to compared to other LAN systems, and the capability of providing a single active station with full capabity of the channel.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.2
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• pp.253-260
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• 2015

Love which is one of the emotional of mankind, has been studied in sociology and psychology as a matter of grate concern. In this paper we represent romantic behaviors in the love equation of Romeo and Juliet as time series and phase portraits in the case of with and without time delay. And we also analyze their difference.

• Journal of the Korea Society for Simulation
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• v.10 no.3
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• pp.71-82
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• 2001

Considering material handling delay which occurs between storage and processing stations, we propose an algorithm to estimate the required storage capacity, i.e., number of aisles and number of openings in vertical and horizontal directions in each aisle, of an automated storage/retrieval(AS/R) system. Due to the random nature of storage and retrieval requests, proportion of single and dual commands is not known in advance. Two design criteria, maximum permissible overflow probability and maximum allowable storage/retrieval(S/R) machine utilization, are used to compute the storage capacity. Most of studies assume that storage capacity of AS/R systems is given, although it is a very important decision variable in the design phase. Therefore, the proposed model can be effectively used in the design phase of new AS/R systems.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.2
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• pp.254-259
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• 1987

This paper describes the CMOS standard cell library implemented in double metal single poly gate process with 3\ulcornerm design rule, and its results of testing. This standard cell library contains total 33 cells of random logic gates, flip-flop gates and input/output buffers. All of cell was made to have the equal height of 98\ulcornerm, and width in multiple constant grid of 9 \ulcornerm. For cell data base, the electric characteristics of each cell is investigated and delay is characterized in terms of fanout. As the testing results of Ring Oscillator among the cell library, the average delay time for Inverter is 1.05 (ns), and the delay time due to channel routing metal is 0.65(ps)per unit length.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.4
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• pp.1-6
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• 1999

When continuous media are transmitted over the communication networks, asynchrony which can not maintain temporal relationships among packets my occur due to a random transit delay. There exist two types of synchronization schemes ; for guaranteed or non-guaranteed resource networks. The former which applies a resource reservation technique maintains delay characteristics however, the latter supply a best-effort service. In this paper, I propose a intra-media synchronization scheme to transmit continuous media on general networks not guaranteeing a bounded delay time. The scheme controls transmission times of the packets by estimating next delay time with the delay distribution So, the arriving packets my be maintained within a limited delay boundary, and playout will be performed after buffering to smoothen small delay variations. To prevent network congestion and maintain minimum quality of service the transmitter performs media scaling-down by dropping the current packet when informed excessive delay from the receiver.