• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.1
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• pp.85-98
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• 1994

The distribution of random sum of i. i. d. exponential random variables is called GHP (Generalized Phase-Type) distribution. The class of GPH distributions is large enough to include PH (Phase-Type) distributions and has several properties which can be applied conveniently for computational purposes. In this paper, we show that any distribution difined on R$^{+}$ can be app-roximated by the GPH distribution and demonstrate the accuracy of the approximation through various numerical examples. Also, we introduce an efficient way to compute the delay and waiting various numerical examples. Also, we introduce an efficient way to compute the delay and waiting time distributions of the GPH/GPH/1 queueing system which can be used as an approximation model for the GI/G/1 system, and validate its accuracy through numerical examples. The theoretical and experimental results of this paper help us accept the usefulness of the approximations based on GPH distribution.n.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.726-747
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• 2013

In order to support a large number of mobile stations (MSs) with statistical multiplexing in cellular networks, a random access scheme is widely used for uplink (UL) bandwidth request (BR). In the design of a random access based BR scheme, there are two important requirements: short connection delay and diverse Quality of Services (QoSs) support. Such requirements are crucial for IMT-Advanced systems like IEEE 802.16m to provide various types of fourth generation (4G) data services. IEEE 802.16m provides advanced UL BR schemes for non-real time polling service (nrtPS) and best-effort (BE) service to meet the requirements of short connection time and multiple QoS level support. In order to provide short connection time and multiple QoS support, three-step and differentiated BR procedures are adopted. In this paper, a novel modelling of IEEE 802.16m contention based BR scheme is proposed that uses a 2-dimensional discrete time Markov chain. Both the short access delay three-step BR procedures and normal five-step BR procedure are considered in the model. Our proposed model also incorporates the IEEE 802.16m differentiated BR procedure. With the proposed model, we extensively evaluate the performance of IEEE 802.16m BR for two different service classes by changing QoS parameters, such as backoff window size and BR timer. Computer simulations are performed to corroborate the accuracy of the proposed model for various operation scenarios. With the proposed model, accurate QoS parameter values can be derived for the IEEE 802.16m contention-based BR scheme.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1348-1351
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• 1996

In field bus network, field device are connected with a medium. Because a medium must be shared for transmitting data, there are random delay time when data arrive destination station. It is difficult that all data packets are guaranteed synchronization and real-time restriction. In this paper, we show an algorithm that makes network utilization to maximum, guarantees real-time restriction, calculates sampling time at all control loop.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.11
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• pp.786-792
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• 2004

A wavelet based ECG data compression has become an attractive and efficient method in many mobile tele-cardiology applications. But large data size required for high compression performance leads a serious delay. In this paper, new wavelet compression method with minimum delay is proposed. It is based on deciding the type and compression ratio(CR) of block organically according to the standard deviation of input ECG data with minimum block size. Compression performances of the proposed algorithm for different MIT ECG Records were analyzed comparing other ECG compression algorithm. In addition to the processing delay measurement, compression efficiency and reconstruction sensitivity to error were also evaluated via random noise simulation models. The results show that the proposed algorithm has both lower PRD than other algorithm on same CR and minimum time in the data acquisition, processing and transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.940-949
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• 1998

The paper proposes an effective mechanism hiring the adaptive buffer control schemes on the mobile seceiver's side that can resolve the problems of delay spikes caused by the handover process onthe cell boundaries when they transmit real-time moving images through the high speed wireless channels. to confirm the effectiveness of the proposed schemes, we have modeled the characteristics of the random errors on the wireless channels, the burst errors and that of the transmission delay by the handover. We also compared the rate of the delay-adaptation of the receive buffers caused by the delay and delay spikes. the comparison was done by testing the suggested schemes against the existing schemes by applying tehm to the packet delay model. We also could identify the noticable reduction of the casesof buffer delay and overflow compared with the conventional schemes, by applying the suggested algorithm to the video image compressed by H.263.

• The KIPS Transactions:PartC
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• v.19C no.4
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• pp.247-252
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• 2012

Network coding has been shown to improve various performance metrics in network systems. However, if network coding is implemented as software a huge time delay may be incurred at encoding/decoding stage so it is imperative for network coding to be parallelized to reduce time delay when encoding/decoding. In this paper, we compare the performance of parallelized decoders for random linear network coding (RLC) and pipeline network coding (PNC), a recent development in order to alleviate problems of RLC. We also compare multi-threaded algorithms on multi-core CPUs and massively parallelized algorithms on GPGPU for PNC/RLC.

• ETRI Journal
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• v.34 no.3
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• pp.462-465
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• 2012

This letter proposes a new distributed scheduling scheme combined with routing to support the quality of service of real-time applications in wireless mesh networks. Next, this letter drives average end-to-end delay of the proposed scheduling scheme that sequentially schedules the slots on a path. Finally, this letter simulates the time division multiple access network for performance comparison. From the simulation results, when the average number of hops is 2.02, 2.66, 4.1, 4.75, and 6.3, the proposed sequential scheduling scheme reduces the average end-to-end delay by about 28%, 10%, 17%, 27%, and 30%, respectively, compared to the conventional random scheduling scheme.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.4
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• pp.292-297
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• 2016

The first-order plus dead time(FOPDT) and second-order plus dead time(SOPDT), which describes a linear monotonic process quite well in most chemical and industrial processes and is often sufficient for PID and IMC controller tuning. This paper presents an application of heuristic harmony search(HS) optimization algorithm to the identification of linear continuous time-delay systems from step response. This recently developed HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. The effectiveness of the proposed identification method has been demonstrated through a number of simulation examples.

• 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.