• Journal of the Korea Society of Computer and Information
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• v.6 no.4
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• pp.94-99
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• 2001

Recently a lot of informations is interchanged among many users through the network such as Internet. In this situation. multimedia data transfer has some problems. that are jitter, the difference of delay in arriving packets, and loss of data due to the various delay between sender and receiver. The arriving data packets are not synchronized because of those problems. Especially, an efficient method is needed to revise the sudden large changes of the delay, called spike-like delay. which is occured in explosive growth of networking. We propose efficient synchronization algorithm which controls synchronization interval and adjusts to sudden changes in networks. The algorithm, a receiver-driven adaptive synchronization method, is to synchronize the arriving data packets against spike-like delay and decrease the loss of them. In addition, another method is proposed in this paper. The method uses the probabilistic features of delay distribution appearing in general network. It is evaluated for the loss of data packets and the delay times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.240-248
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• 2006

In this paper, we consider an OFDM receiver algorithm design for IEEE 802.11a/p system, which targeting large coverage area while keeping the transmission format unchanged. Particularly, taking into account the inter-symbol interference(ISI) and inter-carrier interference(ICI) that can be induced with large RMS delay spread, we employ channel shortening time-domain equalizer(TEQ) and evaluate the receiver performance in terms of SINR and packet error rate(PER). The preamble defined in IEEE802.11a/p is used to estimated the initial equalizer tap coefficients. Primary purpose of the paper is to give an answer to the question, though partially, whether or not 16-QAM constellation can be used in none line of sight environment at the boundary of a large coverage area. To this end, we first analyze the required TEQ parameters for the target channel environment and then perform simulation for PER performance evaluation in a generic frequency selective fading channel with exponential power-delay profile.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8
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• pp.2543-2554
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• 2000

Packet schedulers for real-time communication must provide bounded delay and efficient use of network resources such as bandwidth, buffers and so on. In order to satisfy them, a large number of packet scheduling methods have been proposed. Among packet scheduling methods, an EDF (Earliest Deadline First) scheduling is the optimal one for a bounded delay service. A disadvantage of EDF scheduling is that queued packets must be sorted according to their deadlines, requiring a search operation whenever a new packet arrives at the scheduler. Although an RPQ (Rotating Priority Queue) scheduler, requiring large size of buffers, does not use such operation, it can closely approximate the schedulability of an EDF scheduler. To overcome the buffer size problem of an RPQ scheduler, this paper proposes a new scheduler named MRPQ (Multiple Rotating Priority Queue). In a MRPQ scheduler, there are several layers with a set of Queues. In a layer, Queues are configured by using a new strategy named block Queue. A MRPQ scheduler needs nearly half of buffer size required in an RPQ scheduler and produces schedulability as good as an RPQ scheduler.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.577-584
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• 2010

In this paper, a cooperative MAC protocol that is reliable over bad wireless channel environments and thus can enhance the system performance much more is proposed. Its performance is evaluated with the computer simulation. The system throughput and average waiting delay are used as performance measures. According to numerical results, the proposed MAC protocol provides better system throughput by 24% than the traditional rDCF scheme. From the average waiting delay point of view, when the number of terminals is small, the proposed MAC protocol has the better performance in an average view-point than the rDCF scheme. However, when the number of terminals is large, the proposed MAC protocol provides a little worse performance than the rDCF scheme. That is because, when the number of terminals is large, the dominant factor affecting the system performance is channel contention procedure, which results in lots of collisions. However, if the queuing delays in the waiting buffers are included for calculating the average waiting delay, then the total system delay will be smaller than the rDCF scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.205-214
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• 2008

To transfer large amount of packets fast in sensor network, it is necessary that the delay between successive packet transmissions should be minimized as possible. In Sensor network, since the Operating Systems are worked on the event driven, the Timer Event is used to transfer packets successively. However, since the transferring time of packet completely is varies very much, it is very hard to set appropriate interval. If interval is too long, delay also becomes too long but if interval is too short, the fail of transfer request would increase. In this paper, we propose ESTEO which reduces the delay between successive packet transmissions by using SendDone Event which informs that a packet transmission has been completed. In ESTEO, the delay between successive packet transmissions is shortened very much since the transmission of next Packet starts at the time when the transmission of previous packet has completed, irrespective of the transmission time. Therefore ESTEO could provide high packet transmission rate given large amount of packets.

• Journal of Fisheries and Marine Sciences Education
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• v.10 no.1
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• pp.1-14
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• 1998

Transportation provides an infrastructure vital to economic growth, and it is also an integral part of production. As a port is regarded as the interface between the maritime transport and domestic transport sectors, it certainly play a key role in any economic development. Ship's delay caused by port congestion has recently has recently attracted attended with the analysis of overall operation in port. In order to analyse complicated port operation which contains large number of variable factors, queueing theory is needed to be adopted, which is applicable to a large scale transportation system in chiding ship's delay in Inchon port in relation to ship's delay problem. The overall findings are as follows ; 1. The stucture of queueing model in this port can be represented as a complex of multi-channel single-phase 2. Ship's arrival and service pattern were Poisson Input Erlangian Service. 3. The suitable formula to calculate the mean delay in this port, namely, $W_q={\frac{{\rho}}{{\lambda}(1-{\rho})}}{\frac{e{\small{N}}({\rho}{\cdot}N)}{D_{N-1}({\rho}{\cdot}N)}}$ Where, ${\lambda}$ : mean arrival rate ${\mu}$ : mean servicing rate N : number of servicing channel ${\rho}$ : utilization rate (l/Nm) $e{\small{N}}$ : the Poisson function $D_{(n-1)}$ : a function of the cumulative Poisson function 4. The utility rate is 95.0 percents in general piers, 75.39 percents in container piers, and watiting time 28.43 hours in general piers, 13.67 hours in container piers, and the length of queue is 6.17 ships in general piers, 0.93 ships in container piers, and the ship turnaround time is 107.03 hours in general piers, 51.93 hours in container piers.

• Journal of Cadastre & Land InformatiX
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• v.53 no.2
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• pp.67-77
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• 2023

As cities become overcrowded and concentrated, the demand for public services continues to increase due to the improvement of the living standards of urban residents. Among them, fire service can be seen as one of the important public services by reducing damage caused by accidents in emergency situations and affecting the improvement of access to medical services for urban residents. Rapid movement of patients and medical institutions within golden time and proper first aid are essential elements in emergency situations, and Seoul is a super-large city with a large population of about 10 million people and has a large number of emergency medical patients. Therefore, this study used spatial regression analysis to examine the factors affecting the delay factors of emergency dispatch in Seoul to secure golden time, and derived management priorities, and suggested implications for the management of emergency vehicle dispatch delay factors. As a result of the main analysis, land-use characteristics were the most influential factor in emergency vehicle dispatch time, and land-use mixing, commercial area density, average patient age, and average road length were found to affect emergency vehicle dispatch time in order. This study can be used as important basic data for an accurate understanding of the delay factors for emergency dispatch and preparing countermeasures according to priorities.

• ETRI Journal
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• v.22 no.4
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• pp.40-50
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• 2000

We apply a "sliding-window" Maximum Likelihood(ML) estimator to estimate traffic parameters On-Off source and develop a method for estimating stochastic predicted individual cell arrival rates. Based on these results, we propose a simple Connection Admission Control(CAC)scheme for delay sensitive services in broadband onboard packet switching satellite systems. The algorithms are motivated by the limited onboard satellite buffer, the large propagation delay, and low computational capabilities inherent in satellite communication systems. We develop an algorithm using the predicted individual cell loss ratio instead of using steady state cell loss ratios. We demonstrate the CAC benefits of this approach over using steady state cell loss ratios as well as predicted total cell loss ratios. We also derive the predictive saturation probability and the predictive cell loss ratio and use them to control the total number of connections. Predictive congestion control mechanisms allow a satellite network to operate in the optimum region of low delay and high throughput. This is different from the traditional reactive congestion control mechanism that allows the network to recover from the congested state. Numerical and simulation results obtained suggest that the proposed predictive scheme is a promising approach for real time CAC.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1009-1012
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• 1998

An efficient algorithm for clock skew optimization is proposed in this paper. It construct a new clock routing topology which is the generalized graph model while previous methods uses tree-structured routing topology. Edge-insertion technique is used in order to reduce the clock skew. A link-edge is inserted repeatedly between two sinks whose delay difference is large and the distance is small. As a result, the delay of a sink which has the longer delay is decreased and the clock skew is reduced. The proposed algorithm is implemented in C programming language. From the experimental results, we can get the total wire length minimization under the given skew bound.

• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.124-129
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• 2009

Although the maximum sum-rate capacity of multiple-input multiple output(MIMO) broadcast channels(BCs) can be achieved by dirty-paper coding(DPC), the results were obtained without fairness considerations in uncorrelated MIMO channels. In this paper, we propose new multiuser scheduling algorithms, which find a best user set for approaching the maximum sum-rate capacity while maintaining fairness among users. We analyze the performance of the proposed algorithms using zero-forcing dirty paper coding(ZF-DPC) in the correlated MIMO BCs for throughput and delay fairness, respectively. Numerical results demonstrate that a large time window can reduce the average throughput difference between users, but it increases head-of-line(HOL) delay jitters in the case of delay fairness.