• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.479-484
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• 2003

In the current Internet, it is difficult for an Internet Phone to guarantee the QoS due to variable network conditions such as packet loss rate, delay and bandwidth. In addition, the QoS of an Internet Video Phone is more hard to guarantee because of video data. In this paper, we investigate application-level QoS control schemes that can adapt to variable network conditions, and describe an error control scheme and a congestion control scheme. Based on these QoS control schemes, we have designed and implemented an Internet Video Phone System that supports adaptive audio and video delivery. Through experiments, we found that the Internet Video Phone can reduce the packet loss rate considerably as well as adjust the transmission rate considering other TCP flows.

• Journal of the Korea Society of Computer and Information
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• v.7 no.3
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• pp.143-148
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• 2002

Congestion may take place in the ATM network because of high-speed cell transmission features, and cell delay and loss also can be caused by unexpected traffic variation. Thus, traffic control mechanisms are needed. One of them to decrease congestion is the Cell shaping. This paper proposes a hybrid type cell shaper composed of a Leaky Bucket with token pool, Tn with time window, and a spacing control buffer. The simulator BONeS with the ON/OFF traffic source model evaluates the performance of the proposed cell shaping method. Simulation results show that the cell shaping concerning the respective source traffics is adapted to and then controlled on the mean bit rate.

• The Transactions of the Korea Information Processing Society
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• v.4 no.1
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• pp.224-236
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• 1997

In order to control the flow of traffic in ATM networks and optimize the usage of network resources, an appropriate control mechanism is necessary to cope with congestion or prevent degradation of network performance caused by congestion. While the conventional UPC algorithm provides only unstable preventive function unrelated with the state of networks and is unable to recover congestion, the proposed adaptive UPC algorithm supervises the situation of ATM networks using the information from OAM cell. Then the monitor of the proposed adaptive UPC algorithm controls leaky rate and buffer threshold value according to QOS. Therefore, the proposed algorithm can cope with congestion as well as prevent and react sensitively to buffer delay. In proportion to the diversity of traffic and the increase of transmission rate in networks, the adaptive UPC-BT algorithm proposed in this paper can be effectively used in ATM networks with wide applications. This paper shows that the proposed algorithm efficiently uses in ATM networks with application. This paper shows that the proposed algorithm efficiently use network resources and provides QOS to users for various kinds of traffics by comparing with conventional UPC algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2653-2663
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• 1997

The successive and parallel interference cancellation schemes are two well-known types of multi-stage interference cancellation schemes using the conventional correlator receivers as a basic building block, which has been known to significantly improve the performance of DS/CDMA system in the multiple access communication. Performance comparison between these two schemes is made strictly based on the analytical and it has been shown that the successive interference cancellation (SIC) scheme is more resistant to fading than the parallel interference cancellation (PIC) scheme. We further investigate the performance of the successive IC scheme subject to the delay constraint, which may be imposed typically on most of service applications with a real-time transmission requirement, including speech and video applications. Our analysis demonstrates that the performance may be significantly improved by the groupwise successive interference cancellation (GSIC) scheme, which can be properly optimized to meet the given delay constraint.

• The Transactions of the Korea Information Processing Society
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• v.5 no.11
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• pp.2954-2972
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• 1998

It is expected that the transport of compressed video will become a significant part of total network traffic because of the widespread introduction of multimedial services such as VOD(video on demand). Accordingly, VBR(variable bit-rate) encoded video will be widely used, due to its advantages in statistical multiplexing gain and consistent vido quality. Since the transport of video traffic requires larger bandwidth than that of voice and data, the characterization of video source and traffic modeling is very important for the design of proper resource allocation scheme in ATM networks. Suitable statistical source models are also required to analyze performance metrics such as packet loss, delay and jitter. In this paper, we analyzed and described on the characterization and traffic modeling of MPEG video sources. The models are broadly classified into two categories; i.e., statistical models and deterministic models. In statistical models, the models are categorized into five groups: AR(autoregressive), Markov, composite Marko and AR, TES, and selfsimilar models. In deterministic models, the models are categorized into $({\sigma},\;{\rho}$, parameterized model, D-BIND, and Empirical Envelopes models. Each model was analyzed for its characteristics along with corresponding advantages and shortcomings, and we made comparisons on the complexity of each model.

• Journal of KIISE
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• v.44 no.8
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• pp.749-759
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• 2017

The weapon system based on voice call can cause delay, error or damage to the message during the exchange of information. Furthermore, since the weapon system has a unique message format, it has limited data distribution. Therefore, a Korea Variable Message Format(KVMF) has been developed in this study to utilize a standard sized data format to guarantee the transmission quality and minimize the transmission amount. The ground tactical data link system quickly and accurately shares tactical information by incorporating a field management system that utilizes the KVMF standard message in the mobile weapon system. In this study, we examine the possibility of performing the mission immediately by recovering the state of network joining when a normal/abnormal termination situation of the battlefield management system occurs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1048-1057
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• 2015

In this paper, we propose a fast MAS reallocation method that can avoid reservation conflicts in the DRP process of WiMedia system in real time. WiMedia MAC DRP has been developed aimed QoS support for audio and video transmission that generate traffic periodically. The size variation of the video streaming data causes DRP reservation conflicts frequently, so that DRP could not support QoS of the video streaming service which is delay-sensitive. Fast MAS reallocation method could avoid reservation conflicts in real-time analyzing reservation requests information of the other device. Our proposed method is evaluated with test sequences using the software simulation and implemented in hardware/software with the integrated WiMedia MAC/PHY system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.307-312
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• 2000

Asynchronous transfer mode(ATM) is flexible to support the various multimedia communication services such as data, voice, and image by applying asynchronous time-sharing and statistical multiplexing techniques to the existing data communication. ATM service is categorized to CBR, VBR, UBR, and ABR according to characteristics of the traffic and a required service qualities. Among them, ABR service guarantees a minimal bandwidth and can transmit cells at a maximum transmission rate within the available bandwidth. To minimize the cell losses in transmission and switching, a feedback information in ATM network is used to control the traffic. In this paper, predictive control algorithms are proposed for the feedback information. When the feedback information takes a long propagation delay to the backward nodes, ATM switch can experience a congestion situation from the queue length increases, and a high queue length fluctuations in time. The control algorithms proposed in this paper provides predictive control model using slop changes of the queue length function and previous data of the queue lengths. Simulation shows the effectiveness result of the proposed control algorithms.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.871-878
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• 2004

Recenty, there has been great interest in MANET from various areas. In this paper we focus on performance analysis of on demand routing protocols surf as DSR, AODV, and TORA in MANET. We have conducted several simulations concerned with application service data such as sensor, text. voice, and video data. And then, we have evaluated the performance of three protocols in a pre-designed ad hoc network, which is consisted of 20 nodes. As a result, we have obtained quantitative data for packet delivery fraction, average end to-end delay, routing load, channel utilization from upper layer and supportable routing protocol for application service data. The results can be used for designing specific-purposed ad-hoc networks.

• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.109-115
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• 2024

The Concept of Operations (ConOps) document issued by the Korean Government (K-UAM ConOps) for urban air mobility (UAM) services takes into account not only aviation voice communication but also the use of 4G and 5G mobile communication to support the initial phase of UAM services. This paper studies a methodology to establish communication performance requirements for UAM traffic management and presents the analyzed results for communication performance requirements. To accomplish this, the operational scenarios of UAM developmental stages outlined in the K-UAM ConOps and FAA ConOps are scrutinized, and the diverse messages that must be communicated among various stakeholders for effective UAM operations are identified. A draft of communication performance requirements is also calculated by considering packet sizes, transmission frequencies, acceptable latencies, and availability. The outcomes of this study are expected to stand as a pioneering effort in defining communication requirements for UAM services, providing a crucial foundation for future initiatives such as the design of dedicated communication networks for UAM and the determination of required frequency bandwidth.