• Journal of The Korean Association of Information Education
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• v.2 no.1
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• pp.10-18
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• 1998

In a VOD server, media data are usually encoded by VBR compression technique such as MPEG, therefore, media stream rates vary. We propose a striping strategy called VCS considering VBR compression in Clustered VOD servers. Simulation are conducted to evaluate and compare the new strategy with a known striping strategy. The results show that the VCS strategy improves the performance.

• The Microorganisms and Industry
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• v.18 no.3
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• pp.69-74
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• 1992

최근 Okamoto등(18)이 처음으로 VB receptor 유전자인 vbr A의 cloning 및 vbr A의 E. coli 유래의 필수 유전자인 Nus G와의 높은 상동성(36%)으로부터 전사, 번역기구의 필수 유전자로서 가능성의 보고와, Miyake등(19)은 A-factor receptor의 repressor로서의 기능을 보고함에 따라 이들 자기조절인자의 항생물질등 2차 대사산물의 생합성에 있어서 signal전달에 따른 전사조절의 switch on-off 기구 연구에 박차를 가하에 되었으며 본고에서는 VB를 중심으로한 유도인자의 기능면 및 응용면을 소개하고자 한다.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.8
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• pp.15-21
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• 1996

This paper describes data placement schemes that provide uniform and balanced to multiple disks load for retrievals of VBR (variable bit rate) video at varying retrieval speeds. To support maximum concurent users at arbitrary-speed playbacks in a disk-arry based system, the hot spot disks should be carefully avoided. In this paper, we extend the proposed scheme, prime round-robin(PRR), for VBR video. In addition, we have compared the performance of PRR and PRR (PRR extension).

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.3011-3018
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• 2000

On ATM networks, ABR services are provided using the remained bandwidth after allocating CBR and VBR traffic. Realtime services such as transmitting audio or video data may be provided using CBR and VBR which have a constrained transmission delay, but in these cases, the communications bandwidth may be wasted. This paper proposes an efficient bandwidth allocation algorithm to transfer real-time data using ABR service. The proposed algorithm guarantees MCR and allocates bandwidth to each connection proportional to its MCR. The proposed algorithm divides the connections in two groups - a satisfied state group and a bottlenecked state group - and enhances bandwidth utilization by allowing the remained bandwidth after allocating the connections in the satisfied state to be allocated to the connections in the bottlenecked state. Our algorithm uses a Queue control function proposed by Ghani[5] to keep the Queue length within some boundary, which makes the transmission delay constant. We simulate and compare the performance of the proposed algorithm with that of the algorithms proposed by ATM Forum[1] and Kalampoukas[2].

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.2940-2947
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• 2000

In the wireless ATM networks, a Medium Access Control (MAC) protocol is required to support an integrated mix of multimedia traffic services. The MAC protocol should be designed in a way that the limited wireless bandwidth can be efficiently utilized maximizing the Quality of Service (QoS) guarantees for various traffic service classes. In this paper, a Dynamic Resource Allocation-based MAC protocol, which satisfies QoS of each traffic service class in the wireless ATM environment, is proposed. The proposed MAC protocol adopts the dynamic channel allocation schemes for a mix of different traffic service classes. The suggested MAC protocol is designed to provide the QoS guarantees for Constant Bit Rate (CBR) or real-time Variable Bit Rate (VBR) traffic through fixed or dynamic reservation. For Available Bit Rate (ABH) traffic, which has the lowest priority among the traffic classes, large improvement in delay by reserving the minimum bandwidth is shown. And for real-time VBR traffic, increase in throughput of transmission is demonstrated because of bandwidth, which is allocated through contention at the initial phase and without contention thereafter.

• Journal of Korea Multimedia Society
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• v.15 no.6
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• pp.814-826
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• 2012

In this paper, we propose scheduling algorithms for transporting variable-bit-rate video stream using playback buffer level of the clients over wireless communication networks. The proposed algorithms attempt to maximize the utilization of limited bandwidth between the central video server and the clients over a mobile network. Since a video server may serve several video request at the same time, it is important to allocate and utilize network bandwidth to serve them fairly and efficiently. In order to improve the quality of service and real-time performance of individual video playback, the video server attempts to allocate temporarily more network bandwidth to serve a video request with the lower buffer level preferentially. The simulation results prove the fair service and load balancing among the mobile concurrent clients with different buffer levels and hence maximizing the number of frames that are transported successfully to the client prior to their playback times.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.31-41
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• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To improve these limit, in this paper, we First, we propose priority polling algorithm which additionally considers the size of MSI and TXOP based on EDD algorithm to increase number of QSTAs. We also propose a dual token bucket TXOP allocation algorithm to reduce congestion caused by stations which enters network with considerable delay variance. TSPEC parameters, Maximum Burst Size (MBS) and Peak Data Rate (PR), are applied to design depth and token generation rate of two buckets. Simulation results show that the proposed algorithm has much higher performance compared with reference and SETT-EDD scheduler in terms of throughput and delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1178-1190
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• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To efficiently assign resource for VBR traffic, in this paper, we propose TXOP algorithm based on dual leaky bucket using average resource allocation and peak resource allocation. The minimum TXOP of each station is obtained by using statistical approach to maximize number of stations of which performance satisfy QoS target. Simulation results show that the proposed algorithm has much higher performance compared with reference scheduler in terms of throughput and delay.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.1
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• pp.1-13
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• 2001

In this paper, we propose a new dynamic bandwidth allocation and call admission control for VBR video sources with QoS constraints to support an efficient resource management and at the same Lime to satisfy the user's quality or service requirements. For the dynamic bandwidth allocation, first the next amount of traffic is predicted using a modified adaptive linear prediction method that considers abrupt scene change effects. And then, we dynamically allocate the necessary bandwidth to each connection based on the currently provided quality degree by the network with respect to the user's QoS requirements in terms of average delay and loss ratio. For the admission control, we determine the acceptance or rejection or a new connection based on the quality satisfaction degrees of the existing connections. Simulation results show that our proposed dynamic schemes are able to provide a stable service, which well meets the user's quality requirements.

• Journal of Broadcast Engineering
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• v.12 no.6
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• pp.574-584
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• 2007

As the real time multimedia service become more popular, the needs of transmission with low delay and high quality are getting more stronger. Among those video compression technologies, the rate control method dose an important role in getting the effective data transmitting and the high image quality. In this paper, we combined the feature of CBR and VBR coding methods to propose a new bit-rate control method witch allows each frame to generates bits in the defined fluctuation range and applies a scene change detection at a part of frame and also can maintain low-delay and high quality even if the perfect VBR transmission environment is not guaranteed. The experiment result shows the proposed algorithm provides more effective method than TMN8 in real time application.