• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.666-676
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• 2004

We must design the buffer algorithm that protects traffic congestion and decreasing throughput at satellite communication network. It is important that buffer algorithm is satisfied with the good performance of transmission packet, responsibility of many connecting traffic and the 005 for connecting character. Old buffer algorithms are not the suitable algorithms when we have the satellite communication network environment. RED buffer algorithm is proposed by Floyd. It has a better performance than old buffer algorithm. But this algorithm is not well adapted a number of connecting TCP packet and changing network, so this algorithm has a bad Performance on satellite communication network that is many of connecting user at same time. This paper Propose the TARED(Target Adaptive RED). It has a good performance, adaptation and stability on satellite communication network and has not overflow and underflow of the buffer level.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.483-494
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• 2005

The standard streaming delivery Is mostly based on UDP with no end-to-end congestion control. For this reason, wide usage of multimedia applications in Internet might lead to congested networks. To avoid such a situation, studies on the congestion controlled streaming delivery has been increasingly done after the 1990s. However, by considering only the stability aspect of network, these works ignore the characteristics of multimedia streaming applications. Moreover, most of previous works have no consideration on the network delay which produces an effect on streaming service. In this thesis, in order to overcome limitations of the previous transmission schemes for streaming, we propose a new transmission scheme called 'BEST(Buffer-driven Efficient STreaming)'. The BEST takes a hybrid approach that considers both user-level requirements and network-level requriements. Therefore, the BEST improves the stability of networks by adjusting the sending rate suitable for network status and it also provides the smoothed playback by preventing buffer underflow or overflow. The BEST is designed to consider high-delay networks. Through the simulation, we prove that the BEST satisfies both user-level and network-level requirements in a high-delay network environments.

• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.3
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• pp.63-72
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• 1999

Recent studies on the Constant Bit Rate and Variable Bit Rate transmissions have mainly focused on the frame by frame encoder rate control based on the quantization parameter. With the existing approaches it is difficult to guarantee a consistent video quality. Also, the rate control overhead is too high for the real-time video sources. In this paper, a channel rate allocation scheme based on the control period is proposed to transmit a real-time video, in which the control period is defined by a pre-specified number of frames or group of pictures. At each control period, video traffic information is collected to determine the channel rate at the next control period. The channel rate is allocated to satisfy various channel rate constraints such that the buffer occupancy at the decoder is maintained at a target level. If the allocated channel rate approaches the level at which the negotiated traffic descriptions may be violated, the encoder rate is decreased through adjusting quantization parameters in the MPEG encoder. In the experimental results, the video quality and the overflow and underflow probabilities at the buffer are compared at different control periods. Experiments show that the video quality and the utilization of network bandwidth resources can be optimized through the suitable selection of the control period.

• Journal of Broadcast Engineering
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• v.6 no.2
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• pp.148-159
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• 2001

This paper presents a selective duality control system to control relative picture quality among the video programs in terms of Peak Signal-to-Noise Ratio (PSNR) . The selective quality control system allows variable bit rate (VBR) for each video program to maintain the pre-determitted relative picture Quality among aggregated video programs while keeping a constant bit rate for alt programs to be transmitted over a single constant bit rate (CBR) channel. Thus is achieved by simultaneous controlling the video encoders to generate VBR video streams at the central controller. furthermore, we also suggest a buffer regulation method based on the analysis of the constraints Imposed by sender/receiver buffer sizes and the total transmission rate. Through various simulation results, it is found that the proposed quality control system guarantees that the video buffers neither overflow nor underflow and the quality control errors do not exceed 0.1 dB.

• Journal of Korea Multimedia Society
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• v.2 no.3
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• pp.265-276
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• 1999

Video on Demand (VOD) system is definitely one of main applications in upcoming multimedia era. In this research, we have designed and implemented a host-based scalable VOD system (SVOD) which is composed of low cost PC servers and runs on Linux kernel that is currently spotlighted in enterprise and research domains. Our contribution is as follows: first, the previous Ext2 file system was modified to efficiently support continuous media like MPEG stream. Second, the storage server features a host-based scalable architecture. Third, a software MPEG decoder was implemented using Microsoft's DirectShow$\circledR$COM. Finally, flow control between client and server is provided to suppress overflow and underflow of client circular buffer and supports FF VCR operation. We have known that it is possible to develop a thread-based and scalable VOD system on low cost PC servers and free Linux kernel.

• KIISE Transactions on Computing Practices
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• v.22 no.7
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• pp.310-314
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• 2016

Currently, several research studies are looking to improve the quality of DASH (Dynamic Adaptive Streaming over HTTP) based live streaming services. However, conventional DASH based streaming schemes cannot provide seamless playback while maintaining the low buffering and it adversely affects the QoE (Quality of Experience). To address this problem, we propose the QoE driven segment scheduling scheme. The proposed scheme adaptively schedules the segment request message according to the time and variation of segment fetching. Simulation results indicate that the proposed scheme improves the QoE of live streaming service by maintaining the low buffering delay and reducing the buffer underflow events.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.315-323
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• 2004

In this paper we present a method to generate the bit stream of static video test patterns for testing the picture quality in DTV system. The proposed user-defined quantization table is suitable for the static video test pattern and for minimizing the deterioration of picture quality by quantization, the underflow or overflow of video buffer generated on the process of coding the static video test pattern is compensated by a adaptive zero stuffing algorithm so that optimal picture quality is implemented. Experimental result showed that the test pattern stream encoded by MPEG-2 software with the proposed algorithm had a stable bit rate and good video quality during the decoding process, which is about 3 dB higher than that of the conventional case.

• Journal of Broadcast Engineering
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• v.22 no.5
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• pp.618-631
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• 2017

In this paper, we propose a modification of fuzzy logic based DASH adaptation algorithm(FDASH) for seamless media service in time-varying network conditions. The proposed algorithm selects more appropriate bit-rate for the next segment by the modification of the Fuzzy Logic Controller(FLC) and reduces the number of video bit-rate changes by applying Segment Bit-rate Filtering Module(SBFM). Also, we apply the Start Mechanism for clients not to watch the low quality videos in the very beginning stage of streaming service and add the Sleeping Mechanism to avoid any buffer overflow expected. Ultimately, we verified by using NS-3 Network Simulator that the proposed method shows better performance compared to FDASH. According to the experimental results, there is no buffer underflow/overflow within the limited buffer size, which is not guaranteed in FDASH on the other hand. Also, we confirmed that mFDASH has almost the same level of average video quality against FDASH and reduces about 50% of number of video bit-rate changes compared to FDASH in Point-to-Point network and Wi-Fi network.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.345-354
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• 2003

IP Multicast is required of more little network resources than one in unicast. Furthermore, reliable multicast has been researched for supporting reliability at IP Multicast mechanism. Although these studies are carried out, they only have focused on general data. In other words, in case that realtime packet, they can not support reliability since they do not consider realtime properties such as dependency of interframe and playback in time. Besides, we also request to support scalability because we are based on Mobile IP network together with internet. Thus, we need a mechanism to guarantee reliability and scalability of realtime stream data. In this paper, we propose PER (Preceding Error Recovery) that reflect characteristics of the realtime data, especially for H.323. PER provides scalable reliability because it is based on tree-based multicast basically and helps to support scalable relibility as reducing control packet and recovers stream buffer space from underflow status as soon as possible. PER shows much better scalable and reliable than existing works.

• Journal of KIISE
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• v.44 no.5
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• pp.545-552
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• 2017

Because of the explosive growth of mobile devices and development of network technologies, HTTP (Hypertext Transfer Protocol) adaptive streaming has become a new trend in video delivery to provide efficient multimedia streaming services. As interest in personalized broadcasting grows, the study of interactive multimedia has been actively pursued. The interactive multimedia service is a method of playing media according to a scenario selected by the user. Providing the interactive multimedia service with the existing HTTP adaptive streaming causes switching delay and buffer underflow according to the point in time when the user selects the scenario while the client streams the interactive multimedia and therefore decreases the user QoE (Quality of Experience). In this paper, we propose an adaptive streaming scheme for interactive multimedia service in HTTP adaptive streaming to provide seamless playback. We design the architecture and prefetching scheme for interactive multimedia streaming.