• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.355-362
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• 2009

In real-time communication services, delay constraints are among the most important QoS (Quality of Service) factors. In particular, it is difficult to guarantee the delay requirement over wireless channels, since they exhibit dynamic time-varying behavior and even severe burst-errors during periods of deep fading. Channel throughput may be increased, but at the cost of the additional delays when ARQ (Automatic Repeat Request) schemes are used. For real-time communication services, it is very essential to predict data deliverability. This paper derives the delay distribution and the successful delivery probability within a given delay budget using a priori channel model and a posteriori information from the perspective of queueing theory. The Gilbert-Elliot burst-noise channel is employed as an a Priori channel model, where a two-state Markov-modulated Bernoulli process $(MMBP_2)$ is used. for a posteriori information, the channel parameters, the queue-length and the initial channel state are assumed to be given. The numerical derivation is verified and analyzed via Monte Carlo simulations. This numerical derivation is then applied to a rate control scheme for real-time video transmission, where an optimal encoding rate is determined based on the future channel capacity and the distortion of the reconstructed pictures.

• The Journal of the Korea Contents Association
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• v.7 no.10
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• pp.10-18
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• 2007

Today, third-generation(3G) of mobile communication service executing the video and TV. And low cost, high speed data rate will emerge communication of the fourth generation(4G) in future. So, in this paper we studied occupied frequency bandwidth of common technique criteria among the technique criteria for the 4G mobile communication of FDD-based on Up/Down-link. The mobile communication traffic is predicted Up/Down-link of non-symmetric in future. So we proposed the PHY layer parameters of occupied frequency bandwidth of Up/Down-link with both 1:3 and 1:6. We also verified this through the simulation. We proposed the occupied frequency bandwidth for the 4G mobile communication in this paper.

• Journal of IKEEE
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• v.12 no.4
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• pp.196-203
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• 2008

The IEEE 802.11e working group has announced a new distributed MAC(Medium Access Control) called EDCA(Enhanced Distributed Channel Access) to provide service differentiation among classified traffics. In comparison with the 802.11 legacy MAC, the EDCA provides QoS mechanism by differentiated channel access which is called AC(Access Category) to the frames with different priorities. In multimedia applications, however, the EDCA has some difficulties to achieve QoS throughput because of using fixed AC parameters and never considers overall throughputs, i.e. fairness, for classified services. In this paper, AC parameter control technique is proposed to achieve overall QoS throughputs with differentiated services. The proposed technique controls AC parameters dynamically in real time. Simulation is used to verify the technique and the simulation shows that QoS fairness is improved by 13% in throughput deviation in multimedia environments including voice, video and data service.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.9
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• pp.1325-1332
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• 2013

The first frame of a GOP, an I frame, is encoded in intra mode which generates a larger number of bits. In addition, the I frame is used for the inter mode encoding of the following frames. Thus the intial QP for the I frame affects the first frame as well as the following frames. In our previous work, we analyzed the number of bits for an I frame and showed that the ratio of the number of bits which maximizes the PSNR of a GOP maintains similar value regardless of GOP's. In this paper, we propose a R-Q model which can be used for the calculation of the initial QP given the amount of bits for an I frame. The proposed model is simple and adaptively modifies model parameters, so it can be applicable to the real-time application. It is shown by experimental results that the proposed model captures initial QP characteristics effectively and the proposed method for model parameters accurately estimates the real values.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.107-115
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• 2020

This study verified the motivation to use Tiktok for Chinese teenagers. This paper investigated the influence of adolescents'use motivation on use satisfaction and continuous use intention. In addition, this study was to grasp the relationship between use motivation and sustained use intention as a mediating effect of use satisfaction. The survey was conducted online and offline, 315 adolescents were selected for analysis. For the data, factor analysis, multiple regression analysis, and effect analysis of parameters were conducted using the SPSS 25 program. As a result of the study, information/entertainment pursuit, communication, and self-expression were derived as motivation for use. Among these motivations, information/enterprise pursuit and communication were found to have a significant effect on use satisfaction and continued use intention. In addition, it was confirmed that use satisfaction has a mediating effect on intention to use continuously. But it is found that the self-expression factor handled as reuse intention have no significant influence on the use satisfaction and continuous use intention of Tiktok.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.63-70
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• 2016

To increase throughput efficiency and improve performance, FTN(Faster Than Nyquist) method and LDPC(Low Density Parity Code) codes are employed in DVB-S3 system. In this paper, we proposed efficient turbo equalization model to minimize inter symbol interference induced by FTN transmission. This paper introduces two conventional scheme employing SIC(Successive Interference Cancellation) and BCJR equalizer. Then, we proposed new scheme to resolve problems in this two conventional scheme. To make performance improved in turbo equalization model, the outputs of LDPC and BCJR equalizer are iteratively exchange probabilistic information. In fed LDPC outputs as extrinsic informa tion of BCJR equalizer. we split LDPC output to separate bit probabilities. We compare performance of proposed scheme to that of conventional methods through using simulation in AWGN(Additive White Gaussian Noise) channel. We confirmed that performance was improved compared to conventional methods as increasing throughput parameters of FTN.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.218-226
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• 2001

The MPEG-2 Test Model 5 (TM5) algorithm is widely used for bit rate control. In TM5, however, the target number of bits and the number of actual coding bits for each picture do not match well. Therefore, buffer overflow and picture quality degradation may occur at the end of the GOP. In this paper, we propose a new bit rate control algorithm for matching the target and the actual coding bits based on accurate bit allocation. The key idea of the proposed algorithm is to determine quantization Parameters which enable us to generate the number of actual coding bits close to the target number of bits for each picture, while maintaining uniform picture quality and supporting real-time processing. The proposed algorithm exploits the relationship between the number of actual coding bits and the number of estimated bits of the previous macroblock.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1447-1454
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• 2014

In H.264 standard, an intra frame is the first frame of a GOP (Group of Pictures) and all macroblocks of an intra frame are encoded using the same quantization parameter. In addition, an intra frame is used for encoding the following frames of the same GOP so the encoding results of an intra frame affect the encoding results of the entire GOP. Thus, it is important to find the optimal quantization parameter of an intra frame for improving the quality of a GOP. In this paper, we propose an searching method for an optimal quantization parameter of an intra frame in real time. The proposed method uses a gradient descent method to find the optimal value based on characteristics of the optimal quantization parameters. Experimental results show that the proposed method captures the characteristics of the optimal quantization parameter and accurately estimates the optimal value.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.1
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• pp.39-44
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• 2009

The advance of communication and networking technology enables high bandwidth multimedia data transmission. The development of high performance compression technology such as H.264 also encourages high quality video and audio data transmission. The trend requires efficient protection system for digital media rights. We propose an efficient digital media protection system using elliptic curve cryptography. Only key parameters are encrypted to reduce the burden of complex encryption and decryption in the proposed system, and the digital media are not played back or the quality is degraded if the encrypted information is missing. We need a playback system with an ECC processor to implement the proposed system. We implement an H.264 decoding system with a configurable ECC processor to verify the proposed protection system We verify that the H.264 movie is not decoded without the decrypted information.

• Journal of the Korea Computer Industry Society
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• v.4 no.4
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• pp.547-552
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• 2003

In this thesis, interference phenomena of bluetooth networks requiring Security were minimized; strengthened security of piconet by assigning an identical PIN code to bluetooth devices, which was establishing a specific piconet during authentication stage. To establish a bluetooth piconet system. an unique ID was assigned to each bluetooth device, communication algorithms having different data formats between devices was designed, and an embedded hardware module using ARM processor and uCOS-II RTOS was implemented. About 30% of CPU efficiency in the module was increased by modifying functions including block parameters to work as nonblocking; by the increased efficiency of total piconet, the module could be used as an access point. The module could transmit maximum 10 frames of image and also audio signal by switching the packet effectively according to channel condition. By above-mentioned process, video, audio, and data could be well transmitted by the bluetooth managing program and the possibility of a commercial remote control system using bluetooth technology was suggested.