• Journal of Korea Multimedia Society
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• v.7 no.4
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• pp.518-531
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• 2004

This paper discusses a testbed architecture for implementing scalable service differentiation in the Internet. The differentiated services (DiffServ) testbed architecture is based on a model in which a bandwidth broker (BB) can control network resources, and the ALTQ can reserve resources in a router to guarantee a Quality of Service (QoS) for incoming traffic to the testbed. The reservation and releasemessage for the ALTQ is contingent upon a decision message in the BE. The BB has all the information in advance, which is required for a decision message, in the form of PIB. A signaling protocol between the BB and the routers is the COPS protocol proposed at the IETF. In terms of service differentiation, a user should make an SLA in advance, and reserve required bandwidth through an RAR procedure. The SLA and RAR message between a user and the BB has implemented with the COPS extension which was used between a router and the BB. We evaluates the service differentiation for the video streaming in that the EF class traffic shows superb performance than the BE class traffic where is a network congestion. We also present the differentiated service showing a better packet receiving rate, low packet loss, and low delay for the EF class video service.

• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.163-170
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• 2007

The next generation communication environment consists of various wireless access networks with distinct features that are configured as an overlay topology. In the network environments, the frequency of hand overs should be minimized and the error propagation should be solved in order to provide high-quality multimedia services to mobile users. Therefore, we propose an performance enhancement approach, based on mSCTP, that provides high quality multimedia services to mobile users by ameliorating the error propagation problem. We utilizes the following four functions: 1) the separation of transmission paths according to the types of frames. 2) retransmission strategy to minimize the loss rate of frames, 3) Foced vertical handover execution by utilizing bicasting, 4) using the stability period in order to reduce the effect of the ping pong phenomenon. The simulation results show that the proposed approach provides seamless multimedia service to mobile users by achieving error resilience.

• Progress in Medical Physics
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• v.9 no.3
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• pp.143-154
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• 1998

The image intensifier is the key component which determines the imaging characteristics in a fluoroscopic imaging system. A system performance program for clinical evaluation of two image intensifiers, that is simple, non-invasive and time effective, was described. Tests were grouped into three headings: x-ray generator, image quality, and collimation. For the x-ray generator, the kVp accuracy and the automatic exposure control operation were compared. Low- and high-contrast resolution measurements, and mesh pattern study belong to the image quality tests and those tests were performed for the video monitor and photospot images. For the collimation, usable field diameter and image distortion of image intensifiers were measured and quantified. The procedures and the results are hoped to be used for the clinical evaluation of system performance and/or acceptance tests for image intensifiers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.679-689
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• 2006

Delivering multicast stream is one of the cost-saving approach in the large scale VOD environment. Because implementing VCR-like interactions for user's convenience in the multicast streaming system involves complex problems, we need the proper solutions for them. In this paper, we propose a hybrid scheme which uses the general P2P and the patching scheme with the Collaborative Interaction Streaming Scheme(CISS). CISS provides jumping functionability to the appropriate multicast session after VCR-like interaction in the environment in which multiple peers transmit VCR-like interaction streams to the VCR-like functionability request node to reduce the loads generated by frequent join or departure of peers at the multicast tree during providing VCR-like functionability. Therefore, with the proposed scheme we can distribute network traffic and reduce control overhead and latency. And to evaluate the performance of proposed scheme we compare it in the aspect of the performance of streaming delivery topology, control overhead and streaming quality with P2Cast[10] and DSL[11]. The simulation result shows that proposed P2Patching reduces about 30% of process overhead and enhances about $25{\sim}30%$ of streaming quality compared with DSL.

• Journal of the Korean Society of Radiology
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• v.10 no.6
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• pp.395-401
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• 2016

Upper gastrointestinal series is a diagnostic test that X-ray passes through the stomach after administering contrast media such as barium or gastrografin. Upper gastrointestinal series with an advantage of no side effect except temporary constipation or abdominal pain has been widely used to diagnose diseases of the gastrointestinal system. However, image degradation and diagnostic accuracy frequently occurred when improper movement and breath control were carried out by lack of understanding the overall inspection process for the upper gastrointestinal series. The movie of the upper gastrointestinal series was made for improving inspection accuracy and image quality. The examinees encouraged to see the movie for waiting time before doing upper gastrointestinal series. In this study, image quality and diagnostic accuracy was examined for the effect of the movie about upper gastrointestinal series. 60 patients composed of each 10 people from 30s to 80s were selected randomly among both 2,940 examinees in 2014 and 3,076 examinees in 2015. Image quality was evaluated by the full width at half maximum of profile for each image using the Image J. The measurement of the full width at half maximum showed 0.208 mm and 0.133 mm for after and before seeing the movie. Thus it was verified that the movie education could improve the image quality and diagnostic accuracy for upper gastrointestinal series.

• 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.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.2
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• pp.33-40
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• 2008

Streaming video has become a popular form of transferring media over the wired/wireless network. TCP-friendly rate control (TFRC) is used as a streaming media transport protocol. Using the TCP congestion response function and current network conditions, TFRC adjusts its sending rate to yield the maximum TCP-friendly throughput. Since TFRC was designed for applications that would prefer to maintain a slowly-changing sending rate, it is less responsive to changes in handover between wireless heterogeneous networks such as 3G network, WLAN, and so on. This paper shows a new TFRC method for vertical handover over wireless heterogeneous network. The proposed TFRC method has features of low quality interruption and fast rate adaptation to a new target network. The simulation results show that the proposed one provides better QoS and throughput support than the traditional TFRC scheme during vertical handover.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.63-69
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• 1998

In this paper, we propose a new Bit-Rate control algorithm based on bit usage matching to substitute encoded GOP(s) for new GOP(s) in MPEG-2 bitstream. It iteratively encodes current picture according to quantization value of previous picture and records bit-usage of each slice until nearly target bits are used. With target bits falling in two output bits, quantization value of slice should be changed to alleviate output bit error. We use recorded bit-usage information to decide which slices should be encoded with one quantization value and others with another. As every macroblock has different activity, we change macroblock quantization value using slice quantization value and activity value. The simulation results demonstrate that the fluctuation of the output bits can be kept within few-several tens of bits while maintaining the quality of the reconstructed pictures at a relatively stable level.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.5
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• pp.70-78
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• 2001

We have developed a novel driving system of 5' true color FED using voltage controlled PWM method which has current control effect. The proposed method has the advantage of voltage controlled pulse width modulation method and current control method. Also, we propose a new circuit model of FED subpixel for circuit simulation of FED driving circuits, considering some parasitic effects, i.e., cross talk, line coupling effect and leakage current to the adjacent cathode lines. Output stage of the data driving circuit is optimized using the proposed circuit model. In video data processing, FED controller uses the parallel processing of R.G.B input data, so duty ratio is maximized and brightness of FED increases. With this results, no noise and high quality performance is achieved in display of 5' true color FED.

• Journal of Digital Contents Society
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• v.3 no.1
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• pp.47-57
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• 2002

Recently, wireless networks have been pursuing multimedia data service as voice, data, image, video and various form of data according to development of information communication technology. It guarantees cell delivery delay of real time data in efficient real time multimedia data transfer. Also, it minimizes cell loss rate of non-real time multimedia data. In the wireless ATM, there are based on Asynchronous Transfer Mode(ATM). It implies that there are various service with difficult transmission rates and qualities in the wireless communication network. As a result, it is important to find out the ways to guarantee the Quality of Service(QoS) for each kind of traffic in wireless network. In this thesis, we propose an improved TCRM scheduling algorithms for transmission real-time multimedia data service in wireless ATM Networks. We appear real time multimedia scheduling policy that apply each different method to uplink and downlik to wireless ATM network. It can guarantee QoS requirements for each real time data and non-real time data. It also deals the fairness problem for sharing the scarce wireless resources. We solve fault of TCRM as inefficient problem of non-real data by using arbitrary transmission speed and RB(Reservation Buffer) through VC(Virtual Control) and BS(Base Station).