• Journal of KIISE:Computing Practices and Letters
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• v.13 no.5
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• pp.260-270
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• 2007

Owing to the improved wireless communication technologies, it is possible to provide streaming service of multimedia with PDAs and mobile phones in addition to desktop PCs. Since mobile client devices have low computing power and low network bandwidth due to wireless network, the transcoding technology to adapt media for mobile client devices considering their characteristics is necessary. However, since mobile clients use wireless network and the wireless network have less stable bandwidth according to distance from AP and environments, it is hard to support stable QoS to mobile clients. In this paper, we propose a dynamic bit rate control method for transcoding in order to supprot stable QoS of streaming media service to mobile clients via wireless network. The proposed method is shown to serve seamless streaming media service with adaptive bit rate control according to state of wireless network in real time and to reduce transmission failure from experiment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.1-7
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• 2012

Cognitive radio, a new paradigm for wireless communication, is being recently expected to support various types of multimedia traffics. To guarantee Quality of Service (QoS) from SUs, a static packet priority policy can be considered. However, this approach can easily satisfy Quality of Service of high priority application while that of lower priority applications is being degraded. In the paper, we propose a fuzzy-based dynamic packet scheduling algorithm to support multimedia traffics in which the dynamic packet scheduler modifies priorities of packets according to Fuzzy-rules with the information of priority and delay deadline of each packet, and determines which packet would be transmitted through the channel of the primary user in the next time slot in order to reduce packet loss rate. Our simulation result shows that packet loss rate can be improved through the proposed scheme when overall traffic load is not heavy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1195-1207
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• 1999

Wireless channel has high error rate and limited bandwidth. In order to guarantee the quality of service for multimedia through wireless channel, wireless ATM network requires the cell structure with error control schemes and an efficient medium access control protocol. In this paprt, an efficient medium access control protocol, which is considered of cell structure and the QOS, is proposed for wireless ATM networks. Many kinds of ATM cell structures are analyzed in terms of cell error rate and cell loss rate to choose the proper cell structures for this proposed MAC protocol. And a bandwidth allocation algorithm is also designed to satisfy the priority of services. The performance of proposed MAC protocol are evaluated in terms of channel utilization, call blocking and packet discard probability accotding to different kinds of cell structure through simulation.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.217-226
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• 2001

In this paper, for continuous media access operations performed by Clustered Continuous Media Storage Server (CCMSS) system, we present the analytical model based on the open queueing network, which considers simultaneously two critical delay factors, the disk I/O and the internal network, in the CCMSS system. And we derive by using the analytical model the stochastic model for the total service delay time in the system. Next, we propose the integrated stochastic admission control model for the CCMSS system, which estimate the maximum number of admittable service requests at the allowable service failure rate by using the derived stochastic model and apply the derived number of requests in the admission control operation. For the performance evaluation of the proposed model, we evaluated the deadline miss rates by means of the previous stochastic model considering only the disk I/O and the propose stochastic model considering the disk I/O and the internal network, and compared the values with the results obtained from the simulation under the real cluster-based distributed media server environment. The evaluation showed that the proposed admission control policy reflects more precisely the delay factors in the CCMSS system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.60-66
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• 2011

LTE (Long Term Evolution) supports QoS (Quality of Service) with several service classes. For each class of traffic, a big difference exists on BER (Bit Error Rate) requirement. This leads to a considerable difference in transmission power for various classes of traffic. In this paper, a novel scheduler is designed and proposed for LTE which supports CoS (Class of Service) with the consideration of priority as well as target BER. By the CQI (Channel Quality Indicator) and QCI (QoS Class Identifier), a minimum transmission power is assigned from the target BER for each class of traffic per each user. Hence, with the other information such as user's used rate in the past and the priority of traffic, the probability of occupying channels is determined. The simulation results of Service Class scheduling are compared with that of Maximum Rate and Proportional Fair. The results show that the service class-aided scheduling can improve the throughput of whole system significantly.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.1
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• pp.40-47
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• 2009

Recently, dynamic proxy caching has been proposed on the distributed environment so that media objects by user's requests can be served directly from the proxy without contacting the server. However, it makes caching challenging due to multimedia large sizes, low latency and continuous streaming demands of media objects. To solve the problems caused by streaming demands of media objects, this paper has been proposed the grouping scheme with fuzzy filtering based on partition and mapping. For partition and mapping, this paper divides media block segments into fixed partition reference block(R$_f$P) and variable partition reference block(R$_v$P). For semantic relationship, it makes fuzzy relationship to performs according to the fixed partition temporal synchronization(T$_f$) and variable partition temporal synchronization(T$_v$). Simulation results show that the proposed scheme makes streaming service efficiently with a high average request response time rate and cache hit rate and with a low delayed startup ratio compared with other schemes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.4
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• pp.423-430
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• 2019

The convergence of the automotive industry and the ICT technology can be broadly divided into the commercial service sector and the Cooperative-ITS (C-ITS) service sector. The C-ITS service sector is using V2X communication technology as a field that aims to provide safer transportation, more green and efficient transportation, and more predictable and productive mobility. The recent convergence of self-driving cars and connected cars requires high data rates, low transmission delays, and low transmission error rates. Interest in comparison of performance between WAVE and C-V2X (LTE-V2X, 5G-V2X) has been amplified and application services by communication technology are being studied. In this paper, we design the application performance evaluation method of Hybrid V2X communication system and confirm that the decrease of packet error rate (PER) performance is caused by the increase of communication distance, not the vehicle speed.

• Journal of Broadcast Engineering
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• v.17 no.4
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• pp.640-658
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• 2012

One of the existing terrestrial multi-channel DTV service frameworks, called KoreaView, provides four programs, composed of MPEG-2 based one HD video and H.264/AVC based three SD videos within one single 6MHz frequency bandwidth. However the additional 3 SD videos can not provide enough quality due to its reduced spatial resolution and low target bitrates. In this paper, we propose a framework, which is called a terrestrial multi-channel high quality hybrid DTV service, to overcome such a weakness of KoreaView services. In the proposed framework, the three additional SD videos are encoded based on an H.264/SVC Spatial Base layer, which is compliant with H.264/AVC, and are delivered via broadcasting networks. On the other hand, and the corresponding three additional HD videos are encoded based on an H.264/SVC Spatial Enhancement layer, which are transmitted over broadband networks such as Internet, thus allowing the three additional videos for users with better quality of experience. In order to verify the effectiveness of the proposed framework, various experimental results are provided for real video contents being used for DTV services. First, the experimental results show that, when the SD sequences are encoded by the H.264/SVC Spatial Base layer at a target bitrate of 1.5Mbps, the resulting PSNR values are ranged from 34.5dB to 42.9dB, which is a sufficient level of service quality. Also it is noted that 690kbps-8,200kbps are needed for the HD test sequences when they are encoded in the H.264/SVC Spatial Enhancement layer at similar PSNR values for the same HD sequences encoded by MPEG-2 at a target bitrate of 12 Mbps.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.127-133
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• 2011

This study proposed the PHB mapping model for combining services with DiffServ in the MPLS network capable of high-speed switching, and the effective differential bandwidth service model in the MPLS network on the basis of the proposed mapping model. The result of simulation on the service model using PRI showed that the transmission rate was achieved as much as the assigned bandwidth regardless of the increase of traffic as far as the EF PHB did not exceed the assigned bandwidth at the peak rate when the overall traffic increased.

• Korean Journal of Health Education and Promotion
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• v.10 no.1
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• pp.98-105
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• 1993

최근 경제수준 향상과 소자녀 가치관의 확립, 그리고 전국민 의료보험 실시 등으로 인하여 모자보건 대상자의 대부분은 민간 의료시설의 전문인력으로부터 서비스를 제공받게 되었고, 모자보건 수준도 급격히 향상, 1992년 시설분만율의 경우, 99%에 도달하였다. 이렇듯 의료시설 이용의 증가와 의료기술의 발전에도 불구하고, 영아사망율 및 모성사망율이 최근 몇년동안 같은 수준에 머무르고 있음은, 보다 질적인 관리측면으로 사업의 방향이 전환되어야 함을 의미하는데 이는 곧 공공성을 띠고 있는 모자보건사업을 국가가 관리하여야 할 필요성을 더욱 크게 한다. 공공부문에서는 취약대상을 위하여 민간 전문인력과의 유기적인 연계체계를 마련하여 계속적인 관리를 제공할 수 있도록 하고, 보건교육 강화를 위한 관련 홍보물(모자보건수첩 활용, 모유수유 권장, 제왕절개수술 지양 등)을 제작하며 신경아세포종 검사 등과 같은 새로운 예방사업 개발에 중점을 두어야 할 것이다. 또한 영유아관리는 저체중아 및 장애아에 대한 추구관리서비스까지 확대되어야 할 것이다. 현 우리나라 주산기구급이송체계는 응급의료체계내에서 이루어지고 있다고 볼 수 있는데 주산기관리를 위한 의료여건이 성숙되어 있지 못하고 있는데다(이 시기의 집중관리를 통하여 사망 및 장애아 예방이 가능) 관련 제도마저 취약하여 민간의료부문에서는 영아사망 및 모성사망을 낮추기 위해서는 이 부문에 대한 노력이 집중되어야 할 것이다. 첫째, 주산기학, 신생아학 전문인력의 훈련제도 확립파 주산기 관리시설의 지역적 적정분배(분만 2,000건에 1개 시설마련), 둘째, 집중적인 인력과 고가장비가 투입되는 주산기 의료활동 강화를 위한 관련 의료제도의 수정 및 보완, 세째, 질적관리가 매우 중시되는 고위험 신생아의 집중관리를 위한 '표준 의료관리지침서' 마련, 네째, 동 시설 및 관리에 준하여 주산기 의료시설에 대한 감독 및 감시기능 강화를 위한 제도적 장치가 마련되어야 할 것이다.