• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.539-545
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• 2016

In this paper, the use of an amplify-and-forward (AF) helper station in a cellular network with device-to-device (D2D) communication links is considered to enhance D2D rates and control the interference caused by D2D users to the cellular network. Two design criteria for the AF helper station are considered to improve the overall system quality-of-service (QoS). One is maximization of the worst D2D user rate under a constraint on interference caused by D2D users to the cellular network and the other is its dual, i.e., minimization of interference caused by D2D users to the cellular network with minimum rate guarantee for each D2D user. It is shown that the considered problems reduce to semi-definite programming (SDP) problems. Numerical results show that the proposed AF helper station significantly improves the system performance.

• Korean Circulation Journal
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• v.53 no.7
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• pp.483-496
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• 2023

Background and Objectives: Atrial fibrillation (AF) is associated with decreased cardiac resynchronization therapy (CRT) benefits compared to sinus rhythm (SR). Effective biventricular (BiV) pacing is a determinant of CRT success, but AF can interfere with adequate BiV pacing and affect clinical outcomes. We investigated the effect of device-detected AF on clinical outcomes and optimal BiV pacing in patients with heart failure (HF) treated with CRT. Methods: We retrospectively analyzed 174 patients who underwent CRT implantation between 2012 and 2019 at a tertiary center. The optimal BiV pacing percentage was defined as ≥98%. Device-detected AF was defined as an atrial high-rate episode ≥180 beats per minute lasting more than 6 minutes during the follow-up period. We stratified the patients without preexisting AF at pre-implantation into device-detected AF and no-AF groups. Results: A total of 120 patients did not show preexisting AF at pre-implantation, and 54 had AF. Among these 120 patients, 19 (15.8%) showed device-detected AF during a median follow-up of 25.1 months. The proportion of optimal BiV pacing was significantly lower in the device-detected AF group than in the no-AF group (42.1% vs. 75.2%, p=0.009). The devicedetected AF group had a higher incidence of HF hospitalization, cardiovascular death, and all-cause death than the no-AF group. The device-detected AF and previous AF groups showed no significant differences regarding the percentage of BiV pacing and clinical outcomes. Conclusions: For HF patients implanted with CRT, device-detected AF was associated with lower optimal BiV pacing and worse clinical outcomes than no-AF.

• Journal of Preventive Medicine and Public Health
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• v.53 no.1
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• pp.56-63
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• 2020

Objectives: The objective of this study was to determine the effect of atrial fibrillation (AF) on the risk of dementia in the Korean elderly. Methods: A 10-year retrospective cohort study was conducted using the National Health Insurance Service-Senior Cohort database. We excluded those who were under 65 years of age as of January 2006 (n=46 113), those who were diagnosed with dementia between 2002 and 2005 (n=9086), and those with a history of stroke prior to AF diagnosis (n=8392). We used a Cox proportional hazards model with a time-varying covariate to determine whether AF is associated with the risk of dementia after adjusting for potential confounders. Results: In univariable Cox regression, the hazard ratio (HR) of dementia according to AF status was 1.28 (95% confidence interval [CI], 1.23 to 1.33). After adjusting for potential confounders, AF was found to increase the risk of dementia (HR, 1.12; 95% CI, 1.07 to 1.17), Alzheimer dementia (HR, 1.12; 95% CI, 1.07 to 1.17), and vascular dementia (HR, 1.10; 95% CI, 1.03 to 1.18). In patients diagnosed with AF, the incidence of dementia was lower (HR, 0.50; 95% CI, 0.47 to 0.52) in patients who were treated with oral anticoagulants. Conclusions: Investigating the potential risk factors of dementia in an aged society is important. We found a slightly higher risk of dementia in those with AF than in those without AF, and we therefore concluded that AF is a potential risk factor for dementia.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.346-350
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• 2009

Digital Multimedia Broadcasting (DMB) is the mobile TV service based on a digital radio transmission system that provides high quality audio/video and other auxiliary data services. As users want to store the DMB content in their device to be consumed later or to be shared among users, a standardized format needs to be specified to guarantee the interoperability for the DMB contents for various devices. DMB AF (Application Format) specification defines a file format for DMB contents and services. It specifies how to combine the variety of DMB contents with associated information for a presentation in a well-defined format that facilitates storage, interchange, management, editing, and presentation of the DMB contents in protected, governed, and interoperable ways. In this paper we present our implementation of DMB AF as part of the development of DMB AF reference software. Our implementation of DMB AF is developed as the reference software for the standard specification that consists of a three applications: packager, media player, metadata browser and collection of supporting libraries used by the applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.649-652
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• 2015

Previous marking policy for the AF service of TCP traffic in the Diffserv network have no sufficient consideration on the effect of RTT and target rate. In this paper, in order to improve fairness Index by the effect RTT difference of TCP traffic, we propose the modified TSW3CDM(Time Sliding Window Three Color Dynamic Marker) based on average transfer rate estimation and the flow state. The proposed algorithm is dynamic marking policy that do allocate band width in proportion to transmission rate. To evaluate the performance of the proposed algorithm, We accomplished a computer simulation using NS-2. From simulation results, the proposed TSW3CDM algorithm improves fairness index by comparison with TSW3CM.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.1-8
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• 2001

Adaptive and Strict Packet Dropping mechanism we proposed in this paper drops adaptively packets for the congestion control, as predicting traffic pattern between each cycle. Therefore the proposed mechanism makes up for the drawback of RIO mechanism and minimizes the wastes of the bandwidth being capable of predicting in Dynamic and Strict Packet Dropping (DSPD) mechanism. And we executed a simulation and analyzed the throughput and packet drop rate based on the Sending Drop Precedence changing dynamically depending on the network traffic and compared RIO and the DSPD. The results show that the proposed mechanism provides better performance on drop precedence levels and stricter drop precedence policy for AF class than RIO and the DSPD mechanism.

• Proceedings of the Korea Information Assurance Society Conference
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• 2004.05a
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• pp.43-50
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• 2004

Diffserv Network DSCP(Differentiated Service Code Point)는 8bit로 구성되어 있고, 그 중 6bit만 사용되고, 나머지 2bit는 비워져 있는 상태로 있다. 이 2bit를 사용하여, DF(Default Forwarding), EF(Expedited Forwarding), AF(Assured Forwarding)의 DSCP 에 각각의 Service Class Code Point를 부여해서 사용자의 패킷을 구분하여 서비스하는 DiffServ 같은 경우 상용화가 되었을 때, DiffServ를 서비스하는 망에서 동일한 DiffServ 정책을 설정해서 사용할 수 있는 기법을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4B
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• pp.255-269
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• 2006

The differentiated services(DiffServ) architecture provides packet level service differentiation through the simple and predefined Per-Hop Behaviors(PHBs). The Assured Forwarding(AF) PHB proposed as the assured services uses the RED-in/out(RIO) approach to ensusre the expected capacity specified by the service profile. However, the AF PHB fails to give good QoS and fairness to the TCP flows. This is because OUT(out- of-profile) packet droppings at the RIO buffer are unfair and sporadic during only network congestion while the TCP's congestion control algorithm works with a different round trip time(RTT). In this paper, we propose an Adaptive Regulating Drop(ARD) marker, as a novel dropping strategy at the ingressive edge router, to improve TCP fairness in assured services without a decrease in the link utilization. To drop packets pertinently, the ARD marker adaptively changes a Temporary Permitted Rate(TPR) for aggregate TCP flows. To reduce the excessive use of greedy TCP flows by notifying droppings of their IN packets constantly to them without a decrease in the link utilization, according to the TPR, the ARD marker performs random early fair remarking and dropping of their excessive IN packets at the aggregate flow level. Thus, the throughput of a TCP flow no more depends on only the sporadic and unfair OUT packet droppings at the RIO buffer in the core router. Then, the ARD marker regulates the packet transmission rate of each TCP flow to the contract rate by increasing TCP fairness, without a decrease in the link utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.342-352
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• 2002

In this paper, we compare the performances of RIO and RIO-DC buffer management schemes for DiffServ AF PHB standardized in IETF. For the comparison, we relatively differentiate maximum delay for each Assured Service subclass in Differentiated Services by allocating bandwidth to each subclass differently. In addition, we set the values of RIO and RIO-DC parameters considering the buffer size determined by the network topology and the ratio of bandwidth allocated to each subclass. In this simulation environment, the performances of RIO and RIO-DC schemes are analyzed focusing on the throughput of the In-profile traffic, the link utilization and the fairness. Simulation results show that the performance of RIO-DC scheme is comparable to that of RIO scheme with regard to the throughput of the In-profile traffic and the link utilization. However, under the simulation condition RIO-DC scheme improves the fairness between flows much better than RIO scheme.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.152-164
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• 2012

DMB provides various kinds of data services such as BWS and TPEG service in addition to audio and video services. But recently the necessity of new business models creating profit has been on the rise due to the saturation of DMB receiver market and break-down of market barrier between mobile IPTV and DMB services. This paper introduces DMB filecasting service technology, which can be expected a new profit-creative business model. The purpose of DMB filecasting service is to transmit non-real time multimedia contents based on DMB AF format to the users through DMB channels. It makes possible to consume DMB contents with any DMB-installed device anytime, anywhere and share them with others. Also DMB filecasting service makes consumption and request of DMB contents possible to be extented to a variety of networks as well as DMB channels. The paper explains the standardization status of DMB filecasting service and various DMB filecasting service scenarios. And also it proposes a signalling methode, a transmission and reception protocol and a receiver structure using DMB broadcasting program guide information.