• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.189-198
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• 2019

In recent years, visual-inertial odometry(VIO) algorithms have been extensively studied for the indoor/urban environments because it is more robust to dynamic scenes and environment changes. In this paper, we propose loosely coupled(LC) VIO algorithm that utilizes the velocity vectors from both visual odometry(VO) and inertial measurement unit(IMU) as a filter measurement of Extended Kalman filter. Our approach improves the estimation performance of a filter without adding extra sensors while maintaining simple integration framework, which treats VO as a black box. For the VO algorithm, we employed a fundamental part of the ORB-SLAM, which uses ORB features. We performed an outdoor experiment using an RGB-D camera to evaluate the accuracy of the presented algorithm. Also, we evaluated our algorithm with the public dataset to compare with other visual navigation systems.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.213-216
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• 2008

The voltages for pixel electrodes on LCD panels are supplied with analog voltages from LCD Driver ICs (LDIs). The latest LDI developed for large LCD TV's has suffered from the degradation of analog output characteristics (target voltage: AVO and output voltage deviation: dVO). By the failure analysis, humps in $I_D-V_G$ curves have been observed in high voltage (HV) NMOS devices for input transistors in amplifiers. The hump is investigated to be the main cause of the deviation for the driving current in HV NMOS transistors. It also makes the matching between two input transistors worse and consequently aggravates the analog output characteristics. By simply modifying the active layout of HV NMOS transistors, this hump was removed and the analog characteristics (AVO &dVO) were improved significantly. In the help of the improved analog characteristics, it also became possible to reduce the size of the input transistors less than a half of conventional transistors and significantly improve the integration density of LDIs.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.884-888
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• 2009

Vehicular Adhoc Networks (VANET), a Vehicle-to-Infrastucture or Vehicle-to-Vehicle communication technology, is an area that makes more specific use of Mobile Adhoc Networks(MANET). VANET's Quality of Service(QoS) focuses on preventing possible emergencies like car crash from happening by immediately transmitting information to the cars around, while MANET's QoS is being studied for the quality of multimedia data such as Video on Demand(VoD), Video streaming, Voice over IP(VoIP), etc. In this paper, I structure the actual network configuration using Link State Routing(LSR), implement QoS Provisioning Model using Common Open Policy Service(COPS), and suggest more effective k-hop Cluster and inter-domain policy negotiation which fit better to the characteristics of VANET.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10B
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• pp.919-928
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• 2006

A periodic broadcasting is known as an efficient technique for delivering popular videos to reduce bandwidth requirements for transmitting streaming video to viewers in video-on-demand (VoD) services. However, the most periodic VoD schemes approach needs frequency channel hopping, many segments of video managing, and using many channel at the same time. These make it difficult to implement. In this paper, we propose a Staircase Staggered broadcasting scheme which has a simple structure and substantially improved VoD efficiency. The numerical results demonstrate that the viewer's waiting time of the Staircase Staggered broadcasting scheme is close to the staircase broadcasting scheme and the maximum buffer requirements of this can be adapted for demanding rate by adjusting the short front part of a video sizes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2042-2051
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• 1998

VBR compressed, pre-recorded video is known to exhibit significant, multiple time-scale bit rate variability. To reduce the variability and burstiness of the aggregated transmission rate as low as possible, in this paper, we present an adaptive bandwidth smoothing algorithm, that can be effectively applicalble for VoD services over a shared-medium channel. For these environments where many clients are connected to a single server, by introducing the conventional MVBA(minimum variability bandwidth allocation) algorithm and controlling adaptively the conventional MVBA(minimum variability bandwidth asllocation) algorithm and controlling adaptively the aggregated transmission rate whenever a new clients request is arrived at the server side, the proposed algorithm effectively reduces the burstiness and variability of the aggregated transmission rate. Through computer experiments, it is shown that the proposed method perporms better than the convertional non-aggregated bandwidth smoothing schemes in terms of the peak rate, standard deviation, number of rate changes for the aggregated traffic.

• Korean Management Science Review
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• v.23 no.3
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• pp.133-156
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• 2006

The ubiquitous technology, leading the stream of change in telecommunication market, makes VoIP a foundation technology to enter NGN era. With this trend in mind, VoIP providers try to satisfy customer needs and invest on R&D in order to survive in this emerging market. The critical issues to VoIP providers are two fold the first one is to find out the quality attributes of Internet telephony service; and the second one is to assess the impact they have on customer satisfaction, customer loyalty and customer performance. In this study, we attempt to empirically answer the above two issues employing SEM (structural equation modeling) and AHP (analytic hierarchy process), and suggest strategic guidelines for successful deployment of Internet telephony service.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.602-607
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• 2007

최근 4G 이동통신 시스템의 진화를 위한 단계로 기존의 이동통신 시스템을 유지하면서 효율 극대화를 통한 비용 절약 측면과 고 주파수 대역을 이용한 셀 간격의 협소화로 인해 나타나는 문제점에 대한 대안으로 커버리지 확대와 데이터 처리율 향상을 위한 IEEE 802.16j 표준화 작업이 진행 중에 있다. 향후 VoIP 서비스를 위한 업링크 스케줄링 기법으로 몇 가지가 IEEE 802.16j에 제시되어 있으나, 본 논문에서는 보이스 트래픽 특성 및 수학적 모델링을 통하여 기존 방법들보다 더 효율적인 대역 이용을 통해 같은 대역폭 대비 성능과 용량 면에서 개선된 스케줄링 기법인 eertPS를 제시하여 IEEE 802.16j Multi-Hop 환경하에서도 대역 효율적인 VoIP 서비스를 이용할 수 있도록 한다.

• Journal of the Korea Society for Simulation
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• v.21 no.1
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• pp.45-54
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• 2012

Advances in mobile communication and digital video technology enable to commercialize converged multimedia services such as VoD in the mobile networks. Media convergence is evolving into U-Cloud and mobile IP-TV services constituted by high-speed mobile multimedia networks and integrated personal devices. This paper proposes a resource allocation scheme to guarantee QoS of converged mobile multimedia services, and simultaneously maximize legacy services in heterogeneous wireless networks. Performances are analyzed by the simulation.

• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.547-551
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• 1999

The phase change upon Bi substitutions in $Ca_{1.5-1.5x}Bi_xVO_4$ has been systematically studied. The x value corresponding to the maximum Bi substitutions reades to 0.14 and in this range($x{\leq}0.14$), the single phasic $Ca_3(VO_4)_2$ can be identified. However, a new phase of $BiV_{1.025}O_{4+x}$ is apparently formed along with the $Ca_3(VO_4)_2$ phase, when the x value exceeds beyond 0.18 ($x{\geq}0.18$). As a result of Bi substitution in the range of x$\leq$0.14, the interplanar space($d_300$) becomes larger as the Bi content increases. Since the composition of single phasic $Ca_{1.29}Bi_{0.14}VO_4$ (x=O.14) is, however, incongruent melting one, no definite melting point could be observed. But we found that its solidus temperature was 1182$^{\circ}C$ by DTA analysis.

• Journal of the Korean Society of Industry Convergence
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• v.14 no.4
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• pp.135-142
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• 2011

Convergence between telecom and broadcasting is today a worldwide phenomenon. Diverse services like VoD, mobile broadcasting, IPTV and interactive services have already made their market debut or are currently being commercialized. Regulatory systems are also being revised to appropriately regulate this new breed of services. We propose the new model of educational broadcasting system using the internet network, it is not different conventional coaxial cable methods. Especially, we design the multicast method of the network using the limited channel and resource, propose the method of intercommunication in the school between the broadcasting system and database system.