• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1279-1283
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• 2008

Satellite Digital Multimedia Broadcasting(SDMB) needs Gap Fillers(GFs) to cover the non-service areas. However, SDMB mobile phones which are not located in GFs service area receive signals directly from the satellite because it is impossible to cover all SDMB service with GFs. Therefore, there is a border between the GFs service coverage and the satellite service coverage and it causes a time delay in signals which are from the GFs or the satellite. The time delay is the reason why SDMB service deteriorates. In this paper, I show how to reduce the deterioration of SDMB service in the border area between the GFs and the satellite adding the time delay to the satellite signal and the GFs signal. I think that this method is helpful in reducing the deterioration, especially in the early stages of SDMB service, which the GFs are not spread all over the nation yet.

• Journal of Korea Multimedia Society
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• v.12 no.2
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• pp.219-230
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• 2009

With the development of broadcasting technology from analogue to interactive digital, the number of TV channels and TV contents provided to audiences is increasing in a rapid speed. In this multi-channel world, it is difficult to adapt to the increase of the TV channel numbers and their contents merely using remote controller to search channels. For these reasons, the EPG system, one of the essential services providing convenience to audiences, is proposed in this paper. Collaborative filtering method with multi-step filtering is used in EPG to recommend contents according to the preference of audience groups with similar preference. To implement our designed TV contents recommendation EPG, we prefer DiTV and use JavaXlet programming based on MHP. The European DVB-MHP specification will be also our domestic standard in DiTV. Finally, the result is verified by OpenMHP emulator.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.56-62
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• 2006

In this paper, we simulated terrestrial digital broadcasting system and analyzed the performance of 8-VSB signal and carried out baseband simulation of tranceiver modeling by standard parameter and passband simulation for interchannel interference. Also, an error rate equation for fading and interference of 8-VSB signal is derived. As a result, the case not to consider Rician fading, the influence of the interference did not exist if frequency interval fell off over the 20MHz. The case to consider Rician fading, the system had the degradation of the performance.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.372-377
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• 2009

This paper evaluates the performance of three methods for predicting resources requested by mobile's calls and a call admission algorithm based on these predicting methods respectively in wireless networks. The first method is based on Wiener prediction model and the second method is based on the MMOSPRED algorithm and the third method is based on the neural network. The proposed call admission algorithm is based on prioritized handoff call in resource allocation. The resources for future handoff calls are therefore predicted and reserved in advance, and then new calls are admitted as long as the remaining resources are sufficient. We compare their performances in terms of prediction error, new call blocking and handoff dropping probabilities by simulation. Results show that the CAC based on Wiener prediction model performs favorably due to exact resources prediction.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11A
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• pp.1253-1262
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• 2004

The Data Over Cable System Interface Specification (DOCSIS) protocol enables the delivery of Internet Protocol(IP) traffic over Cable TV networks with significantly higher data rates. In this paper, we assessed the performance of the DOCSIS protocol using the OPNET. The simulation can be used to predict the upstream system throughput, mean access delay and channel utilization on varying packet size and transmission stream and wid/without concatenation, and it has shown that maximum system throughput is 4.6 Mbps for channel capacity of 5.12 Mbps and packet size of 1500 bytes. The mean access delay varies depending on the offered load, and it is assumed that the offered load does not exceed the capacity of the channel. Excess offered load causes service starvation according to the assigned priority.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.79-86
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• 2017

Precise Point Positioning-Real Time Kinematic (PPP-RTK) refers to a technology that combines PPP with network-RTK in which a user does not directly receive observed data from a reference station but receives State-Space Representation (SSR) messages corrected for error components from a central processing station through Networked Transport of RTCM via Internet Protocol (NTRIP) or Digital Multimedia Broadcasting (DMB) for purposes of positioning. SSR messages, which refer to corrections used in PPP-RTK, are generated by a central processing station using real-time observed data collected from reference stations and account for corrections needed due to the ionosphere, troposphere, satellite orbital errors, satellite time offsets, and satellite biases. This study used a type of SSR message provided in South Korea, known as Korea-SSR (K-SSR), to implement a PPP-RTK algorithm based on code-pseudorange measurements and validated its accuracy within the reference station network. In order to validate the accuracy of the implemented algorithm outside of the network, the K-SSR was extrapolated and applied to positioning in reference stations in Changchun, China (CHAN) and Japan (AIRA). This also entailed a quantitative evaluation that measured improvements in accuracy in comparison with point positioning. The results of the study showed that positioning applied with extrapolated K-SSR correction data was more accurate in both AIRA and CHAN than point positioning with improvements of approximately 20~50%.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1405-1408
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• 2005

An embedded system has been applied to many fields including households and industrial sites. In the past, user interface products with simple functions were commercialized .but now user demands are increasing and the system has more various applicable fields due to a high penetration rate of the Internet. Therefore, the demand for embedded system is tend to rise In this paper, we Implementation of an embedded system for image tracking. This system is used a fixed IP for the reliable server operation on TCP/IP networks. A real time broadcasting of video image on the internet was developed by using an USB camera on the embedded Linux system. The digital camera is connected at the USB host port of the embedded board. all input images from the video camera is continuously stored as a compressed JPEG file in a directory at the Linux web-server. And each frame image data from web camera is compared for measurement of displacement Vector. That used Block matching algorithm and edge detection algorithm for past speed. And the displacement vector is used at pan/tilt motor control through RS232 serial cable. The embedded board utilized the S3C2410 MPU Which used the ARM 920T core form Samsung. The operating system was ported to embedded Linux kernel and mounted of root file system. And the stored images are sent to the client PC through the web browser. It used the network function of Linux and it developed a program with protocol of the TCP/IP.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.4
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• pp.18-24
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• 2010

This paper presents the improvement of the field uniformity in a reverberation chamber which can be substitute an anechoic chamber for the electromagnetic interference (EMI) and immunity test. Nowadays, there are many EMI issues due to the increasing use of wireless local area network (LAN), digital multimedia broadcasting (DMB), and mobile internet. With this reason, this paper studied the field characteristics in a reverberation chamber for 2.3 GHz band. In this paper, the finite difference time domain (FDTD) method is used to analyze the field characteristics in a reverberation chamber. To improve the field uniformity in the reverberation chamber, this paper adopted a 2D cubical residue diffuser (CRD) with varying the disposition and number of CRD. For each case, the tolerance and standard deviation of the electric field strength are evaluated. In comparison with the reverberation chamber without any CRD, the reverberation chamber with two CRDs showed improved results; 1.98 dB improvement in standard deviation and 3.6 dB improvement in tolerance.

• 한국HCI학회:학술대회논문집
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• 2007.02b
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• pp.512-517
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• 2007

다양한 디지털 가전제품을 제조하는 회사들은 초기에 제품 하나하나에 제품의 사용경험을 담는데 비중을 높여 개발을 하였다. 하지만 제품이 알려지고 종류가 많아지면서 각 제품들을 아우르는 사용자 경험요소 통합화가 필요하게 되었다. 이에 다양한 화면 사이즈와 Input Device를 가진 Handheld Device들 간의 일관된 사용 경험(user experiences)을 제공하는 것을 목적으로 하는 연구가 진행되었다. 대상이 된 제품들은 Digital Media Broadcasting의 수신, Multimedia 파일이 재생, 파일 creation 등이 가능한 Handheld Devices였고, 각 제품들은 특정 기능에 충실한 UI를 구현하고 있다는 특징이 있다. 따라서, 기존 제품의 사용성을 저해하지 않는 수준의 표준화가 필요하며 기존 UI 사용성과 표준화 UI 사용성 간의 조화가 중요 하였다. 기존 제품의 개별 특징을 분석하고 Handheld Device의 사용자 요구사항을 조사를 통해 사용경험 요소를 발굴하고 Navigation, Menu Hierarchy, Screen Layout 등의 설계를 통해 Prototype 개발을 하고 Usability Test를 통해 보완을 하였다. Usability Test는 한국, 미국, 영국, 중국 4개국에서 광범위한 사용자 조사가 이루어졌다. 국가 선정은 제품의 주요 시장 및 각 대륙을 대표하는 기준으로 선정되었다. 사용자 그룹은 연령, 지식 수준, 성별에 구분되었고 Web Survey 1000명, Usability Test는 각 국가별 총 100명이 넘는 참석자에 의한 데이터 분석이 이루어 졌다. 이렇게 조사된 데이터를 바탕으로 UI 사용경험 요소를 정의하고 제품의 공통 가이드와 개별 가이드를 개발하는 일련의 프로세스를 확립하고 검증하였다. 본 논문을 통해 대상 제품들의 다양한 특성을 살리면서도 user Interface의 일관성 원칙을 설립하기 위해 시도했던 방법과 과정을 기술하고, 이 과정을 통해서 얻은 결과와 실제적인 경험을 소개한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.78-84
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• 2008

In this paper, the reconfigurable annular ring slot antenna with circular polarization diversity is proposed for SDMB(Satellite Digital Multimedia Broadcasting) system. The proposed antenna consists of a ring slot with four tuning stubs. Four PIN diodes are attached to switch circular polarization diversity. By switching the diodes ON or OFF, the proposed antenna can be operated either RHCP mode or LHCP mode. The experimental result shows that the proposed antenna has an impedance bandwidth(VSWR${\leq}$2) of 570MHz(2.47-3.04GHz) at LHCP mode, an impedance bandwidth (VSWR${\leq}$2) of 560MHz(2.45-3.01GHz) at RHCP mode, a maximum gai of 3.1dBi at RHCP mode, 4.76dBi at LHCP mode. The 3dB CP bandwidth of about 100MHz at both RHCP and LHCP mode is achieved at the center frequency 2.63GHz. The proposed antenna is suitable for application such as mobile satellite communications, WLAN(Wireless Local Area Networks), and broadband wireless communication systems.