• Journal of Broadcast Engineering
• /
• v.13 no.3
• /
• pp.365-379
• /
• 2008

In this paper we consider technological requirements of the on-channel repeater to broadcast the terrestrial digital multimedia broadcasting (T-DMB) signals using single frequency networks (SFN) and propose the configuration and implementation method of the equalization on-channel repeater (OCR) that meet such requirements. The proposed equalization OCR not only has short time delay, but shows high output power and good quality of output signal by removing a feedback signal due to incomplete antenna isolation and multipath signal existing between the main transmitter and the OCR. In addition, computer simulations and laboratory tests results are provided to figure out performance of the proposed equalization OCR.

• Journal of Broadcast Engineering
• /
• v.18 no.2
• /
• pp.249-260
• /
• 2013

Recently, High-Efficiency Video Coding (HEVC) has been developed as a new video coding standard mainly focusing on the coding of ultra high definition (UHD) videos as the high resolution and high quality videos are getting more popular. Furthermore, the scalable extension of HEVC is being standardized for more efficient provision of HD and UHD services in the communications-broadcasting convergence environment. In this paper, we propose an improved scalable video coding method of H.264/AVC to achieve high coding efficiency particularly for UHD and HD videos. The basic idea is to allow large block size in H.264/AVC SVC, which results in more efficient inter-layer prediction and syntax elements coding. The experimental results show that it achieves an average 4.53% reduction in BD-rate relative to H.264/AVC SVC.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.12B
• /
• pp.805-810
• /
• 2005

According to the user requirements for continuous and real-time multimedia information, the concept of Quality of Service (QoS) has emerged as a main issue in mobile ad-hoc networks. QoS routing is to find the route that meets the QoS requirements of the users. In this paper, we propose a routing protocol that is based on AODV over TDMA, one of the typical routing protocols for mobile ad-hoc networks, by making a bandwidth reservation for QoS guarantee. While the existing schemes calculate the maximum available bandwidth for each candidate path, our scheme is to check only if the bandwidth of a given path satisfies the end-to-end QoS requirement and then to make a reservation by allocating time slots efficiently in the wireless environment. In order to evaluate the performance of the proposed QoS routing protocol, some simulations are carried out in the ad-hoc environment.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.27 no.2
• /
• pp.213-222
• /
• 2017

Online advertisement has many benefits comparing to offline advertisement but it also has many challenging problems by online ad abuses. Advertisement injection (Ad injection) is one of the threats that surreptitiously inserts advertisements without a permission of site owners. Users are exposed to additional ads and redundant web traffic by injected ads can cause a service quality problem. Moreover, advertisers can have economic loss when injected ads are different from original ones. Although ad injection leads to these problems it has not been fully studied yet. A few ad injection researches are done by online advertising providers such as Google. In this paper, we analyze ad injection activities to Korean major portal, Naver. We classify 6 types of ad injections and describe their characteristics by analyzing 27 downloaders and 199 installed programs.

• Journal of KIISE:Information Networking
• /
• v.33 no.2
• /
• pp.139-148
• /
• 2006

Recently with the advancement of local wireless communication technologies, digital trends of audio contents and devices are paving the way for new experiences to network-based audio streaming services. In this paper, we present the Wireless Audio Sharing (WASH) technology over Bluetooth and Wireless Local Area Network (WLAN). WASH system provides an audio sharing mechanism over multiple users and also provides stereo audio streaming between Bluetooth-enabled devices and Universal Plug and Play (UPnP) media devices connected to wired/wireless LANs. To achieve these, we extended the Bluetooth audio distribution profile and combined the extended profile with the UPnP AV architecture. With the implementation of this WASH technology, we show some experimental results of the stereo audio streaming in a real environment.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.4 no.4
• /
• pp.409-417
• /
• 2003

In recent years, better quality in power electric services is being required with the development of information industries and the improvement of living standards. Also, the small scaled dispersed storage and generation (DSG) systems are being interconnected with the distribution systems and customers by the influence of the recent issues such as deregulation and global environmental problems in power system. Under these circumstances, it is very important to maintain the customer voltages within allowable limits for the distribution system which is located at the most sensitive part in the power system. To overcome these problems, this paper shows the basic concepts of FRIENDS which is considered as one of the power delivery system in the near future and also presents an evaluation method on the impacts of customer voltages by operation models of FRIENDS. The FRIENDS can change the system configuration in a flexible manner by using the static switches and offer the different power qualities in power services through the power quality control centers which play the most important role in FRIENDS. Numerical examples are shown in order to indicate the efficiency of the proposed method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.7A
• /
• pp.560-568
• /
• 2012

Spectrum sensing and spectrum decision are the main functions that cognitive radios (CRs) have to perform in order to get the best available spectrum band for the establishment of a wireless communication. These problems are worsened in the presence of users with different demands and spectrum channels with different properties in a heterogeneous network. The primary objective in this work is to design and simulate a new spectrum decision algorithm for heterogeneous cognitive radio system. To this end, first, we consider all cognitive users are separated into different traffic classes according to their Quality of Service (QoS). The cognitive users within one traffic class perform spectrum sensing in centralized group-based cooperative spectrum sensing system and the users of different traffic classes share the sensing results. Second, we propose a novel use of the Analytic Hierarchy Process (AHP) to optimally select available bands according to user requirements and detected spectrum channel characteristics (SCC). In this paper, utility function is used as spectrum decision algorithm. Simulation results demonstrate that the proposed method shows can effectively select the best available spectrum channels with a low complexity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.10A
• /
• pp.1057-1064
• /
• 2007

Cognitive radio(CR) technique which utilizes empty frequency bands allocated to private business but not being used temporally has been researched. According to the standard, CR users detect the primary user using the same channel, CR users should move to the another channel to guarantee the primary user's decodability. Thus, CR systems cannot use the same channel and support the CR user's QoS(Quality of Service) during the channel moving time. In this paper, we propose a radio resource sharing method that CR basestation controls the transmission power with the primary user's SNR(Signal to Noise Ratio) to increase the spectral efficiency of area and to minimize the outage of CR users. In addition, computer simulation demonstrates show that the proposed method improved spectral efficiency of area and decreased outage probability of CR users.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.6A
• /
• pp.624-634
• /
• 2008

The mobile station which is about to do handover in IEEE 802.16e networks scans its neighboring base station channels to decide its next target base station. However, due to the lack of location information of its subscribers, the serving base station cannot provide any reliable candidate channel which is actually attachable by the scanning mobile stations, which makes the mobile station suffer from the long scanning time. Sometimes, long scanning time may cause the degradation of quality of service due to repeatable scan-duration or failure to start the handover procedure in time. To overcome these problems, in this paper, we propose a new protocol so called fast group scanning scheme, in which multiple mobile stations form a group to scan their neighboring base station channels simultaneously. Main contribution of this proposal is to find and decide a reliable target base station within a short scanning time. The fast group scanning scheme can be deployed to the cell network of the serving base station with a dynamic neighboring base station list management.

• Journal of Korean Society for Geospatial Information Science
• /
• v.17 no.2
• /
• pp.133-143
• /
• 2009

Next Generation Digital Maps on demand Updating System is a system for setup of efficient on-demand updating system, keeping up-to-date data and conducting high-quality service and efficient management. The system is designed that object-based continuous Digital Maps may have on-demand updating available, as well as the exiting feature-based digital maps, and the relevant development is being done. This study presented some problems and improvement plans related to the system operation, by means of implementing object-based continuous Digital Maps and feature-based digital maps updating test, for the next generation digital maps on demand updating system, in order to contribute to present plans to apply next generation digital maps and to secure competitiveness. And, for the economical efficiency of the next generation digital maps on demand updating system, this study analyzed expenses and benefit resulted from introduction of on demand updating system for 1:5,000 digital maps, intended for National Geographic Information Institute. and the land category which have an effect on the officially assessed land price and it using GIS technology.