• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.625-632
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• 2009

This paper presents the mobile IPTV system for the transmission of FGS-encoded video stream over WiMAX network. The proposed system is implemented to provide more subscribers with an improved mobile IPTV service considering the scarce resource constraint. The proposed system pursues an efficient tradeoff between the number of subscribers that receive the enhancement layer stream and their IPTV service quality. In the proposed system, some parts of the enhancement layer are transmitted with the modulation scheme and the coding rate adaptive to wireless link states of subscribers. Finally, experimental results are provided to show the performance of proposed mobile IPTV system.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.11-27
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• 2007

T-DMB(Terrestrial-Digital Multimedia Broadcasting) for portable and mobile broadcasting service was officially launched in the metropolitan area of Korea in December 2005. The development of interactive data services and the expansion of T-DMB network have been now progressed, and the regional T-DMB broadcasters will be selected in the near future. Although it is important to evaluate service area and reduce a fringe area for optimizing RF coverage of T-DMB, there was no professional system to support those works, and therefore lots of resources in budget, manpower and time were required. The measurement considering characteristics of SFN(Single Frequency Network) is essential in the implementation of T-DMB network which needs to control synchronization, spacing and output power of transmitters. In addition, mobile measurement, enough measured parameters for many-sided analysis of reception quality, efficient management of enormous measured data and representation of measured results on the electronic map are also important in evaluating service area. In this paper, we derived requirements for a new measurement system in T-DMB by considering the above details, and we proposed and developed an integrated measurement and analysis system. The developed system was applied to the implementation of T-DMB network of KBS and field tests, and it proved its efficiency and accuracy in result.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.25-28
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• 1999

Consider connection-oriented wireless cellular net-works. To establish a circuit or virtual circuit in such a network, a paging message is broadcast over a region at which the destined mobile station is presumed to reside, (identified as a paging area). For an effective paging mechanism, it is desirable to provide the location information of mobile stations to the network. In this paper, we consider a mobile controlled location update scheme under which each mobile station periodically reports its current location information to the network by using an inherent timer (without measuring the power of signals transmitted from base stations). Based on the latest information about a mobile station's location, a paging area is selected to page the mobile station. Note that under this scheme, a mobile station may not yet have reported its location change while sojourning out of the current paging area. In such situation, the mobile station can not receive a paging message destined to it. Frequent location updates can reduce the paging failure rate incurred by mobile stations'sojourning out of the paging area. However, larger bandwidth is needed for location update as the location update rate is increased. On the other hand, as the size of the paging area is increased, the paging failure rate is decreased, while larger bandwidth is required for paging. Thus, we first present a model for mobility, paging and location update processes, and secondly investigate the effect of network parameters on the paging failure rate and the amount of bandwidth used for paging and location update. Finally, we formulate problems to find proper values for the location update rate and paging area size under the constraints on the bandwidth usage levels for location update and paging.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.315-325
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• 2005

In mobile computing environments, a mobile host caches the data items to use the bandwidth efficiently and improve the response time of transactions. If the data items cached in mobile host are updated in the server, the server broadcasts an invalidation report for maintaining the cache consistency of mobile hosts. However, this method has a problem that the response time of mobile transactions can be long since their commit decision is delayed until receiving the invalidation report from the server In this paper, we propose the USR-MT method for improving the response time of mobile transactions. As the UGR-MT method can make a commit decision by using the data group information before receiving the invalidation report, the response time of mobile transactions can be improved. Also our method can improve the cache's efficiency since it prevents all the contents of a cache from being invalidated in the case that the disconnection of a mobile host is longer than the broadcast period of invalidation report.

• Journal of the Korea Convergence Society
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• v.8 no.9
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• pp.231-236
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• 2017

This study analyzes the characteristics of mobile live streaming service, the illegal and harmful information characteristics of mobile live streaming service for the purpose of eradicating illegal and harmful broadcasting, and shows illegal and harmful broadcast on the mobile live streaming service and eradication plan. First, we reviewed the mobile live streaming service, illegal and harmful broadcasts through literature review, and secondly surveyed illegal and harmful broadcasts of mobile live streaming services and their awareness and countermeasures. As a result, it is confirmed that the mobile live streaming service is illegal, harmful broadcasting exposure frequency is high, illegal, and harmful broadcasting exposure is caused by characteristics of real time broadcasting rather than user's. In order to eradicate the illegal and mobile information about the mobile live streaming service, it is necessary to fix the illegal service and harmful broadcasting reporting system, but the government has confirmed the requirements for regulatory measures. From a microscopic point of view, it will be necessary to investigate the illegal use of mobile live streaming services and the eradication of harmful information.

• The KIPS Transactions:PartD
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• v.16D no.3
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• pp.441-450
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• 2009

This paper describes the design and implementation of Personal Mobile Broadcasting Service which bases on embedded Linux and it supports personal broadcasting in wireless network environments. Recently, with the advent of various wireless networks and the increased use of high performance mobile devices, the demand for personal mobile broadcasting is being increased. The personal mobile broadcasting service makes it possible that mobile users create contents using their own mobile devices while they are moving or they are in any place. And then, it sends the created contents to server in real-time where their blogs are. Users connected to the content creator's blog can play the contents in real-time. With the implemented personal mobile broadcasting service, mobile users can share multimedia contents in real-time through wireless networks. And, it also helps users to construct their own broadcasting stations where they can broadcast the scene of the accident or public performance in real-time.

• Journal of Broadcast Engineering
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• v.17 no.2
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• pp.388-399
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• 2012

In the paper, we propose enhanced feature extraction and matching methods for a mobile environment based on modified SURF. We propose three methods to reduce the computational complexity in a mobile environment. The first is to reduce the dimensions of the SURF descriptor. We compare the performance of existing 64-dimensional SURF with several other dimensional SURFs. The second is to improve the performance using the sign of the trace of the Hessian matrix. In other words, feature points are considered as matched if they have the same sign for the trace of the Hessian matrix, otherwise considered not matched. The last one is to find the best distance-ratio which is used to determine the matching points. We find the best distance-ratio through experiments, and it gives the relatively high accuracy. Finally, existing system which is based on normal SURF method is compared with our proposed system which is based on these three proposed methods. We present that our proposed system shows reduced response time while preserving reasonably good matching accuracy.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.693-704
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• 2011

As mobile devices become multi-functional, and converge into a single platform, there is a strong need for a codec that is able to provide consistent quality for speech and music contents. MPEG-D USAC standardization activities started at the 82nd MPEG meeting with a CfP and approved Study on DIS at the 96th MPEG meeting. MPEG-D USAC is converged technology of AMR-WB+ and HE-AAC V2. Specifically, USAC utilizes three core codecs (AAC, ACELP, and TCX) for low frequency regions, SBR for high frequency regions, the MPEG Surround for stereo information, and window transition technology for smoothing transition between various core coder. USAC can provide consistent sound quality for both speech and music contents and can be applied to various applications such as multi-media download to mobile devices, digital radio, mobile TV and audio books.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.285-296
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• 2005

In mobile distributed systems the data on the air can be accessed by a lot of mobile clients. And, we need an indexing scheme in order to energy-efficiently access the data on the wireless broadcast stream. In conventional indexing schemes, they use the values of primary key attributes and construct tree-structured index. Therefore, the conventional indexing schemes do not support content-based retrieval queries such as partial-match queries. In this paper we propose an indexing scheme, called B2V-Tree, which supports partial match queries on wireless broadcast data stream. For this purpose, we construct a tree-structured index which is composed of bit-vectors, where the bit-vectors are generated from data records through multi-attribute hashing.

• Journal of Broadcast Engineering
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• v.10 no.2
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• pp.166-173
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• 2005

In this paper, we propose a mobile channel estimation algorithm using matching pursuit algorithm for orthogonal frequency division multiplexing (OFDM) systems. Least square (LS) algorithm, which is used as a conventional channel estimation algorithm for OFDM systems, has error probability of channel estimation affected by effects of noise. By estimating the channel of sparse type, the proposed algorithm reduces effects of noise during time intervals that multi-path signal doesn't exist. The proposed algorithm estimates a mobile receivingchannel using pilot information transmitted consequently. We compare performance of the proposed algorithm with the LS algorithm by measuring symbol error rate with 64QAM under a mobile multi-path fading channel model.