• Journal of Korea Spatial Information System Society
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• v.8 no.2 s.17
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• pp.75-89
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• 2006

LBS (Location-Based Service) systems have become a serious subject for research and development since recent rapid advances in wireless communication technologies and position measurement technologies such as global positioning system. The architecture named the GALIS (Gracefully Aging Location Information System) has been suggested which is a cluster-based distributed computing system architecture to overcome performance losses and to efficiently handle a large volume of data, at least millions. The GALIS consists of SLDS and LLDS. The SLDS manages current location information of moving objects and the LLDS manages past location information of moving objects. In this thesis, we implement a monitoring technique for the GALIS prototype, to allow dynamic load balancing among multiple computing nodes by keeping track of the load of each node in real-time during the location data management and spatio-temporal query processing. We also propose a buffering technique which efficiently manages the query results having overlapped query regions to improve query processing performance of the GALIS. The proposed scheme reduces query processing time by eliminating unnecessary query execution on the overlapped regions with the previous queries.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1184-1195
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• 1998

In this paper, we compare vaious input-buffered ATM switch architectures in structures on input buffer and switching fabric, the resons for performance improvement and degradation, arbitration scheme and maximum throughput, and present comparative merits and demerits of each architecture under random and bursty traffic. We also analyze the prformance of combined architectures of windowing scheme, destination-queueing based input-port expansion schemeand output-port expansion scheme, and show that it is possible to achieve 100% throughput with combined scheme of destination-queueing based input-port expansion scheme and output-port expansio scheme when the number of output group is 2 and output port expansion ratio is 2.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8
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• pp.2543-2554
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• 2000

Packet schedulers for real-time communication must provide bounded delay and efficient use of network resources such as bandwidth, buffers and so on. In order to satisfy them, a large number of packet scheduling methods have been proposed. Among packet scheduling methods, an EDF (Earliest Deadline First) scheduling is the optimal one for a bounded delay service. A disadvantage of EDF scheduling is that queued packets must be sorted according to their deadlines, requiring a search operation whenever a new packet arrives at the scheduler. Although an RPQ (Rotating Priority Queue) scheduler, requiring large size of buffers, does not use such operation, it can closely approximate the schedulability of an EDF scheduler. To overcome the buffer size problem of an RPQ scheduler, this paper proposes a new scheduler named MRPQ (Multiple Rotating Priority Queue). In a MRPQ scheduler, there are several layers with a set of Queues. In a layer, Queues are configured by using a new strategy named block Queue. A MRPQ scheduler needs nearly half of buffer size required in an RPQ scheduler and produces schedulability as good as an RPQ scheduler.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.587-594
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• 2005

In the paper, after we propose a viterbi decoder which has multiple buffering and parallel processing decoding scheme through expanding time-divided imput signal, and map a FPGA, we implement a channel coding system together with PC-based software. Continuous input signal is buffered as order of decoding length and is parallel decoded using a high speed cell for viterbi decoding. Output data rate increases linearly with the cell formed the viterbi decoder, and flexible operation can be satisfied by programming controller and modifying input buffer. The tell for viterbi decoder consists of HD block for calculating hamming distance, CM block for calculating value in each state, TB block for trace-back operation, and LIFO. The implemented cell of viterbi decoder used 351 LAB(Logic Arrary Block) and stably operated in maximum 139MHz in APEX20KC EP20K600CB652-7 FPGA of ALTERA. The whole viterbi decoder including viterbi decoding cells, input/output buffers, and a controller occupied the hardware resource of $23\%$ and has the output data rate of 1Gbps.

• The Journal of the Korea Contents Association
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• v.2 no.4
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• pp.85-92
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• 2002

This paper proposes the cell scheduling algorithm proper to high-speed ATM switch. The proposed algorithm is the VRR(Variable weight Round Robin) combined the FRR to variant QLT. The FRR performs the cell service of the fixed weight by each buffer. So, FRR don't support the QoS of ATM service classes although it is easy to implement a high speed switch. VRR uses the method expaned to variable weight according to buffer state as well as schedules the cell according the Fixed weight based FRR. The simulation to evaluate the proposed algorithm was done by AweSim arid Visual C++. The result graphs show that the proposed algorithm is excellent, especially in the aspect of cell loss. This area is engaged by English Abstract.

• Journal of the Korea Computer Industry Society
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• v.3 no.9
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• pp.1251-1260
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• 2002

Real-time application programs have synchronization constraints which need to be met between media-data. Synchronization method represents feedback method including virtual client-side buffer. This buffer is used in buffer level method. It is client-leading synchronization that is absorbing variable transmission delay time and that is synchronizing by feedback control. It is the important factor for playback rate and QoS if the buffer level is normal or not. To solve the problems, we can control the start of transmission in multimedia server by appling filtering, control and network evaluation function. Synchronization method is processing for smooth presentation without cut-off while media is playing out. When audio frame which is master media is in high threshold buffer level we decrease play out time gradually, otherwise we increase it slowly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1743-1749
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• 2011

The multimedia data for video-on-demand(VOD) service has large, continuous and real time characteristics. The frequent disk I/O operations takes much time and decrease the system performance in multimedia services. Therefore the efficient buffer management is needed in order to reduce the disk accesses to multimedia data. This paper addresses how to increase the buffer hit ratio and the number of users in a multimedia service like VOD by increasing the utility of buffer. This paper also simulated various resource management algorithms and strategies and evaluated, compared and analyzed their performances.

• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.391-398
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• 2008

To provide IPTV service over mobile networks, the mechanism that reduce packet loss and interrupt of multimedia service during the handover should be supported. Especially, buffering based mechanism is preferable for supporting IPTV services in the way of preserving streaming service using stored data and recovering non-received data after handover. But previous research doesn't consider the buffer allocation for applying various environments which can change handover time or end to end delay of relay node. This paper propose DBAHAJ mechanism that optimize buffer size of mobile nodes and relay node for supporting seamless IPTV service over mobile environments. Mobile node determines buffer size by checking handover time and maximum difference of sequence to keep playing video data. And multicast agent recovers packet loss during the handover by sending buffered data. By these two procedure, node supports seamless IPTV service on mobile networks. We confirm performance of this mechanism on NS-2 simulator.

• Information and Communications Magazine
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• v.14 no.7
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• pp.156-166
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• 1997

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1992.06a
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• pp.94-97
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• 1992