• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.1009-1018
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• 2003

A new fading channel estimation technique is proposed for an OFDM based modem In the ITS system. The algorithm is based on the transfer function extraction of the channel using the pilot signals and compensated the channel preceding the equalization. The newly derived algorithm is division-free arithmetic operations allows the faster circuit operation and the smaller circuit size. Proposed techniques compensate firstly the distortion which is generated at fading channels and secondly eliminate inter-symbol interference. All algorithms are suitability estimated and improved for a system implementation using digital circuits. As the results, the circuit size is reduced by 20% of the conventional design and achieved about 10% performance improvement at low SNR under 10dB in case of ITS system adapted 16-QAM mode.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8B
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• pp.1444-1455
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• 1999

In the standard location strategy such as IS-41 and GSM, Home Location Register(HLR) and Visitor Location Register(VLR) databases are used to manage the location of mobile terminals. The primary goal that location management schemes investigate is to reduce the cost of database access and the traffic for signaling network. When mobile terminals move frequently, one of problems in the standard location management scheme is that HLR database is highly updated and the traffic in signaling network can be occurred significantly due to high message transfer rate between HRL and VLR. As a solution to these problems, this paper proposes the location management scheme using VLR Gateway(VG) to reduce the both traffics of HLR update and signaling network which are resulted from location registration requirements of mobile terminals whenever they cross their registration area boundary. VG is a kind of database that is placed between HLR and VLR. It integrates one or more registration area defined in a system into one group and plays a role on behalf of HLR in a integrated registration scope so that the call delivery and the movement of mobile terminals are possible without HLR access in the scope. In order to evaluate performance of IS-41 and proposed scheme, we simulate two schemes based on wide range of call to mobility ratio. Its experiment result shows that in the proposed scheme total database cost increased slightly whereas HLR and signaling traffic decreased remarkably.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.8
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• pp.473-486
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• 2004

NUMA systems have remote access caches(RAC) in each local node to reduce the overhead for repeated remote memory accesses. By this RAC, memory latency and network traffic can be reduced and the performance of the multiprocessor system can be improved. Until now, several cache replacement policies have been proposed in recent years, and there also is cache replacement policy for multiprocessor systems. In this paper, we propose a cache replacement policy which is based on cache line coherence information. In this policy, the cache line that does not have an ownership is replaced first with respect to cache line that has an ownership. Like this way, the overhead to transfer ownership is avoided and the memory latency can be decreased. We also propose “Keeping-Ownership replacement policy with MRU (KOM)” and “Keeping-Ownership replacement policy with Reference Bit(KORB)” to reduce the frequent replacement penalty of the ownership-lacking cache line. We compare and analyze these with LRU and Pseudo LRU(PLRU). The simulation shows that KOM outperforms the PLRU by 25%, and KORB outperforms the PLRU by 13%. Although the hardware cost of KOM is very small, the performance of KOM is nearly equal to that of the LRU.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.278-285
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• 2013

The suppression of residual settlement is required on earthwork sections as concrete track is introduced. Use of pile-slab structure is one of the settlement restraining methods applied on soft ground. The slab distributes the upper embankment load and piles transfer the load from the slab to the stiff ground. While this method is very effective in terms of load transfer, it has not yet been established for dealing with the vibration transfer effects and interaction characteristics between a structure and the ground. It is possible that vibration caused by a moving train load is propagated in the upper embankment, because the slab acts as a reflection layer and waves are multi-reflected. In this present paper, wave propagation generated by a moving train load is evaluated in the time and frequency domains to consider a roadbed structure using an artificial impact load and field measured train load. The results confirmed the wave reflection effect on the pile-slab structure, if the embankment height is sufficient, vibration propagation can be stably restrained, whereas if the height is not sufficient, the vibration amplitude is increased.

• Journal of Information Technology and Architecture
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• v.11 no.4
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• pp.449-462
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• 2014

In big data era, there are a number of considerable parts in processing systems for capturing, storing, and analyzing stored or streaming data. Unlike traditional data handling systems, a big data processing system needs to concern the characteristics (format, velocity, and volume) of being handled data in the system. In this situation, virtualized computing platform is an emerging platform for handling big data effectively, since virtualization technology enables to manage computing resources dynamically and elastically with minimum efforts. In this paper, we analyze resource utilization of virtualized computing resources to discover suitable deployment models in Apache Hadoop and HBase-based big data processing environment. Consequently, Task Tracker service shows high CPU utilization and high Disk I/O overhead during MapReduce phases. Moreover, HRegion service indicates high network resource consumption for transfer the traffic data from DataNode to Task Tracker. DataNode shows high memory resource utilization and Disk I/O overhead for reading stored data.

• Journal of KIISE
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• v.42 no.6
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• pp.807-816
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• 2015

The Internet of Things (IoT) has recently been showered with much attention worldwide. Various kinds of devices, communicating with each other in the IoT, demand multiple communication technologies to coexist. In this environment, mobile devices may utilize the vertical handover between different wireless radio interfaces such as Wi-Fi and Bluetooth, for efficient data transfer. In this paper, an IoT broker is implemented to support the vertical handover, which can also support and manage heterogeneous devices and communication interfaces. The handover is activated based on RSSI, Link Quality values, and real time traffic. The experimental results show that the proposed handover system substantially improves QoS in Bluetooth and reduces power consumption in mobile devices as compared with a system using only Wi-Fi.

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.313-322
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• 2005

In this paper, we implement and verify performance monitor for parallel signal processing system, using DSP Starter Kit(DSK) of which the basic Processor is TMS302C6711 chip. The key ideas of this performance monitor is, using Real Time Data Exchange(RTDX) for the Purpose of real-time data transfer and function of DSP/BIOS, the ability to measure the Performance measure like DSP workload, memory usage, and bridge traffic. In the simulation, FFT, 2D FFT, Matrix Multiplication, and Fir Filter, which are widely used DSP algorithms, have been employed. Using performance monitor and Code Composer Studio from Texas Instrument(Tl) , the result has been recorded according to different frequencies, data sizes, and buffer sizes for a single wave file. The accuracy of our performance monitor has been verified by comparing those recorded results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.437-440
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• 2007

Recently embedded system developed a lot. Physically, embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants. This paper focuses on implementation of portable device which is applicable to the child-kidnap or missing child prevention system in residential area or public area. To be specific, this device is to transmit video data which comes from the camera in the device into the host PC via WLAN. Embedded hardware platform consists of s3c2440 with ARM9 core, WindowsCE OS and other sensors. OS enables the platform to do multitasking jobs which are handling GPS data, taking video, capturing audio via microphone in the device and transfer all kind of realtime data to the host PC.

• Journal of Service Research and Studies
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• v.9 no.4
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• pp.19-40
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• 2019

Mobility as a Service is a service conception to achieve the intelligent transportation system. Its aims to improve the travel experience. In one platform, it connects various transportation modes to offer service and users only need to pay in one time for the whole travel. But the single MaaS platform easily faces the problems such as low user traffic, low retention rate and the access to markets of the this service is still unfound. From the perspective of bicycle-sharing, this research makes the MaaS concept into bicycle-sharing to build a better service model. The bicycle-sharing combine with the MaaS concept is innovative in business model, travel model and service architecture. In addition, this research also tests users' expectations for service model. The research shows that MaaS-based bicycle-sharing could offer flexible and convenient travel experience in the aspects of combined transportation, travel, transfer and payment, and it also makes it possible to make travel services according to need, and sustainable transport.

• The KIPS Transactions:PartB
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• v.11B no.5
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• pp.603-610
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• 2004

The distributed Information Retrieval System centrally controlled by mediator or meta search engine result in congestion of heavy traffic and int he problem of increment of cost for the reason of the design of complicated algorithm for central control and installation of hardware. So to figure out this problem, the way is needed that has independent retrieval functionality and can cooperate each other without dependency. In this paper, we overview a few works involved in distributed information retrieval system, then, implement algorithm and design the frame-work of distributed information retrieval system using sequential transferring method(STM) including multiple information retrieval system separated from central control. For this first of all, we present a web partition policy which devide and manage web logically and we present the sequential query processing way by means of illustration through changing numbered information retrieval system. Then, we also present 3-layered structure of framework and function and module of each layer suitable for information retrieval system. Last of ail, for effective implementation of STM algorithm we analysis module structure and present description of pseudocode of this, and show that the proposed STM algorithm works smoothly by demonstration of sequential query transfer process between servers.