• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.2
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• pp.36-45
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• 2003

This paper presents a way to maximize transmission efficiency and reception ability through transmission diversity technology, which can be adapted to wireless multimedia OFDM (orthogonal FDM) system. The presented method gives a comparative analysis between a case where parameter a for time average is 0.3, i with consideration of channel presumption and two types of rms delayed proliferation, which is 50nsec, 150nsec, for the performance analysis of STTC (Space-Time Trellis Code) using time-space code method which is appropriate for MIMO channel, and performance, in the case, where presumed channel value from long training column section is applied to the according frame in a single frame. The result shows that BER brought SNR improvement of 1.0dB in $10^{-3}$ when a was 0.3 than using only the long training column, and shows an increasement of general performance improvement when the time average factor is used.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.719-724
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• 2011

Most recent birth rate at home raising children, only one has come out well. Accordingly, children born to parents is to have a strong interest, and healthcare (Healthcare) sector, while emerging as a new growth industry (Baby Care) Baby Care also increased the interest. Baby Care products until now the food, toiletries and clothing, etc. Although it advances the development of ubiquitous computing environment with the development of the healthcare industry, Baby Care Electronics products have been developed. Europe and the U.S. infant from another room deungeseoneun feeder. At this time SIDS infants to prevent this phenomenon often takes place in order to measure the status of children and away from parents to children, also can check the status of children was used to implement the Platform. In this paper, using the radio frequency real-time observation of data storage without the parents were determined only by the speed of the ARM11-based systems using the S3C6410 CPU and wireless WI-FI (IEEE8.2.11) technology to prevent sudden infant death using Platform for the implementation study was conducted.

• The KIPS Transactions:PartD
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• v.8D no.3
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• pp.221-232
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• 2001

Due to rapid advance of wireless communication technology, demand on data services in mobile environment is gradually increasing. Caching at a mobile client could reduce bandwidth consumption and query response time, and yet a mobile client must maintain cache consistency. It could be efficient for the server to broadcast a periodic cache invalidation report for cache consistency in a cell. In case that long period of disconnection prevents a mobile client from checking validity of its cache based solely on the invalidation report received, the mobile client could request the server to check cache validity. In doing so, some schemes may be more efficient than others depending on the number of available channels and the mobile clients involved. In this paper, we propose new cache consistency schemes, effects, efficient especially (1) when channel capacity is enough to deal with the mobile clients involved or (2) when that is not the case, and evaluate their performance.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.188-194
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• 2012

Cognitive networks (CNs) are capable of enabling dynamic spectrum allocation, and thus constitute a promising technology for future wireless communication. Whereas, the implementation of CN will lead to the requirement of an increased energy-arrival rate, which is a significant parameter in energy harvesting design of a cognitive user (CU) device. A well-designed spectrum-sensing scheme will lower the energy-arrival rate that is required and enable CNs to self-sustain, which will also help alleviate global warming. In this paper, spectrum sensing in a multi-user cognitive ad hoc network with a wide-band spectrum is considered. Based on the prospective spectrum sensing, we classify CN operation into two modes: Distributed and centralized. In a distributed network, each CU conducts spectrum sensing for its own data transmission, while in a centralized network, there is only one cognitive cluster header which performs spectrum sensing and broadcasts its sensing results to other CUs. Thus, a wide-band spectrum that is divided into multiple sub-channels can be sensed simultaneously in a distributed manner or sequentially in a centralized manner. We consider the energy consumption for spectrum sensing only of an analog-to-digital convertor (ADC). By formulating energy consumption for spectrum sensing in terms of the sub-channel sampling rate and whole-band sensing time, the sampling rate and whole-band sensing time that are optimal for minimizing the total energy consumption within sensing reliability constraints are obtained. A power dissipation model of an ADC, which plays an important role in formulating the energy efficiency problem, is presented. Using AD9051 as an ADC example, our numerical results show that the optimal sensing parameters will achieve a reduction in the energy-arrival rate of up to 97.7% and 50% in a distributed and a centralized network, respectively, when comparing the optimal and worst-case energy consumption for given system settings.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2B
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• pp.178-187
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• 2009

Cognitive radio (CR) technology is to maximize the spectrum utilization by allocating the unused spectrums to the unlicensed users. In CR environment, it is strictly required for the unlicensed users not to interference with the licensed users. Thus, it is essential to rely on the scheduling algorithm to avoid the interference when utilizing spectrum holes that are changing in time and frequency. However, the existing scheduling algorithms that are applied for the wireless communication environment considering the licensed users only is not appropriate for CR environment. In this paper, we propose downlink scheduling algorithm based on probability of incumbent user presence for cognitive radio networks. With computer simulations, it is shown that the proposed scheduling algorithm outperforms the conventional scheduling algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1360-1368
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• 2010

Recently, as the development of Radio Frequency Identification (RFID) technology becomes active, the demand for services which can electronically manage the history and location information of major trees, including trees for cultural heritage restoration and nurse trees, has been increased. This information has been managed by separated drawings and documents or storing its information into PDAs and then structuring data files through input and computation. But, these methods imply limitations in terms of its extensibility and scalability. This paper has designed and implemented an RFID based Tree History Information System (THIS) for cultural heritage restoration. The purpose of the proposed system is to support to be able to effectively and consistently manage historical information of major trees and improve working processes by implementing mobile RFID services through wireless Internet or Local Area Network (LAN) as mobile communication networks. Through implementation, it is confirmed that the proposed system can manage the historical information of major trees more effectively than conventional methods and also improve previous field working conditions.

• Spatial Information Research
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• v.20 no.5
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• pp.57-66
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• 2012

Recent development in wireless communication technology like GPS as well as mobile equipments like PDA and cellular phone makes location-based services (LBSs) popular. However, because users request a query to LBS servers by using their exact locations while moving on the road network, users' privacy may not be protected in the LBSs. Therefore, a mechanism for users' privacy protection is required for the safe and comfortable use of LBSs by mobile users. For this, we, in this paper, propose a road network distance based cloaking scheme supporting user privacy protection in location-based services. The proposed scheme creates a cloaking area by considering road network distance, in order to support the efficient and safe LBSs on the road network. Finally, we show from our performance analysis that our cloaking scheme outperforms the existing cloaking scheme in terms of cloaking area and service time.

• Journal of the Korea Society of Computer and Information
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• v.18 no.5
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• pp.103-111
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• 2013

This paper provide a framework for an IGILMS(internet-based global integrated logistics management system) which can access and mediate cargo transportations among small- and medium-sized domestic/international logistics corporations as regards cargo, registration and search for space, public tender and negotiation, contract, payment and safety-guarantee, transportation through the internet, wireless communication means, or smart phone etc. In addition, we describe a model to provide customized services in the B2B e-market for IGILMS and the structure and the control of its fulfillment process, and provide technical architecture of the IGILMS for an internet-based global logistics management system. To validate an efficiency of the proposed system, we develop a simulation model and analyze the performance of the proposed system.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.29-36
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• 2005

As computing environments are more rapidly developed, an adaptive and intelligent services using post PC such as PDA. Laptop, and Tablet PC in case of rounding and examining patients are highly demanded. The objective of this study is to design and implement a context-awareness support system based on voice service for medical environments. To achieve it, we propose a context middleware which plays an important role in recognizing a client with PDA by using a Bluetooth wireless communication technology as well as in executing an appropriate execution module, like delivery for diagnosis information of patients, according to the staff's context acquired from a context server. In addition, the context server functions as a manager that efficiently stores context information such as client's current status, physical environment, and device resources into a database server. Finally, for verifying the usefulness of the proposed system, we develop an application system which provides voice playing services for notification of other physicians through our context middleware.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.4
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• pp.61-71
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• 1999

The recent trend toward higher frequencies, miniaturization and lower-cost in wireless communication equipment is demanding high density packaging technologies such flip chip interconnection and multichip module(MCM) as a substitute of conventional plastic package. With analyzing the recently reported research results of the RF flip chip, this paper presents the technical issues and advantages of RF flip chip and suggest the flip chip technologies suitable for the development stage. At first, most of RF flip chips are designed in a coplanar waveguide line instead of microstrip in order to achieve better electrical performance and to avoid the interaction with a substrate. Secondly, eliminating wafer back-side grinding, via formation, and back-side metallization enables the manufacturing cost to be reduced. Finally, the electrical performance of flip chip bonding is much better than that of plastic package and the flip chip interconnection is more suitable for Transmit/Receiver modules at higher frequency. However, the characterization of CPW designed RF flip chip must be thoroughly studied and the Au stud bump bonding shall be suggested at the earlier stage of RF flip chip development.