• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.1014-1017
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• 2009

Ubiquitous makes it possible to expand a short-distant wireless communications infra and provide various services. Especially, it is very important to develop multimedia contents service technology through ZigBee and WPAN technology. But because the data transmission rate of IEEE 802.15.4 Standard ZigBee is low, there are many barriers for multimedia contents services. In this paper, to improve ZigBee that has the limitation of transmission rate in IEEE 802.15.4 Standard, an upgraded model to 1Mbps through MAC Layer remodeling is designed. And Zigbee-based broadcasting multimedia contents services system is designed and implementation to provide the service in Ubiquitous environment.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.12
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• pp.863-870
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• 2012

The market trends of automatic meter reading associated with smart water meters were investigated. Also, recent developments and field applications of key technology for automatic meter reading associated with smart water meters were analyzed. Smart water meters have been manufactured mostly in United States and Europe and have been expanded their business to Asia. Integrated water management system combining with the additional functions such as real-time consumption metering, cost notification, water conservation, leak detection, water quality monitoring, and flow control have been operated in automatic meter reading. Both water quality and quantity data measured from smart water meters and sensors were transferred to data concentration units through neighborhood area network, and then were transferred to integrated server through wide area network. The data transfer methods were determined by comprehensively considering urban scale, density of smart water meters, power supply and network topologies. Common data collection methods such as fixed network to data concentation units, vehicles drive by, people walk by, and drone fly by have been applied. The automatic meter reading associated with smart water meters are spread throughout the world, and both water and energy savings result in saving the money and reducing the greenhouse gases emission.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.951-959
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• 2011

The low power consumption modulation is required for short range communication. In this paper, we analyze performance of low power consumption modulation scheme such as PSPM, PSSK and QAPM using OFDM transmission in AWGN channel. A PSPM, PSSK and QAPM modulation scheme are decrease in bandwidth efficiency but improved power efficiency than existing PSK and QAM. These modulation schemes can achieve power efficiency because every symbol of modulations has a zero-envelope period like PPM techniques. The OFDM system is high bandwidth efficiency than single carrier system. In this paper, we are propose the frequency domain mapping method for OFDM transmission using low power consumption modulation method. Also, we compare low power OFDM communication system regard to BER performance, throughput and PAPR.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.25-31
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• 2004

fireless LAN can offer high data rate communication between wireless terminals. In IEEE 802.11 wireless LAN, a basic service unit is called a Basic Service Set (BSS), which consists of one AP and more than one wireless terminals. Terminals far from the AP may not communicate with high data rate because signal strength is weakened as they move away from the AP. In this paper we propose a method to permit high speed data transmission by grouping terminals and by using part of wireless terminals as repeaters. We analyze the proposed and algorithm via simulations. Our proposed grouping mechanism is shown to be an effective way to increase the distance for high rate transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.2
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• pp.137-145
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• 1986

The contention resolution algorithm with the limited packet delay time as well stable distribution as the packet delay time is proposed and implementes for improving the mean packet delay time in the network employing CSMA/CD as the access method. The implementation of node controller is based on IEEE 802.2 standard logical link control(LLC) and IEEE 802.3 standard medium access control(MAC). Some portion of IEEE 802.3 Standard MAC, and the Binary Exponential Back-off(BEB) algorithm is replaced by the proposed algorithm. From the view of normalized mean packet transmission delay time, the controller implemented here can be applicable to the office-automation system, and the factory-and laboratory-automation environment where the limited time criterion is very significant.

• Convergence Security Journal
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• v.8 no.3
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• pp.73-81
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• 2008

We can find easily about researches or technical development that deal with grasping the location of an object with GPS(Global Positioning System) in order to use them as a useful information. Most researches or technical development on application of tracing have been developed for the purpose of tracing objects in broad area as physical distribution or transportation, but recently, there are many researches on tracing materials in premise area as a fork lift, carts, or the equipment of work. In general, a system that utilizes location information of objects needs data communication network to transmit location data and it ensures data communication network by using common networks(SK, LG, KFT) or wireless LAN. However these two methods need monthly payment for the rental fee or require considerable amount of investment for the early stage so it is difficult to use them merely for tracing premise subjects. This study was conducted to build a tracing system for premise area by local area RF relay algorithm with low cost applying RF relay algorithm to local area wireless communication(ZIGBEE, 424MHz, Bluetooth, 900MHz) system in order to supplement these demerits and included relay algorithm, RF locating information terminal, local area RF gab-fillers, a plan for collection server of locating information, and the way of realization as they are needed in this system. I consider that this study would be applicable with flexibility in the industry area that needs tracing solution within a specific area or needs ensuring data communication network, to transmit data in ubiquitous environment, by easier and more rapid way with lower cost.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.259-266
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• 2013

Since the wireless communications have a limited transmission, the devices just around a master node can exchange data. Though Bluetooth and Zigbee support ad hoc, they are not appropriate for real-time voice communications. In this paper, we present a TDMA-based relay protocol for several users to communicate simultaneously. The proposed protocol can relay data or voice to other nodes in real-time by the multi-hop transmission method using TDMA. And the proposed protocol improves the network performance by allocating different frequencies to the slaves depending on the routing path scheduled by the routing table. NS-2 simulation shows that the performance of the proposed protocol is good in terms of the transmission delay and pecket loss probability in the real-time voice transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.850-857
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• 2005

Sensor networks consist of sensor nodes with small size, low cost, lowpower consumption, and multi-functions to sense, to process and to communicate. The main issue in sensor networks has been focused on minimizing power consumption of sensors to maximize network life time. In some critical applications, however, the most important issue is to transmitsensing information to the end user (the sink node) with reliability. Reliable information forwarding using multiple paths in sensor networks (ReinForM) has been proposed to achieve desired reliability in the error-prone channel, but it needs increasing transmission riverhead as the channel error rate becomes high and the number of hops between the source node and the sink node increases. In this paper, we propose a reliable transmission rnechanissmusing intermediate source nodes in sensor networks (ReTrust) to reduce packet overhead while keeping the desired reliability. ReTrust has beenshown to provide desired reliability and reduced overhead via simulationsand analysis.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.520-523
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• 2001

In this paper, a system that transmits ECG signals which get from hand baggage ECG is implemented by using Bluetooth technology. Bluetooth technology is a close range wireless communication used wireless frequency 2.4GHZ bandwidth. This technology consumes very small power and provides high reliability also self error correction with high speed frequency hopping. Because every device which uses Bluetooth protocol can communicate each other. These can connect between the system implemented and any devices such as mobile telephone with Bluetooth module, notebook, and the personal mobile device. Also, the paper proposes capability of transmission to the sever of hospital through each type of wireless communication device that acquired medical information signals in mobile medical machine. The system consists of hardware parts with Bluetooth module and host part, and software parts with bluetooth protocol stacks. The host precesses a connection with other device and transmits ECG signals with bluetooth frequency hopping sequence.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.82-88
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• 2009

Video proxy server which is located near clients can store the frequently requested video data in storage space in order to minimize initial latency and network traffic significantly. However, due to the limited storage space in video proxy server, an appropriate video selection method is needed to store the videos which are frequently requested by users. Thus, we present a virtual caching technique to efficiently store the video in video proxy server. For this purpose, we employ a virtual memory in video poky server. If the video is requested by user, it is loaded in virtual memory first and then, delivered to the user. A video which is loaded in virtual memory is deleted or moved into the storage space of video poxy sewer depending on the request condition. In addition, virtual memory is divided into each segment area in order to store the segments efficiently and to avoid the fragmentation. The simulation results show that the proposed method performs better than other methods in terms of the block hit rate and the number of block deletion.