• Journal of electromagnetic engineering and science
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• v.8 no.2
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• pp.84-89
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• 2008

In a wireless channel above microwave frequency, rain attenuation is very important. In order to predict rain attenuation, 1-min. rain rate distribution is required. This paper discusses appropriate conversion methods to estimate 1-minute rain rate from that of other integration time. Based on the measurement data filed in ITU-R WP3J including ETRI data for 6 consecutive years, distributions of rain rate with 1-, 5-, 10-, 20-, 30-minute integration time were analyzed, both on the global and regional basis, and the parametric relationship between the statistical characteristics of 1-minute and other measurement data were investigated to deduce the conversion methods. It is shown that the global model works good with good accuracy for 5-, 10-, 20-min integration time, and the global model is also applicable globally with good accuracy for 5-, 10-, 20-min integration time. The global conversion model was adopted last year as an ITU-R document for new recommendation. The regional conversion model would also be very useful for locations of similar climatic zone.

• International journal of advanced smart convergence
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• v.2 no.1
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• pp.1-5
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• 2013

This study proposes a remote monitoring of patients and emergency notification system with a camera and pulse wave sensor for U-Healthcare. The proposed system is a server client model based U-Healthcare system which consists of wireless clients that have micro-controller, embedded-board for patient status monitoring and a remote management server. The remote management server observes the change of pulse wave data individually in real-time sent from the clients that is to be remote-monitored based on the pulse wave data stored by users and divides them into caution section and emergency section. When the pulse wave data of a user enters an emergency situation, the administrator can make a decision based on the real-time image information and pulse rate variability. When the status of the monitored patient enters the emergency section, the proposed U-healthcare system notifies the administrator and relevant institutions. An experiment was conducted to demonstrate the pulse wave recognition of the proposed system.

• The Transactions of the Korea Information Processing Society
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• v.6 no.5
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• pp.1143-1152
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• 1999

A Mobile computing environment is a new paradigm which provides users with the access to information irrespective of users' location. A transaction scheduling method for the mobile computing environment must be designed so that database consistency is maintained with considering the limited performance of mobile hosts and the narrow bandwidth of a wireless network. The scheduling method using a lock has some problems: the high message overhead between a server and a mobile host for maintaining a lock and the high abort ratio of the mobile transactions owing to violating the serializability when a mobile host uses a cache. So, in this paper, we propose an efficient transaction management method using timestamp to resolve these problems. The proposed method is used in the environment under which a mobile host uses a cache having two versions for each cached data item and a server maintains several versions for each data item. So, even though a mobile transaction is executed during several broadcasting interval, can be committed. As a result, the proposed method can improve the commit ratio of the mobile transactions by maintaining multiversion for each data item and does not require the additional message exchange to schedule transactions by using timestamp.

• 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 the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.1-8
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• 2008

Recently, there is developing various ubiquitous application services using sensor networks based on TinyOS represented the operating system of sensor node. These sensor networks perform the collection and the transmission of sensing data from sensor node to get the context information. In this paper, we proposes the sensor node control algorithm which converts a sensor node to sleep, active, power off mode according to monitoring result of the voltage state of sensor node. Also, we designs and implement the sensor control module on server, sink, sensor node of sensor networks using this algorithm. It designs a sensor voltage control module of sensor node, data receive and display module of USN server using a java language and TinyOS. And, it checks the voltage state of sensor node, and it changes one of the sleep or power off modes in case of high voltage loss. Accordingly, we effectively use the power of sensor nodes as changing control modes of sensor nodes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.139-145
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• 2015

This paper proposes to increase the node energy effienciecy, which rapidly drops during the transmission of LEACH (Low Energy Adaptive Clustering Hierachy), using the method of DL-LEACH (Dual-hop Layered LEACH). By introducing dual-hop method in the data transmission, the proposed single-hop method for short-range transmission and multi-hop transmission method between the cluster heads for remote transmission was introduce. By introducing a partial multi-hop method in the data transmission, a single-hop method for short range transmission method between the cluster heads for remote transmission was introduces. In the proposed DL-LEACH, the energy consumption of cluster head for remote transmission reduces and increases the energy efficiency of sensor node by reducing the transmission distance and simplifying the transmission routine for short-range transmission. As compared the general LEACH, it was adapted to a wider sensor field.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.73-79
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• 2014

Visible light communication is a communication method using an LED having a high-speed ON / OFF rate data to be transmitted, it is used as a wireless high speed data transmission. VLC system evolves, the problem of basic research is intended to improve performance and ensure reliability of the communication. The nature of the visible light communication, communication is performed only in the reach of the light, which indicates a big difference by the emission angle of the light. Therefore, in this paper, in the case of indoor environments generally, with the attributes of the multiple LED is equipped, was applied to a MIMO (Multiple Input Multiple Output) communication system. and analyzed SNR performance and total power can be obtained on the reception side by changing the emission angle of the transmitter. As a result of the simulation was run against this, it was confirmed that there is a significant impact on the performance of BER and SNR performance by the emission angle of the transmitter.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.283-288
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• 2018

In this paper, it is required that the next generation wireless transmission system can support a large number of users without distortion of transmission signal with high data rate in various different propagation environment while using limited resources as efficiently as possible, and therefore an efficient transmission system is continuously required. Because of the large amount of data to be handled in a limited frequency band, a very complex digital modulation scheme is adopted. the linearity of the power amplifier determines the linearity of the entire communication system, and thus a linear amplifier is required. In cognitive radion systems, there is a power control issue in the relationship between primary and secondary users. This problem is solved by simulating the communication system so as to select the cognitive radio power while power control while overcoming linearity by using feed-forward PA.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.103-109
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• 2018

One of the 5G goals is provide to high data rates for users moving at high speeds, such as trains. High mobility scenarios such as high speed train (HST) scenarios are expected to be typical scenarios for fifth generation communication systems. As the HST develops rapidly, it is necessary to transmit wireless communication data to train passengers, and the communication speed required by users is gradually increasing. HST users require high network capacity and stable communication services regardless of the location or speed of the HST communication system. Therefore, a transmission frame is constructed for the 5G mobile communication system in the mm band to be used for the fifth generation mobile communication, the HST communication system is implemented, and the performance of the wideband non-stationary MIMO HST channel is analyzed in the HST scenario.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.191-196
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• 2012

The tactical training system that was applied to wire at open terrain and field is no training accomplishment in conformity with battlefield situation portrayal. Therefore, this paper developed the tactical training and evaluation system for growing fruitfully that is installed as a tactical training monitoring system by USN WMN through controlled sensing interlock for collecting sensing data and guaranteed training equipment status and report training result for serviceability of manager. additionally we implemented controller for managing server of sending and manipulating of being gathered training data by sensor using USN and system as GUI methods. This system is easy for adapting new and improved protocol in order to processing many function of H/W and algorithms which is generated by controlled system is applicable easily.