• The Journal of the Acoustical Society of Korea
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• v.14 no.3
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• pp.105-113
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• 1995

For the case of using analog FM system and CDMA system together in the mobile communications, we experimentally calculate the appropriate frequency offset to improve the frequency efficiency by analizing the interference between both systems. As the results of the analysis, we obtained that frequency offset is 840KHz(Path Loss : 80dB) and 720KHz(Path Loss : 120dB) for the Path Loss when a output of CDMA Base Station is 0.91 W ERP. Therefore, to minimize the frequency offset, a output of Base Station will be controlled corresponding to Cover Area.

• Smart Structures and Systems
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• v.14 no.4
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• pp.617-641
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• 2014

The energy constraint is still a common issue for the practical application of wireless sensors, since they are usually powered by batteries which limit their lifetime. In this paper, a practical compound energy efficiency strategy is proposed and realized in the implementation of a real time wireless sensor platform. The platform is intended for wireless structural monitoring applications and consists of three parts, wireless sensing unit, base station and data acquisition and configuration software running in a computer within the Matlab environment. The high energy efficiency of the wireless sensor platform is achieved by a proposed adaptive radio transmission power control algorithm, and some straightforward methods, including adopting low power ICs and high efficient power management circuits, low duty cycle radio polling and switching off radio between two adjacent data packets' transmission. The adaptive transmission power control algorithm is based on the statistical average of the path loss estimations using a moving average filter. The algorithm is implemented in the wireless node and relies on the received signal strength feedback piggybacked in the ACK packet from the base station node to estimate the path loss. Therefore, it does not need any control packet overheads. Several experiments are carried out to investigate the link quality of radio channels, validate and evaluate the proposed adaptive transmission power control algorithm, including static and dynamic experiments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.846-849
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• 2008

In recent years there has been growing interest in wireless sensor networks (WSNs) for a variety of indoor applications. In this paper, we present the RSSI-based localization in indoor environments. In order to evaluate the relationship between distance and RSSI, the log-normal path loss shadowing model is used. By tagging users with a sensor node and deploying a number of nodes at fixed position in the building, the RSSI can be used to determine the position of tagged user. This system operates by recording and processing signal strength information at the base stations. It combines Euclidean distance technique with signal strength matrix obtained during real-time measurement to determine the location of user. The experimental results presented the ability of this system to estimate user's location with a accuracy.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.67-73
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• 2008

This paper describes a system for location tracking wireless sensor nodes in an indoor environment. The sensor reading used for the location estimation is the received signal strength indication (RSSI) as given by an RF interface. By tagging users with a mobile node and deploying a number of reference nodes at fixed position in the room, the received signal strength indicator can be used to determine the position of tagged users. The system combines Euclidean distance technique with signal strength obtained by measurement driven log-normal path loss model of 2.4 GHz wireless channel. The experimental results demonstrated the ability of this system to estimate the location with a error less than 1.3m.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.517-525
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• 2008

In this paper, we cary out system level simulations to investigate the effect of cell shape(i.e., different base station displacements in the two directions defined by the street grid) on minimizing transmitter power, interference power, and blocking probability for CDMA system in urban microcellular environments. In urban microcell, path loss to the base station depends on the orientation of the street where the mobile is located. Interference from mobile stations to the base station in the reference cell is considered up to second tier. The wrap around method is used to include the second tier interference with realistic computational complexity without reducing the accuracy of interference calculations. The investigation shows that the transmitter power, interference power, and blocking probability in a cell can be reduced by proper selection of the efficient cell shape.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.430-435
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• 2007

In this paper, we propose an intelligent deployment of sensor network for reliable communication. The proposed method determines optimal transmission range based on the wireless channel characteristics, and searches the optimal number of sensor nodes, and optimal locations with SOFM. We calculate PRR against a distance uses the log-normal path loss model, and decide the communication range of sensor node from PRR. In order to verify the effectiveness of the proposed method, we performed simulations on the searching for intelligent deployment and checking for link condition of sensor network.

• Computers and Concrete
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• v.17 no.3
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• pp.305-322
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• 2016

The work is intended to demonstrate that the loss of bond between concrete and flexural steel which led in recent years a number of flat-slab structures to punching collapse under service loading conditions is also relevant to ultimate limit-state design. It is based on a comparative study of the results obtained from numerical experiments on flat slab-column sub-assemblages. The slabs were designed for punching either in compliance with the EC2 code requirements, which do not allow for such loss of bond, or in accordance with the compressive force-path method which considers the loss of bond between concrete and the flexural reinforcement in tension as the primary cause of punching. The numerical experiments are carried out through the use of a nonlinear finite element analysis package for which, although ample published evidence of its validity exists, additional proof of its suitability for the purposes of the present work is presented.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.104-107
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• 2009

In this paper, we analyze the effect of interference between DTV system and IEEE 802.11n. We set DTV as a victim receiver and IEEE 802.11n as an interfering system. When they exist in the same area, they can make an interference effect. Therefore, we calculate a minimum coupling loss (MCL) and compare the resulting value with a path loss for determining whether there exists a potential interference or not. The minimum separation distance is determined when the path loss is larger than the MCL.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.704-709
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• 1994

The insertion loss is the measured change in power flux at a specified receiver, when the acoustic transmission path between it and the source is modified by the insertion of silencer element. Such measurements have clear and valid physical meaning particularly if the source impedance remains while the transmission path is altered. When the invarient condition is satisfied, the insertion loss is given by the ratio of the acoustic pressure in upstream to that in downstream of the silencer, and that of the particle velocity. The measurement is consisted of using an adaptation of the two microphone method to obtain the complex amplitude of the sound in upstream tube as well as in downstream tube of the silencer. Examples of the data, reduced and presented in terms of the pressure ratio and particle speed ratio, are compared with the theoretical calculations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.3
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• pp.477-493
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• 2011

The IEEE 802.16 mobile multi-hop relay (MMR) task group 'j' (TGj) has introduced the multi-hop relaying concept in the IEEE 802.16 Wireless MAN, wherein a relay station (RS) is employed to improve network coverage and capacity. Several RSs can be deployed between a base station and mobile stations, and configured to form a tree-like multi-hop topology. In such architecture, we consider the problem of a path selection through which the mobile station in and outside the coverage can communicate with the base station. In this paper, we propose a new path selection algorithm that ensures more efficient distribution of resources such as bandwidth among the relaying nodes for improving the overall performance of the network. Performance of our proposed scheme is compared with the path selection algorithms based on loss rate and the shortest path algorithm. Based on the simulation results using ns-2, we show our proposal significantly improves the performance on throughput, latency and bandwidth consumption.