• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.41-48
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• 2020

Currently, the industry uses MODBUS communication method using RS485 as a communication method used when constructing distributed equipment and networks. However, this method has a rather good transmission and reception distance, but has a disadvantage of being a half-duplex communication method. Therefore, there is a great need for a full-duplex communication method that can simultaneously transmit and receive two-wire communications. Therefore, in this paper, we propose a new communication hardware equipment that can implement full-duplex communication method by communication signal level to overcome the disadvantage of communication speed. The proposed communication hardware is a structure that can transmit and receive at the same time on the same communication line in two equipments communicating in a two-wire system. The characteristic of this communication hardware is that the transmitter generates two-level signal for data transmission, but the receiver generates three-level electric signal according to the status of the transmission data generated by the receiver. The data transmission signal information of the receiver is present at the same time. Therefore, the receiving side can analyze the received signal based on the information on the current transmission signal and can analyze the signal only in the two communicating devices, so it can be seen that the communication security is very excellent.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.8
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• pp.2663-2674
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• 2014

For cognitive radio sensor networks (CRSNs) that use underlay-based spectrum access, the location of the primary user (PU) plays an important role in the power control of the secondary users (SUs), because the SUs must keep the minimum interference level required by the PU. Received signal strength (RSS)-based localization schemes provide low-cost implementation and low complexity, thus it is suitable for the PU localization in CRSNs. However, the RSS-based localization schemes have a high localization error because they use an inexact path loss exponent (PLE). Thus, applying a RSS-based localization scheme into the PU localization would cause a high interference to the PU. In order to reduce the localization error and improve the channel reuse rate, we propose a RSS-based PU localization scheme that uses distance calibration for CRSNs using underlay model-based spectrum access. Through the simulation results, it is shown that the proposed scheme can provide less localization error as well as more spectrum utilization than the RSS-based PU localization using the mean and the maximum likelihood calibration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.652-659
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• 2006

The routing algorithm is one of the key research areas in ad hoc networks. The most of existing routing algorithms depends on current availability of wireless link when finding the feasible path. Dependence on current information may mislead to a fragile communication path. Some routing approaches that take statistical average on received signal power enhance the possibility to find the most stable path, but have limitation on considering only the average power level. In this paper, we propose routing algorithm based on link stability for ad hoc network. The proposed algorithm not only takes statistical average, but also traces the degree of variations in received signal power. The simulation result support that the proposed algorithm is more likely to find the most stable path under the severe communication environment.

• ETRI Journal
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• v.29 no.5
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• pp.703-705
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• 2007

An image fidelity assessment using the edge histogram descriptor (EHD) of MPEG-7 is presented. Neither additional data nor fragile watermarking is needed, and there is no need to access the original image as a reference. Only the EHDs of the original image and the received image are required. The peak signal-to-noise ratio (PSNR) obtained by comparing the EHD extracted from the received image and that of the original image is used to assess the noise level of the received image. Experimental results show that the PSNRs calculated from the conventional pixel-to-pixel gray level and from the proposed bin-to-bin EHD maintain a proportional relationship. This implies that the EHD can be used instead of image data for the image fidelity assessments.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.725-733
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• 2010

A simulator is proposed in this paper for predicting the RF signal level after propagating over sea and land surfaces. Various sea and land types and transmit/receive antenna patterns, as well as the locus of the transmit antenna, are considered for this simulator. At first, microwave reflection characteristics of various sea surfaces have been computed, based on an empirical formula which is developed in this study for the relation between the sea surface roughness and wind speed. Then, microwave reflections from land surfaces such as forests, agricultural areas, and bare surfaces, are computed using the first-order vector radiative transfer theory. Finally, the signal paths over sea and land surfaces are found using the ray tracing technique and the digital elevation model, and the signal level received by a receiving antenna is computed by the using the reflection coefficients of sea and land surfaces and the signal paths.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.8
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• pp.742-747
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• 2004

Outdoors we can easily acquire our accurate location by GPS. However, the GPS signal can't be acquired indoors because of its weak signal power level. Adequate positioning method is demanded for many indoor positioning applications. At present, wireless local area network (WLAN) is widely installed in various areas such as airport, campus, and park. This paper proposes a positioning algorithm using WLAN signal strength to provide the position of the WLAN user indoors. There are two methods for WLAN based positioning, the signal propagation method uses signal strength model over space and the empirical method uses RF power propagation database. The proposed method uses the probability distribution of the power propagation and the maximum likelihood estimation (MLE) algorithm based on power strength DB. Test results show that the proposed method can provide reasonably accurate position information.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.1
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• pp.25-35
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• 2018

This paper describes the measurement of pulse positioning (input time) to calculate a time of arrival (TOA) that takes from transmitting a signal from the target of multilateration (MLAT) system to receiving the signal at the receiver. In this regard, this paper analyzes performances of simple threshold method and level adjust system (LAS) method, which is one of the adaptive threshold detector (ATD) methods, among many methods to calculate pulse positioning of signal received at the receiver. To this end, Cramer-rao lower bound (CRLB) with regard to pulse positioning, which was measured when signals transmitted from a transponder mounted at the target were received at the receiver, was induced and then deviation sizes with regard to pulse positioning, which was measured with simple threshold and LAS methods through MATLAB simulations, were compared. Next, problems occurring according to a difference in amplitude of signals inputted to each receiver are described when pulse positioning is measured at multiple receivers located at a different distance from the target as is the case in the MLAT system. Furthermore, LAS method to resolve the problems is explained. Lastly, this study analyzes whether a pulse positioning error occurring due to the signal noise satisfies the requirement (6 nsec. or lower) recommended for the MLAT system when using these two methods.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1116-1118
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• 1990

This paper describes the required frequency bandwidth which is used as a measure for the quality of the PFM transmission system to transmit the control signals. First, the PFM signal which has been distorted due to the frequency bandwidth limit on the transmission line is analyzed by Fourier transform and secondly distortion which has been observed at the receiver is numerically analyzed to make the frequency bandwidth required for transmitting the PFM signals. According to the analysis heretofore, the 50% threshold level for shaping the received PFM signal, which is of 50 % in TTL level, is superior than the 10- and 90-% threshold levels.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.38-44
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• 2014

This paper presents design of a FMCW (Frequency Modulated Continuous Wave) level meter as well as simulation result of the designed system. The system is designed to measure maximum range of 20m since FMCW radar can be used for measuring short range distance. The distance is measured by analyzing the beat signal which is generated as result of mixing transmitting signal with the reflected received signal. The Fast Fourier Transform is applied to analyze the beat signal for calculating the displacement and Zoom FFT technique is used to minimize measurement error as well as increase the resolution of the measurement. The resolution of the measurement of the designed system in this paper is 2.2mm and bandwidth of 1.024GHz is used for simulation. Thus the simulation results are analyzed and compared in various conditions in order to get a comprehensive idea of frequency resolution and displacement resolution.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.4223-4249
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• 2015

A novel jamming detection technique to detect the presence of jamming in the downstream direction for cluster based wireless sensor networks is proposed in this paper. The proposed technique is deployed in base station and in cluster heads. The proposed technique is novel in two aspects: Firstly, whenever a cluster head receives a packet it verifies whether the source node is legitimate node or new node. Secondly if a source node is declared as new node in the first step, then this technique observes the behavior of the new node to find whether the new node is legitimate node or jammed node. In order to monitor the behavior of the existing node and new node, the second step uses two metrics namely packet delivery ratio (PDR) and received signal strength indicator (RSSI). The rationality of using PDR and RSSI is presented by performing statistical test. PDR and RSSI of every member in the cluster is measured and assessed by the cluster head. And finally the cluster head determines whether the members of the cluster are jammed or not. The CH can detect the presence of jamming in the cluster at member level. The base station can detect the presence of jamming in the wireless sensor network at CH level. The simulation result shows that the proposed technique performs extremely well and achieves jamming detection rate as high as 99.85%.