• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.3
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• pp.276-282
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• 2003

OFDM is effective for the high speed data transmission. However, the nonlinear distortion is a serious problem because of the high PAPR due to many subcarriers. The conventional SLM selects the OFDM signal with the lowest PAPR. In this method, OFDM data can be correctly recovered only if the side information about the phase sequence is transmitted to receiver. This paper proposes a new method of side information insertion into the conventional SLM and reduces the computational complexity by adaptive method. Performances are compared in case that three kinds of phase sequences are used for phase rotation factor. The adaptive SLM method has the same PAPR reduction as the conventional SLM method. The required BER can be guaranteed by the proposed method. When subcarrier number N=32, computational complexity is reduced to 48 %, 72 % and 51 % for the branch number U=4, 8 and 16, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2B
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• pp.176-183
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• 2011

In this paper, we propose the implementation and performance analysis of power line communication based on SISO/MIMO-OFDM which focuses on high speed data transmission in smart grid and future power line grid. We employ Zimmermann frequency model and Middleton Class A model as the multipath power line fading channel and impulse noise channel, respectively. In this paper, in order to improve the three-phase or single-phase PLC performance, we introduce a new MRC (called a&f-MRC) which effectively sums up multiple antenna diversity gain and multipath fading diversity gain. Via simulation, we prove the performance advantage over existing SISO/MIMO systems. In addition, we offer the tradeoff on system design through comparing with MRC, EGC and SC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2B
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• pp.120-130
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• 2011

Recently the multicast based contents transmission is rapidly increasing due to the various multimedia services and the importance of switching technology to handle it is increasing as a consequence. Though the CICQ architecture has advantages that reduction of HoL blocking probability and simple scheduling using cross point buffer, it has disadvantage that the processing rate of multicast traffic can be significantly degraded corresponds to the traffic load increment. Several schemes have been proposed to solve this problem however they still can't provide enough processing ratio for multicast traffic. Therefore this paper proposes the BA cell assignment scheme and the VT scheme, and the processing rate of multicast traffic can be guaranteed by reducing the HoL blocking probability of multicast traffic and reservation of cross point buffer. Also simulation results verify that using the proposed scheme, the QoS of multicast service can be improved.

• Parasites, Hosts and Diseases
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• v.44 no.4 s.140
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• pp.355-360
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• 2006

Cutaneous leishmaniasis (CL), due to Leishmania major, is endemic in different parts of Iran and has long been recognized in most provinces of Iran. This study was conducted to determine the prevalence of childhood leishmaniasis in 3 areas at the southeast of Kashan, A descriptive study was carried out on all children referred to central laboratories during a 3-year period. Initial information including age, sex, sites of ulcer on the body, number of lesions, address, and the place of the disease was obtained. The study gathered 117 children, and the results showed a prevalence of 7.2% in patients with lesions among the population and 4.2% of people displayed lesion and scar. The ages of subjects were from 6 to 15 years (average 9.75 years). The boy: girl ratio was 1.2. All of our patients lived in an endemic area. The face was affected in 47.0% of cases. The encountered forms of leishmaniasis are as follows: papulonodular 27.4%, ulcer 60.7%, sporotrichoid 6%, impetiginous 2.5%, and erysipeloid 3.4%. Treatment with intramuscular meglumine antimoniate 20-30 mg/kg/day was done for 93 patients. Meglumine antimoniate treatment was tolerated with no side effects. All leishmaniasis lesions healed within an average period of 2-14 months. Hyperpigmented scars were formed in 25.6% of the patients, atrophic scars in 4.3%, and hypopigmented scars were in 3.4%, respectively The findings of this study indicate increased prevalence of CL in the villages at the area of Kashan and Aran-Bidgol. The clinical finding patterns belonged to different endemic strains of L. major in Isfahan, which indicates the possible transmission of infection from Isfahan to this area.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.352-360
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• 2016

In this paper, a novel multiple multicast feed-back scheme for improving multimedia multicast and broadcast system based on IEEE 802.11. The proposed scheme improves multicast PPDU delivery ratio of next generation wireless LAN by utilizing multicast feed-back information. By using the proposed scheme, regardless of its size of multicast group, an AP STA could collect transmission failure information by receiving simultaneous NAK frame. The proposed scheme shows large performance enhancement in broadcast or multicast system of Intelligent Transport System and Passenger Entertainment Service. According to the analysis results, the proposed scheme could enhance wireless LAN multicast and broadcast performance significantly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.52-57
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• 2016

We introduce a hybrid scheduling in a multi-path poor scattering full-duplex (FD) system, which consists of one multi-antenna FD base station and a large number of single-antenna half-duplex mobile stations. Our hybrid scheduling utilizes partial channel state information at the transmitter. In particular, unlike the conventional scheduling method using opportunistic transmission for both uplink and downlink, the proposed scheme combines a random transmit beamforming for downlink and a zero forcing beamforming for uplink. As our main result, via computer simulations, it is shown that the proposed scheme has a superior sum-rate performance than that of the conventional scheduling method beyond a certain signal-to-noise ratio regime.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.1013-1019
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• 2016

This paper describes a novel Context-awareness Markov Chain Prediction (CMCP) algorithm based on movement prediction using Markov chain in Delay Tolerant Network (DTN). The existing prediction models require additional information such as a node's schedule and delivery predictability. However, network reliability is lowered when additional information is unknown. To solve this problem, we propose a CMCP model based on node behaviour movement that can predict the mobility without requiring additional information such as a node's schedule or connectivity between nodes in periodic interval node behavior. The main contribution of this paper is the definition of approximate speed and direction for prediction scheme. The prediction of node movement forwarding path is made by manipulating the transition probability matrix based on Markov chain models including buffer availability and given interval time. We present simulation results indicating that such a scheme can be beneficial effects that increased the delivery ratio and decreased the transmission delay time of predicting movement path of the node in DTN.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.2
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• pp.53-65
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• 2016

Static wireless multi-hop networks, such as wireless mesh networks and wireless sensor networks have proliferated in recent years because of they are easy to deploy and have low installation cost. Two key measures are used to evaluate the performance of a multicast tree algorithm or protocol : end-to-end delay and the number of transmissions. End-to-end delay is the most important measure in terms of QoS because it affects the total throughput in wireless networks. Delay is similar to the hop count or path length from the source to each destination and is directly related to packet success ratio. In wireless networks, each node uses the air medium to transmit data, and thus, bandwidth consumption is related to the number of transmission nodes. A network has many transmitting nodes, which will cause many collisions and queues because of congestion. In this paper, we optimize two metrics through a guaranteed delay scheme. We provide an integer linear programming formulation to minimize the number of transmissions with a guaranteed hop count and preprocessing to solve the aforementioned problem. We extend this scheme not only with the guaranteed minimum hop count, but also with one or more guaranteed delay bounds to compromise two key metrics. We also provide an explanation of the proposed heuristic algorithm and show its performance and results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.409-413
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• 2014

GIS partial discharge that occurred in the UHF band signal is effectively detected by the method to IEC60270 5pc the apparent minimum discharge can be detected over the GIS arrangement of the sensor interior and exterior of the UHF in accordance with the optimized position signal by considering the damping ratio is selected so that the signals can be obtained to be mounted. 362kV, 800kV GIS is installed on the internal and external sensors are UHF band signal attenuation is set by measuring the reference value, but the operation, 170kV case 362kV, 800kV on the basis of the measurement data and to be installed and operated. When 170kV per 1Bay by installing the built-in sensor 1 for detecting a partial discharge signal, But, GIS signal attenuation is large in the case of an internal partial discharge signal is not detected in some cases. Where the attenuation is great UHF signal of the sensor by increasing the quantity of partial discharge signals were acquired to allow relocation. The greater the spacing between the sensor and the sensor is applied simplifies the installation and reduces the cost in terms of maintenance of appropriate optimal position is calculated to detect the partial discharge signal is needed. Thus 170kV GIS signal power attenuation of a partial discharge by measuring the UHF sensor, and by relocating the proper position is calculated in accordance with the sensor signal decay rate and minimize the error of omission in detecting a partial discharge signal was optimized.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.65-75
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• 2016

Aiming at analyzing the power flow of the distribution systems with distribution transformer (DT) branches and PV nodes, a hybrid three-phase power flow methodology is presented in this paper. The incidence formulas among node voltages, loop currents and node current injections have been developed based on node-branch incidence matrix of the distribution network. The method can solve the power flow directly and has higher efficiency. Moreover, the paper provides a modified method to model DT branches by considering winding connections, phase shifting and off-nominal tap ratio, and then DT branches could be seen like one transmission line with the proposed power flow method. To deal with the PV nodes, an improved approach to calculate reactive power increment at each PV node was deduced based on the assumption that the positive-sequence voltage magnitude of PV node is fixed at a given value. Then during calculating the power flow at each iteration, it only needs to update current injection at each PV node with the proposed algorithm. The process is very simple and clear. The results of IEEE 4 nodes and the modified IEEE 34 nodes test feeders verified the correctness and efficiency of the proposed hybrid power flow algorithm.