• Transactions on Electrical and Electronic Materials
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• v.17 no.5
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• pp.275-279
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• 2016

This is a brief review on light trapping in Si based thin film solar cells with textured surfaces and transparent conducting oxide front electrodes. The light trapping scheme appears to be essential in improving device efficiency over 10%. As light absorption in a thin film solar cells is not sufficient, light trapping becomes necessary to be effectively implemented with a textured surface. Surface texturing helps in the light trapping, and thereby raises short circuit current density and its efficiency. Such a scheme can be adapted to single junction as well as tandem solar cell, amorphous or micro-crystalline devices. A tandem cell is expected to have superior performance in comparison to a single junction cell and random surface textures appears to be preferable to a periodic structures.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.5
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• pp.1-10
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• 1998

Satellite communication is getting more important in the coming 21st century because of its wide areas sevice capability, ease of access, and fast channel establishment. As such, satellite communication networks will be the basis of the global communication system in cooperation with the ground ATM networks. In this paper, we consider an efficient transmission methodology of ATM cells over the satellite communication channel. We first analyze possible bottlenecks and performance deterioration factors in the case, and then propose an enhanced cell trasmission mechanism. In order to use satellite channel for ATM cell transmission, the application of complicated channel coding is inevitable. However, the forwared error control such as convolutional encoding brings forth burst errors, which calls for the application of some kind of interleaving mechanism to randomize the burst errors at the receiver. Another aspect which should b econsidered in satellite communication system is the inherent transmission delay, which can be very considered in satellite communication system is te inherent transmission delay, which can be very critical to the delay-sensitive ATM traffic. Therefore, we propose that the processing delay at the block interleaving stage should be controlled propose a variable-size block interleaving mechanism which utilizes the predicted transmission delay for each traffic in the queues of the transmitter. According to the computer simulation, the proposed mechanism could improve the overall performance by drastically reducing the ATM cell drop rate owing to the excessive transmission delay.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.6
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• pp.81-87
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• 2023

SAE J2601 and SAE J2799, the communication protocols between a hydrogen refueling station and a fuel cell electric vehicle, only cover hydrogen charging. In this paper, we measure the hydrogen detection, current, and voltage of a fuel cell electric vehicle and transmit the sensor data to the hydrogen refueling station by changing the WiFi protocol. A small-scale laboratory model was built using Raspberry Pi for sensing, controlling, and transmitting sensor data of a fuel cell electric vehicle. The sensor data was stored in the database of the hydrogen refueling station, and a dashboard was configured using Grafana to analyze the stored data. When hydrogen is detected, the dispenser valve of the hydrogen refueling station is locked. Then, we measured the average transmission delay according to the WiFi protocol. The results showed that IEEE 802.11a is the most suitable WiFi protocol for transmitting sensor data between the hydrogen refueling station and the fuel cell electric vehicle.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.794-799
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• 2015

To manage cell outage problem in indoor wireless communication systems, we should resolve the problem of abrupt network failure quickly. In this paper, we propose a near-optimal cell outage management (NoCOM) scheme to support seamless services to users. In consideration of system throughput, user fairness, and the guarantee of QoS simultaneously, the NoCOM scheme finds the solution of subchannel and power allocations using a non-convex optimization technique and allocates radio resources to users iteratively. Through intensive simulations, we verify the outstanding performances of the proposed NoCOM scheme with respect to the average cell capacity, user fairness, and computational complexity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.321-326
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• 2016

Minimizing the carrier recombination and electrical loss through surface passivation is required for high efficiency c-Si solar cell. Usually, $SiN_X$, $SiO_X$, $SiON_X$ and $AlO_X$ layers are used as passivation layer in solar cell application. Silicon oxide layer is one of the good passivation layer in Si based solar cell application. It has good selective carrier, low interface state density, good thermal stability and tunneling effect. Recently tunneling based passivation layer is used for high efficiency Si solar cell such as HIT, TOPCon and TRIEX structure. In this paper, we focused on silicon oxide grown by various the method (thermal, wet-chemical, plasma) and passivation effect in c-Si solar cell.

• Journal of Integrative Natural Science
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• v.14 no.2
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• pp.50-56
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• 2021

Due to the recent increase in the mobile streaming market, mobile traffic is increasing exponentially. IMT-2020, named as the next generation mobile communication standard by ITU, is called the 5th generation mobile communication (5G), and is a technology that satisfies the data traffic capacity, low latency, high energy efficiency, and economic efficiency compared to the existing LTE (Long Term Evolution) system. 5G implements this technology by utilizing a high frequency band, but there is a problem of path loss due to the use of a high frequency band, which is greatly affected by system performance. In this paper, small cell technology was presented as a solution to the high frequency utilization of 5G mobile communication system, and furthermore, the system performance was improved by applying machine learning technology to macro communication and small cell communication method decision. It was found that the system performance was improved due to the technical application and the application of machine learning techniques.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2B
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• pp.151-157
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• 2004

In this paper, we investigated ultra high speed wireless communication cell backbone net of city using of wireless communication transceiver for millimeter wave band. A new type of 60GHz wave band wireless transceiver using NRD waveguide. This 60㎓ transceiver has excellent signal's absorption characteristics of oxygen molecule than the other millimeter wave bands. We constructed to wireless networks interval within 500m to 3km on wireless backbone node using 60GHz transceivers, and did it so that city type wireless communication cell backbone networks of 155.52MbpsATM(OC-3) may be possible. Therefore, if use transceiver, it is possible that city type ultra high speed wireless communication cell backbone networks construction of 100Mbps, 155.52Mbps, 622Mbps, 1Gbps, and 1.2Gbps degrees.

• Journal of Navigation and Port Research
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• v.45 no.5
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• pp.231-237
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• 2021

Enhancing the performance of maritime wireless communication has been highlighted by the issue of cell planning in the sea area because of lack of an appropriate Propagation Loss Model (PLM). To resolve the cell planning issue in vast sea areas, it was essential to develop the (PLM) matching the intended sea area. However, there were considerable gaps between the prediction of legacy PLMs and field measurement in propagation loss and there was a need to develop the adjusted PLM (A-PLM). Therefore, cell planning was performed on this adjusted model, including modification of the base station's location, altitude, and antenna azimuth to meet the quality objectives. Furthermore, in order to verify the availability of the cell planning, Communication Service Quality Monitoring System (CS-QMS) was developed in the LTE-Maritime project to collect LTE signal quality information from the onboard equipment at regular intervals and to ensure that the service quality was high enough to satisfy the goals in each designated grid. As a result of verification, the success rate of RSRP was 95.7% for the intensive management zone (IMZ) and 96.4% for the interested zone (IZ), respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.42-48
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• 2006

In this paper a joint detection method for other cell interference cancellation is proposed in the next generation hybrid TD-CDMA mobile communication systems. A joint detection technique, a most characteristic feature of hybrid TD-CDMA mobile communication systems. retrieves users' data in the same time slot simultaneously with the elimination of multiple user interference. Previously a two stage joint detection method was proposed to cancel other cell interference as well as multiple user interference in the target cell. However the previous scheme does not have concrete ways to recognize other cell users who give major interference to the target cell. Thus all users in neighbor other cells has to be jointly detected and it causes huge complexity of the two stage joint detection. In this paper a method is proposed to perform two stage joint detection according to users' interference with the target cell. Performances of the proposed scheme are investigated through simulations and compared to the previous method the proposed method has no performance degradation and also lower the complexity of two stage joint detection significantly.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2627-2640
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• 1998

In this paper, we analyze the performance of the virtual cell system[1] for the transmission of IP datagrams in mobile computer communications. A virtual cell consistsof a group of physical cells shose base stationsl are implemented b recote bridges and interconnected via high speed datagram packet switched networks. Host mobility is supported at the data link layer using the distributed hierachical location information of mobile hosts. Given mobility and communication ptems among physical cells, the problem of deploying virtual cells is equivalent to the optimization cost for the entire system where interclster communication is more expesive than intracluster communication[2]. Once an iptimal partitionof disjoint clusters is obtained, we deploy the virtual cell system according to the topology of the optimal partition such that each virtual cell correspods to a cluser. To analyze the performance of the virtual cell system, we adopt a BCMP open multipel class queueing network model. In addition to mobility and communication patterns, among physical cells, the topology of the virtual cell system is used to determine service transition probabilities of the queueing network model. With various system parameters, we conduct interesting sensitivity analyses to determine network design tradeoffs. The first application of the proposed model is to determine an adequate network bandwidth for base station networking such that the networks would not become an bottleneck. We also evaluate the network vlilization and system response time due to various types of messages. For instance, when the mobile hosts begin moving fast, the migration rate will be increased. This results of the performance analysis provide a good evidence in demonsratc the sysem effciency under different assumptions of mobility and communication patterns.