• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1042-1047
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• 1999

In this paper, two kinds of digital predistorters are proposed and their performances are analyzed in order to minimize ACI and SNR degradation caused by nonlinearly amplified TC-16QAM signal and to transmit high speed data in power and bandwidth limited land mobile satellite channel. Our simulation results show that LUT predistorter reduces the out-of-band ACI more efficiently as compared to intersymbol interpolated predistorter. Regarding the reduction of in-band SNR and total power intersymbol interpolated predistorter outperforms LUT predistorter. In the simulation mobile satellite channel and nonlinear HPA are modeled by Rician channel and Fujitsu SSPA, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.1-7
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• 2000

In this paper, we proposed a complex multirate filter bank(CMRFB) based adaptive notch filtering technique to solve the co-existence narrowband interference problem of DS-CDMA and TDMA systems. We have discussed error performance of co-existence of DS-CDMA and TDMA system by using complex multirate filter bank in land mobile channel and computer simulation results show that the proposed scheme can eliminate the narrowband interference(TDMA signals) effectively.

• ETRI Journal
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• v.20 no.2
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• pp.133-148
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• 1998

The objective of this paper is to present an adaptive algorithm for computing the weight vector which provides a beam pattern having its maximum gain along the direction of the mobile target signal source in the presence of interfering signals within a cell. The conjugate gradient method (CGM) is modified in such a way that the suboptimal weight vector is produced with the computational load of O(16N), which has been found to be small enough for the real-time processing of signals in most land mobile communications with the digital signal processor (DSP) off the shelf, where N denotes the number of antenna elements of the array. The adaptive procedure proposed in this paper is applied to code division multiple access (CDMA) mobile communication system to show its excellent performance in terms of signal to interference plus noise ratio (SINR), bit error rate (BER), and capacity, which are enhanced by about 7 dB, ${\frac{1}{100}}$ times, and 7 times, respectively, when the number of antenna elements is 6 and the processing gain is 20 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.8
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• pp.2033-2042
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• 1996

In this papre, we describe a recently implemented echo canceller for digital cellular communication of Code Division Multiple Access(CDMA) that features time sharing of digital signal processor(DSP) over four channels in one DSP to reduce per channel costs. In the Public Land Mobile Network(PLMN), it is important to cancel the echo reflected from the Public Switched Telephone Network(PSTN) side. In case of digital mobile system, the round-trip delay of the echo is in excess of about 180 milliseconds due to frame-by-frame voice coding. It is necessary to cancel the echo in PLMN. We have developed a multi-channel echo canceller tht operates with Time Switch Module in a Mobile Switching Center(MSC). The general echo canceller needs PCM trunk interface circuits and the tone detection and disabling circuits, but the multi-channel echo canceller linked with Time Switch Module does not need them. Therefore we could develop the effective and economical echo canceller.

• The Transactions of the Korea Information Processing Society
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• v.2 no.1
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• pp.81-94
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• 1995

By intergrating technologies for protable computers, radio communications, and computer networking, the Land Mobile Computer Network(LMCN) is supposed to overcome the time and space limitation of present computer communication network. However, because the MHs(mobile hosts) do move any time, the network connectivity is often changed causing temporarily duplicated lost, or out-of-sequenced message delivery as well as frequent communications for maintainning the network connectivity. Previous works solved the problems through message flooding, used also in multicasting, resulting in high communication cost(i.e., number of communication messages). In this paper, new protocols for efficient mobility management and multicasting are proposed. The protocols define location update, handover, and multicasting procedure of a MH over a hierarchical LMCN architecture. The protocol specification is presented, and it is shown that the communication cost of the new protocols is superior to the existing ones in terms of the communication cost.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1451-1454
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• 2002

In recent years, there are growing concerns about land mobile satellite (LMS) communication systems and mobile stratospheric communication systems (SCS) for the purpose of service upgrade of personal and mobile communications in near future. It is important to possess accurate channel model for prediction of the above system performance. Thus, in this paper, we evaluate the bit error rates of a coded BPSK system based on realistic channel model which can be applied to stratospheric communication systems. The channel data was made by fitting the parameters of probability distribution model to measured data. This approach was proposed by Corraza〔1〕and modified by You〔2〕. And also the effects of channel codings on the system performance are analyzed. As results, we can get the performance curve characteristics on realistic Rician log-normal fading channels with various communication environments.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.1
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• pp.1-14
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• 2013

The world largest land reclamation project in the name of Saemangeum(Ariul) from 1991 to the present has been implementing in a part of the west coast of Korea. In the Saemangeum reclamation project, the large-scale project cost is used for the landfill reclamation. A number of landfill reclamation methods have been studied in order to reduce the large-scale cost of the Saemangeum project under construction. There are many studies related to the on-site real-time monitoring with mobile systems for operating a wide range of landfill. In order to apply the work method for efficient cost-savings in the landfill operations to the Samangeum project, this paper develops a mobile management system that is composed of a mobile interface module, a data server module for data transmission and storage, and an analysis server module to analyze the input data and derive the results. The mobile system is designed by analysing user's and system requirements, functional interactions, and data flow using unified modeling language(UML). The user interface is developed for the on-site real-time monitoring through the status and related attributes of land reclamation by using the digital maps of the Samangeum coverage via mobile devices. Finally, a mobile management system would be developed that can provide a 3D GIS service based on the Dry Internal Project Site Digging Reclamation Method(DIPSDRM).

• Journal of information and communication convergence engineering
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• v.11 no.4
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• pp.253-257
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• 2013

Mobile computers can process large amounts of data at high speeds, and it is feasible and easy to implement a remote monitoring system utilizing mobile computers. Because of their portability and convenience, these computers have been employed in various research areas to develop such monitoring systems. Existing monitoring system is a bit difficult to real time monitoring the scattered offshore facilities. So this paper compensate the existing system by using mobile computers such as a tablet PC-based monitoring system. Also, the scattered offshore facilities can be monitored in real-time through the tablet PC. The developed monitoring system is a fully Internet-based monitoring platform that enables one to monitor and control remote oceanic applications at any time and any place where it is possible to access the Internet. It can be applied to many oceanic applications as well as the unmanned systems and remote monitoring systems on land.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.690-697
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• 2012

Approximately 67% of the total land area of the Korea is covered by forest. Eutrophication, defined as the enrichment of waters beyond natural levels, principally by the nutrient phosphorus (P), is a serious cause of concern at the present time. The contribution of forestry to P loading in catchment waters has not been intensively studied in Korea, but is potentially important because forests are often located in near-pristine environments. Phosphorus is retained by most mineral soils and, as a consequence, losses are usually negligible. However, it is much more mobile in organic soils where it can be relatively easily leached or lost through surface runoff, as these soils have a low capacity to retain free phosphate. This report has been prepared to study the influence of arable land used for paddy, upland, and forestry on water quality in the basin of Daechung reservoir.

• Journal of Korea Spatial Information System Society
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• v.11 no.1
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• pp.1-8
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• 2009

The u-GIS national land information providing technology is the technology which maximizes the application of u- GIS data through the national land information platform technique of the next generation web and provides a user with the on-demand national land information in the ubiquitous environment. Recently, as the environment emphasizing the web as a platform 'Web 2.0' emerges, the where 2.0 which is paradigm is diffused in the spatial information area. And the Geo-spatial Web technology develops in a center. Moreover, it is changed to the open platform of the user participation trend. And the consumer of the geo-spatial information is changed to the end-user center from the public institution. The geo-spatial technique is technologically faced with the new challenge. In this paper, we analyze the technical tendency about a paradigm, And we present the u-GIS national land information platform technique, the u-GIS national land information visualization technology, the u-GIS national land information GeoDRM integrative technique, and the u-GIS national land information mobile application technology as the essential elemental technology for overcoming this.