• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12C
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• pp.983-990
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• 2008

In communication systems, initial acquisition is required for the reliable transmission performance, and the analysis of the acquisition performance over various communication environments including different signal-to-noise ratios plays an important role in communication system design. Usage of differential correlation methods in initial synchronization procedure is desired when frequency offsets exist, and additional performance improvement can be achieved through proper modifications of conventional correlation schemes. In this paper, we derive the error probability of the initial acquisition and express it in terms of the Marcum Q-function, via statistical modeling of the differential correlator output. The result is generalized to the error probabilities of the extended differential correlation methods using the complex- and magnitude-sum of the correlator outputs. The derived probabilities can be applied for the acquisition performance verification of various communication systems including the DVB-S2 standard.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.83-88
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• 2006

Future communication systems are to be designed to support and serve multimedia and multipledata transmission. Nowadays, requirement of mobile subscribers for the various information such as movie, GPS(Global Positioning System) information, news-is increasing significantly. However, due to practical reasons, the capacity and number of capable channels are limited. To solve this problem, a large number of methods and schemes have been proposed and are under research. In this paper, we demonstrate how satellite DMB (Digital Multimedia Broadcasting) system works with hierarchical modulation scheme. By using hierarchical modulation, we can analyze the capacity. Meanwhile, system performance os evaluated and compared to conventional DMB system without using hierarchical modulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.183-188
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• 2008

Satellite DMB(Digital Multimedia Broadcasting) uses the Cap Filler(GF) that provides a service to the wave shade area of the satellite signal that is a non-line of sight area. The GF is the repeater and the Satellite DMB Systems certainly must construct the GF Network toguarantee the movement reception of the terminal. As the coverage of the GF is formed the Cell or Sector, when the multiple GF is established to be contiguous, the problem of the interference will be able to occur. This paper describes the Satellite DMB system and the GF, and it investigate the design fundamentals plan of the GF Network that it will be able to reduce this problem. As a result, in case of the distance that GF and terminal unit is above 4.6Km, service is not provided because of quality degradation according to mutual interference.

• Korean Journal of Remote Sensing
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• v.21 no.5
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• pp.371-382
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• 2005

We present a processing system for the Atmospheric Infrared Sounder (AIRS) sounding suite onboard Aqua satellite. With its unprecedented 2378 channels in IR bands, AIRS aims at achieving the sounding accuracy of radiosonde (1 K in 1-km layer for temperature and $10\%$ in 2-km layer for humidity). The core of the processor is the International MODIS/AIRS Processing Package (IMAPP) that performs the geometric and radiometric correction for generation of Level 1 brightness temperature and Level 2 geophysical parameters retrieval. The processor can produce automatically from received raw data to Level 2 geophysical parameters. As we process the direct-broadcast data almost for the first time among the AIRS direct-broadcast community, a special attention is paid to understand and verify the Level 2 products. This processor includes sub-systems, that is, the near real time validation system which made the comparison results with in-situ measurement data, and standard digital information system which carry out the data format conversion into GRIdded Binary II (GRIB II) standard format to promote active data communication between meteorological societies. This processing system is planned to encourage the application of geophysical parameters observed by AIRS to research the aqua cycle in the Korean peninsula.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.84-88
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• 2015

In this paper, we present that design and implementation of digital extreme-low-frequency (ELF) magnetic meter including wireless monitoring feature. In our lifetime, it is necessary to study how much magnetic field effects to human body. In this paper, we use 3-axis coil-type magnetic sensor, magnetic measurement range is 0.03~10uT and frequency range is 40~180Hz. As magnetic sensor characteristic, frequency loss is occurred that compensated using digital equalize based on DSP processor. Measurement value can be monitored on PC through Wifi communication and measurement error is observed within 6%.

• Journal of Digital Convergence
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• v.5 no.1
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• pp.117-130
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• 2007

This paper examines whether there exists discrimination of the information usage pattern between tenants of permanent and temporary public rental housing in Korea. Moreover, we focus to examine on that matters between two groups, $7{\sim}12$ pyeongs and $11{\sim}24$ pyeongs that indicate permanent and temporary public rental housing respectively. The results derived in this paper can be summarized as follows: there exists statistical significance in using computer, internet, communication and broadcasting, on the other hand, insignificance in using satellite communication and telephone between them. The implication of this results shows that as widen income gap, also widen gaps in using computer and internet between them. Thus government public rental housing policy should focus to make narrow income gap to diminish information gap between those groups.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1831-1836
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• 2016

Phase noise spectrum distributions of signal generators for next-generation VSAT satellite system based on DVB-RCS2 were analyzed in this paper. The forward link of VSAT system utilizes the APSK higher-order modulation methods based on the DVB-S2 ACM, the modulation methods of the return link utilizes the higher-order PSK and QAM based on the DVB-RCS2. In digital satellite system using the higher-order modulation techniques, the phase noise have an effect on transmission performance, the transmission performance is dominantly degraded by the phase noise of signal generators in the transmission system. The phase noise spectrum distribution of signal generators are analyzed by considering the ACM conditions that adopts the modulation techniques and data rates due to satellite transmission environment. The proper phase noise spectrum distribution for next-generation VSAT system based on DVB-RCS2 are proposed from the analyzed phase noise spectrum characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.10
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• pp.1518-1526
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• 1993

It has been known that the amplifiers for high power signal in satellite communication channels suffer from nonlinear distortions, which reduce the performance of the communication channel significantly. In order to compensate the nonlinear distortion, a new data predistortion method with the LMS algorithm is proposed in this paper, Whereas the previous approach handles this problem by assigning corresponding predistorter to each symbol for the case of 16-QAM, the proposed approach uses the same memory for the symbols, which have identical amplitudes, and predistors the input of high-power amplifiers by the amplitude and phase differences, resulting in better adaptive data predistorter with small number of digital memory (3 predistorters) and fast convergence rate. Superiority of the proposed approach in the paper is demonstrated by comparing it with the previous approach.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.183-186
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• 2004

The proposed system in this paper utilizes the SIP and self-defined control protocol to provide global wireless communication over the data link of Orbcomm system. Main processor board connected to Orbcomm communication subscriber is designed to interface with digital I/O and AD/DA convertor for various application of control and .measurement. Hardware system implemented in this paper also includes the function of real-time clock and position report using GPS receiver The experimental result of the proposed global wireless communication system is evaluated via real-time experiments, and we have confirmed it works well according to the protocol designed in this paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.101-109
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• 2006

A broadband, DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by adding transmission lines in the conventional Switched-T attenuator and optimizing the transmission line parameters. Momentum simulation was performed in design for accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify the performance stability against the MMIC process variation. The attenuator has been fabricated with $0.15\;{\mu}m$ GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic ranges. High attenuation accuracy has been achieved over all attenuation ranges and 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies. The measured IIP3 of the attenuator is 33 dBm.