• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2A
• /
• pp.166-173
• /
• 2004

Satellite communication system uses a high non-linear HPA(high power amplifiers) in the earth station and satellite transponder. Therefore, it is important to consider the nonlinear effect of HPA on the communication system. In this paper, we find the variation of power spectrum density by nonlinearity HPA and the change of harmonic component according to IBO (input back-off). When the BPSK is used for satellite communication system, we analyze BER performance including the external co-channel interference (CCI) and the adjacent channel interference (ACI) resulting from the HPA nonlinearity. BER degrades as ACI magnitude grows up when the uplink SNR, uplink SIR (signal to co-channel interference power ratio) and downlink SIR are constant at some level. In case there is only non-linear HPA in the satellite, it is shown that BER considerably depends on the ACI magnitude ACI. When there are two non-linear HPAs in the both earth station and satellite, much BER degradation results from the CCI and ACI.

• Korean Chemical Engineering Research
• /
• v.52 no.1
• /
• pp.68-74
• /
• 2014

In the spiral wound module of the pressure-retarded osmosis (PRO) system for the salinity gradient power generation, effects of the inlet pressure differences between feed-channel and draw-channel were studied. Fluxes of water and solute through membrane and power were estimated. The water flux through membrane decreased along the x-direction and increased along the y-direction with the increase of inlet pressure differences between two channels. On the other hand, the solute flux through membrane showed the opposite trend. The concentration of flow in the feed-channel increased a lot along the y-direction and that in the draw-channel decreased along the x-direction. In our system, for the inlet pressure differences of 1~11 atm, the flow rate in the feed-channel decreased about 8~13% and that in the draw-channel increased by the same amount. The power density increased and then decreased with the increasing inlet pressure difference.

• Journal of Digital Convergence
• /
• v.11 no.6
• /
• pp.43-55
• /
• 2013

This study was to examine the operation strategy of terrestrial broadcasting system on channel image and N-screen service. Nowadays, terrestrial broadcasting system provides video streaming service based on internet. In other words, terrestrial broadcasting system provides N-screen service through TV-PC-Smart phone-Tablet PC. But it is different for terrestrial broadcasting system to analysis the choice criterion of program. Only, channel image of terrestrial broadcasting system expanded into N-screen. Finally, channel image of terrestrial broadcasting system is the competition strategy. It is necessary for terrestrial broadcasting system to prepare the strategy of program choice for users, original contents, new platform and service in connection with N-screen.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.468-470
• /
• 2002

We have designed X-ray detection system and multi-channel data acquisition system for Spiral CT application. X-ray detection system consists of scintillator and photodiode. Scintillator converts X-ray into visible light. Photodiode converts visible light into electrical signal. The multi-channel data acquisition system consists of analog, digital, master and backplane board. Analog board detects electrical signal and amplifies signal by 140dB. Digital board consists of MUX(Multiplex) which routes multi-channel analog signal to preamplifier, and ADC(Analog to Digital Converter) which converts analog signal into digital signal. Master board supplies the synchronized clock and transmits the digital data to image reconstructor. Backplane provides electrical power, analog output and clock signal. The system converts the projected X-ray signal over the detector array with large gain, samples the data in each channel sequentially, and the sampled data are transmitted to host computer in a given time frame. To meet the timing limitation, this system is very flexible since it is implemented by FPGA(Field Programmable Gate Array). This system must have a high-speed operation with low noise and high SNR(signal to noise ratio), wide dynamic range to get a high resolution image.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.3A
• /
• pp.203-208
• /
• 2005

To solve the cost problem of micro/picocell system, the fiber-optic cellular system was proposed. In this system, all channel elements are managed in Central Station, not in each base station. Also, all channel elements in a system can be dynamically assigned when the Spectrum Delivery Switch (SDS) is used. In this paper, we propose and analyze a new intergroup handoff scheme in the fiber-optic cellular system. The proposed scheme supports handoff with keeping current channel. Performance is evaluated with respect to the blocking probability and the handoff refused probability in both systems with SDS and without SDS. The numerical results show that the proposed scheme provides better performance than conventional soft handoff scheme.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.11
• /
• pp.10-18
• /
• 1996

In this paper, performance of a hybrid direct-sequency/slow-frequency-hopped (DS/SFH) spread-spectrum (SS) system with coherent BPSK modulation is analyzed. The bit error probability is derived over a frequency=-selective rician fading channel in the presence of multiple tone jamming. The fading channel is modeled as the wide-sense stationary uncorrelated scattering (WSSUS) model. Numerical evaluations are presented for some combinations of system parameters. The performance of a hybrid DS/SFH SS system is shown to be inferior to that of a ure DS SS system at low jamming-to-signal power ratio (JSR). At high JSR, the performance of a pure DS SS system is shown to be the smae as the worst case performance of a hybrid DS/SFH SS system.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.398-402
• /
• 2003

In this paper, we have analyzed the performance enhancement of OFDM/QPSK-DMR(Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio)system using BL-PSF(Band Limited-Pulse Shaping Filter) over the microwave channel. For performance enhancement, we apply the one-tap adaptive equalizer for OFDM/QPSK-DMR system and compare with the BER performance of single carrier DMR system. Computer simulations confirm that the OFDM/QPSK-DMR system using one-tap adaptive equalizer has the same BER performance for the single carrier DMR system.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.85-86
• /
• 2006

In this paper, we propose an adaptive turbo system for a varying channel between being frequency-flat and frequency-selective. The proposed system unites a turbo code and a turbo equalization and selects one of two algorithms adaptively to the channel variation with the feedback information from the receiver. The performance of the proposed system in varying channel is evaluated by computer simulation when the feedback delay exists. It is shown that when the feedback delay is moderate, the proposed system outperforms both the conventional turbo code system and turbo equalization system without increasing the complexity.

• Asia pacific journal of information systems
• /
• v.23 no.1
• /
• pp.45-63
• /
• 2013

The purpose of this research is on the identification of the effects of perceived interactivity formed by the electronic collaborative referral system on the organizational loyalty. Two channels through which the effects proceeded were investigated. One is the "system channel" which consists of "interactivity of the inter-organizational system ${\rightarrow}$ intention of using the system ${\rightarrow}$ organization loyalty" (hypothesis 1, 2), that is the channel which anticipates that a better understanding on the interactivity of the inter-organizational system makes the intention of the using the system strong, and this strong intention results the higher organization loyalty. The other is "organization channel" which consists of "interactivity of the inter-organizational system ${\rightarrow}$ perceived interactivity on the counterpart ${\rightarrow}$ perceived relation benefits with the counterpart ${\rightarrow}$ organization loyalty" (hypothesis 3, 4, 5). The channel means that as the perceived interactivity of users on the inter-organizational system becomes greater, the perceived interactivity with the counterpart is increasing. And this makes the users feel that more benefits can be obtained by the relationship with system providing organization, and finally makes the organization loyalty that is the intention to maintain the relationship greater. The corroborative evidence data confirm the two channels are obtained by questing on the electronic referral system of Samsung Medical Center to the doctors of the first and second collaborated hospitals or clinics, and by analyzing statistically. The verification result for the "system channel" showed that as the perception on the interactivity of inter-organizational system was increasing, the intention for consistent using increased(support hypothesis 1), and then the organization loyalty that is the relationship maintaining indication by using the referral system also increased(support hypothesis 2). And the confirmation result for the "organization channel" indicated that the perceptive interactivity on the counterpart increased as the understanding on the interactivity of inter-organizational system increased(support hypothesis 3), consecutively, with the intuitive relation benefits increase with the counterpart(support hypothesis 4) the organization loyalty means the intention to maintain the relationship was confirmed to increase(support hypothesis 5). These results demonstrate that when the perceived interactivity in using many systems at the collaboration between organizations is increasing, the positive image on the systems creates the consistent system using intention, and the positive image increases the wants for preserving the relationship with counter organization. In addition, the perceived interactivity of inter-organizational system users affects directly on the perceived interactivity of the counter organization, so the important role of inter-organizational system in promoting the interactivity between cooperative counterparts was recognized. And the perceived interactivity on the counter organization become greater, the influence on the perceived benefits from cooperation is positive. Therefore, the perceived interactivity by using inter-organizational system was confirmed as a prerequisite for the continuous relationship.

• Proceedings of the IEEK Conference
• /
• 2000.06a
• /
• pp.45-48
• /
• 2000

The use of multi-level modulation scheme in the wireless LAN(Local Area Networks) system requires an accurate channel estimation. In this paper, we present sequential least squares(LS) channel estimation scheme based on decision-directed channel tracking scheme. The proposed scheme improves the performance of the conventional LS estimator for wireless LAN. In addition, its structure is suitable for the high-rate wireless LAN. Simulation results show that the proposed scheme achieves about IdB Packet Error Rate(PER) gain compared to the LS scheme in a frequency selective channel.