• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.541-546
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• 2004

Space-Time Coding(STC) is a technique that utilizes joint correlation of transmitted signals in both time and space domains. Through this approach, diversity and coding gains can be simultaneously obtained. In this paper, we use SPW simulation tool to implement the IEEE 802.11a system. Based on this system, OFDM system with STC and convolutional coder concatenated is implemented. The system performance is analyzed and compared with the performance of the IEEE 802.11a system. The simulation results show that the performance with concatenated codes at a data rate of 6Mbps shows approximately a 5dB gain over the system with the convolutional code only. At a data rate of 12Mbps, the performance with concatenated codes is further improved by approximately 6dB.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.19-25
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• 2008

In this paper, the front end module (FEM) was proposed for 2.4GHz WLAN band by LTCC multilayer application. The FEM was composed of power amplifier IC, switch IC, and LTCC module. LTCC module consists of output matching circuit and lowpass filter as Tx part, bandpass filter as Rx part. Design of output matching circuit for LTCC was used matching parameter from output matching circuit based on lumped circuit on the PCB board. The dielectric constant of LTCC substrate is 9. The substrate was composed of total 26 layers with each 30um thickness. Ag paste was used for the internal pattern as the conductor material. The size of the module is $4.5mm{\times}3.2mm{\times}1.4mm$. The fabricated FEM showed the gain of 21dB, ACPR of less than -31dBc first side lobe and Less than -59dBc second side lobe and the output power of 23Bm at P1dB.

• Journal of Korea Multimedia Society
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• v.13 no.10
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• pp.1525-1533
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• 2010

With the digital terrestrial television broadcasting transition, terrestrial television broadcasting have required the replacement of retransmission facilities for the analog broadcasting installed in the existing apartment, building, cable TV station, MATV system and so on. In addition, new standards have been enacted for retransmission of the digital television broadcasting in MATV system. To deal with this issue, in this paper, we propose a new 8-VSB remodulator that can retransmit signals of the terrestrial digital television broadcasting. Moreover, we present a standard and the process composition of the 8-VSB remodulator, and an experimental environment configuration for performance evaluation. To achieve this, we have implemented the 8-VSB remodulator with the sequential process components comprised of the RF signal retransmission, the TS stream modulator, the RF signal reception and demodulation. Through the simulation, we analyze the performance standard from the measured data such as spurious and phase noise. And then, we measure SNR and EVM of each attenuation step of the signal obtained by the signal processor and the 8-VSB remodulator with the same retransmission environment and conditions. Experimental results show that both the 8-VSB remodulator and the signal processor can be used as equipment for the retransmission of the terrestrial digital television broadcasting. In addition, the 8-VSB remodulator performed well to improve the transmission efficiency for the digital broadcasting signal, compare to the existing signal processor.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.59-71
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• 2003

The channel scheduler is suggested the radio resource management method in order to provide service with guaranteeing fairness and throughput to the users who use limited wireless channel. Proportional fairness scheduling algorithm is the channel scheduler used in the AMC(Adaptive Modulation and Coding)/TDM system, and this algorithm increases the throughput considering the user's time fairness. In this paper is suggested the channel scheduler combining CDM scheme available in AMC/TDM/CDM system. Unlike the system which only uses TDM which provide the only one user at the same slot, this scheduler can service a lot of users since this uses the CDM scheme with multi-cord channel. At every moment, allocation of transmission power to multi-channel users is problematic because of CDM scheme. In this paper, we propose a water-filling scheduling algorithm to solve the problem. Water-filling fairness(WF2) scheduling algorithm watches the average channel environment. So, this modified method guarantees fairness for each user in terms of power and service time.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.603-620
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• 2021

A land nodal seismic system was employed to acquire seismic reflection data using stand-alone cable-free receivers in a land-river area. Acquiring reliable data using this technology is very cost effective, as it avoids topographic problems in the deployment and collection of receivers. The land nodal airgun system deployed on the mouth of the Hyungsan River (in Pohang, Gyeongsangbuk Province) used airgun sources in the river and receivers on the riverbank, with subparallel source and receiver lines, approximately 120 m-spaced. Seismic data collected on the riverbank are characterized by a low signal-to-noise (S/N) and inconsistent reflection events. Most of the events are represented by hyperbola in the field records, including direct waves, guided waves, air waves, and Scholte surface waves, in contrast to the straight lines in the data collected conventionally where source and receiver lines are coincident. The processing strategy included enhancing the signal behind the low-frequency large-amplitude noise with a cascaded application of bandpass and f-k filters for the attenuation of air waves. Static time delays caused by the cross-offset distance between sources and receivers are corrected, with a focus on mapping the shallow reflections obscured by guided wave and air wave noise. A new time-distance equation and curve for direct and air waves are suggested for the correction of the static time delay caused by the cross-offset between source and receiver. Investigation of the minimum cross-offset gathers shows well-aligned shallow reflections around 200 ms after time-shift correction. This time-delay static correction based on the direct wave is found essential to improving the data from parallel source and receiver lines. Data acquisition and processing strategies developed in this study for land nodal airgun seismic systems will be readily applicable to seismic data from land-sea areas when high-resolution signal data becomes available in the future for investigation of shallow gas reservoirs, faults, and engineering designs for the development of coastal areas.