• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.3-4
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• 2008

We propose an efficient uplink bandwidth request-allocation algorithm for variable-rate real-time service in IEEE 802.11 broadband wireless access networks. By introducing a notion of target delay under the framework of dual feedback, the proposed algorithm can assure the desired level of QoS while minimizing wastage of bandwidth allocation.

• ETRI Journal
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• v.34 no.5
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• pp.767-770
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• 2012

This letter presents a novel compact circularly polarized patch antenna for Global Positioning System/Global Navigation Satellite System (GPS/GLONASS) applications. The proposed antenna is composed of a simple square radiating patch fed by a capacitive dual-feeder to increase the impedance bandwidth and a lumped element hybrid coupler to achieve the broadband characteristic of the axial ratio (AR). The realized antenna dimensions are $28mm{\times}28mm{\times}4mm$, which is the most compact size among the dual-band GPS/GLONASS antennas reported to date. The measured results demonstrate that the proposed antenna has a gain of 2.5 dBi to 4.2 dBi and an AR of 0.41 dB to 1.51 dB over the GPS/GLONASS L1 band (1.575 GHz to 1.61 GHz).

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.2089-2094
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• 2010

The importance of broadband wireless communication implemented at subway tunnels is growing up. At 18GHz wireless video transmission system, the transmitter requires a digital modulation method. At subway tunnel, A 18GHz's influence of the multi-pass padding is strong. OFDM digital modulation that is strong for multi-pass padding is recommended. In this paper, Suitable to a subway wireless video transmission OFDM receiver is designed. OFDM receiver system has 6dB gaion because uses diversity of space diversity and MRC(Maximum Ratio Combining) diversity. The transmitter system use C&ITechnologies's transmitter board. IF frequency of receiver is 480MHz. OFDM modulation parameter is as follow, The bandwidth is 8MHz, The numuber of carrier if 2,000, The modulation methode is QAM16, The guard interval is 1/32.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.4
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• pp.445-459
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• 2008

This paper addresses a call admission control(CAC) scheme giving handoff calls a priority over new calls for OFDMA wireless communication systems. The characteristics of OFDMA system and a variety of user QoS (Quality of Service) requirements are incorporated into the proposed CAC scheme which consists of several optimization modules for the system resource(subcarriers and power) allocations. The mathematical models and its solution methods for the embedded resource allocation problems are proposed. Some extensive computational experiments are conducted to illustrate the superiority of our CAC.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.4
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.118-123
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• 2014

For multi parameter optimization of Raman Fiber Amplifier (RFA), a simple genetic algorithm is presented in the scenario of a 320 channel Dense Wavelength Division Multiplexed (DWDM) system at channel spacing of 25 GHz. The large average gain (> 22 dB) is observed from optimized RFA with the optimized parameters, such as 39.6 km of Raman length with counter-propagating pumps tuned to 205.5 THz and 211.9 THz at pump powers of 234.3 mW, 677.1 mW respectively. The gain flattening filter (GFF) has also been optimized to further reduce the gain ripple across the frequency range from 190 to 197.975 THz for broadband amplification.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.9 no.1
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• pp.29-34
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• 2010

In this study, we realized the broadband home gateway system of dual mode based upon EDR 2~3Mbps transmission speed and 300Mbps of 802.11n, In broadcasting and telecommunication convergence networks to deliver multimedia services, high-quality home. The bluetooth module is designed to use general low rate data speed service and the 802.11n module also is designed to use high rate speed service at various home network situation. The dual mode home gateway system, bluetooth and 802.l1n module, is well realized for many specification such as emission power, spurious power, impedance matching, frequency channel test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.119-124
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• 2000

The 3-stage centrifugal compressor is used in order to measure the noise spectra of compressor, and analyze the results. Two cases are investigated for compressor noise components. Case I includes total system such as compressor, inter-cooler, motor, and Case II excludes cooling system. BPF tonal noise is important in compressor, and cooling system including inter-cooler contributes to broadband noise. Also, motor, gear box, and motor cooling fan are the second contributions to total compressor noise. Centrifugal compressor flow-field is calculated using two-dimensional grid and Navier-Stokes equations. Static pressure increases, and total pressure decreases, as air passes through the compressor components.

• Journal of IKEEE
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• v.23 no.2
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• pp.395-402
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• 2019

In this paper, we implemented an Ultra-Wideband radar system using Stripmap Synthetic Apertrure Radar algorithm to recognize objects inside a box. Different window functions such as Hanning, Hamming, Kaiser, and Taylor functions to improve image recognition performance are applied and implemented to radar system. The Ultra-Wideband radar system with 3.1~4.8 GHz broadband and UWB antenna were implemented to recognize the conductor plate located inside 1m3 box. To obtain the image, we use the propagation data in the time domain according to the 1m movement distance and use the Range Doppler algorithm. The effect of different window functions to improve the recognition performance of the image are analyzed. From the compared results, we confirmed that the Kaiser window function can obtain a relatively good image.

• Journal of Information Processing Systems
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• v.15 no.4
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• pp.890-903
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• 2019

The single carrier frequency domain equalization (SC-FDE) technology is an important part of the broadband wireless access communication system, which can effectively combat the frequency selective fading in the wireless channel. In SC-FDE communication system, the accuracy of timing synchronization directly affects the performance of the SC-FDE system. In this paper, on the basis of Schmidl timing synchronization algorithm a timing synchronization algorithm suitable for FPGA (field programmable gate array) implementation is proposed. In the FPGA implementation of the timing synchronization algorithm, the sliding window accumulation, quantization processing and amplitude reduction techniques are adopted to reduce the complexity in the implementation of FPGA. The simulation results show that the algorithm can effectively realize the timing synchronization function under the condition of reducing computational complexity and hardware overhead.