• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.391-399
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• 2005

Laser-generated ultrasonic inspection system is a non-contact scanning inspection device with high spatial resolution and wide bandwidth. The amplitude of laser-generated ultrasound is varied according to the energy of pulse laser and the surface conditions of an object where the CW measuring laser beam is pointing. In this paper, we correct the generating errors by measuring the energy of pulse laser beam and correct the measuring errors by extracting the gain information of laser interferometer at each time. h dynamic stabilizer is developed to stably scan on the surface of an object for an laser-generated ultrasonic inspection system. The developed system generates ultrasound after adaptively finding the maximum gain time of an laser interferometer and processes the signal in real time after digitization with high speed. In this paper, we describe hardware configuration and control algorithm to build a stable laser-generated ultrasonic inspection system. Also, we confirmed through experiments that the proposed correction method for the generating errors and measuring errors is effective to improve the performance of a system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.455-464
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• 2005

In this paper, we implement resource allocation algorithm based on the WiBro system which including OFDMA, TDD, and we propose the algorithm in order to increase bandwidth efficiency. In this algorithm, data is allocated from the subchannel which has large channel gain to the subchannel which has small channel gain with maximum modulation order. The moment total power is more than available power, the modulation order of the latest subchannel is adjusted. The problem of decreasing of throughput in large channel attenuation environment is solved by allocating additional power. Still, this algorithm has large bandwidth efficiency.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.2
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• pp.60-67
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• 2000

When the eigenvalues of the input covariance matrix of an array system spread by orders of magnitude, conventional adaptive arrays can't remove all the interference signals effectively In this paper, an Applebaum array adopting an adaptive gain controller (AGC) in the feedback loop of the array is proposed When eigenvalue spreaded interferences are incident to an array, a high power interference is removed easily in several iterations while a relative low power interference which is a cause of eigenvalue spread is still remained In the array output After some initial iterations, the proposed array increases the correlation between the low power interference and the array output by amplifying the output signal of the array As a result, the weights vector adapts to the direction of the low power interference as well as that of the high power interference Computer simulation results show that the proposed array gives high output signal to interference plus noise ratio (SINR) and a fast convergence speed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.918-927
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• 2004

WCDMA system is 3rd generation wireless mobile system specified by 3GPP. In WCDMA downlink, two power control schemes are operated. One is inner loop power control operated in every slot. Another is outer loop power control based on one frame time. Base station (BS) can estimate proper transmission power by these two power control schemes. However, because each MS's transmission power makes a severe effect on BS's performance, BS cannot give excessive transmission power to the specific user. 3GPP defined Power Control Dynamic Range (PCDR) to guarantee proper BS's performance. In this paper, we propose Adaptive PCDR algorithm. By APCDR algorithm, Radio Network Controller (RNC) can estimate each MS's current state using received signal to interference ratio (SIR). APCDR algorithm changes MS's maximum code channel power based on frame. By proposed scheme, each MS can reduce wireless channel effect and endure outages in cell edge. Therefore, each MS can obtain better QoS. Simulation result indicate that APCDR algorithm show more attractive output than fixed PCDR algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1048-1057
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• 2004

WCDMA system is 3rd generation wireless mobile system specified by 3GPP. In WCDMA downlink, two power control schemes are operated. One is inner loop power control operated m every slot Another is outer loop power control based on one frame time. Base staion (BS) can estimate proper transmission power by these two power control schemes. However, because each MS's transmission power makes a severe effect on BS's performance, BS cannot give excessive transmission power to the speclfic user 3GPP defined Power Control Dynamic Range (PCDR) to guarantee proper BS's performance. In this paper, we propose Adaptive PCDR algorithm. By APCDR algorithm, Radio Network Controller (RNC) can estimate each MS's current state using received signal to interference ratio (SIR) APCDR algorithm changes MS's maximum code channel power based on frame. By proposed scheme, each MS can reduce wireless channel effect and endure outages in cell edge. Therefore, each MS can obtain better QoS. Simulation result indicate that APCDR algorithm show more attractive output than fixed PCDR algorithm.