• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.327-330
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• 2001

CDMA2000 1x 기반의 무선 인터넷 서비스가 가능해짐에 따라 무선 멀티 미디어 서비스에 대한 수요가 점점 늘어나고 있다. 화상 전화나 VOD 서비스와 같은 실시간 멀티 미디어 서비스에 사용되는 UDP는 현재의 유선과 무선이 혼합된 망에서는 패킷 전송 주기와 패킷의 크기에 따라 매우 다른 성능을 보여준다. 무선 구간에서 전송 효율을 높이기 위해서는 대역폭과 패킷손실률 그리고 채널의 타임슬롯 시간을 고려해 야 한다. 본 논문에서는 CDMA2000 1x 망에서 망 측정을 통하여 실시간 멀티미디어 전송에 적합한 QoS 인자를 추출하여 이를 개선 향상을 위해서 하고 실시간 멀티 미디어 서비스를 위한 대안을 제시하였다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.8
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• pp.510-516
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• 2005

Rapid advances in telecommunication make emergency telemedicine possible that specialist offers medical care to an emergency case in moving vehicle. Although there were many telemedicine projects delivering the image or video of patient over several wireless networks, none of them considered effective solutions for optimizing video transmission over error-prone environments, such like wireless links. To alleviate the effect of channel errors on compressed video bit-stream, this paper analyzed the error resilient features of MPEG-4 standard and measured the quality of transmitted MPEG-4 encoded video over commercially available CDMA2000 1xEV-DO networks, transmitting different IP packet sizes and RM positions. we propose an error resilient transmission methods for emergency telemedicine over real 3G network.

• Annual Conference of KIPS
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• 2003.05b
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• pp.1405-1408
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• 2003

유선망에 최적화되도록 진화해온 TCP 는 GPRS, CDMA2000-1X 등의 무선망에서는 제 성능을 발휘하지 못한다는 것은 이미 널리 알려진 사실이며, 이를 극복하기 위한 방법들이 상당수 제안되었다. 하지만 제안된 연구들의 대부분은 이미 3G 서비스의 링크 계층에서 상당부분 해결된 무선 링크에서의 손실을 혼잡으로 오해하는 TCP 의 문제점을 해결하기 위한 것이다. 본 논문에서는 무선 링크에서의 손실보다는 무선 링크로 인해 야기되는 길고 변화가 심한 전송시간으로 인해 발생하는 TCP 의 문제점을 제시하고, 이를 해결하기 위한 방법을 제안한다. 특히, 본 연구에서는 시뮬레이션이 아닌 실제 CDMA2000-1X 망에서 단말기를 통해 측정된 자료를 기반으로 문제점을 도출하여 기존에 제안된 연구들과 차별화 한다.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.38-42
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• 2010

This paper shows that beamfoming module deign to adapt smart antenna system in CDMA2000 environments. The designed beamfroming module has been implemented on a general-purpose DSP as a test-bed to confirm the superior performances based on real-time processing. From the various simulation result, it is confirm that beamforming module is provide a superior beampattern in smart antenna system.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.3
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• pp.229-233
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• 2011

The existing approaches for analyzing the data service capacity of CDMA2000 1X EV-DO (Evolution-Data Only) systems have focused on deriving the maximum number of active customers assuming that the data rates provided to the customers can be determined beforehand. However, we have seen that through real experiment, the data rates actually provided to the customers adaptively change according to the number of active customers. In this paper, we propose new capacity analysis model considering the data rate adaptation. Numerical examples are also presented to obtain the maximum input traffic rates for various values of the length of data burst and the required mean delay bound.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.136-138
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• 2003

인터넷은 이미 대중화되어 있으며, 이러한 인터넷 망을 기초로 한 All-IP 망으로의 망 진화에 대한 논의가 활발하게 진행되고 있다. 또한 현재 상용중인 IPv4에 이동성을 부여한 이동 인터넷(Mobile IPv4)에 대한 연구는 IETF(Internet Engineering Task Force)를 중심으로 활발하게 진행 중에 있으며, 이에 대한 구현 및 개발은 이미 많은 연구단체에서 많은 성과를 보여주고 있다. 본 논문에서는 3세대 이동통신 모델 중의 하나인 CDMA2000 1x 환경에서 기 구현된 Wire-less LAN에서의 이동 인터넷(Mobile IPv4)을 연동하여, 이기종 망(Heterogeneous Network)에서의 이동 인터넷(Mobile Ipv4) 모델을 제시한다. 제시된 이동 인터넷(Mobile IPv4) 프로토콜은 Layer-2망으로서 Wireless LAN과 CDMA2000 1x을 모두 사용하며, 하부 망(Layer-2 Network)의 변화에 능동적으로 반응하여, 통신을 유지한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.72-80
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• 2003

This paper proposed the method of finding optimal weight vectors for enhancing the performance of an adaptive array antenna system by adopting a novel beam-forming algorithm in CDMA (code division multiple access) channel. This algorithm is a liberalized power method, based on power method, with the total computational load, O(4N). Where, N denotes the number of antenna elements. The performance of the proposed algorithm is shown in terms of SER (symbol error rates), allowable capacity, and the convergence characteristic in IS2000 1X CDMA channel. As a result of simulations, the adaptive way antenna system allows 6-10 times more users than the conventional one in a cell of a base station. Furthermore, the proposed algorithm shows superior performance to the conventional one regarding symbol error rates, converging characteristics, and computational load.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.291-297
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• 2002

Due to the increasing demand for high data multimedia service, there has been progressing study of adaptive smart antenna to increase both the performance and capacity using limited wireless resource. IS-95 scheme in the origin of cdma2000 of IMT-2000 standard uses signals of spreading and Walsh-Orthogonal Modulation in reverse link. But, in the case of reverse lint there exists difficulty in synchronous of signals transmitted from users. Therefore, orthogonality between users is not satisfied. So, asynchronous MC-CDMA scheme may yield low performance. In this paper, MC/DS-CDMA scheme to reverse link transmission in adaptive array antenna environment is proposed for spreading the S/P-converted data streams using a given spreading code. Due to frequency diversity effect, simulation results show that the proposed system provides improved BER performance and narrow band interference supple psi on.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6A
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• pp.397-404
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• 2003

In this paper, we have analyzed the level of cross-modulation noise required for CDMA mobile station and proposed a guideline for optimum design. From the analysis, the level of cross-modulation noise is determined by the system's noise figure(NF) and VCO's phase noise and there is a trade-off relationships between them. In addition, we have determined the value of LNA's IIP3 and duplexer's isolation to satisfy the above level in designing the system. Therefore, this paper will give a guideline for a selection of components in designing cdma2000 mobile station.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.853-864
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• 2001

In this paper, system model is based on proposed standardization by 3GPP(Asynchronous IMT-2070 system), and we have analyzed the performance of the DS-CDMA/QPSK which cancelled self-interference, so that occurs when the received signal time is delay by multipath fading. We proposed the new scheme that designed for self-interference cancellation and the system performance is calculated in Rician fading and Rayleigh fading channel. The proposed rake receiver can be achieved a gain of about 1 [dB]∼6 [dB] more than generally rake receiver, and will be a very effective method to improve the performance of IMT-2000, and these data can be available for modem design of DS-CDMA.