• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.527-535
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• 2003

In this paper, the performance of W-CDMA system with smart antenna is analyzed for angular spread in realistic wideband multipath channel. The realistic wideband channel is assumed, one of which is JTC channel model. And each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipaths within one chip are distinguished into each one and the strongest signal is selected. As a result, the performance of the W-CDMA system with smart antenna in realistic wideband multipath channel has been considerably improved in proportion to the increase of angular spread.

• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.196-203
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• 1999

In this paper, the DS(direct sequence)-CDMA and MC(multi-carrier)-CDMA, which are being researched recently as a synchronous IMT-2000 scheme for next-generation mobile multimedia communications, are studied in terms of BER(bit error rate) performance. The BER performance of MC-CDMA with EGB, MRC, and improved MMSEC detection scheme are analyzed and compared to that of conventional DS-CDMA adopting RAKE receiver through the computer simulations under the environments of synchronous IMT-2000 transmission channel. Not only single user case but also multiuser case is considered in the given system. As a result, it is shown that MC-CDMA with MMSEC detection outperforms all other schemes improved the $E_b/N_o$ by about 5 [dB] and 6 [dB] when the BER is $2{\times}10^{-3}$, for the indoor/outdoor fading channel and synchronous IMT-2000 transmission channel, respectively. Also in the multiuser case, MC-CDMA with MMSEC detection scheme exhibits better performance than all the other schemes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.1-9
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• 2009

In this paper, we describe DSSS transceiver development robust to jamming signals as an investigation of ECCM transceiver for UAV uplink. The jamming margin is 15dB or greater with the development target of transceiver because the jamming margin is more important than the transmission rate of data and the spreading code can be changeable. The rake receiver is applied to combine multipath components and turbo code which the coding gain is 7.2dB as a FEC. In this paper, the whole structure, design method and functional test result about the designed modem are described and a conclusion is made.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.344-352
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• 2020

Covertness and performance are very important design goals in the underwater communications. To satisfy both of them, we proposed efficient underwater communication model which combined multiband and direct sequence spread spectrum method in order to improve performance and covertness simultaneously. Turbo coding method with 1/3 coding rates is used for channel coding algorithm, and turbo equalization method which iterately exchange probabilistic information between equalizer and decoder is used for receiver side. After optimal threshold value was set in Rake processing, this paper analyzed the performance by varying the number of chips were 8, 16, 32 and the number of bands were from 1 to 4. Through the simulation results, we confirmed that the performance improvement was obtained by increasing the number of bands and chips. 2~3 dB of performance gain was obtained when the number of chips were increased in same number of bands.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.193-196
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• 2000

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz, 5MHz) and different channel environments (rural, urban). For the analysis of smart antenna system, the vector channel model having the spatio-temporal correlation is needed. Hence, the channel is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. A simulation is carried out by dividing several multipaths within one chip into each one and searching the strongest signal. DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.587-590
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• 2001

본 논문에서는 스마트 안테나를 적용하여 서로 다른 대역폭(1.25MHz, 5Mhz)과 서로 다른 환경(rural, urban)에서 W-CDMA 시스템의 성능을 분석하였다. 먼저 스마트 안테나 시스템의 성능을 분석하기 위해서 시·공간 상관특성을 갖는 채널이 필요하다. 이를 위해 시간 정보를 고려하기 위해 시변 선형 필터로 모델링하였고, 공간 정보를 고려하기 위하여 배열 응답 벡터를 삽입하였다. 이 때 공간적으로는 일정량의 각도 퍼짐을 갖는 부-다중경로 성분으로 구성된 한 개의 반사파가 한 방향으로부터만 수신된다고 가정하였다. 또한 한 칩 내에 들어오는 다중 경로 성분을 분리하여 가장 큰 신호 성분만을 찾아내어 원하는 사용자의 신호로 사용하는 방법으로 모의 실험을 실행하였다. 모의실험 결과, 협대역 CDMA를 사용하는 스마트 안테나 시스템보다 광대역 CDMA를 사용하는 스마트 안테나 시스템이 더 나은 성능을 보임을 확인할 수 있었다. 또한 스마트 안테나는 2D-RAKE receiver를 사용했을 때 urban area에서 보다 더 효과적임을 확인할 수 있었다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.79-82
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• 2000

In this paper, the performance of 05-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz, 5MHz) and different channel environments (rural, urban). For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipaths within one chip are distinguished into each one and the strongest signal is selected. DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.42-45
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• 1998

Adaptive array antenas have emerged as a useful technique to enhance the cell capacity of mobile communications. In this research, to analyze the noncoherent CDMA systems employing adaptive array antennas, we modeled the transmitting signal of CDMA systems using M-ary orthogonal modulation. And we induced the conditional probability density function about the decision variable, the output of 2D-RAKE receiver and mean symbol error prabability through statistical analysis about MAI(Multiple Access Interference), SI(Self Interference) and Noise. Also, we analyzed the charateristics of adaptive array antenna for noncoherent CDMA systems using M-ary orthogonal modulation according to the distance between the array elements, doppler frequency and AOS(Angle of Spread).

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1689-1692
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• 2002

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz, 5MHz) and different channel environments (rural, urban). For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time- variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipaths within one chip are distinguished into each one and the strongest signal is selected. DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.83-86
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• 2004

In this paper, the performance of wideband CDMA system with smart antenna is analyzed for different bandwidth(1.25MHz, 2.5MHz, 5MHz) and angular spread at base station. In detail, the spatio-temporal wideband multipath vector channel model is proposed. And the received signals in 2D-RAKE receiver are rigorously analyzed in proposed vector channel model. We consider the effect of correlation between any two elements of antenna array. Several multipahts within one chip are distinguished into each one and the strongest signal is selected as a desired one. As a result, the performance of W-CDMA system with smart antenna in spatio-temporal wideband vector channel has been improved in proportion to the increase of angular spread and bandwidth.