• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.835-842
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• 2004

In this paper, we have analyzed the MC-DS/CDMA system with input signal synchronized completely through adjustment of the gain in the PLL loop, by using the hybrid SC/MRC-(2/3) technique, which is said to one of the optimal diversity techniques under the multi-path fading environment, assuming that phase error is defined to the phase difference between the received signal from the multi-path and the reference signal in the PLL of the receiver. Also, assuming that the regarded radio channel model for the mobile communication is subject to the Nakagami-m fading channel, we have developed the expressions and performed the simulation under the consideration of various factor, in the MC/DS-CDMA system with the hybrid SC.MRC-(2/3) diversity method, such as the Nakagami fading index(m), $the\;number\;of\;paths\;(L_p),$ the number of hybrid SC.MRC-(2/3) $diversity\;branches\;(L,\;L_c),$ the number of users (K), the number of subcarriers (U), and the gain in the PLL loop. As a result of the simulation, it has been confirmed that the performance improvement of the system can be achieved by adjusting properly the PLL loop in order for the MC/DS-CDMA system with the hybrid SC/MRC-(2/3) diversity method to receive a fully synchronized signal. And the value of the gain in the PLL loop should exceed 7dB in order for the system to receive the signal with prefect synchronization, even though there might be a slight difference according to the values of the fading index and the spread processing gain of the subcarrier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.645-654
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• 2012

In this paper, we consider a two-way relay (TWR) system, where two user nodes exchange their information within two transmission phases, by the help of a relay node adopting physical layer network coding. In the system, two users transmit their binary phase shift keying symbols simultaneously in the first phase, and the relay node decodes the XORed version of two user data and broadcasts it back to two users in the second phase. The performance of the system is analyzed in terms of the average end-to-end symbol error probability in Nakagami-m fading channels, for which a tight upper bound is derived in a closed form to provide an accurate and handy estimate on the performance. The results show that our upper bounds are almost indistinguishable from simulation results for various channel and system configurations. In addition, the optimal relay location and power allocation for various conditions can be obtained quickly with our analysis.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.457-460
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• 2000

The effect of code selection for a multicode DS/CDMA system is evaluated for a high deta rate transmission, The performance is evaluated in terms of bit error and outage probabilities. The multipath fading channel is modeled as a Nakagami-m distribution which has been known to be appropriate to model the multipath fading in urban as well as indoor channels. From simulation results, it is shown that the concatenated sequence of Walsh code and Gold sequence is most promising among many code selections. The considerations in this paper can be applied to the next-generation mobile communication systems such as IMT-2000 which requires high bit rate transmissions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.684-687
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• 2001

본 논문에서는 이동통신 시스템에서 성능 열화의 주요 원인인 주파수 선택성 페이딩과 전자기기에서 발생하는 임펄간 간섭 환경에서 DS/CDMA 시스템의 성능 개선을 정량적으로 분석하였다 시스템으로 고려한 변식은 비동기식 MFSK와 MDPSK를 이용한 MFSK-MBPSK 결합변조 방식이다. 분석 결과, 선택성 페이딩에서 합성변조 시스템에 대하여 E$_{b}$/Nn$_{o}$ =20일 때를 기준으로 한 경우, M$_{f}$ =4, M$_{p}$=2인 경우가 가장 성능이 좋았으며, 그 다음으로 M$_{f}$ =2, M$_{p}$=4인 경우, 그리고 M$_{f}$ =4, M$_{p}$=4인 순서대로 오율 성능이 좋았다. 그리고 MRC 다이버시티 기법 및 부호화 기법을 채용한 경우 효과적으로 시스템 성능의 열화를 보상할 수 있었다. 또한, 합성변조기법을 사용함으로써 강한 임펄스 환경에서도 만족할 만한 시스템 성능을 얻을 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1118-1130
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• 1999

In this paper, error performance of DS/FH CDMA system has been analyzed in a radio channel which is characterized by near-far problem and multi-path fading. The DS/FH CDMA system adopts Maximum Ratio Combining(MRC) diversity and BCH(Bose-Chau dhuri-Hocquenghem) coding techniques to enhance system performance. Using the derived error probability equation, the error performance of DS/FH CDMA system has been evaluated and shown in figures to discuss as a function of PN code length(N), hopping rate(q), number of diversity branch(M), coding rate($\gamma$) and bit energy per noise power ratio ${E_b/N_o}$. The results show that DS/FH system is more effective to restrain the affection of near-far problem and multi-path fading than DS system. And there is a substantial enhancement in performance by employing an MRC diversity or BCH coding techniques. Consequently, we expected that proposed system structure is reliable to the voice communication system in near-far problem and multi-path fading channel.

• Journal of the Korea Society of Computer and Information
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• v.7 no.3
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• pp.128-134
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• 2002

In this paper, the performance on the PN code acquisition of DS/CDMA system was analyzed using the Nakagami-m probability density function considered fading environment. The equations on detection probability, $P_D$ and false alarm probability, $P_{FA}$, decision variables affecting the PN code acquisition time were derived and proved using simulation in order to analyze the performance. In conclusion, It was necessary increasing the gain of PLL for correcting phase errors and improving the acquisition performance of PN code in apply to the rake receiver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.355-362
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• 2003

In this paper, we analyzed the DS/CDMA System with Hybrid SC/MRC diversity, as a method to achieve a good performance by reducing the complexity of system, when PLL gain value was revised a phase gulf among branches to make perfect coherent receive signal. The channel is a multipath Nakagami-m fading channel, we consider user(K), processor gain(N), number of paths(Lp) in DS/CDMA system with hybrid SC/MRC diversity. We found that PLL gain values exist to make perfect coherent receive signal. We verified that DS/CDMA system with Hybrid SC/MRC diversity can improve performance when the proper PLL gain values is used in the system. As a result, we verified that the upper limit of PLL gain value is 5dB to make perfect coherent receive signal in the DS/CDMA system with hybrid SC/MRC diversity.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.5
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• pp.77-84
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• 2000

In this paper, we modelized the multipath fading to Nakagami-m distribution fading channel which can be applied to the extended mobile communication channel environment. We assumed that the phase difference with reference signal happened in the received signal and in the receiver PLL(Phase Locked Loop) is the phase error. To correct the error we propose new RAKE receiver using PLL. In addition, we analyze the performance of DS/SS(Direct Sequence/spread Spectrum) system according to the gain of PLL,$\gamma_n$, the number of RAKE receiver branch L and MIP(Multipath Intensity Profile)'s exponential decay $\delta$. As a result, when the proposed RAKE receiver L Is increased and the $\delta$ is decreased the performance of the system gets better. Futhermore when PLL gain was 30dB, phase is identified. That is when the PLL gain is 30dB, the performance equals with the perfect coherent system's. Therefore, we can correct the phase error by using the proposed RAKE receiver and we proved that the PLL's requested limit gain should be 30dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.439-444
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• 2010

In this paper, we derive and analyze the channel capacity of the spread spectrum watermarking (SSW) system as an information-theoretic point of view in closed-form approximation formula in order to analyze the effect of the wireless multipath/shadowing channel. It is important to analyze the channel capacity to transmit an additive data through existing wireless channel by the SSW system. From the results, we confirm that the channel capacity of the SSW system can be determined by the HWR, WNR, PN length and host sampling frequency. Also, we verified that the variation of the channel capacity when the SSW system applied to Nakagami-m fading and Log-normal shadowing channel. The results of this paper can be applied to general spread spectrum watermarking system.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.4
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• pp.403-408
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• 2002

In this paper, the performance on the PN code acquisition of DS/CDMA system was analyzed using the Nakagami-m probability density function considered fading environment. The equations on detection probability, $P_D$ and false alarm probability, ($P_{FA}$, decision variables affecting the PN code acquisition time were derived and proved using simulation in order to analyze the performance. In conclusion, It was necessary increasing the gain of PLL for correcting phase errors and improving the acquisition performance of PN code in apply to the rake receiver.