• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.3
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• pp.53-59
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• 2000

A received signal in mobile communication environments exhibits variation in both amplitude and phase due to the multipath fading. Therefore we analyzed the performance of DS/CDMA(Direct Sequence/code Division Multiple Access) DPSK(Differential Phase Shift Keying) system for the variations of PLL(Phase Locked Loop) gain with Tikhonov probability density function, assuming that the phase difference between transmitter and receiver signals is phase error. As a result, it is discovered that the performance of system could be improved by the control of PLL gain in compared with the DPSK system which does not consider the phase error. If the PLL gain is 1dB, the difference of two systems is 4.8dB and 0.4dB at 7dB. and if 30dB, it coincides. From above, it

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.21-27
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• 2013

This paper proposes an adaptive modulation based incremental hop selection scheme which improves network coverage in half-duplex multi-hop networks. The proposed scheme guarantees wide coverage through the operation of multi-hop network while preventing spectral efficiency loss due to the usage of multiple time phases in the half-duplex protocol. Also, we evaluate the average spectral efficiency performance over Nakagami-m fading channel. The simulation results show that the proposed scheme outperforms the existing schemes and the derived evaluation is valid.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.5
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• pp.1005-1015
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• 2000

In this paper, the performance of Hybrid CDU MFSK system has been analyzed in the environment that narrowband Class-A impulsive noise include Gaussian noise in wireless communication channel and Nakagami fading. The performance of system improved to adopting both of technique MRC diversity and BCH channel coding. The results show that there is substantial degraded in Hybrid CDMA system performance by impulse index is stronger and the fading index is smaller. But also improvement can be obtained when BCH coding techniques are adopted. Additional MRC diversity techniques is more improvement than BCH coding techniques when degraded environment with the low fading index. But BCH coding techniques is more improvement than MRC diversity techniques when fading index has been increased. The Hybrid CDMA MFSK system is incomplete to voice communication standard BER$(10^{-3})$ in Rayleigh fading by independent each adopting techniques BCH coding and MRC diversity. But it's satisfy(improvement can be obtained) to voice communication standard BER in strong impulse noise(24dB over) by adopting techniques BCH coding and MRC diversity at a time. Additional it's a substantial enhancement $(10^{-3})$satisfaction) in fading index (m=3, 22dB) in addition to strong impulse noise and 24dB over with data service standard $(10^{-5})$ BER satisfaction. This result show that there is error performance improved by diversity branch and coding advantage.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.924-944
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• 2014

This paper investigates the power allocation and outage performance of MIMO full-duplex relaying (MFDR), based on orthogonal space-time block codes (OSTBC), in cognitive radio systems. OSTBC transmission is used as a simple means to achieve multi-antenna diversity gain. Cognitive MFDR systems not only have the advantage of increasing spectral efficiency through spectrum sharing, but they can also extend coverage through the use of relays. In cognitive MFDR systems, the primary user experiences interference from the secondary source and relay simultaneously, owing to full duplexing. It is therefore necessary to optimize the transmission powers at the secondary source and relay. In this paper, we propose an optimal power allocation (OPA) scheme based on minimizing the outage probability in cognitive MFDR systems. We also analyse the outage probability of the secondary user in noise-limited and interference-limited environments in Nakagami-m fading channels. Simulation results show that the proposed schemes achieve performance improvements in terms of reducing outage probability.

• 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 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.