• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.362-374
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• 2000

In this paper, trellis coded 16 QAM Multi-Carrior CDMA system is proposed, Using the equivalent signal-to-noise plus interference Power ratio (SNIR) of Multi-Carrier CDMA system in the reverse link, capacity and BER performance of trellis coded 16 QAM Multi-Carrier CDMA system are analyzed taking into account the number of multi-carrier, the number of multiple access user, the number of SC/MRC diversity branch, and Rician fading parameter in multiuser interference and Rician fading channel. And the capacity and the BER performance of trellis coded 16 QAM Multi-Carrier CDMA system using selection combining (SC) and maximal ratio cabining (MRC) diversity are numerically compared. Obtained results show that the capacity of proposed system depends on the number of multi-carrier. ti is found that the trellis coded 16 QAM Multi-Carrier CDMA system with SC/MRC antenna diversity scheme is efficient to combat multipath fading and to increase the maximum number of users in high speed data communication. With the results of analysis. MRC diversity technique provides the performance fro high speed data communications. Finally, we present a numerical approach to derive the capacity and the BER performance and to find the maximum number of multiple access user for Multi-Carrier system in multiuser interference and Rician fading channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.3 s.333
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• pp.9-14
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• 2005

OFDM(Orthogonal Frequency Division Multiplexing) is widely used in wideband wireless communication systems due to its excellent performance. However, OFDM has a disadvantage of high peak-to-average power ratio and SC-FDE(Single-Carrier with Frequency-Domain Equalization) was introduced to overcome the drawback. SC-FDE is less sensitive to nonlinear power amplifiers than OFDM while its complexity and performance is comparable. This paper proposes a frequency diversity technique for single-antenna BPSK SC-FDE systems using repeated QPSK transmissions with rearranged transmission patterns.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.6
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• pp.757-763
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• 2018

It is very difficult to achieve sufficient data rate and required quality of service due to the time-varying nature of the radio channel and various jammers such as path loss, delay, Doppler, shadowing and interference. Especially, the propagation path between the transmitting antenna and the tracking antenna mounted on the fuselage during the test and evaluation of the projectile system considered in this paper is based on the rapid movement of the projectile, the interference due to multipath fading due to the terrain, The propagation path may be blocked. In order to effectively improve the multipath fading occurring in the wireless communication system, a diversity combiner technique is required. In this paper, to derive the design and improvement schemes for the space diversity combiner technique among the diversity combiner schemes, the BER performance of maximum ratio combining (MRC) and selection combining (SC) In an adaptive SC / MRC diversity combiner that operates with MRC when it is lower than the specified threshold criterion when comparing the SNR between two signals received from the channel and operates with SC at high and combines the two received signals The BER performance of the system was compared and analyzed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1588-1603
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• 2014

In space diversity combining, conventional methods such as maximal ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) are commonly used to improve the output signal-to-noise ratio (SNR) provided that the channel is perfectly estimated at the receiver. However, in practice, channel estimation is often imperfect and this indeed deteriorates the system performance. In this paper, diversity combining techniques based on two evolutionary algorithms, namely genetic algorithm (GA) and particle swarm optimization (PSO) are proposed and compared. Numerical results indicate that the proposed methods outperform the conventional MRC, EGC and SC methods when the channel estimation is imperfect while it shows similar performance as that of MRC when the channel is perfectly estimated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.107-110
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• 2003

본 논문에서는 부분대역간섭 (PBI : Partial Band Interference)이 존재하는 다중경로 페이딩 환경에서 하이브리드 SC/MRC-Lc/L 다이버시티 수신 Multi-Carrier DS-CDMA 시스템의 성능을 알아보고, 광대역 DS-CDMA 시스템과 비교 분석하였다. 결과적으로 Multi-Carrier DS-CDMA 시스템에서 부분대역간섭에 대한 영향은 성능 열화정도가 전체 주파수 대역 중 일부대역에서만 받기 때문에 광대역 DS-CDMA 시스템보다는 심각하지 않았다. 또한, 하이브리드 SC/MRC-Lc/L 다이버시티 수신 Multi-Carrier DS-CDMA 시스템은 입력 다이버시티 가지의 수를 적절히 선택함으로서 시스템의 복잡성과 성능 대 비용을 결정할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.34-42
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• 2000

In this paper, the closed form expression for the average bit error probability(BER) is derived for diversity reception using an L-branch maximal ratio combining(MRC) system which has same fading index and different fading index. Also, the BER to have same average power and Nakagami m-distribution for a generalized selection combining(SC) is derived, whereby the signal with the largest amplitude is selected from the original diversity branches in the channel, the order statistics is applied. Especially, when L is 1 in a selective diversity, the derived expression leads to that of DPSK in which SC is not applied in Nakagami fading. Changing the diversity branch L and fading index m, we compare the performance of MRC and SC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1045-1052
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• 2005

The symbol error probability of M-ary PSK (MPSK) and QAM (MQAM) systems using the branch with the largest signal-to-noise ratio (SNR) at the output of L-branch selection combining (SC) in frequency-nonselective slow Nakagami fading channels with an additive white Gaussian noise (AWGN) is derived theoretically For integer values of the Nakagami fading parameter m, the general formula for evaluating symbol error rate (SER) of MPSK signals in the independent branch diversity system comprises numerical analyses with the integral-form expressions. An exact closed-form SER performance of MQAM signals under the effect of SC diversity via numerical integration is presented. These performance evaluations allow designers to determine M-ary modulation methods for Nakagami fading channels.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.489-493
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• 2004

본 논문에서는 다중경로 페이딩 환경에서의 하이브리드 (Hybrid) SC/MRC-L$_{c}$/L 다이버시티 수신기법과 콘볼루션 부호화 기법을 각각 이용할 때의 광대역 DS-CDMA 시스템의 성능을 구하였다. 다중경로 페이딩으로는 라이시안 페이딩 채널을 가정하였고, 다중사용자간섭의 영향을 함께 분석하였다. 그리고 하이브리드 SC/MRC-L$_{c}$/L 다이버시티 기법과 론볼루션 부호화 기법을 채용하여 성능개선정도를 비교, 분석하였다. 하이브리드 SC/MRC-L$_{c}$/L 수신에서는 각각의 반송파에 대하여 상관을 취하고 상관기 출력들 중에서 가장 큰 신호성분을 L$_{c}$개만큼 선택하여 최대비 합성하며, 콘볼루션 부호화는 다중경로 페이딩 및 다중접속간섭에 의하여 발생된 오류를 정정 및 검출한다. 분석 결과, 콘볼루션 부호화의 경우는 부호이득과 전력제한 시스템의 trade off를 고려한 부호화율의 선택과 하이브리드 SC/MRC-L$_{c}$/L 수신의 경우, 다이버시티 가지의 증가는 선택의 폭이 커져 성능개선은 이루어지지만 가지의 배수가 동일할 경우 가지의 수가 적은 것이 시스템의 복잡성과 경제적인 면에서 효율적임을 알 수 있었다

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.423-429
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• 2019

Recently, a variety of methods for the performance improvement of ultra-high speed wideband wireless transmission systems have been suggested. This paper proposes a space-frequency (SF) block coded single side band (SSB) single carrier (SC)-frequency division multiple access (FDMA) transmission system. In the proposed SSB SC-FDMA system, SF block code is implemented with the complex conjugates, which are formed from discrete Fourier transform (DFT) spreading of pulse amplitude modulation (PAM) signals. As a result, transmit diversity gain can be obtained in the proposed SF block coded SSB SC-FDMA system without any significant increase of the system computational complexity. The simulation result shows that the signal-to-noise power ratio (SNR) performance of the proposed SF block coded SSB SC-FDMA system is approximately 4 dB better than the SNR performance of the conventional SSB SC-FDMA system with single transmit antenna at a symbol error rate (SER) of $10^{-2}$.

• Journal of electromagnetic engineering and science
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• v.7 no.4
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• pp.183-189
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• 2007

When the M-ary signal experiences the Rayleigh fading, the diversity schemes can reduce the effect of fading since the probability that all the signals components will fade simultaneously is reduced considerably. The symbol error probabilities for various M-ary signals, such as MDPSK(M-ary DPSK) and MPSK(M-ary PSK), are mathematically derived for the Selection Combining 2(SC-2) and Selection Combining 3(SC-3) demodulation system which requires a less complex receiver than maximum ratio combining(MRC). The propagation model used in this paper is the frequency-nonselective slow Rayleigh fading channel corrupted by the additive white gaussian noise(AWGN). The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.