• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.31-36
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• 2014

Security of chaos communication system that has characteristic of sensitive initial conditions is superior to digital communication systems, but BER(Bit Error Rate) performance is evaluatied badly. So, studies in order to improve the BER performance is important. existing studies, BER performance of proposed chaos transceiver is possible to improve than the CDSK(Correlation Delay Shift Keying) system because it has characteristic that has very few addition elements like noise signal except for the desired signal. Chaos communication system has many symbols because it spreads according to characteristic of chaos map. Therefore, study that can have the good data rate in chaos communication system is required. Information bits of existing chaos modulation system are modulated as -1 and 1 on the basis of BPSK system. However, instead of BPSK system, if chaos communication system is applied high level modulation systems such as QPSK system and 16QAM system, it is possible to have good data rate because more data are transmitted at a time. In the paper, when QPSK system and 16QAM system are applied to proposed chaos transceiver in existing study, we evaluate the SER(Symbol Error Rate) performance and compare the each performance. Also, when QPSK system and 16QAM system are applied to proposed chaos transceiver, we evaluate the anti-jamming performance of proposed system.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.233-236
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• 2000

본 논문에서는 다중 경로 페이딩에 의한 성능의 손실을 보상하기 위하여 간단한 equal gain combining diversity를 갖는 802.11a 무선 LAN용 OFDM 시스템의 HER 성능을 다중경로 환경 하에서 분석하였다. 모의 실험 결과에 따르면, 다중경로채널에서 전송 파워를 살펴보면, 2branch equal gain combining diversity를 사용한 무선 LAN용 OFDM시스템이 diversity를 사용하지 않는 OFDM 시스템보다 BER 10/sup -3/에서 3㏈ 정도의 이득을 줄 수 있었다. Branch 수를 3개를 사용한 경우에는 BER 10/sup -3/에서 branch 2개를 사용한 경우보다 약 2㏈정도 이득을 줄 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.9
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• pp.491-496
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• 2014

We derive an analytical expression for the bit-error rate (ber) of optimal single user detection (osud) of a binary phase-shift keying (bpsk) signal corrupted by a gaussian cochannel interferer (cci). the channel capacity is also calculated to investigate the ber performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.4
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• pp.415-423
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• 2016

High PAPR (Peak-to-Average Power Ratio) characteristic causes some problems like system performance degradation and OOB (Out-of-Band) power increasement under the HPA (High Power Amplifier) nonlinearity condition. UFMC (Universal Filtered Multi-Carrier) and FBMC (Filter Bank Multi-Carrier) are regarded as 5G(Generation) candidate waveforms. In this paper, we evaluate and analyze performance of these systems with DFT-s (Discrete Fourier Transform Spreading) technique under the nonlinear HPA environment. In this paper, we describe OFDM (Orthogonal Frequency Division Multiplexing), UFMC, FBMC, DFT-s-OFDM, DFT-s-UFMC, and DFT-s-FBMC system, and evaluate BER (Bit Error Rate) performance of these systems. As simulation results, BER performance degradation by HPA nonlinearity of DFT-s-OFDM and DFT-s-UFMC is greatly overcome by DFT spreading technique. However, BER performance degradation by HPA nonlinearity of DFT-s-FBMC system is little overcome.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.2
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• pp.54-61
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• 2000

This paper presents the performance evaluation of channel estimation algorithm using RLS algorithm lot W-CDMA reverse link over Rayleigh fading channels. By obtaining BER(Bit Error Rate) performance through computer simulations, the RLS(Recursive Least Square) algorithm is compared with the existing WMSA(Weighted Averaging)(K=1,3) and constant gain algorithm. The channel structure, modulation and pilot patterns are applied to the ARIB (Association of Radio Industries and Business) and 3GPP (3rd Generation Partnership Project) ITU-R proposal for the IMT-2000. The BER performance of RLS algorithm with linear interpolation is similar to that of WMSA(K=1) and slightly superior to that of constant gain algorithm at low Doppler frequencies. Also, RLS algorithm performance is better than that of the WMSA(K=1,3) and constant gain algorithms about 4dB at BER=2.0$\times$$10^{-2}$ and Doppler frequencies $F_D$=320Hz. With increasing Doppler frequency, therefore, the BER performance of RLS algorithm with linear interpolation is superior to WMSA(K=L.3) and constant rain algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.58-65
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• 2016

Satellite communication is a wide area network (WAN) which provides communication service worldwide. However, the performance of TCP can be seriously degraded in the satellite networks due to limited bandwidth, long round-trip time (RTT) and high bit error rate (BER) over satellite links. In order to improve the performance of TCP, this paper proposes cross-layer Performance Enhancing Proxy (PEP) in digital video broadcasting-return channel via satellite (DVB-RCS) networks. The proposed protocol sets TCP Congestion Window (CWND) size by using satellite resource allocation information exchanged between TCP and the link-layer. we implement PEP testbed based on Linux to evaluate the performance of the proposed protocol. The simulation results show that the proposed protocol performs better than standard TCP both in single and multiple sessions in variant BER, because the proposed protocol sets TCP CWND size by using satellite resource allocation.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.216-222
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• 2004

Frequency selective fading is a limiting factor for transmission rate and performance in high-speed multimedia communications. In this paper, we propose a turbo coded adaptive quadrature amplitude modulation (QAM) system for efficient high-speed transmission. By making use of a user-friendly simulation platform of SPW, the proposed turbo coded adaptive QAM system(TuAQAM) is developed and its performance is evaluated in terms of throughput and BER performance. Two channel models having delay spreads of 700ns and 1400ns are created for the simulations. It is shown that the proposed TuAQAM system provides a performance improvement of approximately 3dB and improved throughput for the channel model whose delay spread is 700ns. Similarly, a performance improvement is also achieved for the channel model whose delay spread is 1400ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1043-1050
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• 2004

In this paper, Phase noise is analyzed and a novel approach of the nonlinear approximation including second order term of phase noise is presented to analyze and quantize system performance. As results, in QPSK-OFDM system, when PLL loop bandwidth is 5.0 Hz, 1.0 kHB, 0.5 kHz respectively, there are about 0.6 dB, 1.0 dB, 1.7 dB SNR penalties at BER=10$\^$-4/ compared with system without phase noise in AWGN channel. In 16QAM modulation, there are about 1.9 dB, 3.2 dB, 6.7 dB SNR penalties at BER=10$\^$-4/ respectively. At QPSK-OFDM system, comparing the previous linear approximation method with our proposed nonlinear approximation method, there is similar BER performance at phase noise variance lower than 0.02, but certain difference occurs as variance increases more than 0.02. Furthermore, analytical BER results closely match with simulation results in the OFDM system employing QPSK and 16qAM modulation. And, BER performance of QPSK-OFDM system is considerably degraded because of the BER error floor if the phase noise variance becomes larger than 0.03.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3342-3360
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• 2014

In this paper, the capacity and BER performance of downlink distributed antenna systems (DAS) with transmit antenna selection and multiple receive antennas are investigated in MIMO composite channel, where path loss, Rayleigh fading and lognormal shadowing are all considered. Based on the performance analysis, using the probability density function (PDF) of the effective SNR and numerical integrations, tightly-approximate closed-form expressions of ergodic capacity and average BER of DAS are derived, respectively. These expressions have more accuracy than the existing expressions, and can match the simulation well. Besides, the outage capacity of DAS is also analyzed, and a tightly-approximate closed-form expression of outage capacity probability is derived. Moreover, a practical iterative algorithm based on Newton's method for finding the outage capacity is proposed. To avoid iterative calculation, another approximate closed-form outage capacity is also derived by utilizing the Gaussian distribution approximation. With these theoretical expressions, the downlink capacity and BER performance of DAS can be effectively evaluated. Simulation results show that the theoretical analysis is valid, and consistent with the corresponding simulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.158-165
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• 2000

In this paper, the transmission channels of L-band and Ka-band multi-media satellite communication systems for the land mobile satellite(LMS) communication service are modeled. Trellis coded(TC) 8PSK is proposed as a power and bandwidth efficient digital transmission scheme for the LMS system, and its error probability performance is analyzed. Block interleaving and deinterleaving are applied to the transmitter and receiver of LMS system respectively in order to compensate for the BER performance degradation of TC-8PSK caused by multipath fading. Viterbi equalizer is also employed in the receiver for channel equalization, and the corresponding BER performance improvement is analyzed.