• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.530-539
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• 2009

Wireless Relaying is a promising solutions to overcome the channel impairments and provides high data rate coverage that appear for beyond 3G mobile communications. In this paper we present end to end BER performance of dual hop wireless communication systems equipped with multiple Decode and Forward relays over Rayleigh fading channel with the best relay selection. We compare the BER performance of the best relay with the BER performance of single relay. We select the best relay based on the end to end channel conditions. We further calculate the outage probability of the best relay. It is shown that the outage probability of the best relay is equivalent to the outage probability when all relays take part in the transmission. We apply Orthogonal Space Time Block coding(OSTBC) at the source terminal. Numerical and simulation results are presented to verify our analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4C
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• pp.401-407
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• 2010

In this paper, we consider a low-complex companding technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. For the technique, we propose a novel companding function to compensate the problem of the conventional companding functions which are difficult to design complying with system requirements and deteriorate the bit error rate (BER) performance significantly. The proposed scalable companding function can provide an arbitrary value of the maximum PAPR with which the BER performance changes gracefully. In addition, the proposed companding function can be designed readily according to the PAPR and BER performance required by the system and is observed to provide better BER performance than the conventional clipping and $\mu$-low companding schemes under the similar PAPR condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1492-1498
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• 2000

Pilot symbol aided modulation (PSAM) using the conventional sinc interpolation (CSI) achieves nearly the same BER performance as Caver' optimal Wiener interpolation but with much less complexity. The CSI, however, has to use a non-rectangular window function that is applied to the sinc function to smooth out the abrupt truncation of rectangular window. In this paper, we propose the modified sinc interpolation (MSI). With the weighting factor the MSI scheme with no window has almost the same BER performance as the CSI scheme using window, In addition, if we use the MSI with a window its BER performance gets close to that of the theoretical one. We assume the multicarrier QAM system and an optimal frame structure for performance evaluation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.427-438
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• 1998

The bit error rate(BER) performance of Trellis Coded QPSK signal in the presence of cochannel interference (CCI) and Rician fading is investigated. The trellis coded QPSK system adopts Maximum Ratio Combining (MRC) diversity reception and Reed-Solomon code to enhance system performance. Using the derived error probability equation, the error performance of trellis coded QPSK system has been evaluated and shown in figures to discuss as a function of signal power to noise power ratio (SNR), signal power to interference power ratio(SIR), direct to indirect signal power ratio ($K_R$), the number of diversity branch (M), the frame length of Reed-Solomon code (n), the number of error correction symbol (t), and the number of state of trellis encoder. From the results, we know that proposed system is affected by cochannel interference and fading in microcell environment. Also, BER performance of Trellis Coded QPSK system can be improved as increasing either the power of desired signal or the value of SIR. And the BER floor in microcellular system is caused by the cochannel interference and it occurs at high BER when SIR is low. And Reed-Solomon code (n=15, t=2) is more effective to restrain the affection of CCI and fading than MRC diversity reception (M=2).

• Journal of information and communication convergence engineering
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• v.1 no.3
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• pp.115-118
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• 2003

This paper analyzes Bit Error Rate (BER) performance of a wireless communication system using BPSK modulation technique with a smart antenna at base station. The channels under consideration are Additive White Gaussian Noise (AWGN) channel or a slow, flat Rayleigh fading channel with AWGN. Under the assumptions that the MMSE beamformer is used and the time delays of all users are approximately equal, we first analytically derive closed-form expressions for the BER of the desired user. Then, computer simulation is carried out to verify the theoretical results.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3E
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• pp.97-103
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• 2007

We propose a combined STBC (Space Time Block Coding) and AMC (Adaptive Modulation and Coding) in the underwater multipath communication channel. Performance of UAC (underwater acoustic communication) in shallow water is degraded by complicated multipath and reverberation. For this reason, and considering the variability of the ocean channel, we combined STBC and AMC techniques, which are the spatial diversity in a multi-sensor communication system. BER (Bit error rate) of combined STBC and AMC is improved by 5dB when we compare with the BER of a single sensor based system. The proposed system shows a 3dB improvement when we compare it with the BER of the single sensor based system applying the AMC technique only.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.18-25
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• 2020

In the fifth generation (5G) and beyond 5G (B5G) mobile communication, non-orthogonal multiple access (NOMA) has attracted great attention due to higher spectral efficiency and massive connectivity. We investigate the impacts of the channel estimation errors on the bit-error rate (BER) of NOMA, especially with the single-user decoding (SUD) receiver, which does not perform successive interference cancellation (SIC), in contrast to the conventional SIC NOMA scheme. First, an analytical expression of the BER for SUD NOMA with channel estimation errors is derived. Then, it is demonstrated that the BER performance degrades severely up to the power allocation less than about 20%. Additionally, we show that for the fixed power allocation of 10% in such power allocation range, the signal-to-noise (SNR) loss owing to channel estimation errors is about 5 dB. As a consequence, the channel estimation error should be considered for the design of the SUD NOMA scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.557-567
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• 2005

We evaluate the BER performance of OFDMA system for Wibro services in frequency selective Rayleigh fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. In the uplink OFDMA, nonlinear amplifier and frequency offset introduce larger BER degradation than in the downlink. We explain the reason and obtain the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.51-54
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• 1999

It is well known that the OFDM transmission is weak against the frequency offset. We evaluate the BER performance of the OFDM system with guard interval and simple one-tap equalizer bank. For the small frequency offset, the loss in $E_{b}$ $N_{o}$ is about 1㏈ at required BER = 10$^{-5}$ , when the mean value of the second-ray's attenuation coefficient is 0.25 and the normalized frequency offset, which is normalized about OFDM symbol time, is 5%.%.%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.522-527
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• 2012

In this paper, union upper bound on convolutional coded bit error rates (BER) is derived for downlink orthogonal frequency division multiple access (OFDMA) networks. According to the numerical results, for the small network loads, the BER performance with Laplacian decoding metric outperforms the BER performance with Gaussian decoding metric under downlink OFDMA networks with Viterbi decoder.