• 한국통신학회논문지
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• 제31권12C호
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• pp.1150-1156
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• 2006

본 논문에서는 $M\geq3$이고 $p\equiv{\pm}1$ mod M인 경우에 대해서 주기가 $p^m-1$인 M진 Sidel'nikov 수열의 $F_p$ 상에서의 선형복잡도의 하계와 1-오류 선형복잡도의 상계를 유도한다. 특히 $m\geq4$이고 $p\equiv-1$ mod 3인 경우에는 3진 Sidel'nikov 수열의 정확한 1-오류 선형복잡도를 계산한다. 이 결과들을 바탕으로 선형복잡도와 1-오류 선형복잡도의 주기에 대한 비율의 근사적 특성을 제시한다.

• Journal of Communications and Networks
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• 제5권4호
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• pp.365-373
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• 2003

This paper investigates the performance of M-ary pulse position modulation (PPM) multiuser ultra-wideband (UWB) communication systems in terms of symbol error rate (SER) over fading and additive white Gaussian noise (AWGN) channel. Based on Gaussian approximation for the multiple access interference, an expression for the signal-to-noise ratio (SNR) is derived for the UWB system. This expression is used to derive exact SER expressions for coherent UWB receivers. The effect of pulse selection on the SER of multiuser UWB system is studied. In addition to rectangular pulse, the 2nd derivative Gaussian waveform and Rayleigh pulses were considered. We show that the system capacity and/or SER performance can be significantly increased by using the monocycle pulse in fading channels.

• Journal of electromagnetic engineering and science
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• 제4권4호
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• pp.190-196
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• 2004

An alternative solution to the problem of obtaining acceptable performances on a fading channel is the diversity technique, which is widely used to combat the fading effects of time-variant channels. The symbol error probability of M-ary DPSK(MDPSK), PSK(MPSK) and QAM(MQAM) systems using 2 branches from the branch with the largest signal-to-noise ratio(SNR) at the output of L-branch selection combining(SC), i.e., SC2 in frequency- nonselective slow Nakagami fading channels with an additive white Gaussian noise(AWGN) is derived theoretically. These performance evaluations allow designers to determine M-ary modulation methods for Nakagami fading channels.

• Journal of electromagnetic engineering and science
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• 제7권1호
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• pp.35-41
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• 2007

An alternative solution to the problem of obtaining acceptable performances on a fading channel is the diversity technique, which is widely used to combat the fading effects of time-variant channels. The symbol error probability of M-ary DPSK (MDPSK), PSK (MPSK) and QAM (MQAM) systems using 2 branches from the branch with the largest signal-to-noise ratio(SNR) at the output of L-branch selection combining(SC), i.e., SC2 in frequency-nonselective slow Nakagami fading channels with an additive white Gaussian noise(AWGN) is derived theoretically. These performance evaluations allow designers to determine M-ary modulation methods against Nakagami fading channels.

• 한국통신학회논문지
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• 제23권5호
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• pp.1291-1298
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• 1998

In this paper, a simple algorithm for detection of timing error of a synchronous, band-limited, multi-level data stream is proposed. The proposed algorithm can be applied to multi-level PAM, M-ary PSK, or M-ary QAM. The proposed algorithm for M-ary PSK requires only two samples per symbol for its operation, and it is based on the concept of transition logic table and transition level table. In orer to prove the steady-state operation of the proposed algorithm, its performance is evaluated and compared to BECM by Monte Carlo simulation method under Gaussian noise and fading noise channel environments. The comparison results confirm that the perforance of proposed algorithm is superior to that of BECM in jitter characteristics.

• 한국정보통신학회논문지
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• 제9권2호
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• pp.247-252
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• 2005

본 논문에서는 고속 광대역의 정보신호를 다중경로 페이딩 환경에서 효율적으로 전송하기 위한 M-ary QAM OFDM 전송 시스템을 제안하고 반송파의 주파수 옵셋이 발생하는 동기오차가 수신시스템에 미치는 영향으로 인한 수신 성능을 분석하였다. 결론적으로, 지상 디지털 방송을 위해서 검토한 SP방식 프래임 구성의 64QAM OFDM의 비트 오율 이론과 시뮬레이션에 의한 검토를 하여 이의 당위성을 확인하였다.

• 한국통신학회논문지
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• 제31권1C호
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• pp.1-7
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• 2006

이 논문에서는, 약한 다진 신호에 알맞도록 1부에서 제안한 검파기준을 바탕으로 간섭이 충격성일 때 초광대역 다중접속 시스템에 알맞은 검파 기법을 살펴본다. 제안한 검파기는 최대 비슷함 검파기준을 바탕으로 한 최적 검파기와 견주어 볼 때 얼개가 더 간단하고 성능이 거의 같다. 한편, 간섭이 충격성일 때, 제안한 검파기는 정규 환경에 최적화된 검파기보다 성능이 더 좋다는 것도 보인다.

• Journal of electromagnetic engineering and science
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• 제7권3호
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• pp.109-115
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• 2007

The performances of M-ary PSK(MPSK) systems using L-branch maximum ratio combining(MRC) diversity reception in frequency-nonselective slow Rician fading channels are derived theoretically. Especially we investigate the effect of number of symbols on the difference between the approximation to bit error probability and the exact bit error rate(BER) in evaluating the performance of MPSK signals through numerical analyses. On the other hand, when M-ary DPSK(MDPSK) signals experience the Rician fading channels, the general formula for evaluating BER of MDPSK signals in the independent branch diversity system is presented using the integral-form expressions.

• ETRI Journal
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• 제25권4호
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• pp.231-237
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• 2003

We derive and analyze the exact closed-form expression for the average bit error probability (BEP) of M-ary square quadrature amplitude modulation (QAM) for diversity reception in frequency-nonselective Nakagami fading. A maximal ratio combining (MRC) diversity technique with independent or correlated fading cases are considered. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The presented new expressions offer a convenient way to evaluate the performance of M-ary square QAM with an MRC diversity combiner for various cases of practical interest.

• 전자공학회논문지C
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• 제35C권1호
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• pp.42-54
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• 1998

For decreasing intersymbol interference (ISI) due to band-limited channels in digitalcommunication, the uses of equalization techniques are necessary. Among the useful adaptive equalization techniques, because of their ease of implementation and nonlinear capabilites, the neural networks have been used as an alternative for effectively dealing with the channel distortion. In this paepr, a complex-valued multilayer percepron is proposed as a nonlinear adaptive equalizer. After the important properties that a suitable complex-valued activation function must possess are discussed, a new complex-valued activation function is developed for the proposed schemes to deal with M-ary QAM signals of any constellation sizes. It has been further proven that by the nonlinear transformation of the proposed function, the correlation coefficient between the real and imaginary parts of input data decreases when they are jointly Gaussian random variables. Lastly, the effectiveness of the proposed scheme is demonstrated by simulations. The proposed scheme provides, compared with the linear equalizer using the least mean squares (LMS) algorith, an interesting improvement concerning Bit Error Rate (BER) when channel distortions are nonlinear.