• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1074-1084
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• 1999

In this paper the bit error probability of noncoherent M-ary FSK system is derived from the probability density function of the envelope of the received signal over a frequency-nonselective slowly m-distributed Nakagami fading channel. Also, the performance of coherent M-ray FSK system is theoretically analyzed, using union bound over the similar fading channel. Then we compare uncoded performance results for M-ary FSK and DPSK signals in Nakagami fading channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.643-652
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• 2000

In this paper, we analyze the BER performance of OFDM/QPSK system in frequency selective Rayleigh fading channel with impulsive noise and improve its performance by adopting convolutional coding. When the channel delay time is shorter than the guard band, the OFDM/QPSK system shows a good BER performance while, when the channel delay time becomes longer than the guard band, its BER performance is abruptly degraded. Moreover, when the transmitted signal is contaminated by a strong impulsive noise in the channel, the BER performance falls to about $10^{-1}$. Also, without channel coding technique, the system doesn't meet even the voice service requirement while it meets the data service requirement with convolutional coding in frequency selective Rayleigh fading channel with impulsive noise.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1187-1194
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• 1999

In general wireless mobile channel is modeled as complex random processes having a narrowband spectrum. In this paper, a real-time feneration of fading signals using a DSP chip is described. Real-time simulator is designed so that simulation parameters such as mobile terminal speed, carrier frequency, power ratio of line-of-sight component versus multipath, and variance of received power can be chosen in the window. Design algorithms for the generation of ideal fading signals with a minimum DSP computation and trade-offs are investigated. The accuracy of the statistical characteristics is verified through the comparison of measured results with the theoretical prediction.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1161-1168
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• 2002

In this paper, the throughput performance of an ARQ scheme is analyzed with noisy feedback channel, in order to exactly analysis for performance of an ARQ scheme. An ARQ mechanism is presented by state diagram, and the throughput of an ARQ scheme is mathematically derived using generation function for a signal flow graph. The channel is modeled by the Nakagami-m fading channel which is distributed over far and wide, and the throughput performance of an ARQ scheme, which is applied in BPSK and BFSK systems, according to feedback gain and fading index m is analyzed through computer simulation. In the results, It is shown conformed that the throughput of an ARQ scheme decreased according to the increase of the noise for feedback channel, but it increased according to the increase of the feedback gain and fading index m. Also, it is shown that the throughput of an ARQ scheme using BPSK system is superior to BFSK system because of the difference of bit error probability between BPSK and BFSK systems.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.63-71
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• 2005

This paper proposes the channel estimation method robust to severe frequency selective fading channels in O%M system using wide bandwidth for the high data rate transmission. DDCE, which uses data between the high correlated symbols, is usually used for channel estimation in the slow fading channels. DDCE can get high gains in the non-selective channels. As the bandwidth of system gets wider, it becomes more severe frequency selective fading environments so that the reliability of data becomes lower and error flow is occurred. FE method, this paper proposed, uses the relation between sub-carriers of OFDM in frequency selective fading channels so FE method gets some gains by adapting the power value at a target frequency to the mean value of channel estimated values of adjacent sub-carriers. Because FE uses only preamble unlike DDCE using data, it is independent of data rate related to the reliability of data and the number of multipath. Consequently, FE can obtain considerable gains in the wideband systems where the errorflow of DDCE is occurred, and FE is applicable to frequency selective fading environments.

• The Journal of the Acoustical Society of Korea
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• v.25 no.8
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• pp.356-361
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• 2006

We present the performance of differential space-time block decoders. which does not require the channel state information. We suggest the structure of the multiple blocks differential space time decoders. which does not require the channel state information, and analyze the Performances. In quasi-static flat fading channels. the Performance of multiple blocks differential detection (MD-STC) outperforms that of 2 blocks(D-STC) by 1.5dB. But in the time-selective fading channels due to Doppler frequency $(f_d)$, the performance of MD-STC degrades as the vehicular speed is greater than 200km/hr in 802.16e systems, where the data transmission rate is 144kbps.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.61-70
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• 1996

M-ary differential phase shift keying(DPSK)is a bandwidth efficient digital modulation technique and recently has attracted increased attention in mobile satellite communication application where the available radio bandwidth is limited. Coherent detection offers good BER performance in AWGN channel. However, it requires long acquisition times in fading environment. In this paper, we analyze the BER performance of M-ary DPSK signal using the Multiple Differ- ential Feedback Detection(MDFD) technique in Rician fading and shadowed Rician fading channel. MDFD is an efficient scheme to decrease the performance gap between differential and coherent reception by increasing the complexity of the conventional differential receiver to some extent. Compared to the multiple symbol maximum likelihood detection technique, the multiple differential feedback detection technique has a much simpler structure for hardware implementation. Espe- cially, this technique has application to land mobile satellite channel which can vary in time and space between AWGN and rapidly fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8C
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• pp.754-761
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• 2005

We derive and analyze a bit error rate(BER) expression of a Gray coded rectangular QAM(R-QAM) signal with maximal ratio combining diversity(MRC) reception over Nakagami-n(Rician) fading channels. The derived result is provided in terms of the Whittaker function and the confluent hypergeometric function. In addition, by performance comparison with M-PSK, we see the Nakagami-n fading channel characteristics. Because the derived expression is general, it can readily allow numerical e·valuation for various cases of practical interest such as line-of-sight (LOS) or satellite communication channel analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.6
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• pp.855-865
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• 1999

This paper presents the improvement of BER performance using fading compensation method for 16 QAM-TCM to reduce the effects of multi-path fading in mobile radio environments. We propose the multi-pilot symbol aided fading compensation technique using Gausian interpolation method for inter-symbol interference or fading distortion occured in frequency selective fading channel. The proposed system is combined coding and modulation scheme for improving the reliability of a digital transmission system without increasing the transmitted power or the required bandwidth. In the fading compensation, the pilot symbols from a known sequence is multiplexed into the data symbols at regular intervals to from a frames for transmission. And we use a modified bit reversal block interleaver to randomize burst errors. The results show that significant improvements in the bit-error rate performances can be achieved by the proposed techniques.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.265-267
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• 2013

본 논문에서는 멀티 셀 셀룰러 네트워크에서 채널 환경에 따른 스케줄링 알고리듬의 성능을 평가한다. 무선 통신 환경에서 대표적인 채널모델인 가우시안 채널, 레일리 페이딩 채널, SCME(Spatial Channel Model Extended) 채널 모델에 PF(Proportional Fair)와 MR(Maximum Rate) 스케줄링 기법을 적용했을 때, 시스템 성능을 평가하고 비교한다. 기지국에서 송신된 신호는 채널을 통과하며 변화하고 이는 채널 모델에 따라 달라진다. 채널 모델에 따른 스케줄링 알고리듬 성능 평가 결과 가우시안 채널모델과 레일리 페이딩 채널모델 SCME보다 좋은 성능을 보인다.