• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.29-39
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• 1993

For an economical or timely reason, the types of subscriber loops for ISDN basic rate access service will, at least initially, be that of the pre-existing telephone network, that is, 2-wire twisted-pair metallic cable. Therefore, it is important to assess the high-speed digital transmission capability of the 2-wire subscriber loops. In this paper, the impairments such as intersymbol interference, crosstalk, and impulse niose are modeled. And then, symbol error probabilities in terms of SNR in DSL system using ECH and 2B1Q line code are analytically derived and numerically calculated. Also, the relationship between the quality of service required in ISDN subscriber section and the loop parameters is investigated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10A
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• pp.1639-1644
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• 2001

Two decision feedback equalizer structures employing recurrent neural network (RNN) used for non-linear channels with severe intersymbol interference (ISI) and non-linear distortion are proposed in this paper, which skillfully put the traditional decision feedback structure for linear channels equalization into RNN, replace decision feedback signal with training signal in the learning process and adaptively adjust the learning step. Simulative results of the first type of two new equalizer structures have shown that it has better equalization performances than traditional recurrent neural network equalizer (RNNE) under the same condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1787-1802
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• 1996

In this paper, the performance for FH/CPFSK system with limiter-discriminator detection and integrage-and-dump post-detection filtering under thermal noie, partial-band noise jamming and rayleigh fading have been analyzed. The method of hard-decision diversity of which the transmitter repeated L times on different hops for each data symbol in a way to mutigate the effects of the jamming has been applied, and the receiver has been combined the L chips. Also, error-correcting code have been applied for improving performance of system. The thermal noise and partial-band noise jamming, intersymbol interference for all eight of the possible adjacent bit data patterns, and FM noise click for evaluating systems have been considered. Also optimum parameters to improve performance of FH/CPFSK system have been obtained and validities have been proved through computer simulation.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2424-2426
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• 1998

We propose a robust equalization algorithm to improve the performance of airplane flutter casuing dynamic ghosts. The algorithm is an augumentation of the DFE with training sequence(DFE-TS) with the Modified Stop-and-Go Algorithm(MSGA) based on DFE structure, which is called a DFE-TS/MSGA. This will allow the equalizer to switch itself back to blind mode almost instantaneously when drastic and sudden changes in the channel occur. Test results based on the 8-VSB HDTV receiver show that the proposed algorithm is robust against dynamic ghosts and outperforms the conventional DFE-TS in reducing the intersymbol interference.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2467-2469
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• 1998

We examine the performance of high-speed non-directed infrared links using pulse-position modulation (PPM) with trellis-coded modulation (TCM) to mitigate the effects of multipath-induced intersymbol interference(ISI) on such links. Using the measured characteristics of multipath indoor infrared channels, we calculate BER curves and ISI power penalties for maximum-likelihood sequence detection of 8-PPM links using rate-2/3 trellis codes operation at 10 and 30Mb/s. Our results indicate that the suggested decoder of PPM with TCM is a very promising decoder on high-speed non-directed infrared channels.

• ETRI Journal
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• v.29 no.5
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• pp.607-613
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• 2007

Most signal-to-noise ratio (SNR) estimation techniques in digital communication channels derive the SNR estimates solely from samples of the received signal after the matched filter. They are based on symbol SNR and assume perfect synchronization and intersymbol interference (ISI)-free symbols. In severe channel distortion where ISI is significant, the performance of these estimators badly deteriorates. We propose an SNR estimator which can operate on data samples collected at the front-end of a receiver or at the input to the decision device. This will relax the restrictions over channel distortions and help extend the application of SNR estimators beyond system monitoring. The proposed estimator uses the characteristics of the second order moments of the additive white Gaussian noise digital communication channel and a linear predictor based on the modified-covariance algorithm in estimating the SNR value. The performance of the proposed technique is investigated and compared with other in-service SNR estimators in digital communication channels. The simulated performance is also compared to the Cram$\acute{e}$r-Rao bound as derived at the input of the decision circuit.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.2
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• pp.137-146
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• 2002

In order to remove the intersymbol interference(ISI) phenomenon in data transmission channel, the structure and convergence analysis of the improved multiplication free adaptive digital filter(IMADF) is presented. Under conditions of zero-mean, wide-sense stationary and white Gaussian noise, it is shown that this paper analyze the convergence characteristics of the IMADF with a fractionally-spaced equalizer(FSE). In the experimental results, the convergence characteristics of the IMADF algorithm is almost same as the sign algorithm, but is better than the MADF algorithm. Here, this algorithm has useful characteristics when the correlation of the input signal is highly.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.203-209
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• 2012

Visible light communications (VLC) use modern solid-state light-emitting diodes (LEDs) to broadcast information. Emerging white-light LEDs allow the combination of lighting and optical wireless communication in one optical source. In this paper, a new LED lighting design using one-chip-type white LEDs is proposed for efficient illumination and optical wireless communications under the existence of several obstacles. Lighting and communication performance are analyzed to show the effectiveness of the proposed LED lighting. Specifically, the signal-to-noise ratio considering intersymbol interference and the bit-error rate of variable pulse position modulation (VPPM) with dimming control are considered.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1033-1043
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• 1999

We consider an improved multicarrier(MC) CDMA system that combines both DS-CDMA with a concatenated orthogonal/PN spreading sequence and MC modulation. This system incorporates the advantages of DS-CDMA with a concatenated sequence to achieve large user capacity and MC modulation technique to combat the effects of a multipath fading channel and intersymbol interference(ISI). Considering voice activity and imperfect sectorization, the system performance is analysed for the maximal ratio combiner(MRC) under a multicell, multiuser, and multipath Rayleigh/Rician fading channels. The performance of the system is improved much more for the single path fading channel compared to the multipath fading channel. Also the system is shown to have the more improved average bit error rate(BER) over the orthogonal MC-CDMA with the conventional PN sequence.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.115-121
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• 2013

This paper related with the DSE-MMA (Dithered Sign-Error MMA) that is the simplification of computational arithmetic number in blind equalization algorithm in order to compensates the intersymbol interference which occurs the passing the nonlinear communication channel in the presence of the band limit and phase distortion. The SE-MMA algorithm has a merit of H/W implementation for the possible to reduction of computational arithmetic number using the 1 bit quantizer in stead of multiplication in the updating the equalizer tap weight. But it degradates the overall blind equalization algorithm performance by the information loss at the quantization process compare to the MMA. The DSE-MMA which implements the dithered signed-error concepts by using the dither signal before qualtization are added to MMA, then the improved SNR performance which represents the roburstness of equalization algorithm are obtained. It has a concurrently compensation capability of the amplitude and phase distortion due to intersymbol interference like as the SE-MMA and MMA algorithm. The paper uses the equalizer output signal, residual isi, MD, MSE learning curve and SER curve for the performance index of blind equalization algorithm, and the computer simulation were performed in order to compare the SE-MMA and DSE-MMA applying the same performance index. As a result of simulation, the DSE-MMA can improving the roburstness and the value of every performance index after steady state than the SE-MMA, and confirmed that the DSE-MMA has slow convergence speed which meaning the reaching the seady state from initial state of adaptive equalization filter.