• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.101-106
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• 2019

This paper propose the VSS-FC-MMA algorithm that is possible to improve the equalization performance based on varying step size to the FC-MMA adaptive equalization algorithm in order to reducing the intersymbol interference effect occurred in the nonconstant modulus signal transmission, and improved performance were confirmed. The FC-MMA is possible to improve the convergence speed, and degrades the steady state performance based on the fixed step size and modified dispersion constant considering the level number of signal symbol for obtain the error signal in adaptive equalization compared to MMA. The proposed VSS-FC-MMA uses varying step size and current FC-MMA possible to improve the steady state equalization performance, it was confirmed by computer simulation. For this, the signal recovery capabilities and residual isi, MSE, SER were applied for performance comparison index in the same channel and signal to noise ratio. As a result of computer simulation, the proposed VSS-FC-MMA improve the risidual value in steady state and SER performance than the FC-MMA, but has 1.7 times slow convergence time by using varying step size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.1012-1015
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• 2011

The decision-directed blind equalization algorithm is often used due to its simplicity and good convergence property when the eye pattern is open. However, in a channel where the eye pattern is closed, the decision-directed algorithm is not guaranteed to converge. Hence, a modified Bussgang-type algorithm using a hyperbolic tangent function for zero-memory nonlinear(ZNL) function has been proposed and applied to avoid this problem by Filho et al. But application of this algorithm includes the calculation of hyperbolic tangent function and its derivative or a look-up table which may need a large amount of memory due to channel variations. To reduce the computational and/or hardware complexity of Filho's algorithm, in this paper, an improved method for the decision-directed algorithm is proposed. In the proposed scheme, the ZNL function and its derivative are respectively set to be the original signum function and a narrow rectangular pulse which is an approximation of Dirac delta function. It is shown that the proposed scheme, when it is combined with decision-directed algorithm, reduces the computational complexity drastically while it retains the convergence and steady-state performance of the Filho's algorithm.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.15-22
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• 2007

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye- pattern obtained from algorithm are compared.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.103-108
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• 2020

This paper related with the performance evaluation of mDSE-MMA adaptive equalization algorithm which is possible to reduce the distortion that occurs in nonlinear communication channel like as additive noise, intersymbol interference and fading when transmitting the QAM signal. The DSE-MMA algorithm is possible to reduce the computational load compared to the presently MMA algorithm, it has the degraded equalization performance by this. In order to improve the performance degradation of DSE-MMA, the mDSE-MMA controls the step size according to the existence of arbitrary radius circle of equalizer output is centered at transmitted symbol point. The performance of proposed mDSE-MMA algorithm were compared to present DSE-MMA using the same channel and noise environment by computer simulation. For this, the recoverd signal constellation which is the output of equalizer, residual isi and MD, MSE learning curve which is represents the convergence performance and SER were applied as performance index. As a result of simulation, the mDSE-MMA has more superior to the DSE-MMA in every performance index.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1422-1430
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• 2016

Researches for oceans are limited to military purpose such as underwater sound detection and tracking system. Underwater acoustic communications with low-probability-of-interception (LPI) covert characteristics were received much attention recently. Covert communications are conducted at a low received signal-to-noise ratio to prevent interception or detection by an eavesdropper. This paper proposed optimal covert communication model based on direct sequence spread spectrum for underwater environments. Spread spectrum signals may be used for data transmission on underwater acoustic channels to achieve reliable transmission by suppressing the detrimental effect of interference and self-interference due to jamming and multipath propagation. The characteristics of the underwater acoustic channel present special problems in the design of covert communication systems. To improve performance and probability of interception, we applied BCJR(Bahl, Cocke, Jelinek, Raviv) decoding method and the direct sequence spread spectrum technology in low SNR. Also, we compared the performance between conventional model and proposed model based on turbo equalization by simulation and lake experiment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.105-111
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• 2017

This paper compares the SE-MMA (Signed Error-MMA) and QE-MMA (Quantized Error-MMA) adaptive equalization algorithm in order to compensates the intersymbol interference due to channel in the transmission of spectral efficient nonconstant modulus signal such as 16-QAM. In the currently MMA adaptive equalizer, the error signal is needed for the updating the tap coefficient. The SE-MMA uses the polarity of error signal for reduce the computational operation in that process, the QE-MMA consider the this polarity and finite bit power-of-2 quantized component in that process, so they has different equalization performance. In order to comparing these performance, the computer simulation was performed in the same channel and environment, the output signal constellation of equalizer, residual isi and maximum distortion, MSE, SER were applied. As a result of computer simulation, the QE-MMA have more superior performance than the SE-MMA in every performance index.

• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.295-302
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• 2015

Acoustic channels are characterized by long multipath spreads that cause inter-symbol interference. The way in which this fact influences the design of the receiver structure is considered. To satisfy performance and throughput, we presented consecutive iterative BCJR (Bahl, Cocke, Jelinek, Raviv) equalization to improve the performance and throughput. To achieve low error performance, we resort to powerful BCJR equalization algorithms that iteratively update probabilistic information between inner decoder and outer decoder. Also, to achieve high throughput, we divide long packet into consecutive small packets, and the estimate channel information of previous packets are compensated to next packets. Based on experimental channel response, we confirmed that the performance is improved for long length packet size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1085-1094
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• 1999

In the global system for the mobile communication (GSM) system, the class of training sequences used in a TDMA frame is a preamble sequence with a period of 16 bits for the channel impulse response measurement and the start up equalization during the training period. If the transmitted preamble sequence and the binary sequence in the receiver properly satisfy a condition, this training sequences used for fastly adjusting the tap coefficients and impulse response can be measured by calculating the crosscorrelation function. In this paper, it is used that training sequences have zero values of the autocorrelation at all delays except zero and middle shifts. A comparison of convergence rate, a mathematical approach for fast start-up equalization and correctly channel impulse response measurement are proposed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.61-66
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• 2021

This paper related with the performance comparison of mSE-MMA and mDSE-MMA adaptive equalization algorithm which is possible to reduce the intersymbol interference that occurs in the nonlinear communication channel transmitting 16-QAM signal. This two algorithm is possible to reduce the computational load compared to the current MMA algorithm, it has the degraded equalization performance due to simplified arithmetic in order to applying the mobile communication terminal. In order to improve the performance degradation, they controls the step size according to the existence of arbitrary radius circle of equalizer output compared to transmitted symbol point. The variation of step size according to this principle is applied to the SE-MMA and DSE-MMA, namely mSE-MMA and mDSE-MMA algorithm, the algorithm's performance were compared in the same channel and noise environment by computer simulation. As a result of simulation, the mSE-MMA has more superior to the mDSE-MMA in residual value of every performance index and SER performance, and the vice versa result in convergence speed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.6
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• pp.881-888
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• 1993

A new stabilizing algorithm for the fast transversal filter (FTF) which is known to exhibit a very unstable behavior, due basically to the accumulation in two different ways, we define a emasure counting these at each step of the algorithm in order to reduce the roundoff error. It has been shown that required amount of computation for the proposed algorithm is linearly increased as the order of equalizer and that stability is improved in comparison with the other existing algorithm. It has been shown that the proposed algorithm exhibits a good performance using computer simulation of adaptive equalization for multipath fading channel in urban mobile radio environment.