• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.20 no.6
• /
• pp.27-32
• /
• 2020

This paper compare the adaptive equalization performance according to the values of adaptive step variation speed for adapting in VS-CCA (Variable Stepsize-Compact Constellation Algorithm) based on nonlinear function function of error signal. The VS-CCA algorithm compacts the 16-QAM nonconstant modulus signal into the 4 groups of 4-QAM constant modulus signal constellation in quadature plane, then the error signal is generated using the constant modulus of transmitted signal statistics. The adaptive equalizer coefficient were updated in order to achieve the minimum cost function by varying step based on the nonlinear function of error signal. In this time, the instantaneous adaptive step is determined according to the value of step variation speed of nonlinear function and the different equalization performance were obtained according to the step variation speed value. The equalizer internal index and external index which represents the robustness of external noise were used for the performance comparison index. As a result of computer simulation, it was confirmed that the value of variation speed less than 1.0 give more superior in every performance index compared to the greater than 1.0 in steady state.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.8A
• /
• pp.1126-1132
• /
• 1999

In this paper, we consider the superposed 16-QAM CDMA system for subband coded (SBC) image transmissions. We divide the SBC image bit into two group according to its significance. First, we investigate the average bit error rate (BER) of the overall system when the significance of bits is ignored. Next, we investigate the optimal signal constellation and processing gain that maximizes the peak signal-to-noise ratio (PSNR) of SBC image, subject to a fixed power and bandwidth constraint. We examine the performance improvement over the conventional equal distane, equal processing gain system, and the equal error protection (EEP) system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.8
• /
• pp.1976-1988
• /
• 1996

This paper describes TCM(trellis coded modulation) schemes using 32VSB signal for digital CATV system. First we design optimum encoder with code rate 4/5 for 32VSB by using one dimenstional signal constellation and obtain 0.75-4.38 dB coding gains over the existing uncoded 16VSB. Second by using two dimensional signal constellation we design TCM encoders with code rate 9/10, which are better in the power efficienty (0.5-2.27 dB) and the transmission rate(12.5%), and we also design TCM encoders which have more coding gains than one dimensional TCM encoders for the larger number of states(more than 8 states).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.4
• /
• pp.669-678
• /
• 1994

This paper presents a new data predistortion technique with memory to compensate for the nonlinearities of high-power amplifiers (HPA`s) in digital radio systems employing QAM signal formats. In contrast with the conventional data predistortion technique which is designed to reduce nonlinearity of memoryless HPA`s, the proposed technique in this paper compensates not only for nonlinear warping of the signal constellation but also for clustering of the signal points caused by transmitter pulse sharping filter with memory. A practical implementation method which can reduce the size of memory at the predistortion stage is described by utilizing symmetry of QAM constellation format and Modulo-4 operation.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.21 no.2
• /
• pp.67-72
• /
• 2021

This paper compare the adative equalization performance of the DSE-MMA (Dithered Signed-Error MMA) and QE-MMA (Quantized-Error MMA) which has a simplifies the computational operation of currently used MMA algorithm. The DSE-MMA possible to improve the rubustness to noise by using the dithered signal consider the polarity of error signal in the multiplication part. In QE-MMA, it use the polarity of error signal after performing the nonlinear power-of-two quantizing operation for easiness of H/W implementation. The same channel environment was applied, and it's performance of the output signal constellation, the residual isi and maximum distortion and MSE that means the convergence characteristics, the SER that means the robustness of external noise of algorithm were compared and evaluated. As a result of computer simulation, the QE-MMA has more good in constellation, residual isi, maximum distortion, MSE performanc than DSE-MMA. In SER, the DSE-MMA has more robust due to dither signal than QE-MMA.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.5
• /
• pp.107-114
• /
• 2012

In this paper, the concerned existing blind equalizer convergence rate and residual inter-symbol interference using constellation reduced and cost function by separation the real part and an imaginary part, the dual structure CR-CMA(constellation Reduction CMA). The CMA methed compensates amplitude but does no compensate phase, On the other hand, The CMA method compensates both the amplitude and the phase but it has the convergence rate problem, and the MCMA method is a way to solve the phase problem of CMA method compensates both the amplitude and the phase after respectively calculating the real part and imaginary part components. Proposal a new method that the dual structure of CR-CMA, the cost function and error function and respectively calculating the real part and imaginary part components can advantages by improving the CMA and the MCMA algorithms so that the amplitude and phase retrieval and constellation reduce the residual ISI and faster convergence rate and performance is good SER (Symbol Error Ratio) was confirmed by computer simulations.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.18 no.1
• /
• pp.85-90
• /
• 2018

This paper compares the equalization algorithm of CR-MMA (Constellation Reduction-Multi Modulus Algorithm) and FC-MMA (Fast Convergence-Multi Modulus Algorithm) for the compensation of channel's distortion in transmitting the 2 dimensional 16-QAM signals. The CR-MMA adaptive equalizer use the error signal by reduce the nonconstant modulus signal to constant modulus signal in order to updates the tap coefficient, and the FC-MMA adptive equalizer use the error signal applying the modified dispersion constant considering the number of symbol level instead of signal point reduction. These two algorithm are known to its superior to the convergence characteristic among the MMA series equalizer. In this paper, the other equalization performance including the convergence characteristic was compared by computer simulation. As a result of computer simulation, FC-MMA has more good performance in the residual isi, maximum distortion and SER performance than CR-MMA, but not in convergence speed.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.2632-2635
• /
• 2003

This paper designs a software signal generator for the new GPS L2 civil signal. The CM/CL code and the message structure of L2CS described in GPS ICD PPIRN-200C-007 are used in designing the signal generator. The output of the GPS signal generator is designed as the sampled IF data with the sampling frequency 5.7MHz and stored in the binary data format. By analyzing both the spectrum characteristics of the output signal and the correlation properties of the CM/CL code, the validation of the designed GPS signal generator is shown. It should be mentioned that the modeling of the GPS satellite constellation and the error sources remains for implementing the software space segment of GPS.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.3
• /
• pp.87-92
• /
• 2017

This paper compares the equalization algorithm of CR-MMA (Constellation Reduction-Multi Modulus Algorithm) and RMMA (Region based Multi Modulus Algorithm) for the compensation of channel's distortion in nonconstant modulus signal. In order to obtain the error signal for adaptive equalization, every signal points are reduced to the constant modulus signal in CR-MMA and every signal points are separated into the 4 regions, then the reductions are performed based on this region in RMMA. These two algorithm based on the reduction principle such as in order to updating the tap coefficient in the adaptive equalization, it has different equalization performance. The computer simulation was performed in order to compare the each equalization performance in this paper. As a result of computer simulation, RMMA has more good performance in the residual isi, maximum distortion and SER performance than CR-MMA, but not in convergence speed.

• Journal of Advanced Navigation Technology
• /
• v.16 no.6
• /
• pp.975-981
• /
• 2012

The SNR estimation performance of hierarchical 16QAM system, which is adopted to simultaneous transmission or efficient image transmission system, is analyzed. Hierarchical 16QAM is modulation system which has different constellation shape from conventional QAM and can provide users with high quality and low quality of data services simultaneously by controlling hierarchical modulation parameter. Assuming AWGN channel, SNR estimation performance characteristics are investigated considering hierarchical modulation parameter and type of constellation points. From simulation results, it is found that constellation point showing superior SNR estimation performance relative to other points is exist. Also, it is known that according to hierarchical modulation parameter, SNR estimation range with more accurate estimation performance is divided.