scholarly journals The effects of the cross-entropy stopping criterion and quadrature amplitude modulation on iterative turbo decoding performance

2021 ◽  
Vol 23 (3) ◽  
pp. 1557
Author(s):  
Roslina Mohamad ◽  
Mohamad Yusuf Mat Nasir ◽  
Nuzli Mohamad Anas
Keyword(s):  
Amplitude Modulation ◽  
High Speed ◽  
Signal To Noise Ratio ◽  
Quadrature Amplitude Modulation ◽  
Cross Entropy ◽  
Turbo Decoding ◽  
Stopping Criterion ◽  
Stopping Criteria ◽  
High Modulation ◽  
The Cross

One of the most often-used stopping criteria is the cross-entropy stopping criterion (CESC). The CESC can stop turbo decoder iterations early by calculating mutual information improvements while maintaining bit error rate (BER) performance. Most research on iterative turbo decoding stopping criteria has utilised low-modulation methods, such as binary phase-shift keying. However, a high-speed network requires high modulation to transfer data at high speeds. Hence, a high modulation technique needs to be integrated into the CESC to match its speed. Therefore, the present paper investigated and analysed the effects of the CESC and quadrature amplitude modulation (QAM) on iterative turbo decoding. Three thresholds were simulated and tested under four situations: different code rates, different QAM formats, different code generators, and different frame sizes. The results revealed that in most situations, the use of CESC is suitable only when the signal-to-noise ratio (SNR) is high. This is because the CESC significantly reduces the average iteration number (AIN) while maintaining the BER. The CESC can terminate early at a high SNR and save more than 40% AIN compared with the fixed stopping criterion. Meanwhile, at a low SNR, the CESC fails to terminate early, which results in maximum AIN.

An Improved Simplified-CE Stopping Criterion for BICM-ID System

2013 ◽  
Vol 846-847 ◽  
pp. 1262-1265
Author(s):  
Miao Miao Li ◽  
Jian Ping Li
Keyword(s):  
Iterative Decoding ◽  
Rayleigh Fading ◽  
Signal To Noise Ratio ◽  
Coded Modulation ◽  
Cross Entropy ◽  
Stopping Criterion ◽  
Transmission Scheme ◽  
Stopping Criteria ◽  
Bit Interleaved Coded Modulation ◽  
Efficient Transmission

Bit-interleaved coded modulation iterative decoding (BICM-ID) is an excellent bandwidth efficient transmission scheme,which owns remarkable bit-error-rate (BER) performance both in additive Gaussian noise (AWGN) channel and Rayleigh fading channel.But it leads to the increase of computational complexity and decoding delay at the receiver at the same time. In order to decrease the unnecessary iterations ,a variety of the stopping criteria are put forward . This paper presents an improved simplified cross-entropy (CE) stopping criterion based on Simplified-CE criterion, which calculates the value of CE just one time when Signal to Noise Ratio (SNR) is under 2dB to simplified the iterative process. Simulation results show that the improved Simplified-CE criterion can own the least iterative number when the SNR is under 2dB.And when the SNR is from 2.5dB to 4dB, it is about 12% less than CE criterion in the average iterative numbers.

scholarly journals Influence of amplitude and phase imbalance of quadratures on the noise immunity of coherent reception of signals with quadrature amplitude modulation

2021 ◽  
Vol 9 (1) ◽  
pp. 29-37
Author(s):  
G. V. Kulikov ◽  
A. A. Lelyukh
Keyword(s):  
Amplitude Modulation ◽  
High Speed ◽  
Noise Immunity ◽  
Signal To Noise Ratio ◽  
Phase Error ◽  
Quadrature Amplitude Modulation ◽  
Phase Errors ◽  
Wide Range ◽  
Signal Demodulation ◽  
Amplitude And Phase Errors

Quadrature amplitude modulation (QAM) is used for high-speed information transmission in many radio systems and, in particular, in DVB-S and DVB-S2/S2X digital satellite television systems. A receiver included as a part of the transmitting equipment of such systems has a block for the formation of quadrature oscillations used as a reference for signal demodulation. Due to hardware instabilities, amplitude and phase errors may occur, which leads to quadratures imbalance. These inaccuracies cause additional errors in the received signal demodulation. This can significantly degrade the noise immunity of the reception. The paper investigates the influence of amplitude and phase errors in the formation of quadrature oscillations (imbalance of quadratures) on the noise immunity of coherent reception of QAM signals. Using the methods of statistical radio engineering the parameters of the distributions of processes in the receiver are obtained, and the probability of a bit error is estimated. The dependences of the bit error probability on the amplitude unbalance factor, on the phase error of quadrature formation and on signal-to-noise ratio are obtained. It is shown that the amplitude imbalance of the quadratures leads to a significant decrease in the noise immunity of QAM signals reception  at M ≥  16. The acceptable amplitude deviation in this case can be considered to be equal to 5%. At M= 4, the amplitude imbalance in a wide range of values practically does not affect the noise immunity. The phase imbalance of  quadratures  markedly affects the noise immunity of coherent reception of QAM signals. The permissible phase error is no more than 0.05 rad (3 degrees). As the signals positionality increases, this influence also increases.

scholarly journals Influence of phase and clock synchronization errors on the noise immunity of coherent reception of signals with quadrature amplitude modulation

2021 ◽  
Vol 9 (2) ◽  
pp. 35-43
Author(s):  
G. V. Kulikov ◽  
A. A. Lelyukh ◽  
E. V. Batalov
Keyword(s):  
Amplitude Modulation ◽  
High Speed ◽  
Noise Immunity ◽  
Clock Synchronization ◽  
Signal To Noise Ratio ◽  
Phase Error ◽  
Relative Displacement ◽  
Quadrature Amplitude Modulation ◽  
Digital Television ◽  
Synchronization Errors

Signals with quadrature amplitude modulation (QAM) is widely used for high-speed transmission of information in many radio systems and, in particular, in digital television systems. In the receiver, which is part of the transceiver equipment of such systems, there is a block for the formation of reference oscillations and a clock synchronization block. Due to hardware instabilities and propagation conditions, phase and clock errors may occur, which cause additional errors during demodulation of the received signal, and which can significantly impair the noise immunity of the reception. The paper investigates the effect of phase and clock synchronization errors on the noise immunity of coherent reception of QAM signals. Using the methods of statistical radio engineering, the parameters of the distributions of processes in the receiver are obtained and the probability of bit error is estimated. The dependences of the probability of bit error on the magnitude of the phase error in the formation of the reference oscillations and on the relative displacement of the clock moments, as well as on the signal-to-noise ratio, are obtained. It is shown that these errors can greatly reduce the noise immunity of the reception, and with an increase in the positioning of the signals, this effect increases. If we assume that the admissible reception energy loss is 0.5 dB due to each of these errors, then the allowable phase error is from ~3° at M = 4 to ~1° at M = 64, and the allowable clock synchronization error, respectively, is from ~5% at M = 4 to ~2% at M = 64. To provide more stringent requirements for the magnitude of losses, the requirements for the indicated errors increase significantly.

scholarly journals Experimental Demonstration of Special-Shaped 32-Quadrature Amplitude Modulation Constellations for Visible Light Communications

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Xinyue Guo ◽  
Shuangshuang Li ◽  
Yang Guo
Keyword(s):  
Visible Light ◽  
Amplitude Modulation ◽  
High Speed ◽  
Light Emitting Diode ◽  
Rapid Development ◽  
Average Power ◽  
Visible Light Communication ◽  
Quadrature Amplitude Modulation ◽  
Visible Light Communications ◽  
Transmission Distance

With the rapid development of light-emitting diode, visible light communication (VLC) has become a candidate technology for the next generation of high-speed indoor wireless communication. In this paper, we investigate the performance of the 32-quadrature amplitude modulation (32-QAM) constellation shaping schemes for the first time, where two special circular constellations, named Circular (4, 11, 17) and Circular (1, 5, 11, 15), and a triangular constellation are proposed based on the Shannon’s criterion. Theoretical analysis indicates that the triangular constellation scheme has the largest minimum Euclidian distance while the Circular (4, 11, 17) scheme achieves the lowest peak-to-average power ratio (PAPR). Experimental results show that the bit error rate performance is finally decided by the value of PAPR in the VLC system due to the serious nonlinearity of the LED, where the Circular (4, 11, 17) scheme always performs best under the 7% preforward error correction threshold of 3.8 × 10−3 with 62.5Mb/s transmission data rate and 1-meter transmission distance.

A Simplified CE Stopping Criterion for BICM-ID System

2013 ◽  
Vol 433-435 ◽  
pp. 1530-1534
Author(s):  
Miao Miao Li ◽  
Jian Ping Li
Keyword(s):  
Computational Complexity ◽  
Iterative Decoding ◽  
Rayleigh Fading ◽  
Coded Modulation ◽  
Cross Entropy ◽  
Stopping Criterion ◽  
Stopping Criteria ◽  
Adaptive Thresholds ◽  
Simulation Results ◽  
Bit Interleaved Coded Modulation

The iterative process of bit-interleaved coded modulation iterative decoding (BICM-ID) leads to the increase of computational complexity and decoding delay at the receiver, although it owns remarkable bit-error-rate (BER) performance both in additive Gaussian noise (AWGN) channel and Rayleigh fading channel. A variety of the stopping criteria are put forward to reduce the unnecessary iterations in the process. This paper presents a simplified cross-entropy (CE) stopping criterion based on CE criterion, which sets self-adaptive thresholds for different SNRs to decide whether to calculate the CE in the receiver. Simulation results show that the simplified CE criterion can obtain a better performance and lower computational complexity. The iterative number of the simplified CE criterion is about 12.2% less than the conventional CE criterion.

Preliminary Investigation of Gray Coded M–Quadrature Amplitude Modulation in Orthogonal Frequency Division Multiplexing Over Additive White Gaussian Noise Channel

2012 ◽  
Author(s):  
Nor K. Noordin ◽  
Borhanuddin M. Ali ◽  
S. S. Jamuar ◽  
Tharek A. Rahman ◽  
Mahamod B. Ismail
Keyword(s):  
Bit Error Rate ◽  
Amplitude Modulation ◽  
Gaussian Noise ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Quadrature Amplitude Modulation ◽  
Cyclic Prefix ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Signal To Noise

Dalam makalah ini, kami menyelidik prestasi M–Modulasi Amplitud Kuadratur terkod–Gray dalam sistem penghantaran menggunakan skema Multiplexan Pembahagian Frekuensi Ortogonal (OFDM) melalui saluran hingar Gaussian (AWGN). QAM terkod Gray dengan 1 bit ke 8 bit per simbol bersamaan dengan 2–QAM ke 256–QAM dijana dan dimasukkan ke dalam sistem penghantaran OFDM. Prestasi sistem dalam bentuk kadar ralat bit (BER) diberi berbanding saiz jelmaan Fourier pantas (FFT), bilangan sub-pembawa, panjang prefix-kitaran, dan toleransi terhadap nisbah isyarat kepada hingar (SNR) dalam saluran. Dapatan awal menunjukkan hanya modulasi 16–QAM ke bawah boleh diterimapakai untuk mencapai BER sebanyak 10–3 dengan SNR sekurang-kurangnya 20 dB. Peringkat modulasi yang lebih tinggi seperti 256–QAM memerlukan SNR sebanyak 50 dB untuk mencapai hasil BER yang sama. Kajian juga menunjukkan prestasi sistem ini tidak tergugat dengan perubahan saiz FFT mahupun panjang prefix-kitaran yang dimasukkan ke dalam isyarat yang dihantar. Walau bagaimanapun, bilangan sub-pembawa bergantung kepada peringkat QAM yang digunakan untuk suatu nilai SNR yang diberi. Kata kunci: Multiplexan pembahagian frekuensi ortogonal (OFDM), modulasi kuadratur (QAM), pengkodan gray, dan jelmaan fourier pantas In this paper, we investigate the performance of Gray encoding M–Quadrature Amplitude Modulation (QAM) schemes in Orthogonal Frequency Division Multiplexing (OFDM) transmission over added white Gaussian noise (AWGN) channel. Gray–coded QAM with 1 to 8–bit symbol corresponding to 2 to 256–QAM respectively is generated and fed into OFDM transmission system. Performance in terms of bit error rate (BER) is presented against OFDM fast Fourier transform (FFT) size, subcarrier number, length of cyclic prefix, and tolerance to signal to noise ratio of the channel. Preliminary results show that only 16 and lower level–QAM are attractive to achieve a bit error rate (BER) of 10–3 with signal to noise ratio of at least 20 dB. The higher level QAM such as 256–QAM scheme will require at least a SNR of 50 db to achieve similar outcome. The study also shows that the performance of the system is not affected by the number of fft–points used, or the length of cyclic prefix inserted to the transmitted signal. However, the number of subcarriers does depend on the level of QAM used at a given SNR value. Keywords: Orthogonal frequency division multiplexing (OFDM), quadrature amplitude modulation (QAM), gray coding, fast fourier transform (FFT)

scholarly journals Adaptive filtering of harmonic interference when receiving signals with quadrature amplitude modulation.

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
G. V. Kulikov ◽  
◽  
A. A. Lelyukh ◽  
E. N. Grachenko
Keyword(s):  
Adaptive Filtering ◽  
Adaptive Filter ◽  
Amplitude Modulation ◽  
Communication Channel ◽  
Narrow Band ◽  
Signal To Noise Ratio ◽  
Quadrature Amplitude Modulation ◽  
Useful Signal ◽  
Energy Advantage

Quadrature amplitude modulation (QAM) signals are widely used in modern information transmission systems. The quality of the receiver of such signals is significantly reduced if non-fluctuation interference is present in the communication channel. Narrow-band (harmonic) interference with the frequency of the useful signal is especially dangerous. The aim of this work is to develop and study an adaptive algorithm for suppressing such interference when receiving QAM signals. The algorithm is based on a non-recursive digital filter with adjustable weights. It uses known information about the shape of the phase pulse of the signal. The efficiency of the algorithm is investigated by the method of computer simulation. When checking the performance of the algorithm, the spectrum of the signal and noise, the amplitude-frequency characteristic of the adaptive filter and the change in its shape over time were estimated. For 4-QAM and 16-QAM signals, the dependences of the bit error probability on the intensity of harmonic interference and on the signal-to-noise ratio are obtained. It is shown that the adaptive filter effectively suppresses harmonic interference with a relative intensity µ> 0.2 when receiving a 4-QAM signal. The energy advantage is 2 dB or more. When receiving QAM signals with M ≥16, which also have amplitude modulation, the algorithm remains operational, but the efficiency of using this adaptive filter is much lower. The energy advantage does not exceed 0.5 dB.

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