Quadrature Amplitude Modulation Systems Research Articles

Partial transmit sequence based on discrete particle swarm optimization with threshold about PAPR reduction in FBMC/OQAM system

Partial transmit sequence (PTS) is an effective method to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) system, but it is not suitable for the filter bank multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) system because of the overlapping structure of FBMC/OQAM signals. And PTS needs the traversal method to search for the optimal solution, which will increase the complexity of the system. To overcome this shortcoming, a PTS based on discrete particle swarm optimization with threshold (PTS-DPSO-TH) is proposed and applied to FBMC/OQAM system in this paper. PTS-DPSO-TH uses discrete particle swarm optimization (DPSO) to search for the optimal solution, effectively reducing the excessively high PAPR of the FBMC/OQAM system and avoiding the increase of system complexity. Secondly, the threshold is introduced to decrease the number of iterations and further reduce the system's complexity on the premise of guaranteeing the performance of PAPR reduction. Furthermore, through simulation, the effects of multiple parameters on PAPR reduction performance of PTS-DPSO-TH are compared and analysed.

Joint Symbol Rate-Modulation Format Identification and OSNR Estimation Using Random Forest Based Ensemble Learning for Intermediate Nodes

In this paper, a novel joint symbol rate-modulation format identification (SR-MFI) and optical signal-to-noise ratio (OSNR) estimation scheme using the low-bandwidth coherent detecting and random forest (RF)-based ensemble learning is proposed for intermediate nodes in the flexible dense wavelength division multiplexing (F-DWDM) networks. By leveraging low-bandwidth coherent detecting with small bulk wavelength scanning, no chromatic dispersion compensation and low-complexity RF, the proposed scheme could serve as a reduced-complexity and cost-effective option to realize joint SR-MFI and OSNR estimation at intermediate nodes in F-DWDM networks. To verify the feasibility of the proposed scheme, the comprehensive simulations of 8/16 GBaud polarization division multiplexing (PDM)-4/16/32/64 quadrature amplitude modulation (QAM) systems are conducted. The simulation results show that the identification accuracy of SR-MFI reaches 100% and the mean absolute error of OSNR estimation is within 1 dB. Moreover, the proposed monitoring scheme is verified by 8/16 GBaud PDM-4/16/32QAM coherent transmission experiments.

A low complexity nonlinearity impairment compensation scheme assisted by label propagation algorithm

In this paper, we firstly applied label propagation algorithm (LPA) to coherent optical communication system for nonlinear impairment compensation (NLC), which could exploit the relationship among constellation points to segment the community with only very small amount of label data to predict the label situation on most test data. The effectiveness of the proposed scheme was verified through 28 GBaud polarization division multiplexing (PDM)-16 quadrature amplitude modulation (QAM), PDM-32QAM and PDM-64QAM simulation system. By analyzing the simulation results, we obtained the best propagation coefficient α, which demonstrated that the proposed scheme could effectively make nonlinear decision on received symbols and compensate signal impairment caused by Kerr nonlinear effect and amplified spontaneous emission (ASE) noise, showing a strong robustness and generalization to variations of the transmission environment under different modulation formats, transmission distances, launch power and channel numbers. Then, the proposed scheme was further studied by 20 GBaud PDM-16QAM long-haul transmission experiments. The results demonstrated that the proposed scheme required no training process and exhibited optimistic compensation performance to the coherent optical communication system with nonlinear impairments. Finally, we analyzed computational complexity of the LPA-assisted NLC scheme in detail, which was O(m*N).

Cyclic Shift Based Tone Reservation PAPR Reduction Scheme with Embedding Side Information for FBMC-OQAM Systems

The tone reservation (TR) scheme is an attractive method to reduce peak-to-average power ratio (PAPR) in the filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) systems. However, the high PAPR of FBMC signal will severely degrades system performance. To address this issue, a cyclic shift based TR (CS-TR) scheme with embedding side information (SI) is proposed to reduce the PAPR of FBMC signals. At the transmitter, four candidate signals are first generated based on cyclic shift of the output of inverse discrete Fourier transform (IDFT), and the SI of the selected signal with minimum peak power among the four candidate signals is embedded in sparse symbols with quadrature phase-shift keying constellation. Then, the TR weighted by optimal scaling factor is employed to further reduce PAPR of the selected signal. At the receiver, a reliable SI detector is presented by determining the phase rotation of SI embedding symbols, and the transmitted data blocks can be correctly demodulated according to the detected SI. Simulation results show that the proposed scheme significantly outperforms the existing TR schemes in both PAPR reduction and bit error rate (BER) performances. In addition, the proposed scheme with detected SI can achieve the same BER performance compared to the one with perfect SI.

A deep learning‐based HARQ chase combining for FBMC‐OQAM systems

SummaryHybrid automatic repeat request (HARQ) is a promising link adaptation technique to ensure reliable data transmission in future communication systems. However, it can severely suffer from high distortions, nonlinearities, and interferences caused by the propagation environment. In this paper, we propose an efficient HARQ chase combining (HARQ‐CC) for filter bank multicarrier with offset quadrature amplitude modulation (FBMC‐OQAM) systems using deep learning to combat channel impairments. We model the HARQ‐CC system as a fuzzy inference system that deploys a deep neural network tool to detect the transmitted data packets. Simulation results prove that the proposed approach outperforms the conventional HARQ‐CC method with regard to block error rate (BLER) and root mean square error (RMSE).

Mitigation of nonlinear phase noise in single-channel coherent 16-QAM systems employing logistic regression

We propose and analyze a classifier based on logistic regression (LR) to mitigate the impact of nonlinear phase noise (NPN) caused by Kerr-induced self-phase-modulation in digital coherent systems with single-channel unrepeated links. Simulation results reveal that the proposed approach reduces the bit error ratio (BER) in a 100-km-long 16 quadrature amplitude modulation (16-QAM) system operating at 56-Gbps. Thus, the BER is reduced from 6.88 × 10−4 when using maximum likelihood to 4.27 × 10−4 after applying the LR-based classification, representing an increase of 0.36 dB in the effective Q-factor. This performance enhancement is achieved with only 624 operations per symbol, which can be easily parallelized into 16 lines of 39 operations.

Non-Data-Aided Symbol Rate Estimation for a Low Roll-Off Factor Nyquist WDM Signal

Nyquist signals with low roll-off factors pose a challenge for non-data-aided blind symbol rate estimation problems in long-haul applications. We adopted the nonlinear least squares (NLS) approach to estimate the symbol rate of low roll-off factor signals. This method tolerates chromatic dispersion and additive Gaussian noise. In addition, this method can operate below two samples per symbol, thus enabling low-power-consumption receivers. Simulation and experimental results show that the mean squared error is below $10^{-4}$ with only 3000 samples needed for polarization-division-multiplexed (PDM) quadrature phase-shift keying (QPSK) or quadrature amplitude modulation (QAM) systems with a roll-off factor below 0.1 for an optical signal-to-noise ratio greater than 12 dB. Compared with the maximum likelihood estimation (MLE) method, our proposed method has a more robust performance under low roll-off factor signals and in low-sampling-rate scenarios. The mean squared error remains the same for a nominal symbol rate (i.e., the ratio of the symbol rate to the sampling rate, also widely known as oversampling rate) ranging from 0.1 to 0.9.

Nonlinear/dispersion compensation in dual polarization 128-QAM system incorporating optical backpropagation

Abstract In order to cater long distance optical network units (subscribers), optical networks with prolonged reach are needed. In this study, an optical back propagation (OBP) dual polarization (DP)-128 QAM-based system is proposed to cope with nonlinear impairments in wavelength division multiplexing (WDM) systems. In pre, post and symmetrical configurations, the OBP module consisting of the optical phase conjugator (OPC), Raman fiber amplifier (RFA) and erbium doped fiber amplifier (EDFAs) is examined. Using dispersion compensation fiber (DCF) as RFA with dual directional pumping, ideal OBP conditions are simulated. DP-128 quadrature amplitude modulation (QAM) system is proposed with symmetrical OBP and compared with single channel digital back propagation (DBP), wideband DBP, pre OBP-forward pumping, pre OBP with backward pumping, pre OBP with dual directional pumping, post OBP with dual directional pumping. It is observed that symmetrical OBP configuration with dual direction pumping provide enhanced results and successfully cover 6500 km at bit error rate (BER) 10−3.

New scheme for PAPR reduction in FBMC-OQAM systems based on combining TR and deep clipping techniques

Filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) system is a very efficient multicarrier modulation technique for 5G, but it suffers as all multicarriers designs from large peak-to-average power ratio (PAPR). Tone reservation (TR) is a method designed to solve this problem by reserving several subcarriers called tones in the frequency domain to generate a cancellation signal in the time domain to eliminate high peaks. In this paper, we suggest a serial combination of tone reservation (TR) method with an enhanced version of clipping called deep clipping (DC) method (TR&DC) to enhance the peaks (PAPR) mitigation in FBMC-OQAM signal model without significantly impacting the quality of transmission. Numerical results and analysis show that the new TR&DC approach allows better overall performance and offers remarkable gain in term of PAPR mitigation than the TR method, with similar BER performance to TR over additive white gaussian noise channel and Rapp HPA model.

Channel Estimation Approach with Low Pilot Overhead in FBMC/OQAM Systems

In filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) systems, a large pilot overhead is required due to the existence of the imaginary interference. In this paper, we present an approach to reduce the pilot overhead of channel estimation. A part of pilot overhead is used for transmitting data, and compensating symbols are required and designed to remove the imaginary interference. It is worthwhile to point out that the power of compensating symbols can be helpful for data recovery; hence, the proposed approach decreases the overhead of pilots significantly without the cost of additional pilot energy. In addition, the proposed scheme is extended into multiple input multiple output systems without the performance loss. Compared with the conventional preamble consisting of 3 columns symbols, the pilot overhead is equivalent to 2 column symbols in the proposed preamble. To verify the proposed preamble, numerical simulations are carried out with respects to bit error ratio.

Transmission of a 112-Gbit/s 16-QAM over a 1440-km SSMF with parallel Kramers-Kronig receivers enabled by an overlap approach and bandwidth compensation.

We investigate the parallelized performance of the conventional Kramers-Kronig (KK) and without the digital up-sampling KK (WDU-KK) receivers in a 112-Gbit/s 16-ary quadrature amplitude modulation (16-QAM) system over a 1440-km standard single-mode fiber (SSMF). A joint overlap approach and bandwidth compensation filter (OLA-BC) architecture is presented to mitigate the edge effect caused by the Hilbert transform and the Gibbs phenomenon induced by the FIR filter, respectively. Moreover, the computational complexity of the OLA-BC based parallelized KK/WDU-KK receiver is also discussed. Parallelized KK/WDU-KK receivers based on the presented OLA-BC architecture can effectively mitigate the edge effect and the Gibbs phenomenon together with more than two orders of magnitude improvement in terms of bit-error-ratio (BER) compared with parallelized KK/WDU-KK receivers without OLA-BC receivers in back-to-back (B2B) case. Finally, we successfully transmit the 16-QAM signals over 960-km SSMF with a BER lower than 7% hard-decision forward error correction (HD-FEC) threshold (3.8 × 10-3) and 1440-km SSMF with a BER lower than 20% soft-decision FEC (SD-FEC) threshold (2 × 10-2).

Modulation Format Identification Using Graph-Based 2D Stokes Plane Analysis for Elastic Optical Network

We propose a graph-based modulation format identification (MFI) scheme for elastic optical network (EON), which exploits the trajectory information of the adjacent received symbols to identify six commonly-used modulation formats signals. A uniform grid is constructed in the first quadrant of two-dimensional (2D) Stokes plane to capture the received symbols sequence, and then the corresponding trajectory information is converted into the adjacent matrix via graph theory. The eigenvector associated with the largest eigenvalue of the adjacent matrix is selected as the discriminated-feature of the corresponding modulation format signal. Subsequently, we employ cosine similarity algorithm to obtain the modulation format of the unknown signal by analyzing the angle between the discriminated-features of the canonical modulation formats signals and the unknown signal. Then, the effectiveness of the proposed MFI scheme is verified through 28 GBaud polarization division multiplexing (PDM)-binary phase shift keying (BPSK), PDM-quadrature phase shift keying (QPSK), PDM-8 quadrature amplitude modulation (QAM), PDM-16QAM, PDM-32QAM, and PDM-64QAM simulation systems. The simulation results show that the proposed MFI scheme achieves well performance on the required minimum optical signal-to-noise ratio (OSNR) value, the robustness to the variation of the transmission environment, residual chromatic dispersion (CD) and different group delay (DGD). Finally, the proposed MFI scheme is further verified by 20 GBaud PDM-QPSK/8QAM/-16QAM/-32QAM long-haul transmission experiments, and the results demonstrate that the proposed MFI scheme exhibits good resilience towards fiber nonlinear impairments.

The Impact of Hamming Code and Cyclic Code on MPSK and MQAM Systems over AWGN Channel: Performance Analysis

Designing efficient and reliable data transmission systems is an attractive area of research as it has become an essential requirement for the cutting-edge technologies. Error Control Coding (ECC) is a method used to control errors in a message to achieve reliable delivery through unreliable or noisy channel. Employing ECC in a communication system enable the sender to encode the message with redundant bits to form a codeword and transmits it over a noisy channel to the receiver, and then the receiver detects and corrects the errors which may occur during transmission without requesting for retransmission. In this sense this communication system becomes reliable and energy-efficient. To this end, this paper addresses two techniques of ECC: Hamming code and cyclic code. Besides, this work investigates the impact of these codes on M-ary Phase Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) systems over an Additive White Gaussian Noise (AWGN) Channel in terms of coding gain. The simulation results show significant coding gain for these codes. Another finding is that cyclic codes show better performance than Hamming codes for lower modulation order, while both of them show similar performance for higher modulation order. These findings can provide essential guidance when designing reliable and energy-efficient system.

A Novel DFT-Based Scheme for PAPR Reduction in FBMC/OQAM Systems

In this letter, a novel discrete Fourier transform (DFT)-based scheme is proposed for peak to average power ratio (PAPR) reduction in filter-bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) systems. The key idea is the combination of DFT and the concept of block repetition. Different from the conventional DFT-based PAPR reduction method, the output complex-valued signal of the DFT module is directly transmitted in the proposed DFT-based PAPR reduction method, instead of separating and transmitting the real and imaginary parts of the output signal, respectively. The proposed method can provide a solution to the low PAPR without the cost of high complexity, signal distortion or side information. To validate the performance of the proposed method, simulation results are provided in terms of complementary cumulative distribution function (CCDF) and bit error ratio (BER).

Energy-Efficient Cluster-Based Wireless Sensor Networks Using Adaptive Modulation: Performance Analysis

Wireless Sensor Networks (WSNs) play a vital role in modern technology since they have recently emerged into enormous essential applications of the Internet of Things (IoT). However, WSNs encounter a shortage in the lifetime due to limitations in the power supply. Accordingly, many solutions are reported in literature to deal with energy saving problem in the WSNs. In this paper, a novel method is presented to minimize energy consumption using adaptive modulation that is jointly integrated with clustering technique . This method is considered as a promising solution for dense and sparse cluster-based WSNs to improve energy efficiency. In the suggested solution, the adaptive modulation is implemented in the communication link between cluster members (CMs) and cluster head (CH). Besides, distance-based adaptive modulation step function is proposed in which the optimum modulation order is selected to achieve the minimum energy consumption between CMs and CH. The proposed method is evaluated extensively in order to investigate the impact of adaptive modulation in cluster-based WSNs using M-ary Quadrature Amplitude Modulation (MQAM) system. The performance evaluation addresses both energy consumption and throughput by using two metrics: cluster density, and cluster size. Regarding simulation results, by varying cluster density and cluster size, the adaptive modulation shows significant saving in energy consumption where it constitutes a lower bound for energy consumption. Also, it shows a great impact on throughput where it constitutes an upper bound for the throughput. Moreover, the adaptive modulation shows a considerable leverage on energy saving for small number of clusters, conversely, the energy saving decreases as the number of clusters increase. Finally, it is concluded that these findings can provide a remarkable guidance for designing an energy efficient WSNs.

WITHDRAWN: A Simulation on lattice reduction techniques for wireless communication MIMO QAM 64x64 and above

Abstract In wireless communication system, signal those pass through in transmission and receiving antenna in MIMO (Multi-input multi- output) channel to lattice reduce over a QAM (quadrature-amplitude-modulation) system, which is simulated maximum likelihood (ML) estimation and minimum mean square error (MMSE) . In this paper “A Simulation on Lattice Reduction Techniques for wireless Communication MIMO with QAM 64x64 and above”, here the minimum likelihood (ML) estimation and MMSE for multi-input multi-output (MIMO) channels. Generally, in OFDM (orthogonally frequency division multiplexing) system of a MMSE system completely eliminates interference and the results in suboptimal performance due to noise enhancement in symbol. The main aim simulated MMSE detector that the transmitter must spend within M QAM quadrature- amplitude-modulation () alphabet and the ML, MMSE allow to transmitted signal and remove the interference which comes from in receiver and pass through it. Which is QAM 64x64 above simulated BER (bit error rate) with SNR.

Modified QPSK partition algorithm based on MAP estimation for probabilistically-shaped 16-QAM

Probabilistic shaping (PS) is investigated as a potential technique to approach the Shannon limit. However, it has been proved that conventional carrier phase recovery (CPR) algorithm designed for uniform distribution may have extra penalty in PS systems. In this paper, we find that the performance of QPSK partition algorithm is degenerated when PS is implemented. To solve this issue, a modified QPSK partition algorithm that jointly optimizes the amplitude decision threshold and filter weight is proposed, where the optimization of decision threshold is based on maximum a posterior probability (MAP) estimation. Different from the conventional decision methods which commonly use Euclidean distance metric, the MAP-based decision introduces the statistical characteristics of the received signals to obtain an accurate amplitude partition. In addition, the filter weight is optimized for different decision thresholds to enhance the tolerance of ASE-induced phase noise. We verify the feasibility of the proposed algorithm in a 56 GBaud PS 16-ary quadrature amplitude modulation (16-QAM) system. The proposed algorithm reduces the error of phase noise estimation by nearly half. Compared with conventional QPSK partition, the proposed algorithm could narrow the gap with theoretical mutual information (MI) by more than 0.1 bit/symbol. The channel capacity is increased by 4.2%, 4.3% and 3.6% with signal-to-noise ratio (SNR) from 8 dB to 10 dB respectively. These observations show that the proposed algorithm is a promising method to relieve the penalty of QPSK partition algorithm in PS systems.

Combining designs of precoder and equalizer for MIMO FBMC-OQAM systems based on power allocation strategies

The filter bank multi-carrier (FBMC) technique is hoped to become a potential candidate for advanced wireless multiple intput multiple output (MIMO) systems as the fifth generation (5G) or the sixth generation (6G) owing to its advantages. In this paper, two combining designs of precoder and equalizer for MIMO FBMC offset quadrature amplitude modulation (OQAM) systems are investigated and proposed. These designs are developed basically on power allocation strategies such as the error balance algorithm (EBA) and water-pouring algorithm (WPA). The key idea is how to address bad sub-channels in which they are strengthened with the EBA whereas some really bad sub-channels are discarded with the WPA. The proposed designs are evaluated and compared to outstanding conventional designs based on zero forcing (ZF) and minimum mean square error (MMSE) algorithms via bit error rate (BER) and throughput issues. Simulation results show that the proposed designs can improve significantly the performance of downlink spatial multiplexing systems.

5G NR FR2 Femtocell Coverage Map Using an Omnidirectional Twisted SWAA

This article reports the implementation and coverage map of a mm-waves femtocell, using a high-gain omnidirectional twisted slotted-waveguide antenna array (SWAA). The twisted SWAA provides 14.7 dBi gain and 1.1-GHz bandwidth in the frequency range 2 (FR2) from the 5G new radio (5G NR) standard. A 91-m2 indoor coverage is demonstrated and its coverage map is estimated by measurements of the root mean square error vector magnitude (EVMRMS) parameter at 36-spatially distributed reception points throughout the laboratory. The 5G NR femtocell operates with 50-MHz bandwidth and 30 kHz-spaced subcarriers, giving rise to 104.8 Mbit/s throughput, whose signal quality is analyzed accordingly to the 3GPP Release 15 recommendations. Line-of-sight (LOS) and NLOS (non-LOS) propagation scenarios are evaluated, implying in EVMRMS variation from 3.13% to 19.4%. Coverage of 94% and 89% are achieved for QPSK (Quadrature Phase Shift Keying) and 16-QAM (Quadrature Amplitude Modulation) systems, respectively, demonstrating its applicability to the deployment of 5G NR femtocell operating in mm-waves.

SYMBOL ERROR PROBABILITY OF 16-QAM SYSTEM OVER AWGN AND RAYLEIGH FADING CHANNELS

Wireless communication had transformed the mode of human interactions in recent times, distance is no longer a barrier as messages can be sent several miles apart within few seconds. In addition, the pervasive adoption of mobile communication system had engendered researchers to device new and effective technologies to enhance Quality of Service (QOS) offered by service providers. This is obvious in the deployment of trending mobile generations such as 2G, 3G and 4G systems for high speed voice and data services. Nevertheless, these systems are still embattled with unpredictable impairment such as noise in fading channels that impedes optimal system performance. In this paper, performance evaluation of 16–Quadrature Amplitude Modulation (16-QAM) system over Additive White Gaussian Noise (AWGN) and Rayleigh Channels using simulated and theoretical approach is presented. Theoretical mathematical expression for Symbol Error Rate(SEP) was derived, and simulation was setup using MATLAB/SIMULINK for performance evaluation. The results show that SEP is dependent on signal-noise-ratio (SNR) for both methods. However, SEP wasvery high for Rayleigh channel as compared with AWGN.