Showing papers on "Constellation diagram published in 2021"

Hierarchical Digital Modulation Classification Using Cascaded Convolutional Neural Network.

Abstract: Automatic modulation classification (AMC) aims to identify the modulation format of the received signals corrupted by the noise, which plays a major role in radio monitoring. In this paper, we propose a novel cascaded convolutional neural network (CasCNN)-based hierarchical digital modulation classification scheme, where M-ary phase shift keying (PSK) and M-ary quadrature amplitude modulation (QAM) modulation formats are considered to be classified. In CasCNN, two-block convolutional neural networks are cascaded. The first block network is utilized to classify the different classes of modulation formats, namely PSK and QAM. The second block is designed to identify the indexes of the modulations in the same PSK or QAM class. Moreover, it is noted that the gird constellation diagram extracted from the received signal is utilized as the inputs to the CasCNN. Extensive simulations demonstrate that CasCNN yields performance gain and performs stronger robustness to frequency offset compared with other recent methods. Specifically, CasCNN achieves 90% classification accuracy at 4 dB signal-to-noise ratio when the symbol length is set as 256.

Low-Complexity Geometric Shaping

Abstract: Approaching Shannon's capacity via geometric shaping has usually been regarded as challenging due to modulation and demodulation complexity, requiring look-up tables to store the constellation points and constellation bit labeling. To overcome these challenges, in this article, we study lattice-based geometrically shaped modulation formats in multidimensional Euclidean space. We describe and evaluate fast and low complexity modulation and demodulation algorithms that make these modulation formats practical, even with extremely high constellation sizes with more than $10^{28}$ points. The uncoded bit error rate performance of these constellations is compared with the conventional quadrature amplitude modulate (QAM) formats in the additive white Gaussian noise and nonlinear fiber channels. At a spectral efficiency of 2 bits/sym/polarization, compared with 4-QAM format, transmission reach improvement of more than 38% is shown at the hard-decision forward error correction threshold of $2.26\times 10^{-4}$ .

SCMA Codebook Design Based on Uniquely Decomposable Constellation Groups

Abstract: Sparse code multiple access (SCMA), which helps improve spectrum efficiency (SE) and enhance connectivity, has been proposed as a non-orthogonal multiple access (NOMA) scheme for 5G systems. In SCMA, codebook design determines system overload ratio and detection performance at a receiver. In this paper, an SCMA codebook design approach is proposed based on uniquely decomposable constellation group (UDCG). We show that there are $N+1$ ( $N\ge 1$ ) constellations in the proposed UDCG, each of which has $M (M\ge 2)$ constellation points. These constellations are allocated to users sharing the same resource. Combining the constellations allocated on multiple resources of each user, we can obtain UDCG-based codebook sets. Bit error ratio (BER) performance will be discussed in terms of coding gain maximization with superimposed constellations and UDCG-based codebooks. Simulation results demonstrate that the superimposed constellation of each resource has large minimum Euclidean distance (MED) and meets uniquely decodable constraint. Thus, BER performance of the proposed codebook design approach outperforms that of the existing codebook design schemes in both uncoded and coded SCMA systems, especially for large-size codebooks.

Signal Estimation in Cognitive Satellite Networks for Satellite-Based Industrial Internet of Things

Abstract: Satellite industrial Internet of Things (IIoT) plays an important role in industrial manufactures without requiring the support of terrestrial infrastructures. However, due to the scarcity of spectrum resources, existing satellite frequency bands cannot satisfy the demand of IIoT, which have to explore other available spectrum resources. Cognitive satellite networks are promising technologies and have the potential to alleviate the shortage of spectrum resources and enhance spectrum efficiency by sharing both spectral and spatial degrees of freedom. For effective signal estimations, multiple features of wireless signals are needed at receivers, the transmissions of which may cause considerable overhead. To mitigate the overhead, part of parameters, such as modulation order, constellation type, and signal to noise ratio (SNR), could be obtained at receivers through signal estimation rather than transmissions from transmitters to receivers. In this article, a grid method is utilized to process the constellation map to obtain its equivalent probability density function. Then, binary feature matrix of the probability density function is employed to construct a cost function to estimate the modulation order and constellation type for multiple quadrature amplitude modulation (MQAM) signal. Finally, an improved ${M_2}{M_\infty }$ method is adopted to realize the SNR estimation of MQAM. Simulation results show that the proposed method is able to accurately estimate the modulation order, constellation type, and SNR of MQAM signal, and these features are extremely useful in satellite-based IIoT.

Secure Dual-Functional Radar-Communication Transmission: Exploiting Interference for Resilience Against Target Eavesdropping

Abstract: We study security solutions for dual-functional radar communication (DFRC) systems, which detect the radar target and communicate with downlink cellular users in millimeter-wave (mmWave) wireless networks simultaneously. Uniquely for such scenarios, the radar target is regarded as a potential eavesdropper which might surveil the information sent from the base station (BS) to communication users (CUs), that is carried by the radar probing signal. Transmit waveform and receive beamforming are jointly designed to maximize the signal-to-interference-plus-noise ratio (SINR) of the radar under the security and power budget constraints. We apply a Directional Modulation (DM) approach to exploit constructive interference (CI), where the known multiuser interference (MUI) can be exploited as a source of useful signal. Moreover, to further deteriorate the eavesdropping signal at the radar target, we utilize destructive interference (DI) by pushing the received symbols at the target towards the destructive region of the signal constellation. Our numerical results verify the effectiveness of the proposed design showing a secure transmission with enhanced performance against benchmark DFRC techniques.

A Novel RIS-Assisted Modulation Scheme

Abstract: In this work, in order to achieve higher spectrum efficiency, we propose a reconfigurable intelligent surface (RIS)-assisted multi-user communication uplink system. Different from previous work in which the RIS only optimizes the phase of the incident users’ signal, we propose the use of the RIS to create a virtual constellation diagram to transmit the data of an additional user. We focus on the two-user case and develop a tight approximation for the probability distribution function (PDF) of the minimum distance between constellation points of both users. Then, based on the proposed statistical distribution, we derive the analytical expressions of the average bit error rate of the considered two users. The letter also shows the trade off between the performance of two users as a function of the proposed phase shift at the RIS.

Fast signal quality monitoring for coherent communications enabled by CNN-based EVM estimation

Abstract: We propose a fast and accurate signal quality monitoring scheme that uses convolutional neural networks for error vector magnitude (EVM) estimation in coherent optical communications. We build a regression model to extract EVM information from complex signal constellation diagrams using a small number of received symbols. For the additive-white-Gaussian-noise-impaired channel, the proposed EVM estimation scheme shows a normalized mean absolute estimation error of 3.7% for quadrature phase-shift keying, 2.2% for 16-ary quadrature amplitude modulation (16QAM), and 1.1% for 64QAM signals, requiring only 100 symbols per constellation cluster in each observation period. Therefore, it can be used as a low-complexity alternative to conventional bit-error-rate estimation, enabling solutions for intelligent optical performance monitoring.

Study of the Influence of Changing Signal Propagation Conditions in the Communication Channel on Bit Error Rate

Abstract: The transmission of the information signal through the communication channel is accompanied by the addition of additive white Gaussian noise, industrial interference, atmospheric noise, etc. In addition, the signal may have an additional frequency and phase shift caused by the movement of the receiver concerning the transmitter. The article is devoted to the study of the effect of the listed conditions on the errors number dependence in the communication channel on the signal-to-noise ratio. It also explores the possibilities of reducing the effect of signal propagation conditions in a communication channel by using symbolic synchronization, which is based on a phase-locked loop. The early-late-time and Gardner synchronization error detectors are investigated. The early-late-time synchronization error detector is 1.5 dB more efficient than the Gardner detector at low signal-to-noise ratio and has a simpler implementation scheme. An energy efficiency study of a coherent digital communication system with quadrature phase shift keying modulation at the phase shift in the propagation medium is performed. Increasing of the phase shift from 0 to 40° decreases the energy efficiency by 3 dB at low signal-to-noise ratio. The energy efficiency of a non-coherent digital quadrature phase shift keying modulation system is reduced by 10 dB at the phase shift of 30° in the propagation medium. Adding a symbolic synchronization circle compensates for the rotation of the signal constellation. Increasing of the phase shift in the propagation medium to 45° for a coherent communication system leads to reduction of the energy efficiency by 2 dB. Frequency shifting has a significant impact on the energy efficiency of the communication system. The energy efficiency of the digital communication system decreases by 10 dB when 0.1 Hz frequency offset occurs and symbolic synchronization is missing. Symbol synchronization circuit increases the energy efficiency by 7 dB with a frequency shift of 0.1 Hz. When the value of frequency offset increases, the energy efficiency of coherent communication expands. The efficiency of coherent digital communication is increased by 24 dB with the introduction of frequency shift at 2 Hz.

Adaptive Spatial Scattering Modulation

Abstract: In this paper, two novel adaptive spatial scattering modulation (ASSM) algorithms, namely unequal transmission probability-based ASSM (UTP-ASSM) and equal transmission probability-based ASSM (ETP-ASSM), are proposed to pursue a better tradeoff between the computational complexity and spectral efficiency. According to available channel state information, the proposed ASSM algorithms are conducted to compute the optimal numbers of scatters and the optimal modulation orders constrained by the maximal tolerable symbol error probability (SEP). In addition, the minimal tolerate value of the minimal tolerant signal-to-noise ratio and SEP threshold are computed with a given data rate requirement by the bisection algorithm. At the receiver, a new type of optimal maximum likelihood detector is proposed to enhance the SEP performance. Furthermore, the union upper bound on the SEP is derived and analyzed. In addition, the computational complexity and system performance of the ASSM schemes are analyzed. Simulation results demonstrate that the proposed ASSM algorithms yield a lower SEP than the conventional spatial scattering modulation at the same value of average data rate.

On Self-Interference Cancellation and Non-Idealities Suppression in Full-Duplex Radio Transceivers

Abstract: One of the major impediments in the design and operation of a full-duplex radio transceiver is the presence of self-interference (SI), that is, the transceiver’s transmitted signal, 60–100 dB stronger than the desired signal of interest. To reduce the SI signal below the receiver’s sensitivity before coupling it to the receiver, radio frequency (RF)/analog domain cancellation is carried out. Even after SI cancellation to the required level in the analog domain, the residual SI signal still exits and lowers the transceiver’s performance. For residual SI cancellation, a digital domain cancellation is carried out. RF impairments are the major obstacle in the residual SI cancellation path in the digital domain. Linearization of RF impairments such as IQ mixer imbalance in the transmitter and receiver chain, non-linear PA with memory, and non-linear LNA are also carried out. Performance evaluation of the proposed techniques is carried out based on SINR, the power of different SI signal components, PSD, output to input relationship, SNR vs. BER, spectrum analyzer, constellation diagram, and link budget analysis. The proposed techniques provide attractive RF/analog SI cancellation of up to 80–90 dB, digital residual SI cancellation of up to 35 to 40 dB, total SI cancellation of up to 110 to 130 dB, and an SINR improvement of up to 50 dB.

Energy and Spectrum Efficient Blind Equalization With Unknown Constellation for Air-to-Ground Multipath UAV Communications

Abstract: In unmanned aerial vehicle (UAV) communications, frequency-selective fading can severely deteriorate the quality of transmitted signal by generating undesired and disordered constellation diagrams due to scatters in the air-to-ground (ATG) mutipath channels. In this paper, we propose a low-overhead blind equalization method to combat frequency-selective fading in air-ground multipath UAV channels. Specifically, a pre-equalization method is proposed based on a constant modulus algorithm to restore the contour of the constellation diagram. Moreover, the similarity measure function and the difference measure function are derived using template matching to identify the constellation of M-ary quadrature amplitude modulation. Furthermore, we propose a weighted constant cross algorithm (WXA) to reduce the residual mean square error and construct a cross-shaped modulus value, by utilizing the statistical information of the identified normalized standard constellation diagrams and the equalizer output decision symbols’ weighting value. The proposed method requires less information and no training sequences and pilots, therefore, if achieves energy and spectrum efficient ATG multipath UAV communications. Simulation results show that the proposed WXA algorithm can reduce the residual mean square error convergence value between −22dB and −25dB, making it very useful for the equalization of the frequency-selective fading channel in typical UAV communication scenarios.

Modulation Classification of MQAM Signals Based on Gradient Color Constellation and Deep Learning

Abstract: Modulation classification is a key issue in non-cooperative communication systems, and signal constellation images can be used as input features of deep learning (DL) networks for classification. However, the conventional gray constellation image cannot exactly reflect density and location information of constellation points. To solve this problem, this paper proposes a gradient color constellation (GCC) algorithm based on the density of constellation points, which converts the density of constellation points into color data to realize its visualization, and uses two deep learning network models, i.e., the modified convolution neural network (M-CNN) and the residual network (ResNet), as classifiers. The experimental results show that, compared with the scheme based on gray constellation, the overall classification accuracy of the seven multilevel quadrature amplitude modulation (MQAM) signals under low signal-to-noise ratios (SNRs) is improved by 3%-4%.

Spectrum Anomaly Detection for Optical Network Monitoring Using Deep Unsupervised Learning

Abstract: Accurate and efficient anomaly detection is a key enabler for the cognitive management of optical networks, but traditional anomaly detection algorithms are computationally complex and do not scale well with the amount of monitoring data. Therefore, we propose an optical spectrum anomaly detection scheme that exploits computer vision and deep unsupervised learning to perform optical network monitoring relying only on constellation diagrams of received signals. The proposed scheme achieves 100% detection accuracy even without prior knowledge of the anomalies. Furthermore, operation with encoded images of constellation diagrams reduces the runtime by up to 200 times.

Circularly Symmetric Companding Quantization-Inspired Hybrid Constellation Shaping for APSK Modulation to Increase Power Efficiency in Gaussian-Noise-Limited Channel

Abstract: In this paper we address hybrid probabilistic-geometric constellation shaping (HCS) of amplitude phase shift keying (APSK) constellation based on the reversed model of optimal companding quantization for circularly symmetric sources with the goal to increase the constellation power efficiency in Gaussian-noise-limited channel. To empirically optimize the proposed APSK constellation such that a symbol-error rate (SER) reaches its minimum under given constraints with respect to signal-to-noise ratio (SNR) and the prior probabilities of constellation points, for various settings of constellation parameters, we investigate SER dependence on SNR and determine the constellation parameters achieving minimum SER. The SER dependence on SNR we estimate theoretically by deriving approximate formula for SER of uncoded APSK constellation in Gaussian-noise-limited channel and practically by performing simulation. The obtained results are well-matched verifying the accuracy of approximate SER formula. The results also show that our APSK constellation outperforms some previous APSK and $M$ -ary QAM constellations in terms of power efficiency. Thus, for SER equal to 10−6 the gain in power efficiency amounts up to 2.35 dB, 2.23dB and 1.64 dB compared with the maximum mutual information-optimized 4+12-APSK, 4+12+16-APSK and 4+12+20+28-APSK constellations, respectively. This means that by employing APSK constellation we propose instead the traditional APSK constellations the transmitted signal power can be reduced by a third enabling lower power consumption. The improved power efficiency of our APSK constellation makes it suitable for application in power-limited communications such as fiber-optic communications, satellite communications, power-line communications, and multiple-input multiple-output wireless transmissions.

High-Dimensional Superposition NOMA and its User Pairing Strategy

Abstract: A novel power-domain non-orthogonal multiple access (NOMA) scheme with high-dimensional modulation is proposed. Signals for two users, each of which selected from a high-dimensional modulation constellation matrix, are superimposed on the same time-frequency resource for transmissions. While inter-user interference is treated as noise at the receiver of the far user, successive interference cancellation is used at the receiver of the near user. By analyzing the upper bounds of the detection errors, the power allocation factor is derived, which depends only on the relative power gain of the two users, i.e., the ratio between the squared of the two channel gains, but not on the operating signal-to-noise ratio. This nice feature allows us to perform user pairing easily for a system with more than two users. The optimal user pairing strategy that minimizes the total power consumption is analytically derived. Simulation results show that our proposed design outperforms some benchmark scheme.

Improved Schemes of Differential Spatial Modulation

Abstract: Differential spatial modulation (DSM) is able to transmit additional data bits without increasing the number of radio-frequency chains and power consumption and also avoids pilot overhead. In this paper, we propose two new schemes of DSM to improve the original DSM. One is an increased-rate scheme that transmits one additional data bit per two blocks. The bit mapping and maximum-likelihood detection is particularly designed. The goal of the second scheme is to increase the diversity of DSM. By properly designing block coded modulation and complex antenna-index matrices, the proposed scheme can achieve the desired diversity order. Compared with the existing schemes with the same constellation of the transmitted signals, the proposed scheme achieves higher transmission rates.

The Analysis of the High Power Amplifier Distortion on the MIMO-GFDM System

Abstract: Generalized Frequency Division Multiplexing (GFDM) is a flexible waveform possible choice for the next communication system that offers advantages such as low out-of-band (OOB) and high spectral efficiency. The High Power Amplifier (HPA) is operated close to the saturation region for increased efficiency. However, working in that area will result in nonlinear distortion. We investigated the effect of HPA in the GFDM Multiple Input Multiple Output (MIMO) system. The model used is the Rapp Model. In this paper, the Bit Error Rate (BER) of the MIMO-GFDM system with HPA through the Additive White Gaussian Noise (AWGN) channel will be explored. The output of the simulation shows that the nonlinear distortion effect will cause the signal constellation to propagate. Besides, there was an increase in the BER value for the HPA system.

Index Coded PSK Modulation in Vehicle to Vehicle Communication

Abstract: Vehicle to vehicle (V2V) communication has gained its importance in recent years. In this work we consider the index coding problem (ICP) over noisy channel in V2V communication phase of message dissemination. The ICP in V2V communication is considered as device to device ICP with transmitting nodes as receiving nodes also. An achievable solution for index coding problem in V2V communication is proposed considering vehicles with same download capability. This solution is used in noisy broadcast scenario over AWGN channel and the broadcast vectors are mapped to suitable M-PSK signal constellations to save bandwidth, thus increasing the bandwidth efficiency. An algorithm is proposed to derive suitable mapping of the broadcast vectors to M-PSK signal constellation for improving the error performance. Performance improvement in terms of PSK index coding gain is discussed. While one vehicle transmits, the proposed algorithm provides performance improvement for at least one of the remaining vehicles, in most of the scenarios, while not penalizing the other vehicles.

Optical Wireless Communications Using Signal Space Diversity with Spatial Modulation

Abstract: A signal space diversity (SSD) scheme was proposed to be incorporated with spatial modulation (SM) in an intensity-modulation/direct-detection-based multiple-input-single-output (MISO) indoor optical wireless communication (OWC) system to improve bit-error-rate (BER) performance and system throughput. SSD was realized via signal constellation rotation and diversity interleaving using different channel gains to improve the BER. With SM incorporated, the MISO-OWC system throughput increased. Theoretical BER expressions of the SSD scheme were established for the first time by investigating the distance of neighboring constellation symbols upon maximum-likelihood detection. Such BER expressions were further verified by numerical results. The results showed that, except for the slightly-lower-accuracy performance brought by comparable distances of neighboring constellation symbols in cases of low signal-to-noise ratios, these BER expressions were accurate in most scenarios. Moreover, theoretical investigations of channel gain distributions were performed at different signal constellation rotation angles to show the capability of the SSD scheme to improve the BER. The results showed that a significantly improved BER by two orders of magnitude could be achieved using a reasonably high channel-gain ratio and a larger constellation rotation angle. The SSD-SM scheme provides a promising option to achieve transmitter diversity with an enhanced throughput in high-speed indoor OWC systems.

High-Dimensional OFDM With In-Phase/Quadrature Index Modulation

Abstract: In this paper, we propose a new modulation scheme for wireless communications called high-dimensional orthogonal frequency division multiplexing with in-phase/quadrature index modulation (HD-OFDM-IQ-IM). In the proposed scheme, coordinate values of a symbol of the HD signal constellations are separated. A part of the coordinate values of an HD symbol are mapped to the active in-phase component subcarriers and the rest are mapped to the active quadrature component subcarriers in each OFDM subblock. A simple rule to design the HD constellation using the Gray coding and mapping is also presented. The method increases the minimum Euclidean distance between symbols of an HD signal constellation by increasing the Hamming distance of the binary sequences. As the dimension of the constellation increases, more index patterns can be produced, thus improving spectral and energy efficiency of the HD-OFDM-IQ-IM scheme. A feasible selection of subcarrier component active patterns can also produce additional index patterns to enhance spectral efficiency without additional energy consumption. In the receiver, both maximum likelihood (ML) and reduced-complexity log-likelihood ratio (LLR) detection can be exploited. As a result, the proposed scheme has better bit error performance than the conventional OFDM system with IM techniques in the frequency selective Rayleigh fading channel. In particular, it is noted that the bit error rate (BER) in the high signal-to-noise ratio (SNR) region is tightly limited by the upper bound on bit error probability derived in this paper.

Four-Dimensional Hurwitz Signal Constellations, Set Partitioning, Detection, and Multilevel Coding

Abstract: The Hurwitz lattice provides the densest four-dimensional packing. This fact has motivated research on four-dimensional Hurwitz signal constellations for optical and wireless communications. This work presents a new algebraic construction of finite sets of Hurwitz integers that is inherently accompanied by a respective modulo operation. These signal constellations are investigated for transmission over the additive white Gaussian noise (AWGN) channel. It is shown that these signal constellations have a better constellation figure of merit and hence a better asymptotic performance over an AWGN channel when compared with conventional signal constellations with algebraic structure, e.g., two-dimensional Gaussian-integer constellations or four-dimensional Lipschitz-integer constellations. We introduce two concepts for set partitioning of the Hurwitz integers. The first method is useful to reduce the computational complexity of the symbol detection. This suboptimum detection approach achieves near-maximum-likelihood performance. In the second case, the partitioning exploits the algebraic structure of the Hurwitz signal constellations. We partition the Hurwitz integers into additive subgroups in a manner that the minimum Euclidean distance of each subgroup is larger than in the original set. This enables multilevel code constructions for the new signal constellations.

Efficient Spectrum Utilization via Pulse Shape Design for Fixed Transmission Networks

Abstract: Microwave backhaul links are characterized by high signal-to-noise ratios permitting spectrally-efficient transmission. The used signal constellation sizes and achievable data rates are typically limited by transceiver impairments, predominantly by phase noise from non-ideal carrier generation. In this article, we propose a new method to improve the data rate over such microwave links. We make use of the fact that adjacent frequency channels are inactive in many deployment scenarios. We argue that additional data can be transmitted in the skirts of the spectral mask imposed on the transmission signal by regulation. To accomplish this task, we present a shaped wideband single-carrier transmission using non-Nyquist pulse shapes. In particular, we design spectrum-skirt filling (SSF) pulse shaping filters that follow the spectral mask response, and perform detection using an accordingly increased sampling frequency at the receiver. We evaluate the achievable information rates of the SSF-based transmission considering practical dispersive channels and non-ideal transmitter and receiver processing. To compensate for phase noise impairments, we derive carrier phase tracking and estimation techniques, and utilize them in tandem with nonlinear precoding which mitigates the intersymbol interference introduced by the non-Nyquist SSF shaping filter. Quantitative performance evaluations show that the proposed system design achieves higher data rates in a dispersive microwave propagation environment with respect to the conventional transmission with Nyquist pulse shaping.

To the Matter of Implementation of Radio Engineering Data Transmission System with APSK-N-signal based on the Theory of Resolution Time

Abstract: The paper is dedicated to solution the problem related to the practical implementation of a radio engineering data transmission system which is based on the theory of resolution time, in which amplitude-phase shift signals with N discrete signals are used. In this work, analytical expressions are obtained that allow taking into account the instability of the initial phase of the carrier of information signal when choosing a configuration of signal constellation. Block diagram for considered type ReDTS is presented. The selection data transmission algorithm is presented.

Optical Energy-Constrained Slot-Amplitude Modulation for Dimmable VLC: Suboptimal Detection and Performance Evaluation

Abstract: Energy-constrained slot-amplitude modulation (ECSAM) enables light dimming, eliminates light flicker and constrains the peak optical power while providing robust communication links. However, the complexity of the maximum-likelihood (ML) based ECSAM receiver increases exponentially with required spectral efficiency. This paper provides a comprehensive performance evaluation of ECSAM for the indoor visible light communication (VLC) channel with multipath propagation under realistic illumination constraints and imperfect channel estimation. A sub-optimal receiver that employs a slot-by-slot detection algorithm followed by a slot-correction mechanism for reducing the receiver complexity is proposed. Additionally, the method for optimal selection of parameters when designing the signal waveform is presented. The analytical upper bound on the symbol error rate of ECSAM is derived using the union-bound technique. The results show that the error performance of the sub-optimal receiver are comparable to that of the optimal ML receiver. Compared with conventional power or bandwidth efficient VLC modulation techniques such as multiple pulse position modulation (MPPM) and pulse amplitude modulation (PAM), ECSAM provides complete flexibility in modifying the signal constellation for a desired dimming level to maximise the spectral efficiency and provide a robust bit error rate performance especially in the multipath propagation channel induced intersymbol interference.

The Non-uniform Constellation Optimization Design of MQAM Modulation Based on Lion Swarm Optimization

Abstract: Aiming at the problem that the communication system error rate cannot reach the optimal when using the traditional uniform constellation QAM modulation, this paper proposes the non-uniform constellation MQAM modulation based on lion swarm optimization. By comparing the constellation images and error rate before and after optimization of 16QAM, 64QAM, 256QAM and 1024QAM, verify the feasibility and superiority of the lion swarm optimization in the non-uniform modulation. The algorithm takes the bit error rate as the fitness function, and outputs the constellation diagram and iteration curve through two layers of iteration. Compared with uniformly modulated constellations. The non-uniformly modulated constellations optimized by lion swarm optimization show a phenomenon of density in the middle and dispersion around the periphery, and this phenomenon becomes more obvious with the increase of the modulation order, which is similar to the 1D-NUCs proposed by ATSC3.0. The bit error rates of 16QAM, 64QAM, 256QAM and 1024QAM are all reduced to different degrees by comparing the bit error rates before and after optimization.

Hierarchical Circular θ -QAM

Abstract: Hierarchical modulation provides unequal error protection to transmitted data according to their relative importance. In this article, hierarchical modulation constellation based on circular $\theta $ -quadrature amplitude modulation (CTQAM), 4/ ${M}$ -CTQAM, $M = 2^{k}$ , $k \geq 4$ , is proposed. We provide a construction method and bit-to-symbol mapping for the proposed hierarchical modulation constellation. We then examine the bit error rate performance of 4/ ${M}$ -CTQAM and validate the theoretical results through computer simulations in additive white Gaussian noise (AWGN) and Rayleigh fading channels.

Analysis of Delayed Bit-Interleaved Coded Modulation for APSK

Abstract: In this work, we study delayed bit-interleaved coded modulation (DBICM) on amplitude and phase-shift keying (APSK) constellation. APSK is attractive for satellite communications, including DVB-S2. We find that the capacities of DBICM are identical to the coded modulation capacity. We also show that good performance can be achieved with a small delay value. We show these results by channel capacity analysis and the simulation results using low-density parity-check codes.

Modulation Classification in a Multipath Fading Channel Using Deep Learning: 16QAM, 32QAM and 64QAM

Abstract: A method based on a constellation diagram is proposed to identify QAM modulation of different orders in static, slow, and frequency selective fading channels. Although constellation diagrams have been studied and classified in literature, most of the work focused on noise. Little has been done to study the effect of multipath fading channels. We develop a highly accurate modulation classification method by exploiting deep learning with the constellation diagram. Based on the experimental results, our CNN model achieves a classification accuracy of 100% at −10 dB signal-to-noise ratio (SNR) under a multipath Rayleigh fading channel.