M-quadrature Amplitude Modulation Research Articles

FPGA Realization of an Image Encryption System Using a 16-CPSK Modulation Technique

Nowadays, M-Quadrature Amplitude Modulation (M-QAM) techniques are widely used to modulate information by bit packets due to their ability to increase transfer rates. These techniques require more power when increasing the modulation index M to avoid interference between symbols. This article proposes a technique that does not suffer from interference between symbols, but instead uses memory elements to store the modulation symbols. In addition, the aim of this paper is to implement a four-dimensional reconfigurable chaotic oscillator that generates 16-Chaotic Phase Shift Keying (16-CPSK) modulation–demodulation carriers. An encryption and modulation transmitter module, a reception module, and a master–slave Hamiltonian synchronization module make up the system. A 16-CPSK modulation scheme implemented in Field Programmable Gate Array (FPGA) and applied to a red-green-blue (RGB) and grayscale image encryption system are the main contributions of this work. Matlab and Vivado were used to verify the modulation–demodulation scheme and synchronization. This proposal achieved excellent correlation coefficients according to various investigations, the lowest being −15.9×10−6 and 0.13×10−3 for RGB and grayscale format images, respectively. The FPGA implementation of the 16-CPSK modulation–demodulation system was carried out using a manufacturer’s card, Xilinx’s Artix-7 AC701 (XC7A200TFBG676-2).

Hard Successive Interference Cancellation for M-QAM MIMO Links in the Presence of Rayleigh Deep-Fading.

In our paper, we propose a generalized version of the Alternating Projections Digital Hard Successive Interference Cancellation (AP-HSIC) algorithm that is capable of decoding any order of constellation M in an M-Quadrature Amplitude Modulation (QAM) system. Our approach applies to Rayleigh deep-fading Multiple-Input Multiple-Output (MIMO) channels with high-level Additive White Gaussian Noise (AWGN). It can handle various destructive phenomena without restricting the number of antenna arrays in the transmitter/receiver. Importantly, it does not rely on closed-loop MIMO feedback or the need for Channel-State Information Transmission (CSIT). We have demonstrated the effectiveness of our approach and provided a Bit Error Rate (BER) analysis for 16-, 32-, and 64-QAM modulation systems. Real-time simulations showcase the differences and advantages of our proposed algorithm compared to the Multi-Group Space-Time Coding (MGSTC) decoding algorithm and the Lagrange Multipliers Hard Successive Interference Cancellation (LM-HSIC) algorithm, which we have also developed here. Additionally, our paper includes a mathematical analysis of the LM-HSIC algorithm. The AP-HSIC algorithm is not only effective and fast in decoding, including interference cancellation computational feedback, but it can also be integrated with any Linear Processing Complex Orthogonal Design (LPCOD) technique, including Complex Orthogonal Design (COD) schemes such as high-order Orthogonal Space-Time Block Code (OSTBC) with high-order QAM symbols.

BER analysis of a full-duplex relay-assisted BPSK-SIM based VLC system for indoor applications.

This paper contemplates a relay-assisted visible light communication (VLC) system, where the light source (table lamp) acts as a relay node and cooperates with the main light source. Following the IEEE 802.15.7r1 VLC reference channel model, we assume that there are two different light sources present in an office room. The first one is the source terminal present on the ceiling and another one is the desk lamp that serves as the relay station, which works in a full-duplex method. Because of the loop interference channel, we model the VLC relay terminal using ray tracing simulations. We have analyzed the bit error rate (BER) performance of the relay-assisted VLC system using a binary phase shift keying-subcarrier intensity modulation (BPSK-SIM) technique. The proposed method outperforms existing phase shift keying (PSK) and square M-quadrature amplitude modulation (M-QAM) techniques. The proposed VLC system using the BPSK-SIM technique achieves a BER performance of 10-12 for an SNR of 20dB. The results of the proposed full-duplex and half-duplex relayed VLC systems are evaluated using equal power allocation (EPA) and optimum power allocation (OPA) techniques over three different modulation schemes, which are 2-PSK, square M-QAM, and BPSK-SIM.

Efecto de la técnica de modulación M-QAM para una infraestructura de red convergente Radio sobre Fibra (RoF)

The objective of the research is to analyze, at the simulation level, the effect of the M-Quadrature Amplitude Modulation (M-QAM) technique, in the downlink, for a converged Radio over Fiber (RoF) network infrastructure, implementing the Ortho-gonal Frequency Division Multiplexing (OFDM) technique and the Passive Optical Network architecture, with 10 Gbps capa-city (XG-PON). The evaluation of the effect of the M-QAM modulation technique was done through a pre-established simulation methodology and using the optsim sof-tware for the network model and tests. In the results of the research, the increase of the order of M-QAM modulation for a con-verged OFDM-RoF network infrastructure allows to represent more bits per symbol, however, it requires a higher transmission power. The conclusion derives in the pos-sibility of developing a robust converged OFDM-RoF network infrastructure of XG-PON type, implementing the M-QAM tech-nique, since it efficiently uses the available bandwidth.

Adaptively Equalized Bandwidth Optimization Model using SCADA-DWWAN based Neural Network

Artificial training and learning algorithms, enhanced with semi-supervised or self-supervised feature extraction capacities, employ adaptive decision optimization models. These are often favored over complex deep learning algorithms for achieving better controllability and ease of observation, lower complexity in simulating, building or designing and virtual prototyping of automatic network resource management (ANRM) standards. An Adaptive Linear Neuron type Artificial Neural Network (ADALINE-ANN) which is based on multi-tapered machine learning approach has been simulated in a virtual Supervisory Control and Data Acquisition (SCADA) framework integrated with a Distributed Control System (SCADA/DCS-Net). The system has been virtually simulated considering an adaptively equalized learning and decision approach which utilizes Markov Trained-Steepest Gradient Descent (HMM-SGD) based machine learning model employing Kalman optimization. Affinity clustering is employed for spectrum sensing by extracting the Constellation Nyquist Bands from an M-Quadrature Amplitude Modulation (QAM) orthogonal signal undergoing AWGN and Rayleigh fading as well as co-channel interference (CCI), and ensemble analysis using Channel State-Space plots are used for optimal spectrum allocation in an Adaptive Orthogonal Frequency Division Multiple Access (Adaptive-OFDMA) layout. It has been done by implementing an adaptively equalized Automatic Repeat Request (ARQ) pipelining model which utilizes minimum least square error (MLSE) minimization model. The objective is to improve the bandwidth allocation and usage ensuring most minimum spectrum wastage or loss. Successive Interference Cancellation (SIC) has been implemented to minimize static buffer and interference loss. Thus, spectrum loss due to latency and jitter which occurs from bandwidth congestion is minimized by improving the network resource tracking and allocation. It results in improved and stable bandwidth equalization.

OOK-RSOA Modülasyonunu Kullanan Çift Yönlü Karma Optik IM/DD OFDM WDM-PON Sisteminin Performansının İncelenmesi

In this paper, we have studied and simulated bidirectional hybrid long reach Intensity Modulated and Direct Detected Optical Orthogonal Frequency Division Multiplexing Wavelength Division Multiplexing Passive Optical Network (IM/DD-OFDM-WDM-PON) with 100 Gbps of various M-Quadrature Amplitude Modulation (M-QAM) in transmitted downstream signal and 2.5 Gbps On-Off keying (OOK) upstream signal using wavelength reused technique by Reflective Semiconductor Optical Amplifier (RSOA) at Optical Network Unit (ONU). The simple, low cost and colorless long-haul IM/DD-OFDM-WDM-PON based on RSOA is designed to support extreme data rate signal by utilizing Dispersion Compensating Fiber (DCF). All results prove that IM/DD-OFDM-WDM-PON can achieve good Bit Error Rate (BER) performance over propagation length of (300 km for 4-QAM), (200 km for 16-QAM) and (50 km for 64-QAM). For comparison, the performance of the network is studied in terms of BER, the effect of the propagation length on the constellation diagram, and the relation of BER versus bit energy and noise density ratio (Eb/No).

Random Graph-Based M-QAM Classification for MIMO Systems

Automatic modulation classification (AMC) has been identified to perform a key role to realize technologies such as cognitive radio, dynamic spectrum management, and interference identification that are arguably pivotal to practical SG communication networks. Random graphs (RGs) have been used to better understand graph behavior and to tackle combinatorial challenges in general. In this research article, a novel modulation classifier is presented to recognize M-Quadrature Amplitude Modulation (QAM) signals using random graph theory. The proposed method demonstrates improved recognition rates for multiple-input multiple-output (MIMO) and single-input single-output (SISO) systems. The proposed method has the advantage of not requiring channel/signal to noise ratio estimate or timing/frequency offset correction. Undirected RGs are constructed based on features, which are extracted by taking sparse Fourier transform (SFT) of the received signal. This method is based on the graph representation of the SFT of the 2nd, 4th, and 8th power of the received signal. The simulation results are also compared to existing state-of-the-art methodologies, revealing that the suggested methodology is superior.

Joint communication and radar sensing functions system based on photonics at the W-band

The photonics-based technology has the advantages of wide bandwidth in millimeter wave (mm-wave) communication and radar sensing systems. In the present work, we propose a novel joint communication and radar sensing functions system based on photonics at the W-band. In the proposed system, the broadband linear frequency modulated (LFM) signal and high-speed M-quadrature amplitude modulation (MQAM) signal are simultaneously obtained by heterodyning two free-running external cavity lasers (ECLs). Based on this system, a communication rate of 78 Gbit/s and a radar with a 5-GHz bandwidth is achieved. This is a good solution to incorporate a high-speed communication and high-resolution radar sensing functions system.

An Ingenious Multiport Interferometric Front-End for Concurrent Dual-Band Transmission

This article proposes and presents an innovative approach to realizing the concurrent dual-band transmission with only a single front-end and local oscillator at radio frequency (RF). Fundamentally, the proposed concurrent dual-band front-end is based on the conventional multiport interferometric architecture for single-band operation. Nevertheless, the conventional variable loads are replaced by diode networks with IF input signals to produce the RF signals at their designated center frequencies. Furthermore, due to the linear characteristics of a multiport network, the signals with different data contents will be mixed into both RF channels. To this end, an inverse matrix operation is applied to reversely convert the original data streams before the modulations of IF input signals. As a result, the two original data streams can be effectively modulated into specific RF channels (for transmission) with minimal interchannel interferences based on this configuration. In addition to the theoretical analyses, this innovative concurrent dual-band transmitting front-end has been investigated and verified with M-quadrature amplitude modulation (QAM) signals in simulations and experiments. All outcomes demonstrate excellent performances in concurrent dual-band transmission with significant reductions in both size and biasing power.

Experimental comparison of DSB and CS-DSB mmW formats over a hybrid fiber and FSO fronthaul network for 5G.

The telecommunication world is experiencing the 5th generation (5G) networks deployment including the use of millimeter wave (mmW) frequency bands to satisfy capacity demands. This leads to the extensive use of optical communications, especially the optical fiber connectivity at the last mile access and the edge networks. In this paper we outline fiber and free space optics (FSO) technologies for use as part of the 5G optical fronthaul network. We investigate two different mmW transmission schemes based on (i) the conventional analog radio over fiber transmission using one Mach-Zehnder modulator (MZM) with double sideband (DSB) optical modulation, and (ii) an optical-based frequency doubling with one MZM biased at the null point to introduce carrier suppression DSB (CS DSB) transmission and second MZM used for data modulation. Both systems are assessed in terms of the error vector magnitude, signal-to-noise ratio, dynamic range and phase noise. We consider a configuration for the fronthaul network in the frequency range 2 (FR2) at 27 and 39 GHz with the scale of bandwidth up to 400 MHz with M-quadrature amplitude modulation and quadrature phase shift keying. Results are also shown for FR1 at 3.5 GHz. Moreover, we investigate for the first time the 5G new radio signal transmission under strong turbulence conditions and show the turbulence-induced FSO link impairment. We finally demonstrate the CS DSB scheme performs well under chromatic dispersion-induced fading for the frequency up to 40 GHz and single mode fiber length of 30 km, whereas the DSB format seems more appropriate for an antenna seamless transmission.

Performance analysis of symmetrical and bidirectional 40 Gbps TWDM-PON employing m-QAM-OFDM modulation with multi-color LDs based VLC system

In this work, a full-duplex time and wavelength division multiplexing-passive optical network (TWDM-PON) system is analysed. Orthogonal frequency division multiplexing (OFDM) with m-quadrature amplitude modulation (m-QAM) is employed to improve the performance of TWDM-PON for downstream and upstream transmission. Simultaneously, multi-color (390–750 nm) laser diodes (LDs) are employed for visible light communication (VLC) using various VLC links to encourage the information rate of fiber/VLC optical network. A TWDM-PON utilizing 16-, 32- and 64-QAM OFDM with ten LDs based VLC system has been analysed for full-duplex multi-color VLC signals of the system. The impact of the LDs input current and high transmission rate in the proposed PON/VLC link has been investigated for m-QAM OFDM modulation. The results show that the 40/40 Gbps 16-, 32- and 64-QAM signals over ten 8000 m VLC links and a 50 km fiber link are successfully transmitted at the modulation input current of 9 mA under bit error rate (BER) of 3.8 × 10–3. Also, the proposed system employing 16-, 32- and 64-QAM signals over a 10 km fiber and ten 10 m VLC links provide the maximum transmission rate of 120, 100 and 80 Gbps respectively. Moreover, the measured error vector magnitudes (EVMs) and calculated BER values for 16-QAM downstream and upstream signals, are well below the required FEC limit than high-order modulation formats. Further, the numerical analysis of the proposed system reveals the superiority of the proposed fiber/VLC links.

Joint source-channel coding via model predictive control

We propose a joint source-channel coding (JSCC) scheme based on model-predictive control (MPC) for encoding an analog discrete-time source over a memoryless communication channel. The decoder is assumed to be fixed and given, and the MPC encoder is set to minimize the frequency-weighted mean-squared error (FWMSE) while satisfying a channel input constraint. We derive analytic expressions for the associated finite-horizon optimization MPC problem for an asymptotic (in time) average or sum channel input constraint. For the case of complex additive white Gaussian noise channel and an M-quadrature-amplitude modulation (M-QAM) decoder, these expressions can be written explicitly, which allows for an efficient numerical solution. For the case M=4 and considering a frequency weighting criterion that models the sensitivity of the human hearing, we show by simulations that our proposed scheme yields an FWMSE significantly smaller than that yielded by the corresponding non-JSCC scheme (a 2-bit uniform quantizer in tandem with a 4-QAM channel encoder and decoder).

Interference Spreading through Random Subcarrier Allocation Technique and Its Error Rate Performance in Cognitive Radio Networks

In this letter, we investigate the idea of interference spreading and its effect on bit error rate (BER) performance in a cognitive radio network (CRN). The interference spreading phenomenon is caused because of the random allocation of subcarriers in an orthogonal frequency division multiplexing (OFDM)-based CRN without any spectrum-sensing mechanism. The CRN assumed in this work is of underlay configuration, where the frequency bands are accessed concurrently by both primary users (PUs) and secondary users (SUs). With random allocation, subcarrier collisions occur among the carriers of primary users (PUs) and secondary users (SUs), leading to interference among subcarriers. This interference caused by subcarrier collisions spreads out across multiple subcarriers of PUs rather than on an individual PU, therefore avoiding high BER for an individual PU. Theoretical and simulated signal to interference and noise ratio (SINR) for collision and no-collision cases are validated for M-quadrature amplitude modulation (M-QAM) techniques. Similarly, theoretical BER performance expressions are found and compared for M-QAM modulation orders under Rayleigh fading channel conditions. The BER for different modulation orders of M-QAM are compared and the relationship of average BER with interference temperature is also explored further.

BER analysis of MIMO ZF receiver with imperfect channel estimation under correlated Rician fading channel

Massive MIMO systems operating in spatial multiplexing mode provide greater capacities. Zero Forcing (ZF) is one of the simple detection techniques used in the massive MIMO systems to recover the transmitted data streams at the receiver. In this paper, a generalized expression for the post-detection Signal to Noise Ratio (SNR) of the substream is derived by accounting the spatial correlation and channel estimation error. Further the Average Bit Error Rate (ABER) of ZF receiver for M-Phase Shift Keying (PSK) and M-Quadrature Amplitude Modulation (QAM) is evaluated from the derived post-detection SNR. Also, a closed-form approximation for the ABER of ZF receiver under transmit correlated Rician fading channel with channel estimation error is derived. From the simulation results, it is quite interesting to notice that for equal number of transmitting and receiving antennas and at higher values of average received SNR (Es/N0), the ABER of ZF receiver becomes independent of the receiver correlation. Further, it is also observed that the value of Es/N0 at which the ABER with full spatial correlation converges to the ABER with transmitter correlation varies with respect to the correlation coefficient (ρt,ρr) and Mean Square estimation Error (MSE) (σε2), while keeping the other parameters constant.

M-QAM signal transmission at the photonically generated K-band over thermal-induced turbulent FSO links with different turbulence distributions

We present a theoretical and experimental study on the impact of different thermal-induced free-space turbulence distributions on the M-quadrature amplitude modulation (M-QAM) signal transmission in radio frequency K-band over hybrid optical links of standard single mode fiber (SSMF) and free-space optics (FSO). Frequency multiplication using an external intensity modulator biased at the null transmission point has been employed to photonically generate radio signals at a frequency of 25 GHz , included for the frequency bands for fifth-generation (5G) mobile networks. Moreover, extensive simulations have been performed for 10Gb/s with 4-, 16-, and 64-QAM over 5 km of SSMF and 500 m long FSO channels under scenarios with different turbulence levels and distributions. Proof-of-concept experiments have been conducted for 20 MHz with 4- and 64-QAM over 5 km of SSMF and 2 m long FSO channels under turbulence conditions. Both theoretical and experimental systems have been analyzed in terms of error vector magnitude (EVM) performance showing feasible transmission over the hybrid links in the received optical power range. Non-uniform turbulence distributions are shown to have a different impact on M-QAM modulation formats, i.e., turbulence distributions with higher strength in the middle of the FSO link reveal a 1.9 dB penalty when using 64-QAM signals compared to a 1.3 dB penalty using 4-QAM signals, whereas higher penalties have been measured when 4-QAM format is transmitted over turbulence distributions with larger magnitude in the second half of the FSO link. The results have been validated by theoretical predictions and lead to practical consequences on future networks' deployment.

A comparison of clustering algorithms for automatic modulation classification

In this paper, the k-means, k-medoids, fuzzy c-means, Density-Based Spatial Clustering of Applications with Noise (DBSCAN), Ordering Points To Identify the Clustering Structure (OPTICS), and hierarchical clustering algorithms (with the addition of the elbow method) are examined for the purpose of Automatic Modulation Classification (AMC). This study compares these algorithms in terms of classification accuracy and execution time for either estimating the modulation order, determining centroid locations, or both. The best performing algorithms are combined to provide a simple AMC method which is then evaluated in an Additive White Gaussian Noise (AWGN) channel with M-Quadrature Amplitude Modulation (QAM) and M-Phase Shift Keying (PSK). Such an AMC method does not rely on any thresholds to be set by a human or machine learning algorithm, resulting in a highly flexible system. The proposed method can be configured to not give false positives, making it suitable for applications such as spectrum monitoring and regulatory enforcement.

Usability of a 5G Fronthaul Based on a DML and External Modulation for M-QAM Transmission Over Photonically Generated 40 GHz

In this paper, we numerically and experimentally present the bandwidth constraints of a cost-effective 5G mobile fronthaul based on a directly-modulated laser for data modulation and a Mach-Zehnder modulator-based optical double sideband with carrier suppression scheme for optical millimeter wave (mmW) signal generation. The effect of chirp, fiber dispersion and a combination of both on different bandwidth M-Quadrature Amplitude Modulation (M-QAM) signals, i.e. M = 4, 16 and 64, at 40 GHz has also been investigated. Simulation results are first carried out to evaluate the impact of higher chirp of the directly-modulated laser on the link performance as a function of modulation format and signal bandwidth. We then experimentally demonstrate the same scheme transmitting M-QAM signals with bandwidths ranging from 50 to 1000 MHz over a 10 km long single mode fiber. Both experimental and simulation results show that larger signal bandwidths lead to higher optical power penalties due to the combined effect with the error vector magnitudes (EVMs), however still satisfying the required limits of 3GPP standard for all QAM signals. Experimental measurements also show the feasibility of including free space optics links in the optical distribution network with no further significant penalties. Finally, a multiband signal (three-band) transmission is demonstrated leading to an increase of the total bitrate with the measured EVMs are well below the EVM requirement.

Secure Modulation Based on Constellation Mapping Obfuscation in OFDM Based TDD Systems

In this paper, we propose a secure modulation technique based on constellation mapping obfuscation to harden computational complexity for security at the physical-layer. To obfuscate mapping from bit stream to modulated symbols, our proposed scheme randomly changes a constellation mapping rule at each packet transmission opportunity, instead of employing a pre-determined mapping rule (e.g., Gray-coded mapping) at every packet transmission opportunity. Furthermore, to securely share the mapping rule between the transmitter and the desired receiver, the proposed scheme uses wireless channel based encryption and the fuzzy commitment with an error correction coding. We derive asymptotic bit error rate of the proposed scheme and validate our analysis through extensive simulations. We verify that our proposed scheme can further improve wireless security at the physical-layer irrespective of the upper layers' cryptographic schemes, which can be achieved by computational hardness - M! computations are required for the eavesdropper to crack the mapping rule when M-quadrature amplitude modulation (QAM) is considered (e.g., 64! ≈ 1.27 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">89</sup> combinations for 64-QAM).

Permutation index-quadrature spatial modulation: A spectral efficient spatial modulation for next generation networks

Spatial Modulation techniques (SMTs) offer an exceptional trade-off between spectral and energy efficiencies. In this work, we propose a new SMT termed as permutation index-quadrature spatial modulation (PI-QSM), aiming for enhanced spectral efficiency and better average bit error rate (ABER) performance compared to rival SMTs. To enhance spectral efficiency, PI-QSM exploits permutations of active transmit antennas by conveying additional information bits innovatively through indices of active antenna permutations. PI-QSM also alleviates the major constraint in some of the SMTs, where the total number of transmit antennas need to be a power of two. At any time instance, PI-QSM transmits real and imaginary parts of two complex modulated symbols separately using four different active antennas. To avoid any ambiguities at the receiver and to improve the error performance of the overall system, a rotation angle is introduced between the two modulated symbols before transmission. The rotation angle is optimized for different M-quadrature amplitude modulation (QAM) constellations using extensive Monte Carlo simulations. Performance of PI-QSM scheme is analyzed by deriving closed-form expressions for upper bound and asymptotic average bit error probability (ABEP) over Rayleigh fading channels. The Simulation results substantiate the accuracy of analytical analysis and also indicate that the proposed PI-QSM scheme offers better ABER performance than rival SMTs such as QSM and generalized QSM (GQSM).

Blind Carrier Frequency Offset Estimation in Coherent Optical Communication Systems With Probabilistically Shaped M-QAM

We find that the conventional 4th power and circular harmonic expansion (CHE) algorithms, which are originally devised for blind frequency offset estimation (FOE) in the uniform M-quadrature amplitude modulation (MQAM) systems, cannot work properly for probabilistically shaped (PS)-MQAM under moderate or strong shaping. To solve this issue, two novel blind FOE algorithms, namely the radius directed (RD)-4th power algorithm and the generalized circular harmonic expansion (GCHE) algorithm, are proposed. The former one adopts QPSK-selection based on a radius threshold optimized for a specific constellation entropy; while the later one conducts maximum likelihood (ML) estimation with a theoretically derived nonlinear radius transfer function in the GCHE. Several issues related to the practical implementation, including the optimization of the radius threshold in the RD-4th power algorithm, the impact of SNR-mismatch in the GCHE algorithm, and the computational complexities of the proposed algorithms, are analyzed. The Monte-Carlo simulation results show that: (1) the RD-4th power algorithm works properly in most of the cases except for very weak shaping, whereas the GCHE algorithm offers robust performance regardless of the shaping strength and outperforms the RD-4th power algorithm in all cases; (2) the performance gap between the two algorithms, which have the same computational complexity, enlarges for a larger constellation entropy. These observations indicate that the GCHE algorithm is a promising blind FOE algorithm, in terms of high estimation accuracy and robust performance, for applications that leverage the rate adaptability of the PS-MQAM, such as flexible optical networks.