Digital Modulation Techniques Research Articles

A High-Resolution LED Stimulator for Steady-State Visual Stimulation: Customizable, Affordable, and Open Source.

Visually evoked steady-state potentials (SSVEPs) are neural responses elicited by visual stimuli oscillating at specific frequencies. In this study, we introduce a novel LED stimulator system explicitly designed for steady-state visual stimulation, offering precise control over visual stimulus parameters, including frequency resolution, luminance, and the ability to control the phase at the end of the stimulation. The LED stimulator provides a personalized, modular, and affordable option for experimental setups. Based on the Teensy 3.2 board, the stimulator utilizes direct digital synthesis and pulse width modulation techniques to control the LEDs. We validated its performance through four experiments: the first two measured LED light intensities directly, while the last two assessed the stimulator's impact on EEG recordings. The results demonstrate that the stimulator can deliver a stimulus suitable for generating SSVEPs with the desired frequency and phase resolution. As an open source resource, we provide comprehensive documentation, including all necessary codes and electrical diagrams, which facilitates the system's replication and adaptation for specific experimental requirements, enhancing its potential for widespread use in the field of neuroscience setups.

Deep learning-based modulation recognition with constellation diagram: A case study

Automatic modulation recognition is a promising solution for identifying and classifying signals received in heterogeneous wireless networks. In dynamic and autonomous environments, receivers must extract the relevant signal from various modulated signals to enable further communication procedures. Machine learning, including its sub-branches for classification problems, offers promising operational capabilities. This study utilized the ResNet-50 deep learning method for modulation classification. A dataset consisting of eight digital modulation techniques was generated, with constellation diagrams created as image data over the additive white Gaussian noise (AWGN) channel at signal-to-noise ratios (SNR) of 5 dB, 10 dB, and 20 dB. The deep learning algorithm's performance metrics were evaluated using a confusion matrix, and F1 scores were compared to those of the AlexNet deep learning algorithm. The simulation results clearly indicate the superior performance of ResNet-50 over AlexNet. In terms of average F1 scores, ResNet-50 exhibits a significant advantage, surpassing AlexNet by approximately 67%, 29%, and 10% at SNR values of 5 dB, 10 dB, and 20 dB, respectively.

A Digital Pulse Frequency Modulation Technique for a Series Resonant Converter-based LED Driver

A Digital Pulse Frequency Modulation Technique for a Series Resonant Converter-based LED Driver

CNN-based automatic modulation recognition for index modulation systems

Automatic modulation recognition (AMR) has garnered significant attention in both civilian and military domains, with applications ranging from spectrum sensing and cognitive radio (CR) to the deterrence of adversary communication. Index modulation (IM) represents an innovative digital modulation technique that exploits the indices of parameters of communication systems to transmit extra information bits. This paper aims to examine the performance of a convolutional neural network (CNN)-based AMR across various IM systems, including spatial modulation (SM), quadrature spatial modulation (QSM), and generalized spatial modulation (GSM) with eight digital modulation schemes. In this study, we leverage confusion matrices, receiver operating characteristic (ROC) curves, and F1 scores to illustrate the recognition model’s outputs.

Performance Analysis of Adaptive Equalizers Over Multipath Faded Channels: Error Vector Magnitudes

Due to the increasing popularity of digital transmission systems, the need for channel equalizers has been acknowledged. These techniques are designed to counteract the effects of the inter-symbol interference (ISI) caused by the communication channels. An adaptive equalizer is used to operate on the output of a channel in order to provide an approximation of the transmission medium. An adaptive equalizer usually requires a training period to operate successfully. This method eliminates the effects of the wireless transmission channel and allows the subsequent symbol modulation. The paper presents an overview of the various adaptive equalizers, such as the least mean squares (LMS), decision feedback equalizers (DFE), and the Recursive least squares (RLS). It also explores their performance in terms of error vector magnitudes (EVM) over Rician and Rayleigh channels. The paper looks into the effects of adaptive equalizers on various digital modulation techniques for rectangular quadrature phase shift, amplitude modulation, such as the BPSK, QPSK, 4-QAM, 16-QAM, 64-QAM and 256-QAM. These modulations are analysed and measured in terms of symbol error rates and number of incorrect symbols.

Analysis of learning outcomes in engineering programs

Introduction:The present review article is the product of the research “Teaching digital modulation techniques in engineering: experiential learning theory “ developed at the Franciso de Paula Santander University and Pontificia Universidad Javeriana in 2022.Problem: The learning outcomes correspond to the statements related to what the future engineer is expected to be able to do, learn, understand and demonstrate. Objective: Analyze learning outcomes in engineering programs globally.Methodology: A methodology based on analysis stages is used for information selection through search filters and inclusion and exclusion criteria, design for the classification of information by geographic location and area of knowledge, with qualitative results by location and trends by area of knowledge.Results: Divergence was observed towards the way in which learning outcomes are evaluated, and conver-gence towards the need to involve agents external to the academy in the feedback for the learning outcomes evaluation processes.Conclusion:This allows for the identification of individual and collective strengths and weaknesses, which helps to make informed decisions to improve the quality of education.Originality:Originality is based on the way in which the information is analyzed, considering information by areas of knowledge as well as by continents.Limitations:None given the nature of the literature review.

Error performance analysis for chaotic pulse width position modulation in free space optical communication system

Abstract In this paper, a pulse time modulation method called chaotic pulse width position modulation (CPWPM) is studied for free space optical communication system. This is a digital modulation technique that combines pulse position modulation and pulse width modulation with chaos. In this scheme, the binary information is carried by both the position and width of the pulses, which are modulated by a chaotic signal. Hence, on a single pulse, two bits of information are encoded, which results in higher bit rates, better privacy, and larger effective bandwidth as compared to chaotic pulse position modulation (CPPM) and chaotic pulse width modulation (CPWM) techniques. Probability of error is investigated for different FSO scenarios, i.e., varying turbulence conditions and link lengths for CPWPM scheme. Finally, the performance of CPWPM-FSO system is compared with a commonly used differential chaos shift keying (DCSK) scheme. CPWPM-FSO system shows comparable results as DCSK-FSO system (for probability of error, P e = 10−4 average signal-to-noise ratio (SNR) required for DCSK and CPWPM scheme is 40 dB and 41 dB, respectively, for same length and system conditions), while data rate is doubled in latter, and this verifies the validity of using CPWPM in FSO communication system.

Visible Light Communications: A Survey on Recent High-Capacity Demonstrations and Digital Modulation Techniques

In order to deal with the increasing number of mobile devices and with their demand for Internet services, particularly social media platforms, streaming video, and online gaming, Radio-Frequency (RF) wireless networks have been pushed to their capacity limits. In addition to this, 80% of the total data traffic is carried out by users inside buildings. Therefore, new technologies have started to be considered for indoor wireless communications. Visible Light Communications (VLC) can provide both illumination and communications, appearing as an alternative or complement to RF wireless networks. VLC offers high bandwidth and immunity to interference from electromagnetic sources. This manuscript reviews recent high-capacity VLC demonstrations. The main focus of this work is to present digital-signal-processing techniques used in VLC systems. Different modulation formats are analyzed, which can be divided into two large groups, namely single-carrier and multi-carrier modulation schemes. Finally, some recently proposed capacity-achieving strategies are presented. We discuss how to implement these techniques and how they will be useful for the continued development of VLC systems.

Extremely Accurate, Generic and Tractable Exponential Bounds for the Gaussian Q Function With Applications in Communication Systems

In this letter, we apply the Fejer’s Rule of interpolatory integration in a modified manner to obtain a very generic, tractable and extremely accurate approximation for the Gaussian <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> function. We further show the utility of the proposed approximation by simplifying the error performance metrics like average symbol error probability (ASEP) of popular digital modulation techniques over a very useful κ-μ shadowed fading channel. This eliminates the need of mathematical softwares which require very high processing power (a constraint at the receiver side) yielding simplified and cost effective receiver’s design. In addition, an insight on the asymptotic ASEP (and diversity order thereof) is also highlighted in this letter.

FSO-CDMA system performance enhancement based on new hybrid code and M-ary digital pulse position modulation technique

FSO-CDMA system performance enhancement based on new hybrid code and M-ary digital pulse position modulation technique

INVESTIGATION OF PSK/QAM MODULATED HYBRID FIBER OPTIC AND FREE SPACE OPTIC SYSTEM UNDER VARIOUS ATMOSPHERIC LOSSES

This research aims to investigate how effectively digital modulation performs to transfer data via hybrid fiber optic and free space optic (FO-FSO) channels for last-mile communication systems. Digital modulation techniques investigated are phase-shift keying (PSK) 8-PSK, 16-PSK, quadrature amplitude modulation (QAM) 4-QAM, 16-QAM, and 64-QAM. FSO is line-of-sight technology being a solution to a last-mile communication system for the challenge of fiber optic cables installation. Combining FSO with fiber optic technology avoids bending losses and the implementation challenges of fiber optic cables in metropolitan areas and between buildings. But atmospheric challenges such as haze, fog, and rain cause signal loss while transmitting data in free space. Also, atmospheric turbulence and antenna misalignments lead to signal error. This paper proposed the models of QAM and PSK digital modulated signal transmission over FO-FSO and compared the results to better fiber optic-FSO links to achieve a last-mile communication network. This fiber optic and FSO model is analyzed for the distance up to 100 km of fiber optic channel and 0.4-1.5 km of FSO channel. Constellation diagrams and error-vector magnitude (EVM) concerning received power at the receiver are compared to analyze FSO channel capacity for various weather attenuations.

A New Scheme for Parallel Transmission of Power and Full-Duplex Mode Information Sharing with LCC Topology Based on IPT System

In this study, a full-duplex data communication module is designed and developed for sharing information in a contactless power transfer system. It is realized through LC tank circuits with an inductive power transfer (IPT) system. On both the transmitter and receiver sides, one LCC compensation topology is used. Since Phase Shift Keying (PSK) is less susceptible to error and power-efficient digital modulation techniques, this paper proposes to implement PSK digital modulation technique to data signal modulation for full-duplex communication in a wireless EV charger. The proposed scheme ensures stability, transfers load status, charging level, and emergency messages between the source and load sides of the system, and vice versa. The results are compared with the Amplitude Shift Keying (ASK) digital modulation technique. Further, the impedance-based model is developed to analyze the interference between the power and high-frequency information signals. The inductive power and data transfer (IPDT) prototype is developed in the laboratory and results show that the data rate reaches 288 kbps when 46.6 W of power is transferred from source to load.

MIMO-OFDM Techniques for Wireless Communication System: Performance Evaluation Review

The use of multiple antennas in wireless communication systems has resulted in multiple channels that facilitate the speed of data transfer and improved channel capacity. This technique that basically involves multiple input and multiple output (MIMO) antennas helps to improve system performance by reducing bit error rate (BER) while increasing signal to noise ratio (SNR). Also, the use of orthogonal frequency division multiplexing (OFDM) has helped in mitigating inter-symbol interference (ISI). A combination of MIMO and OFDM produces the MIMO-OFDM scheme. This paper reviewed the performance of BER in MIMO-OFDM system considering various digital modulation techniques. An empirical review of previous studies on MIMO-OFDM system regarding BER performance evaluation was carried out. The study demonstrated the performance of digital modulation schemes in OFDM system with respect the Quadrature Amplitude Modulation (QAM). The results of the simulation based on MATLAB code revealed that lower order modulation yielded better BER performance than higher order. Furthermore,MIMO-OFDM system was modeled in MATLAB/Simulink and simulated to show that the use of multiple antennas at the transmitter and receiver helps in improving the performance of wireless communication system by reducing BER while increasing SNRconsidering two multipath channels – Rayleigh and Rician.

HybNet: A Hybrid Deep Learning-Matched Filter Approach for IoT Signal Detection

Random access schemes are widely used in IoT wireless access networks. They enable a reduced complexity and overcome power consumption constraints. Nevertheless, random access results in high packet losses which are caused by overlapping transmissions. Signal detection methods for digital modulation techniques are typically based on the well-established <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">matched filter</i> , which is proven as the optimal filter under additive white Gaussian noise for minimizing error probability. However, with the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">colored</i> interference arising from the overlapping IoT transmissions, deep learning approaches are being considered a suitable alternative. In this paper, we present a hybrid framework, dubbed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">HybNet</i> , that alternates between deep learning and match filter pathways based on the perceived interference level. This helps the detector to work in a broader range of conditions, optimally leveraging both the matched filter and deep learning advantages. We compare the performance of several possible data modalities and detection architectures concerning the interference-to-noise ratio, demonstrating that leveraging domain knowledge by pre-processing the input data in conjunction with the proposed HybNet surpasses the complex conjugate matched filter performance under interference-limited scenarios.

A Novel Implementation of QPSK Modulator on FPGA

QPSK is one of the digital modulation techniques in communication system that has wide applications in the field of wireless, satellite communication, Bluetooth, OFDM etc. The Conventional QPSK modulators designs are generally based on IQ approach. In these modulators multipliers are used to separate the modulating signal into the in-phase and quadrature phase which increases the hardware complexity. The objective of this work is to implement the digital QPSK modulator with conventional and another approach of digitization. In this approach a digitized carrier wave is generated and QPSK phase shifting is provided by 4:1 multiplexer according to the data bits. The implementations of both the designs are done on Spartan 3E Xilinx FPGA through the verilog hardware description language. The QPSK modulator based on the Digitized approach is simpler in terms of hardware circuitry.

Classifying wireless signal modulation sorting using convolutional neural network

Deep learning has recently been used for this issue with superior results in automatic modulation classification. Previous studies state that it is challenging to categorize a variety of modulation formats using traditional approaches; however, modulation classification is a crucial component of non-cooperative communication in wireless communication. The deep learning network was applied to solve the issue and get decent outcomes. This work uses a deep learning convolutional neural network (DLCNN) to classify three analog and eight digital modulation techniques by generating channel-impaired and synthetic waveforms as training data. The obtained DLCNN is tested by over-the-air indicators and a Software Define Radio(SDR) platform. The trained DLCNN estimates the modulation kind of each frame by taking 1024 samples of channel-impaired signals. The method includes generating several frames of 4-arry pulse amplitude modulation (PAM4) that are impaired with sampling time drift, Additive white Gaussian noise (AWGN), center frequency, and Rician multipath fading. The DLCNN predicts real inputs when receiving a signal with complex samples of baseband. Before updating the network coefficients and on all iterations, the data store transforms data from files and records it. This network takes about 50 minutes to train using in-memory data and 110 minutes to train using disk data. The evaluation of the trained DLCNN is carried out by obtaining the classification accuracy for the test frames. The obtained outcome demonstrates that the developed network can achieve an accuracy of about 94.3 % in roughly 12 epochs for such types of waveforms, which elapsed about 26 minutes for training. This will increase the efficiency of spectrum usage and detect the modulation type of the wireless communication receivers

Principle and Analysis of Anti-interference and Anti-fading Techniques in Mobile Communication

In recent years, with the rapid development of mobile communication, anti-interference and anti-fading has always been an important research topic in mobile communication. There is a lot of interference in mobile channel, and the signal will fade because of various reasons. Designers must consider these factors in the design, development and production of mobile communication systems, so the corresponding anti-interference and anti-fading measures should be studied to ensure that the interference level does not exceed the threshold compared with useful signals during the operation of the system, or ensure that the transmission error rate is within a certain range. This paper introduces diversity technique, error correcting code, spread spectrum, adaptive equalization, digital modulation technique and so on. The advantages and disadvantages of different diversity techniques are analyzed, and their performances in common digital mobile communication systems are compared. Different types of error correcting codes are introduced, and their principles are analyzed. Then, other anti - interference and anti - fading techniques and their principles are briefly introduced. Finally, this paper analyzes the development direction of anti-interference and anti-fading techniques in the future mobile communication.

On the General Error Event Probability Evaluation of Optical Intensity Modulation Schemes

Wireless intensity-modulated optical channels feature some very specific differences compared to wireless radio channels. These properties have a strong impact on the performance of digital modulation techniques. This paper discusses basics to consider when designing optical intensity modulation schemes. We introduce an error event probability expression for such modulation schemes that is generally applicable for all non-negative waveforms. We indicate the importance of amplitude fluctuations and the influence of pulse shaping on the power efficiency in the optical domain. In numerical examples, we apply the error event probability expression to modifications of orthogonal frequency-division multiplexing and to Hadamard coded modulation.

FPGA Implementation of Digital Modulation Schemes Using Verilog HDL

Abstract: This paper describes the design and development of an FPGA-based digital Modulation Scheme for high-resolution Communication Application. We are focusing on implementation of Verilog based code simulation for fundamental and widely used digital modulation techniques such as Binary Amplitude-shift keying (BASK), Binary Frequency-shift keying (BFSK), Binary Phase-shift keying (BPSK) and Quadrature Phase Shift Keying(QPSK). In this work the idea of sinusoidal signals that have been generated is plain sailing in nature and based on fundamentals of signal sampling and quantization. Such concept of sinusoidal signals generation is not unfamiliar but somehow simplified using sampling and quantization in time and amplitude domain, respectively. The whole simulation is done on Modelsim and Xilinx-ISE using VERILOG Hardware descriptive language. The work has been accomplished on Thirty two bit serial data transmission with self-adjustable carrier frequency and bit duration length.

A New RF Satellite Link Analyzing and Antenna Effect on Satellite Communication

Satellite communications (SatComs) recently, have admitted as a new technological advances that attracted and raised special investment and ventures. Space communication technology has found many application areas from costly, one-of-a-sort structures, to utilize again of technology on sequential tasks, to the progress of canonical protocols accepted by space agencies of lots of countries. Satellite communication has accepted as one of the important technologies for 5G backhauling, particularly on bandwidth request increased in 5G mobile broad band (eMBB) applications. This paper presents the efficiency of the satellite communication system using 16 QAM digital modulation technique for the X band. This digital modulation method presents high data rate in transmission without raising the bandwidth compared with other digital modulation methods. Applications are realized in Matlab environment and obtained conclusions are discussed such as power spectrum diagrams, constellation schemas and BER ratio for several bands such as 4, 8, 12, 16 GHz.