Types Of Modulation Schemes Research Articles

Novel filtering and regeneration technique with statistical feature extraction and machine learning for automatic modulation classification

Automatic modulation classification (AMC) plays a crucial role in the stages of processing signals from unknown sources and monitoring the airwaves. This paper presents an AMC method based on machine learning (ML) using constellation diagrams, distribution test function and high-order cumulants (HOCs) and novel filtering and regeneration technique. A data clustering approach based on the signal phase characteristics is utilized to perform filtering, regeneration, and testing distribution functions. NI PXIe-1065 was used as a source of modulated signals, which is a multifunctional experimental complex for generating signals with various types of modulation. In this work, 5 types of modulation schemes were employed, specifically BPSK, QPSK, PSK-8, PSK-16 and PSK-32. The proposed classification method consists of three main stages. At the first stage, the constellation diagram is partitioned into clusters. At the second stage, the phase distribution function of signals within each cluster is analyzed, HOCs were calculated and novel filtering and regeneration techniques were employed. The main concept of the proposed approach is compressing angular ranges depicted on the constellation diagram. This involves filtering points and subsequently regenerating, which means relocating points that fall within adjacent phase ranges. Also, a statistical analysis of the phase transition distribution function in clusters is conducted at this step. At the last stage the obtained data set was trained using XGBOOST ML method. The proposed approach shows excellent results and can be a strong contender to existing NN based AMC methods, achieving 95 % accuracy at an SNR value of 9 dB.

English

Rain-based attenuation (RBA) is a major deteriorating factor affecting radio wave signals operating at microwave and millimetre wave bands for a typical Earth-Space Communication Link (ESCL). Although the international telecommunication union (ITU) recommended a standard model for predicting RBA along the terrestrial and ESCL, the technique underperforms in tropical environments. However, the model can be supported by appropriate modulation to enhance link performance. The present study assesses the performance of selected RBA models, namely the ITU, Moupfouma, and Garcá¼±a-Lὁpez models based on rain types for K-V frequency bands over some selected locations in Southwestern Nigeria. Link performance was further tested based on different modulation scaling to minimize signal degradation. The result shows that Garcίa-Lá½¹pez and ITU models performed well at low rain rate R ≤2 mm/h but underestimated at higher rain rates (except thunderstorms rain type) at the high-frequency band. However, the Moupfouma model performed well for all the rain types irrespective of the selected frequency band, while the ITU model underestimated attenuation for R < 5 mm/h (shower) and R > 30 mm/h (thunderstorm) rain type from the K-V band frequency, Garcia Lopez underestimates the RBA value for R < 5 mm/h and R > 5 mm/h up to the Ka frequency band. Considering the modulation scaling on link performance shows that the bit-error-rate (BER) will severely degrade with a high rain rate compared to the low rain rate across different frequencies. The BER for 8-PPM outperforms the other types of modulation schemes that were used in this study. Overall results revealed that modulation technique DPSK with selective combining diversity gave a marginal improvement with the increase in link distance and operating frequency. Key words: ESCL, rain attenuation models, modulation techniques, K-V frequency bands.

MULTIPLE ACCESS TECHNIQUES FOR 5G NETWORKS

Fifth generation (5G) wireless networks face various challenges in order to support largescale heterogeneous traffic and users, therefore new modulation and multiple access (MA) schemes are being developed to meet the changing demands. As this research space is ever increasing, it becomes more important to analyze the various approaches, therefore, in this article we present a comprehensive overview of the most promising Multiple Access schemes for 5G networks. Our article focuses on various types of non-orthogonal multiple access (NOMA) techniques. Specifically, we first introduce different types of modulation schemes, potential for OMA. We then pay close attention to various types of NOMA candidates, including power-domain NOMA, code-domain NOMA, and NOMA multiplexing in multiple domains. From this exploration, we can identify the opportunities and challenges that will have the most significant impacts on modulation and MA designs for 5G networks.

An Improved Modulation Scheme of Active Commutated Current-Fed Bidirectional dc/dc Converter

Active commutated or naturally clamped techniques have emerged as a new solution to achieve wide range soft-switching and eliminate the necessity of active clamping circuit of current-fed bidirectional dc/dc converter. Multiple typical modulation schemes have been proposed, which include single phase-shift (SPS) modulation, dual phase-shift (DPS) modulation, and discontinuous current SPS (DCSPS) modulation. DCSPS provides the lowest circulating current compared with prior two modulations, but it suffers from the problem of resonance and high peak current at partial loads. This article proposes a DCDPS modulation based on the existing modulations. The duty cycles of the two legs on the high-voltage side are controlled to be unsymmetrical to solve the current resonance problem in DCSPS. Extra phase shift is introduced to achieve much lower circulating current at wide range load conditions. Zero current switching (ZCS) of primary switches and zero voltage switching (ZVS) of secondary switches can be achieved over wide input range and wide load range. A 250-W laboratory converter prototype has been built. Experimental results are presented to validate the analysis and design.

Outdoor Visible Light Communication in Intelligent Transportation Systems: Impact of Snow and Rain

A comprehensive study of outdoor visible light communication (VLC) under snow and rain effects has been conducted in this paper. This paper analyzes the expected rain attenuation of Marshal, Carbonneau, and Japan models at different precipitation levels. Snow attenuation is measured in wet and dry situations at various precipitation levels as well. Therefore, a full comparison is carried out for different attenuation effects on certain outdoor VLC design characteristics such as the maximum signal-to-noise ratio (SNR), optical power received, bit error rate (BER), and maximum coverage area. VLC with various modulation techniques is considered. The ON–OFF Keying (OOK), L-Pulse Position Modulation (L-PPM), Inverse L-Pulse Position Modulation (I-L-PPM), and Subcarrier Binary Phase-Shift Keying (SC-BPSK) are investigated. The simulation results show a considerable difference in the information received under different weather conditions depending on the type of modulation scheme used. The simulation has been done on a two-lane road, and a green traffic light-emitting diode (LED) with a wavelength of 505 nm is used as a transmitter. A non-imaging concentrator coupled with a photodetector is considered to be a cost-effective receiver.

An Enhanced Two Stage MMSE Equalizer for Coded FBMC/OQAM Systems

In this article, the authors investigate the enhanced two stage MMSE (TS-MMSE) equalizer in bit-interleaved coded FBMC/OQAM system which gives a tradeoff between complexity and performance, since error correcting codes limits error propagation, so this allows the equalizer to remove not only ICI but also ISI in the second stage. The proposed equalizer has shown less design complexity compared to the other MMSE equalizers. The obtained results show that the probability of error is improved where SNR gain reaches 2 dB measured at BER compared with ICI cancellation for different types of modulation schemes and ITU Vehicular B channel model. Some simulation results are provided to illustrate the effectiveness of the proposed equalizer.

Multiplexed free-space optical system design using Manchester coding

Free space optics (FSO) has been considered as the alternative to wireless radio communication system because of the inherent advantages such as huge data rate, license-free operation, easy and quick deployability. Nevertheless, the performance of the FSO system is greatly influenced by atmospheric temperature, pressure, humidity etc. To overcome these challenges various techniques have been proposed in the literature, not only in the physical layer but also in the transport layer. Generally, the average bit error rate (BER) and quality factor (Q-factor) are prime parameters to measure the performance of the FSO systems. To improve the average BER and Q-factor, different types of modulation schemes have been analyzed for different weather conditions. In this paper, for the first time, to improve the performance of the system, differential phase shift keying (DPSK) modulation technique with Manchester coding is used. Manchester encoding synchronizes the signal itself; hence, it minimizes the error rate and optimizes the reliability of the proposed system. In addition, a 16-channel wavelength division multiplexing (WDM) FSO system is considered for improving the spectral efficiency of the system. For analyzing, the low to high turbulence level of atmosphere Gamma-Gamma type channel model is preferred.

Multilevel Intensity-Modulation for Rolling Shutter-Based Optical Camera Communication

High data transmission rates are desirable in an optical camera communication (OCC) system. In order to achieve this, a novel multilevel-intensity modulation (m-IM) scheme for a rolling-shutter (RS)-based OCC is introduced in this letter. The proposed multilevel intensity signal is obtained by transmitting the signal pulse time faster than the camera shutter speed, where the shutter speed is highly dependent on the camera exposure time and the RS-effect of CMOS-image sensor of the camera. In addition, pulse width modulation is also used on the transmitter side to control the output intensity (signal pulse) of the LED transmitter. As the optical signal is received wirelessly by the camera, we further propose a novel smartphone-based digital demodulation algorithm for our RS-based OCC system. In this letter, we compare the performance of the proposed system to a typical modulation scheme for OCC system, such as ON–OFF keying. Moreover, an intensive performance test is conducted for different symbol times to determine their relationship to bit error rate and achieved data rate. A data transmission rate >10 kbps over a range of up to 2 m by using a 30 fps smartphone camera can be achieved by using our proposed 4-IM in our proposed scheme.

Minimization of Filter Capacitor for Medium-Voltage Current-Source Converters Based on Natural Sampling SVM

Current-source converters (CSCs) used in high-power (megawatt level) medium-voltage (MV) (2.3–6.6 kV) drives require three-phase capacitors to assist the commutation of switching devices and to filter out harmonics of the converter output PWM current. Different types of modulation schemes with different harmonic performance lead to different capacitor selections. Conventional space vector modulation (SVM) featuring high dynamic performance cannot be used in practice even with the help of active damping, which can effectively damp the possible LC resonance introduced by conventional SVM. Recently, a natural-sampling SVM (NS-SVM) is proposed for MV CSC drives. It features superior low-order harmonics and has been highly considered for MV CSCs in practice. This study, therefore, focuses on two issues. One is why conventional SVM cannot be used in practice even with the help of active damping. On this basis, the second is capacitor minimization based on NS-SVM. Finally, experimental verification is provided.

Modulation and Multiple Access for 5G Networks

Fifth generation (5G) wireless networks face various challenges in order to support large-scale heterogeneous traffic and users, therefore new modulation and multiple access (MA) schemes are being developed to meet the changing demands. As this research space is ever increasing, it becomes more important to analyze the various approaches, therefore, in this paper we present a comprehensive overview of the most promising modulation and MA schemes for 5G networks. Unlike other surreys of 5G networks, this paper focuses on multiplexing techniques, including modulation techniques in orthogonal MA (OMA) and various types of non-OMA (NOMA) techniques. Specifically, we first introduce different types of modulation schemes, potential for OMA, and compare their performance in terms of spectral efficiency, out-of-band leakage, and bit-error rate. We then pay close attention to various types of NOMA candidates, including power-domain NOMA, code-domain NOMA, and NOMA multiplexing in multiple domains. From this exploration, we can identify the opportunities and challenges that will have the most significant impacts on modulation and MA designs for 5G networks.

Adaptive Modulation Using Neuro-Fuzzy (N-F) Controller for OFDM System

As demand for high quality transmission increases, improving spectrum efficiency and error performance in wireless communication systems are important. OFDM is a multi-carrier modulation technique with densely spaced sub-carriers that has gained a lot of popularity among the broadband community in the last few years. One of the promising approaches to next generation communication systems are adaptive OFDM (AOFDM). Fixed modulation systems uses only one type of modulation scheme (or order), so that either performance or capacity should be compromised but in adaptive modulated systems change modulation scheme (or order) depending on instantaneous Signal to Noise Ratio (SNR) to attain superior performance and capacity compared to fixed modulated systems. Neuro-fuzzy controller combines advantages of fuzzy logic and neural networks. Neuro-fuzzy controller provides automatic adaption procedure to fuzzy logic controller. Neural networks requires sufficient prior knowledge to be initialized but neuro-fuzzy systems doesn't requires any prior knowledge to be initialized and is efficient compared to fuzzy logic and neural networks. In this paper we propose an adaptive modulated OFDM system using neuro-fuzzy controller. The proposed system is simulated in MATLAB and compared with existing systems, simulation results shown significant improvement in systems performance.  Index Terms—Adaptive modulation, OFDM, Neuro-Fuzzy controller

Performance Research of Modulation for Optical Wireless Communication System

There are many modulation methods suitable for optical wireless communication. OOK, PPM are adopted widely in optical wireless communication for its high average-power-efficiency. DPPM, DPIM and DH-PIM are three new modulation methods for optical wireless communication, which may be the substitutes of PPM because of their better performance in power efficiency and bandwidth efficiency. In this paper, in combination of the characteristic of the atmospheric optical wireless channel, the bandwidth efficiency, transmission capacity, power efficiency and slot error rate of the typical modulation schemes as OOK, PPM, DPPM, DPIM and DH-PIM for atmospheric optical wireless communications are analyzed. Theoretical analysis and simulation results show that DPPM, DPIM and DH-PIM are more applicable for the future optical wireless communication.

Performance analysis of different modulation schemes using OFDM techniques in Rayleigh fading channel

This paper deals with the communication system that uses M-ary Phase-Shift-Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) to transmit information using OFDM technique over Rayleigh communication channel. In terms of Symbol Error Rate (SER), the performance of different modulation schemes using OFDM techniques in Rayleigh channel is analyzed. For different types of modulation schemes (QPSK, 16-QAM, 16-PSK, 64-QAM, 64-PSK) gray coded bit mapping has been used with OFDM techniques. So, better performance is shown in different modulation scheme by using gray coded bit mapping. Here in this paper, it is our goal to show the way through which the SNR result varies between M-PSK and M-QAM.

Comprehensive Relationship Between Carrier-Based PWM and Space Vector PWM in a Five-Phase VSI

Multiphase machines are nowadays considered for high-power variable-speed drive applications due to numerous advantages that they offer when compared to their three-phase counterparts. Multiphase voltage source inverters are invariably used to provide multiphase variable voltage and variable frequency supply with appropriate pulsewidth modulation (PWM) control. Carrier-based PWM and space vector PWM (SVPWM) are the most common options. This paper is aimed at providing a comprehensive relationship between carrier-based PWM and SVPWM techniques. The relationship is determined in terms of modulation signals and space vectors, modulation signals and space vector sectors, and switching pattern of space vector and type of carrier. Distribution of zero vector is discussed, leading to different types of modulation schemes. The practical implementation issues of carrier-based PWM and SVPWM are discussed. Simulation results and their experimental validation are provided to support the analytical findings.

Cross-Modulation Interference and Mitigation Technique for Ultrawideband PPM Signaling

The detection issues of ultrawideband (UWB) signals depend on the type of modulation scheme that is used during the transmission. Cross-modulation interference (CMI) is a problem that is specific to UWB pulse-position-modulation (PPM) signaling. In this paper, the effects of CMI on the performance of noncoherent UWB receivers are analyzed. The probabilities of error for transmitted-reference (TR) and energy detector (ED) receivers in the presence and absence of CMI are derived. Optimal and suboptimal CMI avoidance algorithms, which are based on novel acquisition techniques, are proposed for Rake receivers. The results show that the performance degradation in both receivers, which is due to the CMI effects, can be significant, depending on the modulation index. TR receivers still can be functional in the presence of CMI, and the target performance level determines the modulation index to be used. It is unlikely that effects of CMI on the performance of ED receivers in the presence of CMI are more severe relative to TR receivers, and the performance level is not acceptable. As a result, PPM signaling is not an appropriate modulation technique for ED receivers that are operating in the CMI region, unless CMI mitigation algorithms can be developed. Furthermore, the proposed optimal and suboptimal algorithms are two promising schemes for avoiding the CMI effects and, consequently, for improving the performance of Rake receivers operating in the CMI region.

Minimizing Spectral Leakage of Nonideal LINC Transmitters by Analysis of Component Impairments

LInear amplification with Nonlinear Components (LINC) is a distortion-free transmitter architecture under ideal conditions. However, in a realistic transmitter, imbalances such as dc offset, differential gain, and differential phase shift present in the quadrature modulators result in generation of out-of-band spectral components, even assuming that both amplifiers have identical characteristics. The level of distortion not only increases with the magnitude of the imbalances but also depends, to a large extent, on their relative phase arguments. The contribution of this paper is to provide a simplified characterization of the spectral leakage in the LINC transmitter in terms of quadrature modulator imbalances, with identical or mismatched amplifiers. This characterization allows identification of the transmitter with minimum spectral leakage under the constraint that the quadrature modulators perform equally well when used individually, i.e., in a transmitter composed of just the quadrature modulator followed by an amplifier. With reasonably small imbalances in the quadrature modulators and realistic amplifier mismatch, the spectral leakage at the output of a LINC transmitter driven by typical modulation schemes can be reduced by up to 10 dB, simply by a wise pairing of modulators

An Iterative Multi-User Bit and Power Allocation Algorithm for DMT-Based Systems

This paper develops an efficient multi-user bit and power allocation algorithm in an iterative fashion for discrete multi-tone systems. The model of the interference channel is considered, where the transmit signal from each user causes interference to the other users. The scheme aims to minimize the total transmit power while satisfying the required data rate of each user. The proposed algorithm is shown to greatly reduce the computational complexity of the existing algorithm with negligible amount of transmit power increment as demonstrated in the simulation results. The proposed methodology can be applied to the DMT-based system, but is also feasible for either wired or wireless communication systems with the model of the interference channel and another type of modulation scheme.

Impact of the power delay profile shape on the bit error rate in mobile radio systems

Typical power delay profiles (PDPs) are simulated using different digital modulation schemes in order to study the influence of the PDP shape on the bit error rate (BER) performance of terrestrial mobile radio communication systems. Therefore, a multitap channel model with Rayleigh and lognormal fading is proposed, which is used for a software simulation. The simulation is focused on the investigation of typical details of the PDP as peaks, slope, attenuation, and distance of a second group of waves. This yields information about the properties, which have essential effects on the BER. Two of the most frequently applied types of modulation schemes, 0.3 GMSK (coherent detection) and /spl pi//4 DQPSK, are considered.

Novel sinusoidal pulsewidth modulation schemes for voltage-source inverters with fluctuating input voltage

The optimum waveform parameters of pulse position and pulse widths for voltage-source inverters with fluctuating input voltage are proposed. Eight types of modulation schemes are described for synthesizing the optimum low-distortion output waveforms, of which the harmonic spectra and the peak fundamental-value are almost insensitive to the input-voltage fluctuation, with a minimum voltampere rating of inverter input filter. For fluctuating inverter input voltage with insufficient filtering, the type-VII and the alternative type-III modulation schemes are found to be especially suitable for practical implementation. Detailed descriptions of the suggested circuits with dual-feedback control for implementing two such modulation schemes are given. A peak-value detector that can rapidly produce the peak value of the inverter output voltage with a minimum time constant is also proposed. The theoretical results of the proposed approaches with one-loop self-regulating property are experimentally verified and compared with the conventional method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>