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This paper proposes a novel modulation scheme called “In Phase and Quadrature-Filter Shape Index Modulation” (IQ-FSIM). It aims to enhance the spectral/energy efficiencies (SE/EE) while generalizing several existing modulations and index modulation (IM) domains. In this system, the bitstream is divided into three sub-streams. The first is mapped using amplitude–phase modulation, and the other two are mapped separately to an index of a filter shape at the in-phase and quadrature components. IQ-FSIM in SISO mode enhances the SE by 2log2N (double FSIM gain), thanks to the independent indexation of N different filter shapes on each component changing at the symbol rate. A low-complexity matched filter-based detector that reaches the optimal joint ML performance is proposed. The theoretical lower bounds for the probability of filter index error and the symbol/bit error rate (SER/BER) are derived and validated. The computational complexity of the proposed IQ-FSIM transceiver is estimated and compared to its predecessor FSIM, where it is shown that IQ-FSIM provides up to 93.7% complexity reduction compared to FSIM along with different advantages. In addition, the results reveal that both IQ-FSIM and its special case FSIM, even with non-optimal filter shapes, outperform the equivalent schemes with/without IM of the same SE in AWGN, flat, and frequency-selective fading channels.

The carrier modulated sinusoidal pulsewidth modulation scheme has been acknowledged for its fundamental fortification and harmonic reduction in DC–AC conversion. This study is focused on how to get a variable output voltage with the least harmonics by changing the amplitude of the carrier wave vertically instead of modulating the reference wave (conventional SPWM). This paper proposes four control schemes for achieving the maximum fundamental voltage in a three phase voltage source inverter. The four schemes are single edge carrier shifted with (i) fixed reference and (ii) variable reference, and double edge carrier shifted with (iii) fixed reference and (iv) variable reference. In addition, the reverse modulation index and mutual modulation index are introduced as new control variables for examination. These schemes are simulated with a three phase inverter and the performance is compared with conventional sinusoidal pulsewidth modulation using MATLAB R2021. The amplitude of the fundamental voltage and the corresponding THD are reported. Digital implementations of the proposed schemes are premeditated by using VHDL language and ModelSim. The validity of the proposed schemes is experimentally investigated through a laboratory prototype of a three phase inverter module incorporated with an FPGA Spartan 6 device. This prototype is tested with a three phase induction motor as the load. The fundamental voltage and THD for the existing and proposed schemes are reported.

An efficient optical modulation technique for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) visible light communication system is proposed in this paper. The proposed modulation technique is termed as extended spatial-index light-emitting diode (LED) modulation. In the proposed technique, the indices (the spatial domain) of the LEDs are exploited in a dynamic style to not only get rid of the optical OFDM time-domain ( OFDM t d ) shaping problem but also to expand the LED indices spatial modulation domain. The indices of the active LEDs in the proposed technique are changed from the two LEDs active situation to the situation where all or several LEDs are active. Moreover, within the selected active LED indices, the power weight distribution and the positions of the OFDM components are varied to expand the resultant spatial domain. Therefore, the proposed technique offers a considerable spectral efficiency improvement over the up-to-date LED index OFDM modulation schemes even with a lower number of LEDs. The key idea of the proposed technique is to maximize the LEDs’ indices spatial position (spatial domain) utilization, where both the power weight allocation and the positions of the complex OFDM time domain components are varying several times over the same active LED indices combination, which improve the optical system spectral efficiency. The simulation results asserted the superiority of the proposed technique, as it improves both the average bit error rate (ABER) and the achievable data rate (R) compared with existing up-to-date OFDM-LED index modulations with even lower computational complexity.

Phase-amplitude coupling is a promising construct to study cognitive processes in electroencephalography (EEG) and magnetencephalography (MEG). Due to the novelty of the concept, various measures are used in the literature to calculate phase-amplitude coupling. Here, performance of the three most widely used phase-amplitude coupling measures - phase-locking value (PLV), mean vector length (MVL), and modulation index (MI) - and of the generalized linear modeling cross-frequency coupling (GLM-CFC) method is thoroughly compared with the help of simulated data. We combine advantages of previous reviews and use a realistic data simulation, examine moderators and provide inferential statistics for the comparison of all four indices of phase-amplitude coupling. Our analyses show that all four indices successfully differentiate coupling strength and coupling width when monophasic coupling is present. While the MVL was most sensitive to modulations in coupling strengths and width, only the MI and GLM-CFC can detect biphasic coupling. Coupling values of all four indices were influenced by moderators including data length, signal-to-noise-ratio, and sampling rate when approaching Nyquist frequencies. The MI was most robust against confounding influences of these moderators. Based on our analyses, we recommend the MI for noisy and short data epochs with unknown forms of coupling. For high quality and long data epochs with monophasic coupling and a high signal-to-noise ratio, the use of the MVL is recommended. Ideally, both indices are reported simultaneously for one data set.

A novel in-phase and quadrature domain index modulation (IQ-SIM) is proposed in this paper to significantly expand the spatial degrees of freedom in multiple-input multiple-output with index modulation (MIMO-IM) systems. Specifically, the in-phase and quadrature components of the spatial symbol are decoupled and then concatenated to form an extended real-valued vector, which is used to modulate a multidimension constellation point. Furthermore, the achievable number of additional bits is analyzed for the IQ-SIM with the identical number of transmit antennas and signal components. Simulation results demonstrate that the proposed IQ-SIM achieves higher spectral efficiency and a bit error rate (BER) performance than existing schemes such as SM-SC and QIM-TDC.

This paper has presented the simulation of single fiber Bragg grating (FBG) characteristics using Optigrating simulation software at the worst case. Various types of the same/different refractive index grating/fiber profiles are employed in order to test the transmittivity/reflectivity, bandwidth, and average group delay ripple factor level measurement of single FBG with optimum case. As well as output pulse intensity spectrum is examined for each case. It is observed that minimum side lobes strength, maximum output pulse intensity spectrum, dominant mode, narrow spectral bandwidth, maximum transmittivity/reflectivity spectral response are achieved with grating (exponential)/core (exponential)/region 1 (Gaussian cladding) FBG profile configuration, and grating (exponential)/core (parabolic)/region 1 (Gaussian cladding) profile configuration. Optigrating simulation results give an idea about the efficiency of the suggested hybrid FBG refractive index profiles to analyze FBG technical characteristics.

Multiphase machines are very essential for industrial applications that require high reliability of operation. In this paper, a comparative study of three-phase and five-phase inverter fed permanent magnet synchronous motors (PMSMs) was evaluated with respect to their performance characteristics under a healthy state and during transient disturbances such as varied load and double line to ground faults. To avert inherent high oscillations in speed and torque ripples during fault condition, the machine load was significantly reduced to 1/4th of the full load and a post fault current limiting series dynamic braking resistance (SDBR) with a bypassed switch was introduced to enhance the machine fault tolerant level and improve its operational performance. Spectral analyses were carried out to determine the magnitude of harmonic distortion during these conditions. The simulation results show that the five-phase PMSM achieved a reduced oscillatory transient and a faster settling time of speed and torque under a varied load. It also exhibited good harmonic profiles as indicated in the respective % THD values when compared to the three phase PMSM which is prone to high harmonic overheat. However, when subjected to a double line to ground fault, their various %THD values in speed and torque increased with five-phase PMSM still having a reduced %THD values over the three-phase PMSM. Therefore, for a higher fault tolerant capability, greater efficiency with proven reliability, a five-phase PMSM with a fault current limiting series dynamic braking resistance is a better substitute when compared with the three-phase PMSM in industrial applications where safety and loss minimization is a top priority. All simulation processes in this paper were achieved in MATLAB 2015.

Differential spatial modulation has garnered significant attention in recent years. As a large-scale multiple-input multiple-output (MIMO) system, it maintains the advantages of a single radio frequency (RF) chain and high spectral efficiency. Furthermore, it eliminates the need for channel state information (CSI), making it particularly promising for scenarios involving high-speed movement. In this paper, a differential quadrature space-time media-based modulation (DQSTMBM) system is proposed. It uses the differential approach to mitigate the challenges of detecting complex CSI. It modifies the channel state through media-based modulation and transmits the codirectional and quadrature components of the constellation symbol across different antennas, thereby conveying additional index information that enhances spectral efficiency. Furthermore, the theoretical bit error rate performance of the DQSTMBM system is derived. The experimental results demonstrate that the theoretical performance aligns with the Monte Carlo simulations, which confirms the validity of the proposed system.

In this paper, a modified code index modulation scheme based on the multi-carrier M-ary DCSK system, referred to as a MC-MCIM-MDCSK system, is proposed. In the proposed MC-MCIM-MDCSK system, a modified code index modulation scheme is carried out, which selects two orthogonal Walsh codes for realizing the M-ary DCSK encoder. The theoretical BER expression of the proposed system is obtained over additive white Gaussian noise (AWGN) and the multipath Rayleigh fading channels. Abundant simulation results showed that the simulation results matched the theoretical results. The energy efficiency (EE), spectrum efficiency (SE), the data rate, and the complexity of the proposed system were carefully analyzed. The BER performance of the proposed system was compared with those of other systems. It is shown that the proposed system has better BER performance than its competitors.

There are different modulation techniques that can be used in medium-voltage and high-power electronic converters, but a few of them provide high efficiency and satisfy power quality requirements. This study presents a modified selective harmonic mitigation pulse-width modulation (SHM-PWM) technique which employs variable DC-link voltages as a degree of freedom in cascaded H-bridge (CHB) inverters. This degree of freedom increases the range of acceptable modulation indices, reduces the number of switching transitions and increases the number of harmonics that can be removed in selective harmonic elimination (SHE) (or SHM) techniques. Hence, in addition to efficiency improvement, a huge number of harmonics can be mitigated in AC side of the converter. Using this approach, triplen harmonics can be restricted to standard limits, in single-phase inverters. In addition, the proposed SHM-PWM approach employs the least number of switching transitions in a fundamental period to limit the specific number of harmonics compared to the alternative SHE or SHM techniques. In this study, the requirements of two well-known grid codes EN 50160 and CIGRE WG 36-05 are well satisfied and the validity of proposed method is verified by several simulations and experiments on a seven-level CHB inverter in single-phase and three-phase operating modes.