Modulation techniques

The working principles and design equations of four different isolated, bi-directional DC to DC converter topologies (a dual active bridge converter, a series resonant converter and two multiple stage topologies) for a 2 kW bi-directional battery charger that can be operated in a wide input and output voltage range are presented in this paper. The results of a detailed mathematical

Phase noise (PN) impact in communication systems is considered as great, especially in wireless communication systems using higher m-QAM modulation schemes. The objective of this evaluation study is to investigate the exact impact of Phase noise in relation to AWGN, within a wide range of QAM schemes, since an implementation, of higher QAM usage, is anticipated to be widely used in modern wireless communication industry.

Delta modulation is a waveform coding technique which reduces the data rate to a larger extent in data communication; the problem encountered in delta modulation is the slope over load error, which is inherent in the system. In order for the signal to have good fidelity, the slope-overload error needs to be as small as possible. Hence there is need for adaptive techniques to be applied to Delta Modulation to reduce the noise. Adaptive delta modulation reduces the slope over load error to a greater extent. ADM attempts to increase the dynamic range and the tracking capabilities of fixed step-size delta modulation. The adaptive algorithms adjust the step size (from a range of step sizes) to the power level of the signal and thus enhance the dynamic range of the coding system appreciably. This paper discusses several Adaptive Delta Modulation techniques for improving the signal-to-noise ratio (SNR) of Adaptive Delta Modulators (ADM) and also their performance comparison is made.

The common term “diatonic modulation” involves two distinct meanings:
modulations into keys whose tonics are diatonic triads in the source keys (this study also distinguishes them from closely related keys) and modulations via a pivot chord that is diatonic in both source and target keys. Modulations may fulfill one condition but not the other.  Modulations can reach a diatonic goal by several means: pivot chords that are chromatic in either the source key, the target key, or both; by means of enharmonic pivot chords; or without any pivot chords. Modulations can also reach some distant goals by means of pivot chords that are diatonic in both source and target keys. A corollary aspect of normative diatonic modulations is a stable phrase rhythm, but this can also be separated from diatonic modulations. The study also suggests pedagogical adaptation of the distinctions made, since they are missing in harmony textbooks.

Un esperimento iniziato nel 2001, e divenuto nel tempo un riferimento culturale su scala nazionale. Ritengo che il fine del mio lavoro sia aiutare a comprendere, e che la cultura debba essere libera e senza ostacoli di accesso. Chi acquista il formato cartaceo, ebook, od effettua una donazione, entra a far parte dei sostenitori del progetto, e può scaricare la versione PDF dell'edizione più recente, perfettamente navigabile e stampabile. L'edizione più recente è di Giugno 2019, la trovi presso https://teoriadeisegnali.it/

Over the last two and half decades free space optical communication is preferred over microwave and radio frequency communication systems because of its license free long range operations. Also it has many advantages such as low cost, high bandwidth and small size and it has few limitations also like beam dispersion, scintillation. A well-known limitation of FSO is the effect of weather condition on it. In this paper we have designed 10gbps FSO system and analyzed of 10gbps FSO system with different weather condition by power and length varying. From the result it is clear, the transmission distance go on decreasing as the weather condition changes from clear to haze, rain and fog and the BER performance of all received signals is also discussed.

Visible light communication (VLC) systems using the indoor lighting system to also provide downlink communications require high average optical powers in order to satisfy the illumination needs. This can cause high amplitude signals common in higher-order modulation schemes to be clipped by the peak power constraint of the light emitting diode (LED) and lead to high signal distortion. In this paper we introduce Hadamard coded modulation (HCM) to achieve low error probabilities in LED-based VLC systems needing high average optical powers. This technique uses a fast Walsh-Hadamard transform (FWHT) to modulate the data as an alternative modulation technique to orthogonal frequency division multiplexing (OFDM). HCM achieves a better performance for high illumination levels because of its small peak to average power ratio (PAPR). The power efficiency of HCM can be improved by reducing the DC part of the transmitted signals without losing any information. The resulting so-called DC-reduced HCM (DCR-HCM) is well suited to environments requiring dimmer lighting as it transmits signals with lower peak amplitudes compared to HCM, which are thus subject to less nonlinear distortion. Interleaving can be applied to HCM to make the resulting signals more resistant against inter-symbol interference (ISI) in dispersive VLC links.

Direct torque control (DTC) is known to produce quick and robust response in alternating current drives. However, during steady state, notable torque and flux ripple occur. They are reflected in speed estimation, speed response and also in increased noise. The electrically excited alternating current induction motor has typically small synchronous inductance values and quite low transient values because of the damper windings mounted on the rotor therefore the torque and stator flux linkage ripples are high in conventional direct torque control due to the implementation of hysteresis control. In this paper, an attempt is made to address this problem using direct torque control scheme with space vector pulse width modulation scheme. It is based on the compensation of the stator flux linkage vector error using the space vector modulation in order to decrease the torque and flux linkage ripples and produced fixed switching frequency under the principle that the torque is controlled by the torque angle on alternating current induction motor. The alternating current induction motor is supplied by a two level thyristor inverter powered by space vector modulation. Conventional principles of direct torque control and space vector pulse width modulation were described. It can be used in various applications like electric vehicles, and industrial control where field weakening operation is required. Simulation research is carried out in Matlab/Simulink which illustrates steady state and dynamic performances of the developed system. Simulation results demonstrate the validity and effectiveness of the torque control response which properly combines with space vector pulse width modulation that shows faster dynamic response, lower torque ripple and lower flux ripple. Moreover, simple Matlab/Simulink model is introduced for two level space vector modulation inverter which can be realized and implemented in practice for three phase alternating current induction.

—The laboratory prototype of a frequency converter (FC) is analyzed using readily available Spartan-3E Field Programmable Gate Array (FPGA) kit and Personnel Computer (PC). The output frequency range has been varied over a wide range by implementing Sinusoidal pulse width modulation (SPWM) technique, in order to minimize the harmonics, using very high speed integrated circuit hardware descriptive language (VHDL). The experimental setup for the FC circuit has also been developed in order to verify the MATLAB/Simulink analysis of the circuit. The Total harmonic distortion (THD) analysis is obtained experimentally for un-modulated and modulated frequency converter. It has been demonstrated that for step-up mode of operation of modulated frequency converter, minimum voltage THD is 6.6 % and current THD is 2.1 %. While during step-down mode of operation, 1.8% is minimum voltage THD and 1.1% is minimum current THD respectively. The THD in voltage and current has been significantly minimized by implementing FC with SPWM technique.

This paper introduces a new hybrid topology of multilevel inverter capable of generating 21-level output voltage. The proposed topology is built using the combination of cross-switched bridge and a conventional full H-bridge. Compared to the conventional topologies and other hybrid topologies, the newly introduced multilevel inverter has the ability to maximize the number of voltage levels utilizing lower number of DC voltage sources, integrated bipolar transistor (IGBT) switches and gate drivers. A low frequency modulation technique is used to generate the ideal multilevel output voltage and gate pulses. Furthermore, the proposed topology is validated by building a hardware prototype and obtaining relevant experimental results. The acquired simulated and experimental results indicate the proper functioning of the proposed hybrid topology along with the compatibility of the applied modulation technique.

The ANPC topology was developed to overcome the unequal power distribution among the semiconductors in NPC topology. By using an accurate switching model it's possible to adjust the thermal distribution between the semiconductors and increase the output power of the converter. This study focuses on the PWM-3 (fpwm = 350Hz), PWM-5 (fpwm = 550Hz), and PWM-7 (fpwm = 750Hz) and defines the optimum switching sequence for each frequency and specifies the maximum current rating of IGCT based ANPC converter for the mentioned optimum switching sequence.

In inverters’ pulse width modulation techniques (PWM) the Space Vector PWM (SVPWM) is a smart contestant due to its direct control in nature with variables which provide the straight forward finds to each inverter switching vector. The industrial drives are acquainting to use SVPWM owing extended speed –torque region operations. However, the extended SVPWM operation is  uses  much  mathematical  calculation  to  predict  the  switching on-times, which demands high digital platform. In order to reduce this calculation in this  paper  a  simple  on-time  calculation  based  SVPWM  is  proposed.  The proposed SVPWM is developed for three-level multilevel inverter and the space perspective of vector analysis are established and explained. The over modulation enhances the proper power utilization capacity of voltage source inverter thereby improve the inverter output voltage and load. This proposed method tailed the similar  mathematical practice as conventional two-level SVPWM for calculating sector identification and triangle determination. The approach finds the circular and hexagonal boundary on-time based on the straightforward  reference  vector  position  identification  and  calculates directly  the  switching  pulse  patterns  for  the  inverter  devices using  an expression based on the definition of the duty cycle. The performance of the proposed  SVM  is  simulated  by  MATLAB  11.b  simulation  software  and validated  with  laboratory  setup  2  kW,  12  switch  neutral  point  clamped (NPC)-MLI fed 1.5 HP squirrel cage 3-phase induction motor open loop v/f control  drive.  The  simulation  and  experimental  results  are  closure  and confirming  the  advantages  of  the  proposed  SVM  method.  The  proposed scheme can be extended to n-level inverter and also applicable to cascaded H-bridge topology.

This paper introduces a new hybrid topology of multilevel inverter capable of generating 21-level output voltage. The proposed topology is built using the combination of cross-switched bridge and a conventional full H-bridge. Compared to the conventional topologies and other hybrid topologies, the newly introduced multilevel inverter has the ability to maximize the number of voltage levels utilizing lower number of DC voltage sources, integrated bipolar transistor (IGBT) switches and gate drivers. A low frequency modulation technique is used to generate the ideal multilevel output voltage and gate pulses. Furthermore, the proposed topology is validated by building a hardware prototype and obtaining relevant experimental results. The acquired simulated and experimental results indicate the proper functioning of the proposed hybrid topology along with the compatibility of the applied modulation technique.

This article shows some modulation techniques for wireless network which is also called :
    Spread Spectrum
    Frequency-Hopping Spread Spectrum (FHSS)
    Direct Sequence Spread Spectrum(DSSS)
    Orthogonal Frequency Division Multiplexing(OFDM) and Variant
    CDMA(Code Division Multiple Access)
    Comparision All Techniques

Free-space optical communication (FSO) is an optical communication technology which uses light, propagating in free space to transmit data wirelessly for telecommunications. It is point to point infrared spectrum based optical communication between optical transceivers that are separated by physical medium known as air. FSO links use modulated low power laser beams to transmit information through the free space. This technology is useful where a fiber optic cable is impractical. FSO uses the light of wavelength 780nm to 850nm and 1550nm to 1600nm. 1550nm wavelength produce higher power and more eyes safe compared to 780nm and 850nm. The first part of this paper introduces the free space optic system its block diagram and previous research done on free space optics. The second part informs about the atmospheric conditions that effect the free space optical communication. The last part will describes the previous work done using different modulation techniques.

FSO enables to provide last mile transmission reach with some advantages such as inherent security and no electrical hazards without laying any fiber or cable. In this paper we have analyzed the performance of free space optics communication system by employing five transmitters (CSNRZ CSRZ DBNRZ MDBNRZ and MDBRZ) for different attenuation values at 10Gbps up to the transmission distance of 1100m. The effect of beam divergence, transmitter losses, receiver losses and receiver aperture diameter is also calculated on the performance of proposed hybrid modulation format based free space optical communication system.

Use of Adaptive Statistical Iterative Reconstruction (ASIR) on CT scan of thorax has been investigated. This study aims is to determine the effect of the use of ASIR on the radiation dose and image quality. The study was conducted using phantom anthropomorphic using CT Scan GE Optima 580 with setting ASIR Dose Reduction 0%-50%. This study was carried out by using two parameters: fixed tube current and Tube Current Modulation (TCM). Analyzing of radiation dose is done by calculation of CTDIvol. While image quality are investigated by calculated Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR). There is a difference in the CTDIvol value, between the fixed tube current and TCM settings. At fixed tube current strength, the CTDIvol value is measured, starting from 0% to 50% ASIR, respectively: 48.60 mGy; 43.74 mGy; 38.88 mGy; 34.02 mGy; 29.16 mGy; and 24.30 mGy. While the CTDIvol value measured in TCM settings uses 0% to 50% ASIR as follows: 21.92 mGy; 20.09 mGy; 18.33 mGy; 16.51 mGy; 14.59 mGy; and 12.75 mGy. Using ASIR with TCM can produce CTDIvol values that are smaller than ASIR with fixed tube current. The difference in the average CTDIvol value is 51.80% between the use of TCM and fixed tube current. The greater the percentage of ASIR regulated, the greater the decrease in the CTDIvol dose. There is no significant difference in the SNR and CNR values produced by 0% to 50% ASIR with a fixed current strength. There is no significant difference in the SNR and CNR values produced by ASIR 0% to 50% with TCM. The average CNR value shown in TCM is higher than that of fixed tube current. The use of ASIR influence in dose radiation decreases without change the image quality.

In Modern Era, communication with zero distortion or with minimum distortion has become crucial for better transmission over the network. Many researchers have used the different techniques likes clipper circuit, equalizer circuit to prevent the impulsive noise and attenuation in the communication using power line communication, they also use Modulation Techniques with different encoding and decoding technique. In This paper we discuss about the modulation technique which are already introduced like PSK, QPSK, 16-QAM, 64-QAM etc. Also analyse the power line communication as a channel with noise and a small analysis of convolution encoder for encoding and Viterbi Algorithm for decoding.

Summary. The article considers important for pedagogy of music education solution of the problem of finding all the possible shortest modulation paths from any key to any key
in conformity with all the possible modulation systems, which presuppose a modulation via a chord serving as a common one for neighbouring keys. A concept of mutual relations between
both close and distant keys is set out in the article and namely in terms of the psychology of aesthetic perception. A method to solve the problem of finding modulation paths is also provided. The method is based on visual presentation using a graphic induction.
Keywords: harmony, modulation, modulation plans, visual representations, pedagogy of music education.

In this paper, two new modulation schemes using multilevel pulse-position modulation (PPM) for application in unipolar optical wireless systems are presented. Balanced incomplete block designs (BIBD) are used for constructing the symbol alphabets. Each symbol is obtained by combining multiple codewords of a BIBD code. In one scheme the symbols have equal energies, and therefore, no threshold is needed to make a decision on the received signal. The other modulation has better performance yet higher complexity. Since cyclic BIBDs are used for constructing the symbols, the transmitters and receivers have simple structures, and can be implemented using shift registers. These schemes can achieve high spectral-efficiencies, and are therefore suitable for systems with bandlimited sources or highly dispersive channels, where intersymbol interference (ISI) has a significant impact on the performance. We also show that using the same receiver structure, the constellation size can be increased by including the complements of the codewords. The performance of the proposed schemes are compared to other modulation schemes for both LED-based non-dispersive and dispersive freespace optical (FSO) systems.

In this work, to overcome the flaws of standard chaotic maps we generated two new cascaded structures, 3D Cubic-Sine and 2D Cubic-Cat chaotic parametric maps, based on a new parameter-varied Cubic map that enhance the chaos complexity and therefore offering a high randomness’s level of the chaotic sequences and a huge key space.To provide optimum security for image transmission, we introduce several methods with a new approaches in Stenography and encryption of quadrature amplitude modulation symbols (QAM)based on the new maps, all in a purpose of enhancement physical layer security. Some of the best results obtained are: the peak signal-to-noise ratio (PSNR) values of 96.2956 dB, 88.767 dB, 78.1094 dB respectively with the three methods, also the entropy of encrypted image reaching much closely the ideal value, being 8 ≈ 7.9999868, strong resistance against differential attack with Number of Pixels Change Rate (NPCR) of 99.63%, Unified Average Changing Intensity (UACI) of 33.54% and high speed ciphering based on 3D Cubic-Sine noise encryption time of 0.024s.The experimental results indicate that these new maps outperforms the most competitive recently proposed maps in multimedia cryptosystems.

Visible light communication (VLC) systems using the indoor lighting system to also provide downlink communications require high average optical powers in order to satisfy the illumination needs. This can cause high amplitude signals common in higher-order modulation schemes to be clipped by the peak power constraint of the light emitting diode (LED) and lead to high signal distortion. In this paper we introduce Hadamard coded modulation (HCM) to achieve low error probabilities in LED-based VLC systems needing high average optical powers. This technique uses a fast Walsh-Hadamard transform (FWHT) to modulate the data as an alternative modulation technique to orthogonal frequency division multiplexing (OFDM). HCM achieves a better performance for high illumination levels because of its small peak to average power ratio (PAPR). The power efficiency of HCM can be improved by reducing the DC part of the transmitted signals without losing any information. The resulting so-called DC-reduced HCM (DCR-HCM) is well suited to environments requiring dimmer lighting as it transmits signals with lower peak amplitudes compared to HCM, which are thus subject to less nonlinear distortion. Interleaving can be applied to HCM to make the resulting signals more resistant against inter-symbol interference (ISI) in dispersive VLC links. Index Terms-Visible light communications (VLC), Hadamard matrix, Walsh-Hadamard transform, orthogonal frequency division multiplexing (OFDM), peak-to-average power ratio (PAPR), LED nonlinearity.

In this work, to overcome the flaws of standard chaotic maps we generated two new cascaded
structures, 3D Cubic-Sine and 2D Cubic-Cat chaotic parametric maps, based on a
new parameter-varied Cubic map that enhance the chaos complexity and therefore offering
a high randomness’s level of the chaotic sequences and a huge key space.To provide optimum
security for image transmission, we introduce several methods with a new approaches
in Stenography and encryption of quadrature amplitude modulation symbols (QAM)based
on the new maps, all in a purpose of enhancement physical layer security. Some of the best
results obtained are: the peak signal-to-noise ratio (PSNR) values of 96.2956 dB, 88.767 dB,
78.1094 dB respectively with the three methods, also the entropy of encrypted image reaching
much closely the ideal value, being 8 ≈ 7.9999868, strong resistance against differential
attack with Number of Pixels Change Rate (NPCR) of 99.63%, Unified Average Changing
Intensity (UACI) of 33.54% and high speed ciphering based on 3D Cubic-Sine noise encryption
time of 0.024s.The experimental results indicate that these new maps outperforms the
most competitive recently proposed maps in multimedia cryptosystems.

In this work a comparative study in an indoor ambient between three optical modulations based on OFDM are presented: DCO-OFDM (DC Clipped Optical-Orthogonal Frequency Division Multiplexing), ACO-OFDM (Asymmetrically Clipped Optical-Orthogonal Frequency Division Multiplexing) Y HACO-OFDM (Hybrid Asymmetrically Clipped Optical-Orthogonal Frequency Division Multiplexing). The comparisons are presented in terms of Spectral Efficiency which is obtained analytically; BER (Bit Error Rate) vs SNR (Signal to Noise Ratio), and PAPR (Peak Average Power Ratio) are obtained by simulations using MATLAB. Index Terms-DCO-OFDM, ACO-OFDM, HACO-OFDM, Li-Fi, BER, PAPR, VLC, OFDM, OWC. I. INTRODUCCIÓN Li-Fi (Light-Fidelity) es una tecnología OWC (Optical Wireless communications) que trabaja dentro del espectro de luz visible mediante el uso de un LED (Light emitting Diode) como transmisor y un fotodetector como receptor, en comparación con las redes inalámbricas de radio frecuencia, como Wi-Fi, donde el espectro se está saturando [1]. La técnica más común para modular y demodular una señal eléctrica en una señal óptica con un LED y un fotodetector se conoce como técnica de modulación por intensidad (IM) y detección directa (DD) respectivamente [2]. Recientemente, las técnicas de modulación que pueden usarse con Li-Fi son uno de los campos de investigación debido a que no todas las técnicas de OWC se acomodan a los requerimientos de iluminación en Li-Fi. Por ejemplo, Li-Fi necesita de una iluminación regulable para que el LED pueda transmitir información aun cuando la luz no sea requerida [3]. Hay una gran variedad de técnicas de modulación que pueden ser usadas por Li-Fi. Una clasificación se presenta en [3] con cuatro diferentes grupos: Modulaciones de una sola portadora (SCM), OFDM (Orthogonal Frequency Division Multiplexing), modulaciones multi-portadora (MCM) que no son OFDM, y modulación en el dominio del color (CSK). Entre ellas, las modulaciones basadas en OFDM son ampliamente usadas por sus características para disminuir los efectos multitrayectoria. Las modulaciones basadas en OFDM más básicas son DCO-OFDM (DC Clipped Optical-Orthogonal Frequency Division Multiplexing), ACO-OFDM (Asymmetrically Clipped Optical-Orthogonal Frequency Division Multiplexing) y PAM-DMT (Pulse Amplitude Modulation-Discrete Multi-Tone). A partir de estas tres modulaciones, se presentan otras modulaciones de carácter híbrido como HACO-OFDM (Hybrid Asymmetrically Clipped Optical-Orthogonal Frequency Division Multiplexing). Li-Fi puede trabajar en dos tipos de escenario: un escenario exterior como postes de luz e iluminación entre vehículos, y un escenario interior, como oficinas, una cabina de avión o en hogares. Estos escenarios pueden ser descritos mediante varios modelos. Así, para ambientes interiores, existen modelos como el modelo de Lambert [2], [4], Ceiling Bounce Model, Hayasaka-Ito Model y un modelo esférico, entre otros [2]. El objetivo de este artículo es presentar un estudio comparativo del desempeño de las técnicas de modulación DCO-OFDM, ACO-OFDM y HACO-OFDM en términos de BER (Bit Error Rate) vs SNR (Signal to Noise Ratio), PAPR (Peak to Average Power Ratio) y eficiencia espectral. Las técnicas de modulación se comparan en un ambiente interior con un modelo de Lambert para describir el canal. El resto del articulo se organiza de la siguiente forma: en la sección II se explican las técnicas de modulación basadas en OFDM. En la sección III se presenta una descripción del canal. Después, en la sección IV se discuten los resultados obtenidos en términos de BER vs SNR, PAPR y eficiencia espectral. Finalmente, las conclusiones se presentan en la sección VI. II. TÉCNICAS DE MODULACIÓN BASADAS EN OFDM Antes de transmitir con IM/DD deben considerarse dos aspectos, debido a que la intensidad de la luz no puede ser negativa, las señales moduladas deben ser reales y positivas [5]. En señales OFDM, cuando las subportadoras se arreglan para cumplir una simetría Hermitica y pasan por el bloque IFFT (Inverse Fast Fourier Transform) la salida es completamente real [5]-[8]. La condición de simetría Hermitica se presenta en (1), donde * representa el

MEIR spectroscopy consists in the use of modulated UV/VIS excitation and phase and amplitude analysis of the modulated components of the IR absorption spectrum. By the modulated excitation the concentration of all particles involved in the photoprocess are modulated.

Visible light communications (VLC) in indoor environments suffer from the limited bandwidth of LEDs as well as from the inter-symbol interference (ISI) imposed by multipath. In this work, transmission schemes to improve the performance of indoor optical wireless communication (OWC) systems are introduced. Expurgated pulse-position modulation (EPPM) is proposed for this application since it can provide a wide range of peak to average power ratios (PAPR) needed for dimming of the indoor illumination. A correlation decoder used at the receiver is shown to be optimal for indoor VLC systems, which are shot noise and background-light limited. Interleaving applied on EPPM in order to decrease the ISI effect in dispersive VLC channels can significantly decrease the error probability. The proposed interleaving technique makes EPPM a better modulation option compared to PPM for VLC systems or any other dispersive OWC system. An overlapped EPPM pulse technique is proposed to increase the transmission rate when bandwidth-limited white LEDs are used as sources.

In inverters’ pulse width modulation techniques (PWM) the Space Vector PWM (SVPWM) is a smart contestant due to its direct control in nature with variables which provide the straight forward finds to each inverter switching vector. The industrial drives are acquainting to use SVPWM owing extended speed –torque region operations. However, the extended SVPWM operation is uses much mathematical calculation to predict the switching on-times, which demands high digital platform.  In order to reduce this calculation in this paper a simple on-time calculation based SVPWM is proposed. The proposed SVPWM is developed for three-level multilevel inverter and the space perspective of vector analysis are established and explained. The over modulation enhances the proper power utilization capacity of voltage source inverter thereby improve the inverter output voltage and load. This proposed method tailed the similar mathematical practice as conventional two-level SVPWM for calculating sector iden...

Multi-level converters are every day attracting research interest due to it tremendous positive contributions they are making in the power industries. The converter has put hope in the minds of power electronic engineers that a time will come when it will break a record by providing an efficient means of utilizing the abundant renewable energy resources.<strong> </strong>The paper presents a review of multilevel voltage source converters that are widely being used in engineering applications. It reports the technological advancements in converter topologies of Flying Capacitor (FC), Neutral Point (NPC) /Diode Clamped, and Cascaded H-Bridge (CHB) with their respective advantages and disadvantages. Recent customized/hybrid topologies of the three-phase multilevel inverter with reduced component count and switching combination are reported. The paper also reviewed different modulation techniques such as the multilevel converter carrier base PWM, Space Vector Modulation tech...

In this letter, we propose a new pulse position modulation (PPM) scheme, called expurgated PPM (EPPM), for application in peak power limited communication systems, such as impulse radio (IR) ultra wide band (UWB) systems and free space optical (FSO) communications. Using the proposed scheme, the constellation size and the bit-rate can be increased significantly in these systems. The symbols are obtained using symmetric balanced incomplete block designs (BIBD), forming a set of pair-wise equidistant symbols. The performance of Q-ary EPPM is better than any Q-ary pulse position-based modulation scheme with the same symbol length. Since the code is cyclic, the receiver for EPPM is simpler compared to multipulse PPM (MPPM).

Localization or Location-based services using Electromagnetic spectrum has attracted many researchers in recent years. Considering the current era, the most trending domain is Wi-Fi. The radio spectrum is being congested due to enormous data traffic load, which is called “Spectrum Crunch”. Consequently, designation of Wi-Fi signals may be carcinogenic and it’s been reported by WHO (World Health Organization).To address this issue, a short range wireless communication based on light illumination from LED’ which has been introduced recently. This new technology is called Light-Fidelity (Li-Fi). Which is considered as a green technology that comes up with more ecologically & economically friendly solutions. The edge of using Li-Fi over Wi-Fi for localization is; generally there are many more LED luminaries in a building in comparison to the number ofWiFi AP’s, which is cost effective. There is now developing of interest in all over the World including; within the bodies’ such as the Wireless world Research Forum (WWRF

The growing usage of wireless services is lacking in providing high-speed data communication in recent times. Hence, many of the modulation techniques are evolved to attain these communication needs. The recent researches have widely considered OFDM technology as the prominent modulation mechanism to fulfill the futuristic needs of wireless communication. The OFDM can bring effective usage of resources, bandwidth, and system performance enhancement in collaboration with the smart antenna and resource allocation mechanism (adaptive). However, the usage of adaptive beamforming with the OFDM leads to complication in the design of medium access layer and which causes a problem in adaptive resource allocation mechanism (ARAM). Hence, the proposed manuscript intends to design an OFDM system by considering different switched beam smart antenna (SBSA) along with the cross-layer adaptive resource allocation (CLARA) and hybrid adaptive array (HAA). In this, various smart antenna mechanism are considered to analyze the quality of service (QoS) and complexity reduction in the OFDM system. In this paper, various SA schemes are used as per the quality of service (QoS) requirement of the different users. The performance analysis is conducted by considering data traffic reduction, bit-rate reduction, and average delay.

In this paper, a novel fine timing algorithm has been tested and developed to synchronize Ultra-Wideband (UWB) signals with pulse position modulation (PPM). By applying this algorithm, we evaluate timing algorithms in both data-aided (DA) and non-data-aided (NDA) modes. Based on correlation operations, our algorithm remains operational in practical UWB settings. The proposed timing scheme consists of two complementary floors or steps. The first floor consists on a coarse synchronization which is founded on the recently proposed acquisition scheme based on dirty templates (TDT). In the second floor, we investigate a new fine synchronization algorithm which gives an improved estimate of timing offset. Simulations confirm performance improvement of our timing synchronization compared to the original TDT algorithm in terms of mean square error.

Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks and link reliability. In this direction, Space-time wireless technology that uses multiple antennas along with appropriate signaling and receiver techniques that offers a powerful tool for improving the wireless performance is used in this thesis work. A special version of STBC called 'Alamouti code' is used. PSK modulation scheme is used for modulation of data. In this thesis work, the Space-Time Block Codes (STBC) is used in WLAN wireless network that uses multiple numbers of antennas at both transmitter and receiver. The STBC which includes the Alamouti Scheme for 2 transmit antenna and a different number of receiving antenna has been studied, simulated and analyzed. The simulation has been done in MATLAB. Throughput and several parameter performance has been analyzed using the MATLAB.A sample image is transmitted to compare the performance of various parameters like RMSE, PSNR, MAE etc. All the parameters are plotted against SNR (in dB) values ranging from-18 to 30. Various observations being made for the improvement in various parameters with increasing SNR and/or with changing diversity scheme. AWGN channel is used here for communication of sampled image data.

In this poster, two direct V-Band and W-Band high data-rate QPSK modulators based on six-port technology are presented and analyzed. In order to evaluate the performances of the proposed modulators under realistic conditions, a six-port model based on the measured S-parameters of fabricated V-Band and W-Band circuits has been implemented in system simulations. The performances in terms of Bit Error Rate (BER) are analyzed for various data-rates of a pseudorandom QPSK signal: 100 Mbps, 500 Mbps and 1 Gbps. Six-port direct millimeter wave QPSK The qi points for 10% of bandwidth. (a) V-band six-port circuit f rom 60 to 66 GH, (b) W-band six-port circuit from 81 to 89 GHz. Test bench setup for On-wafer measurements

In solving the problem of noise immunity in communication systems are widely used compression characteristics PM and LFM signals. Under the
influence noise, such as industrial or specially organized, compression characteristics of complex PM and LFM signals become worse faster. In the simulation method are researching the influence of such interference on the characteristics of signal compression using compression in the time range (matched filtering) and in the frequency range (Fourier Fast Conversion). The comparative analysis of these complex signals Interference and Interference methods of compression. The comparative
analysis of noise protective this complex signals and noise protective methods their compression is held.

Providing network access for multiple users in a visible light communication (VLC) system that utilizes white light emitting diodes (LED) as sources requires new networking techniques adapted to the lighting features. In this paper we introduce two multiple access techniques using expurgated PPM (EPPM) that can be implemented using LEDs and support lighting features such as dimming. Multilevel symbols are used to provide M -ary signaling for multiple users using multilevel EPPM. In the first technique, the M -ary data of each user is first encoded using an optical orthogonal code assigned to the user, and the result is fed into a EPPM encoder to generate a multilevel signal. The second multiple access method uses subsets of the EPPM constellation to apply MEPPM to the data of each user. While the first approach has a larger Hamming distance between the symbols of each user, the latter can provide higher bit-rates for users in VLC systems using bandwidth-limited LEDs. Both techniques are able to support up to 15 simultaneous users transmitting 200 Mb/s with a bit error rate of 10 −3 under normal lighting conditions.