Top PDF Peak to Average Power Ratio Reduction of OFDM Signal by Combining Clipping with Walsh Hadamard Transform

Peak to Average Power Ratio Reduction of OFDM Signal by Combining Clipping with Walsh Hadamard Transform

Peak to Average Power Ratio Reduction of OFDM Signal by Combining Clipping with Walsh Hadamard Transform

Wireless communications have been developed widely and rapidly in the modern world especially during the last decade. Orthogonal Frequency Division Multiplexing (OFDM) has grown to a popular communication technique for high speed communication. Besides of the advantages, one of main disadvantage of OFDM is high peak to average power ratio (PAPR). In this paper, a PAPR reduction method is proposed that is based on combining clipping with Walsh Hadamard Transform (WHT).WHT is a precoding technique which is having less complexity compared to the other existing power reduction techniques and also it can reduce PAPR considerably and results in no distortion. The performance of the proposed scheme is examined through computer simulations and it is found that power reductions are obtained.
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PERFORMANCE IMPROVEMENT FOR PAPR REDUCTION IN LTE DOWNLINK SYSTEM WITH ELLIPTIC FILTERING

PERFORMANCE IMPROVEMENT FOR PAPR REDUCTION IN LTE DOWNLINK SYSTEM WITH ELLIPTIC FILTERING

This paper is concerned with the performance improvement of PAPR reduction of orthogonal frequency division multiplexing (OFDM) signal using amplitude clipping & filtering based design. Note that OFDM is one of the well adept multi-carrier multiplexing transmission scheme which has been implemented in long term evolution (LTE) downlink. Nonetheless peak to average power ratio (PAPR) is the more rattling problem with OFDM, consequently in this paper a reduction procedure of the PAPR by using amplitude clipping and filtering is proposed. Here we used IIR bandpass elliptic filter after amplitude clipping to reduce the PAPR. The performance of the system in terms of bit error rate (BER) is also canvased as a new filter based clipping method. Our results show that the proposed methodology of clipping method with the IIR elliptic band pass filter significantly reduces the PAPR value.
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Peak Reduction in OFDM using Second Order Cone Programming Relaxation

Peak Reduction in OFDM using Second Order Cone Programming Relaxation

Orthogonal frequency-division multiplexing (OFDM) [1] are suitable for high rate transmission over severely time- dispersive channels. For this reason, they were selected for broadband wireless communication systems such as digital video broadcasting (DVB) and long-term evolution (LTE). However, OFDM signals have high envelope fluc- tuations and high peak-to-average power ratio (PAPR), which makes them very sensitive to nonlinear effects and leads to amplification difficulties [2]. For this reason, sev- eral techniques were proposed to reduce the PAPR of OFDM signals. We can reduce the PAPR by using spe- cially designed codes [3], but its application is limited to very specific cases and/or a small number of sub- carriers. Multiple signal representations such as partial transmit sequences (PTS) techniques [4,5] and clipping techniques [6-8,10] are much more flexible and suitable for OFDM signals with a large number of subcarriers.
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Hardware Implementation of PAPR Reduction with Clipping and Filtering Technique for Mobile Applications

Hardware Implementation of PAPR Reduction with Clipping and Filtering Technique for Mobile Applications

In the modern mobile communication systems, one of the major concerns is the nonlinearity of RF amplifiers. The nonlinear power amplifiers degrades quality of the transmitted signal, causing increase in the bit error rate (BER), increase in adjacent channel interference, causing harmonic and phase distortions, gain compression, intermodulation distortions etc. Different techniques are available to analyse linear circuits [1]. But OFDM is required to be used in modern mobile communications systems in order to reduce the power consumption requirement, enhance battery life, reduce weight and size of battery and increased data transmission capability. Apart from that it has additional advantage of high spectrum efficiency and immunity to multi-path fading. OFDM systems are widely used for other applications like, digital high definition tele vision (HDTV) broadcasting, digital subscriber line (DSL), digital video broadcasting (DVB), and digital audio broadcasting (DAB), etc. But one of the major disadvantage of OFDM system is that it exhibits high peak to average power ratio (PAPR). The effect of power amplifier nonlinearity is further gets increased with use of orthogonal frequency division multiplexing (OFDM) owing to its high PAPR.
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Performance of adaptive DD-OFDM multicore fiber links and its relation with intercore crosstalk

Performance of adaptive DD-OFDM multicore fiber links and its relation with intercore crosstalk

Abstract: Adaptive direct-detection (DD) orthogonal frequency-division multiplexing (OFDM) is proposed to guarantee signal quality over time in weakly-coupled homogenous multicore fiber (MCFs) links impaired by stochastic intercore crosstalk (ICXT). For the first time, the received electrical power of the ICXT and the performance of the adaptive DD- OFDM MCF link are experimentally monitored quasi-simultaneously over a 210 hour period. Experimental results show that the time evolution of the error vector magnitude due to the ICXT can be suitably estimated from the normalized power of the detected crosstalk. The detected crosstalk results from the beating between the carrier in the test core and ICXT originating from the carrier and modulated signal from interfering core. The results show that the operation of DD-OFDM systems employing fixed modulation can be severely impaired by the presence of ICXT that may unpredictable vary in both power and frequency. The system may su ffer from deleterious impact of moderate ICXT levels over a time duration of several hours or from peak ICXT levels occurring over a number of minutes. Such power fluctuations can lead to large variations in bit error ratio (BER) for static modulation schemes. Here, we show that BER fluctuations may be minimized by the use of adaptive modulation techniques and that in particular, the adaptive OFDM is a viable solution to guarantee link quality in MCF-based systems. An experimental model of an adaptive DD-OFDM MCF link shows an average throughput of 12 Gb /s that represents a reduction of only 9% compared to the maximum throughput measured without ICXT and an improvement of 23% relative to throughput obtained with static modulation.
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Discrete Cosine Transform-II for Reduction in Peak to Average Power Ratio of OFDM Signals Through μ-Law Companding Technique

Discrete Cosine Transform-II for Reduction in Peak to Average Power Ratio of OFDM Signals Through μ-Law Companding Technique

To reduce the PAPR, the above discussed has been designed and results are shown in the form of CCDF vs. PAPR plot for different modulations and different values of M. In simulation, an OFDM system is considered under an additive white Gaussian noise (AWGN ) channel, where data is randomly generated with subcarriers N=2400, then the signal is modulated by M-PSK and M-QAM respectively. The PAPR reduction capability is measured by the complementary cumulative distribution (CCDF = Prob (PAPR>PAPR0), which indicates the probability that PAPR is above a certain threshold. We compared the simulation results of proposed system with DCT-II precoded OFDM signal and precodedµ-Law companded signal. The results were observed for precoded signal and for precoded µ -Law companded signal.
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AN ADAPTIVE POWER ALLOCATION SCHEME FOR ROBUST TRANSMISSION OF JPEG COMPRESSED IMAGES OVER MIMO-OFDM SYSTEMS

AN ADAPTIVE POWER ALLOCATION SCHEME FOR ROBUST TRANSMISSION OF JPEG COMPRESSED IMAGES OVER MIMO-OFDM SYSTEMS

Abstract: Multiple-input multiple-output (MIMO) wireless technology in combination with Orthogonal Frequency Division Multiplexing (OFDM) is a promising solution for implementing efficient next-generation wireless local area networks (WLANs) and fourth-generation mobile cellular wireless systems. This paper explores the advantages of using the combined effects of MIMO and OFDM for the transmission of JPEG compressed images. The spatially correlated channel is estimated using a pilot tone transmission and a power allocation based on Lagrangian dual is utilized to improve the power efficiency system. It is assumed that the channel state information is fedback from the receiver through a low feedback path. With unequal power allocation it is possible to extent the application of MIMO-OFDM for WLANs to efficient image transmission over a spatially correlated channel. The proposed unequal power allocation gives less error compared to equal power allocation.
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Outage performance of cooperative amplifyandforward OFDM systems with nonlinear power amplifiers

Outage performance of cooperative amplifyandforward OFDM systems with nonlinear power amplifiers

Cooperative diversity and orthogonal frequency division multiplex- ing (OFDM) are two key technologies for future wireless commu- nication systems. One of the main problems of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted sig- nals, which may cause the introduction of intercarrier interference due to the presence of nonlinear power amplifiers (PAs). In this pa- per, a theoretical analysis of the outage probability of an amplify- and-forward (AF) cooperative diversity OFDM system accounting for nonlinear distortions introduced by a nonlinear PA is developed. It is assumed a frequency-selective Rayleigh fading and a downlink transmission, with the base station having a linear PA and the relay having a nonlinear PA. Our analysis shows how the PA parameters affects the outage probability for different SNR levels. The valid- ity of the proposed outage analysis is verified by means of computer simulations.
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A Method To Find The Area Of Sector Without The Usage Of Angle Made By The Chord

A Method To Find The Area Of Sector Without The Usage Of Angle Made By The Chord

As we know that to find the area of sector the angle made by the chord (that is chord which divides the circle) is required. But in the below method we find the ratio of the segments of the circle. Thus by relating the area of segment to the area of sector the area of sector could be found. The ratio of area of segments is related to tangents that are drawn through diameter on either side.

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An Imperialist Competitive Algorithm for Sitting and Sizing of Distributed Generation in Radial Distribution Network to Improve Reliability and Losses Reduction

An Imperialist Competitive Algorithm for Sitting and Sizing of Distributed Generation in Radial Distribution Network to Improve Reliability and Losses Reduction

The Distributed generations (DGs) are small-scale power generation technologies of low voltage type that provide electrical power at a site closer to consumption centre's than central station generation. It has many names like Distributed energy resources (DER), onsite generation, and decentralized energy. DGs are from renewable and artificial models. DGs are the energy resources which contain Renewable Energy Resources such as Wind, Solar and Fuel cell and some artificial models like Micro turbines, Gas turbines, Diesel engines, Stirling engines, Internal combustion reciprocating engines[1]. In the present vast load growing electrical system, usage of DG have more advantages like reduction of transmission and distribution cost, electricity price, saving of the fuel, reduction of sound pollution and green house gases. Other benefits include line loss
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A Study on Improving the Overloaded Speech Waveform to Distinguish Alcohol Intoxication using Spectral Compensation

A Study on Improving the Overloaded Speech Waveform to Distinguish Alcohol Intoxication using Spectral Compensation

Abstract—In this study, speech characteristics from before and after alcohol intoxication has been comparatively analyzed through speech analysis to obtain the degree of intoxication along with its parameters. However, the overload of the input signal must be considered prior to anything else. When distinguishing intoxication under overload conditions, an error cannot be avoided. Therefore, distinguishing the level of intoxication must be conducted by using a method that is not significantly influenced by overload. Thus, reliability of distinguishing the degree of intoxication was enhanced by pre- processing the overload to compensate the spectrum. The SNR and intoxication distinguishment rate resulted comparatively better at about 2 and 5% overload clipping rate, however, resulted in an error and increase at 10% overload clipping rate.
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Simultaneous Determination of Kaempferide, Kaempferol and Isorhamnetin in Rat Plasma by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry and its Application to a Pharmacokinetic Study

Simultaneous Determination of Kaempferide, Kaempferol and Isorhamnetin in Rat Plasma by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry and its Application to a Pharmacokinetic Study

The reference standards of isorhamnetin (purity > 98.0%), kaempferide (purity > 98.0%), and kaempferol (purity > 98.0%) were purchased from Chengdu Must Bio-Technology Co., Ltd. (Chengdu, Sichuan, China). Tinidazole (purity > 99.9%) was used as an internal standard (IS) and purchased from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). SSB was obtained from Suzhou Tianling Chinese Herbal Medicine Co. Ltd. (Jiangsu, China) and identified by Professor Jianwei Chen in Nanjing University of Chinese Medicine. β-Glucuronidase and sulfatase were supplied by Sigma-Aldrich (St. Louis, MO, USA). Methanol and acetonitrile were of HPLC grade (Merck, USA). All other reagents were of AR (analytical reagent) grade. Ultrapure water used for the UHPLC-MS/MS was from Milli-Q system (Millipore, Billerica, MA, USA).
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DIGITAL WATERMARKING SCHEMES FOR AUTHORIZATION AGAINST COPYING OR PIRACY OF COLOR IMAGES

DIGITAL WATERMARKING SCHEMES FOR AUTHORIZATION AGAINST COPYING OR PIRACY OF COLOR IMAGES

DCT based watermarking techniques are robust compared to spatial domain techniques. Such algorithms are robust against simple image processing operations like low pass filtering, brightness and contrast adjustment, blurring etc. However, they are difficult to implement and are computationally more expensive. At the same time they are weak against geometric attacks like rotation, scaling, cropping etc. DCT domain watermarking can be classified into Global DCT watermarking and Block based DCT watermarking. Embedding in the perceptually significant portion of the image has its own advantages because most compression schemes remove the perceptually insignificant portion of the image.
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Comparative Analysis for Discrete Sine Transform as a suitable method for noise estimation

Comparative Analysis for Discrete Sine Transform as a suitable method for noise estimation

When the speech signal corrupted by noise is processed using different transforms like the Discrete Fourier Transform, Discrete Cosine Transform and the Discrete Sine Transform , a comparative analysis proves that the Discrete Sine Transform (DST) is most suitable for de-noising and therefore reconstruction of the original speech. The experimental results show that the discrete sine transform coefficients at the low frequency regions are predominantly speech, and at the high frequency regions are predominantly noise. According to this, a new noise estimation method based discrete sine transform is proposed in this paper. The usage of DST coefficients reveals that the energy distribution throughout the segment of speech is uniform.
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Rev Bras Med Esporte  vol.17 número3 en v17n3a08

Rev Bras Med Esporte vol.17 número3 en v17n3a08

total active extension. The rotation axis of the dynamometer was aligned with the rotation axis of the tested knee joint (lateral femoral condyle), to avoid that the torque measurements were invalidated. The equipment used in this study allows that the limb is weighed and decomposed for more reliable data production, compensating the gravity action. The athletes were assessed by the same evaluator, who encouraged the athlete during the en- tire test with verbal commands to perform his maximal strength.

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Perceptual Zero-Tree Coding with Efficient Optimization for Embedded Platforms

Perceptual Zero-Tree Coding with Efficient Optimization for Embedded Platforms

for identifying edge features is an essential step in the detection and segmentation of objects of interest. Although integrating the LLEC technique with DCT is an efficient approach for producing a low-computation and low-memory-cost image codec, it does not provide a perceptual strategy to improve the visual quality of compressed images. Therefore, this study proposes a block-edge-based perceptual zero-tree coding (PZTC) method that integrates and improves these two image-coding techniques efficiently. Furthermore, this paper presents an adaptive quantization table adjustment scheme based on the statistical analysis of DCT blocks in various types of images. Therefore, the proposed combinative coding scheme adaptively adjusts the quantization tables based on edge feature detection. Thereafter, the LLEC codes the quantized coefficients by using a predetermined quantization table to preserve the highest visual quality in the compressed images.
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Transmitted Power Formulation for the Optimization of Spectrum Aggregation in LTE-A over 800 MHz and 2 GHz Frequency Bands

Transmitted Power Formulation for the Optimization of Spectrum Aggregation in LTE-A over 800 MHz and 2 GHz Frequency Bands

Abstract This work starts by proposing a formulation to calculate the transmitter power needed to cover cells of different sizes, whilst maintaining the average signal to interference- plus-noise ratio constant, and near the maximum, for two Long Term Evolution (LTE) systems operating over non-contiguous frequency bands, 800 MHz and 2 GHz, with an integrated common radio resource management (iCRRM) entity. In the context of spectrum aggregation (SA), iCRRM is able to switch users between the two LTE-Advanced scenarios to facilitate the best user allocation and maximize the total network throughput in these LTE systems. We address a formulation based on the computation of the average received power and average co-channel interference in cellular topologies with frequency reuse pattern K = 3, keeping the presence of coverage holes insignificant, whilst considering the COST-231 Hata path loss model. We have verified how the normalized power increases as the cell radius increases. The objective of applying this formulation in the dimensioning process is to save power for the shortest coverage distances. It has been found that without SA the maximum average cell throughput is observed in the presence of 80 simultaneous users within the cell (40 for each LTE system, operating in different frequency bands). We have considered traced-based video sessions with a (video) bit rate of 128 kbps. In this scenario, through extensive simulations cell average supported throughput of approximately 6,800, 8,500 and 9,500 kbps have been obtained for the cases without SA (considering the sum of the 800 MHz and 2 GHz systems capacities), with a simple CRRM and with iCRRM, respectively. It was also found that when the peak throughput is achieved with 80 users, the average cell packet loss ratio without SA, with CRRM and iCRRM present values of 22, 11 and 7 %. The average cell delay with both CRRM and iCRRM entities is 22 ms, whereas without SA is equal to 32 ms. Finally, the cost/revenue tradeoff is analysed from the operator/service provider’s point of view, whose
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Energy Efficiency of MIMO-OFDM Communication System

Energy Efficiency of MIMO-OFDM Communication System

In order to deal with this problem, a hybrid architecture based on OFDM system using MIMO is modeled and is presented in Fig 1. In this architecture the users located in rural areas are served directly from the satellite spot beam due to lack of infrastructure of terrestrial networks [2] [3]. On the other hand users located in urban areas are served by existing terrestrial system as satellite signal cannot penetrate in buildings [4]. Likewise, the spectrum is being shared between two networks that is terrestrial and satellite for providing throughout connectivity and the multiple antennas at the transmitter and the
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Temperature Dependent IR-Drop Analysis in Graphene Nanoribbon Based Power Interconnect

Temperature Dependent IR-Drop Analysis in Graphene Nanoribbon Based Power Interconnect

The paper proposes a temperature dependent resistive model of graphene nanoribbon (GNR) based power interconnects. Using the proposed model, IR-drop analysis for 16nm technology node latest by ITRS is performed. For a temperature range from 150 K to 450 K, the variation of resistance of GNR intercon- nect is ~ 2-5  times lesser than that of traditional copper based power interconnects. Our analysis shows that GNR based power interconnects can show ~ 2-3 times reduction in Peak IR-drop as compared with copper based interconnects for local, intermediate and global interconnects.
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Emboli detection in middle cerebral artery using continuous wavelet transform

Emboli detection in middle cerebral artery using continuous wavelet transform

Given the different properties of MCA blood flow signals along the cardiac cycle, it is important to study the presence of embolic events in different local- izations within the signal. Thus, embolic events were added in four defined time regions for each generated signal. Those regions were, once defined, kept con- stant for each new simulated signal. The choice of the location of the emboli areas is related to its relevancy along the cardiac cycle signal. Therefore, due to the increased difficulty on detecting embolic events in systole, three embolus were located around the systolic peak - rising curve (1), peak (2) and decaying curve (3) - and only a fourth embolus was located in diastole phase of the cardiac cycle. Figure 3.2 shows the simulated MCA signal generated from the background signal that was shown in Figure 3.1 with added, as described, simulated embolus in each defined area. The emboli areas can be observed by the red delimitation (start and end) in colour visualization or light grey in black and white (B&W) visualization.
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