PAPR reduction for OFDM‐based visible light communication systems using proposed hybrid technique

Orthogonal Frequency Division Multiplexing (OFDM) is utilized with visible light communication (VLC) systems to decrease the impacts of inter‐symbol interference and to achieve communication with high speed of data transmission and huge bandwidth. In any case, the main problem in OFDM‐based VLC systems is high peak‐to‐average power ratios (PAPRs). This paper proposes a hybrid PAPR reduction technique based on signal transformation combined with clipping. The Hadamard transform is used in the proposed technique to reduce the PAPR without affecting the bit error rate (BER) of the VLC systems. The optimum clipping threshold at which the PAPR is reduced simultaneously with the improvement the BER of the VLC systems is also determined. The performance of the proposed system is assessed in terms of complementary cumulative distribution function and the BER. The obtained results demonstrate that the proposed procedure can simultaneously decrease the PAPR and achieve good BER performance compared to the OFDM‐based VLC system.     

Joint low‐complexity equalization and CFO estimation and compensation for UWA‐OFDM communication systems

Frequency synchronization has a great importance in preserving the performance of the underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) systems. The carrier frequency offset (CFO) estimation can be blind or data‐aided. In this paper, the Zadoff‐Chu (ZC) sequences are used for OFDM synchronization in UWA communications, and they are compared with different data‐aided algorithms. We propose a low‐complexity algorithm for CFO estimation based on ZC sequences. Also, a joint equalization and CFO compensation scheme for UWA‐OFDM communication systems is presented. Simulation results demonstrate that the proposed CFO estimation algorithm allows estimation of the CFO accurately with a simple implementation in comparison with the traditional schemes. Also, the performance of the UWA‐OFDM system can be preserved in the presence of frequency offsets.     

Satellite image fusion based on modified central force optimization

Multimedia Tools and Applications - Nowadays, optimization has become a brand methodology for different applications. One of the most promising fields for application of optimization is the image...     

A Chaotic Interleaving Scheme for the Continuous Phase Modulation Based Single-Carrier Frequency-Domain Equalization System

In this paper, we propose a chaotic interleaving scheme for the continuous phase modulation based single-carrier frequency-domain equalization (CPM-SC-FDE) system. Chaotic interleaving is used in this scheme to generate permuted versions from the sample sequences to be transmitted, with low correlation among their samples, and hence a better bit error rate (BER) performance can be obtained. The proposed CPM-SC-FDE system with chaotic interleaving combines the advantages of the frequency diversity, the low complexity, and the high power efficiency of the CPM-SC-FDE system and the performance improvements due to chaotic interleaving. The BER performance of the CPM-SC-FDE system with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between the proposed chaotic interleaving and the conventional block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-SC-FDE system. Furthermore, the results show that this scheme outperforms the conventional block interleaving scheme in the CPM-SC-FDE system. The results also show that, the proposed CPM-SC-FDE system with chaotic interleaving provides a good trade-off between system performance and bandwidth efficiency.     

Efficient remote access system based on decoded and decompressed speech signals

Multimedia Tools and Applications - This paper investigates the effect of both decoding and decompression on the Speaker Identification (SI) in a remote access system. The coding and compression...     

CalcGraph: taming the high costs of deep learning using models

Software and Systems Modeling - Models based on differential programming, like deep neural networks, are well established in research and able to outperform manually coded counterparts in many...     

Cancellable template generation for speaker recognition based on spectrogram patch selection and deep convolutional neural networks

International Journal of Speech Technology - Nowadays, biometric systems have replaced password-or token-based authentication systems in many fields to improve the security level. However,...     

The preterm prediction study: risk factors for indicated preterm births. Maternal-Fetal Medicine Units Network of the National Institute of Child Health and Human Development

This study has compared the efficacy and tolerability of formoterol (FORADIL) dry powder and salbutamol in elderly patients with reversible obstructive airways disease (ROAD). A total of 262 elderly outpatients with clinically stable ROAD participated in a multicentre, double-blind, parallel study. Patients were randomized in equal numbers to receive formoterol 12 micrograms b.i.d. formoterol 24 micrograms b.i.d. or salbutamol 400 micrograms q.i.d. for a 3 month period. All study drugs were inhaled through an Aeroliser device. Daily morning and evening peak expiratory flow (PEF) values, symptom scores and additional bronchodilator use were recorded by the patients throughout the study. Clinic assessment which included spirometry and PEF measurements was made at 4, 8 and 12 weeks. Morning and evening PEF values were significantly higher with both doses of formoterol compared with salbutamol. This difference was statistically significant both for the overall study period and during the week preceding each of the clinic visits (4, 8 and 12 weeks). There was no significant difference for the two doses of formoterol with respect to PEF values. The FEV1 and FVC values between the three treatment groups were similar. The daily use of rescue medication was significantly lower for the formoterol 24 micrograms group compared with the salbutamol group. The percentage of patients rating the therapeutic effect as 'very good' was significantly higher for formoterol: 41% on 12 micrograms; 34% on 24 micrograms; 19% on salbutamol. All treatments were well tolerated. This study demonstrates that formoterol 12 micrograms and 24 micrograms b.i.d. by dry powder inhalation are equally effective and are both significantly superior to salbutamol 400 micrograms q.i.d. in the treatment of ROAD in the elderly.     

Simultaneous Fusion and Denoising of Panchromatic and Multispectral Satellite Images

To identify objects in satellite images, multispectral (MS) images with high spectral resolution and low spatial resolution, and panchromatic (Pan) images with high spatial resolution and low spectral resolution need to be fused. Several fusion methods such as the intensity–hue–saturation (IHS), the discrete wavelet transform, the discrete wavelet frame transform (DWFT), and the principal component analysis have been proposed in recent years to obtain images with both high spectral and spatial resolutions. In this paper, a hybrid fusion method for satellite images comprising both the IHS transform and the DWFT is proposed. This method tries to achieve the highest possible spectral and spatial resolutions with as small distortion in the fused image as possible. A comparison study between the proposed hybrid method and the traditional methods is presented in this paper. Different MS and Pan images from Landsat-5, Spot, Landsat-7, and IKONOS satellites are used in this comparison. The effect of noise on the proposed hybrid fusion method as well as the traditional fusion methods is studied. Experimental results show the superiority of the proposed hybrid method to the traditional methods. The results show also that a wavelet denoising step is required when fusion is performed at low signal-to-noise ratios.