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The influence of Er3+–Mn2+ substitution on the properties of Y-type hexaferrites (chemical composition: Ba2–xErxZn0.6Co0.6Cu0.8Fe12−yMnyO22 (x = 0.0, 0.3, and 0.5 and y = 0.0, 0.4, and 0.6)), which were synthesized by the sol-gel autocombustion method, was investigated. The X-ray diffraction spectra were analyzed by the Rietveld refinement method, and hexaferrite was observed to possess a single-phase crystalline structure, whereas the Fourier-transform infrared spectra clarified the formation of the iron oxide base material. The morphology of the grains revealed that they were hexagonal and without agglomeration. The band gap of the samples decreased as the Er3+–Mn2+ concentration increased. Dielectric and impedance spectroscopies of the prepared samples indicated the role of polarization in the variation in the dielectric and impedance parameters. Particularly, the occurrence of space-charge polarization increased the dielectric constant at lower frequencies. Further, the Cole–Cole plot revealed a semicircle in the lower frequency region, thereby indicating that the grain boundary contributed the most to the dielectric constants. Modulus spectroscopy revealed that the charge mobility increased as the concentration of Er3+–Mn2+ increased. Additionally, the magnetic analysis indicated that Mn2+ preferably replaces Fe3+ at the octahedral site, thereby reducing the magnetization of the prepared samples through a reduced superexchange interaction. Furthermore, increasing the coercivity values thermally stabilized the sample, and this is vital for perpendicular magnetic recording.

We report the synthesis of Sr2+ doped Ba0.9-xCa0.1SrxTi0.8Zr0.2O3 nano-ceramics by the conventional solid-state reaction method. Phase formation of single-phase orthorhombic ABO3 type structure with space group P2mm was confirmed through X-ray diffraction (XRD). The crystallite size increased with increasing doping concentration from 25.46 nm to 52.96 nm as calculated by the Scherrer formula and from 47.1 nm to 88.5 nm by the Williamson-Hall method. The lattice parameter, dislocation density, and apparent density decreased with doping, except for when x = 0.05. The porosity was found to increase up to 16.8% with increasing doping. Field emission scanning electron microscopy (FESEM) shows that samples exhibit a flake-like structure. X-ray photoelectron spectroscopy (XPS) analysis confirms that Sr-ions occupy the Ca-site, for x = 0.05, and force the Ca ions to occupy the Ti-sites. For the higher concentration of Sr, i.e. x ≥ 0.15, no more forced substitution is observed and Sr-ions occupy the Ba-site only, which decreases oxygen vacancies. Diffused rings observed in selective area electron diffraction (SAED) patterns indicate the high crystalline order of the samples. The Fourier-transformed infrared spectroscopy (FTIR) measurements show a single broad peak between 544 and 594 cm−1 for all the compositions, while two prominent peaks are observed for the composition x = 0.05 at 528 cm−1 and 592 cm−1. The Raman spectra show a shift in the most prominent peak, observed approximately 517 cm−1.

Machine learning (ML) techniques are looked upon as an innovative and realistic direction to cope up with nonlinearity issues in fiber optics communication. In this paper, a 64-quadrature amplitude modulation (QAM) based radio over fiber (RoF) system is demonstrated for 10 km of standard single mode fiber length utilizing support vector machine (SVM) method to indicate an effective nonlinearity mitigation in front-hauls. The comparison of SVM is drawn with conventional ML classifiers to optimize symbol decision boundary that will reduce the RoF link impairments. The results are reported in terms of BER, Eye-linearity and Quality factor.

In this paper, we study the synthesis dependence of structural, optical and antimicrobial properties for copper oxide nanoparticles on, synthesized using microwave irradiation CuO(M), co-precipitation CuO(P) and hydrothermal CuO(H) protocols. Structural and morphological properties were studied using XRD, SEM, TEM and SAED techniques. XPS studies confirmed the presence of copper ions in Cu2+ oxidation state, and Raman spectroscopy confirmed the presence of nanostructured phase in all the samples. The synthesized CuO(M), CuO(P) and CuO(H) nanoparticles were investigated for antimicrobial activity against different pathogenic bacteria including methicillin-resistant Staphylococcus aureus. The result showed that maximum inhibition zone was detected in CuO(M) nanoparticles against Gram-negative bacteria i.e. Klebsiella pneumoniae (20 mm). CuO(H) and CuO(P) nanoparticles have antibacterial inhibition zone of 17 mm and 13 mm against K. pneumoniae and S. aureus, respectively. The CuO(P) and CuO(H) nanoparticles displayed mild antimicrobial activity as compared to the CuO(M) nanoparticles.

Cu-doped Co–Zn nanoferrites Co0.5CuxZn0.5 − xFe2O4 (x = 0.0, 0.2 and 0.4) were synthesized by sol-gel auto-combustion. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with EDS, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), and two-probe methods were employed to study the structural, morphological, magnetic and DC electrical resistivity properties, respectively, of the prepared samples. Monotonically decreasing values of the lattice constants with the dopant concentrations were calculated. The crystallite sizes were also recorded in a decreasing pattern. The stretching bond vibrations measured by room temperature FT-IR showed characteristic absorptions in the range of 579.634–393.49 cm − 1. The magnetic parameters were observed to have a tuned value, although decreasing in a non-monotonic pattern. A higher value of the DC resistivity value was recorded for x = 0.2 concentration of the dopant, indicating the optimal concentration for synthesizing materials applicable in high-frequency microwave devices.

This letter presents a comparative evaluation between three different behavioral models to perform digital predistortion (DPD) that enhances the linearity of radio-over-fiber (RoF)-based front haul links for the mobile network. In particular, the intention is to jump out of the volterra box and propose models based on segmentation approach. Especially the decomposed vector rotation (DVR) model is compared to volterra polynomials such as memory and generalized memory polynomial (GMP) architectures. DPD is employed to RoF links that are based on distributed feedback laser emitting at 1310 nm, and standard single-mode fiber for long-term evolution 20-MHz signal with 256-QAM modulation format. The effectiveness of the digital predistortion methodology is investigated for varying input powers in terms of normalized mean square error, adjacent channel power ratio, and error vector magnitude. The experimental results demonstrate that DVR achieves elevated linearization when compared to memory polynomial and GMP models.

In recent years, the demand of efficient and broadband wireless access has escalated, for which Radio over Fiber (RoF) is considered as an appropriate solution. In this paper, we present a Digitized Transmission of 20 MHz LTE signal having 64 quadrature amplitude modulation over 70 Km of Standard Single Mode Fiber (SSMF) for broadband wireless signal transportation and distribution applications. The performance analysis has been evaluated for conventional Analog Radio over Fiber (A-RoF) and proposed Digital Radio over Fiber (D-RoF). The bandpass sampling technique is discussed and employed for digitizing the RF signal. As a figure of merit, the performance evaluation of two architectures is reported by analyzing the Error Vector Magnitude (EVM), Signal to Noise Ratio and Eye-Opening Penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 70 Km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog to digital converter (ADC) resolution bits. An experimental validation of the proposed analytical D-RoF model is done for 30 Km of SSMF, whose experimental results are in line with the analytical ones. The evaluated parameters are within the LTE specifications, proving this is a cost and power effective solution for next generation wireless networks.

Herein, we report the synthesis of nanoparticles and doping of Cu-doped Co–Zn ferrites using the auto-combustion sol–gel synthesis technique. X-ray diffraction studies confirmed the single-phase structure of the samples with space group Fd3m and crystallite size in the range of 20.57–32.69 nm. Transmission electron microscopy micrographs and selected area electron diffraction patterns confirmed the polycrystalline nature of the ferrite nanoparticles. Energy-dispersive X-ray spectroscopy revealed the elemental composition in the absence of any impurity phases. Fourier-transform infrared studies showed the presence of two prominent peaks at approximately 420 cm−1 and 580 cm−1, showing metal–oxygen stretching and the formation of ferrite composite. X-ray photoelectron spectroscopy was employed to determine the oxidation states of Fe, Co, Zn, and Cu and O vacancies based on which cationic distributions at tetrahedral and octahedral sites are proposed. Dielectric spectroscopy showed that the samples exhibit Maxwell–Wagner interfacial polarization, which decreases as the frequency of the applied field increases. The dielectric loss of the samples was less than 1, confirming that the samples can be used for the fabrication of multilayer inductor chips. The ac conductivity of the samples increased with increasing doping and with frequency, and this has been explained by the hopping model. The hysteresis loops revealed that coercivity decreases slightly with doping, while the highest saturation magnetization of 55.61 emu/g was obtained when x = 0.1. The magnetic anisotropic constant was found to be less than 0.5, which suggests that the samples exhibit uniaxial anisotropy rather than cubic anisotropy. The squareness ratio indicates that the samples are useful in high-frequency applications.

This paper demonstrates an unprecedented novel neural network (NN)-based digital predistortion (DPD) solution to overcome the signal impairments and nonlinearities in Analog Optical fronthauls using radio over fiber (RoF) systems. DPD is realized with Volterra-based procedures that utilize indirect learning architecture (ILA) and direct learning architecture (DLA) that becomes quite complex. The proposed method using NNs evades issues associated with ILA and utilizes an NN to first model the RoF link and then trains an NN-based predistorter by backpropagating through the RoF NN model. Furthermore, the experimental evaluation is carried out for Long Term Evolution 20 MHz 256 quadraturre amplitude modulation (QAM) modulation signal using an 850 nm Single Mode VCSEL and Standard Single Mode Fiber to establish a comparison between the NN-based RoF link and Volterra-based Memory Polynomial and Generalized Memory Polynomial using ILA. The efficacy of the DPD is examined by reporting the Adjacent Channel Power Ratio and Error Vector Magnitude. The experimental findings imply that NN-DPD convincingly learns the RoF nonlinearities which may not suit a Volterra-based model, and hence may offer a favorable trade-off in terms of computational overhead and DPD performance.

Sigma-delta radio over fiber (ΣΔ-RoF) is an expedient technology for next-generation networks including 5G cloud/centralized radio access networks (C-RAN). In this article, we demonstrate a realistic experimental scenario for ΣΔ-RoF link targeting C-RAN fronthaul applications, by using baseband second-order 1-bit sigma-delta modulation (ΣΔ-M). The experimental set-up validates the LTE 20 MHz signals having modulation order of 256-quadrature amplitude modulation for a carrier frequency of 3 GHz, up to 10 km of standard single mode fiber. A detailed analysis of the ΣΔ-RoF system performance is reported by adjacent channel leakage ratio and error vector magnitude. Furthermore, an experimental study is evaluated where ΣΔ-RoF is compared with its counterparts. It is deduced that ΣΔ-RoF corroborates the present range of C-RAN fronthaul networks and can be a promising candidate for future mobile haul applications.

This paper reports the performance evaluation and realization of fifth generation (5G) new radio (NR) multiband signals employing Analog Radio-over-Fiber based optical link as a front haul. The proposed 5G NR signals comprise of 3 GHz flexible waveforms and 23 GHz–400 MHz bandwidth. The EVM performance for the system meets the 3GPP Release 16. Furthermore, EVM performance for received optical power is evaluated up to 400 MHz bandwidth. Besides, we perform an evaluation for coexisting 5G and 4G systems with cleaner and lower EVM in limits for offset greater than 15 MHz.

Radio over fiber (RoF) is a promising solution for the next-generation wireless networks including fifth-generation Cloud/Centralized Radio Access Network (C-RAN). There exists a possibility to use Sigma Delta Modulated RoF (S-DRoF) that combines the advantages of analog RoF and digital RoF by means of sigma delta modulation (SDM) at the transmitter side subsequently replacing the employment of expensive and high-speed digital-to-analog converters. In this paper, we demonstrate the usage of second-order SDM for LTE 20 MHz signal having 64 QAM modulation on a central carrier frequency of 1.14 GHz for the implementation of S-DRoF for 20 km of standard single mode fiber with baud rate from 25 to 100 Mbaud. Furthermore, a comprehensive analysis of the design of SDM is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude, constellations and adjacent channel power ratio. The results show that the proposed architecture performance is in with accordance to the limitations set by the 3GPP (Third Generation Partnership Project) standards and is a reasonable choice either for upgrading installed systems as well as for the new deployments.

International audience; The article demonstrates a novel Digital Predistortion (DPD) architecture for Mobile Front Haul links for the advanced Long-Term Evolution (LTE) and upcoming 5G networks. Precisely, the use of a feedback approximation method has been proposed and experimentally demonstrated herein that simplifies the complexities in realizing the practical DPD technique for Multi-Mode VCSELs and Multi-Mode Fibers based Radio over Fiber systems. As a figure of merit, linearization efficiency is provided in terms of Adjacent Channel Power Ratio, Normalized Mean Square Error and Error Vector Magnitude referring to a complete LTE frame occupying 10 MHz with 256-QAM modulation format.

In this paper, we report the synthesis of gadolinium (Gd) and niobium (Nb) co-doped barium titanate (BT) ceramic oxides prepared using a conventional solid-state reaction method. The X-ray diffraction pattern confirmed the formation of tetragonal phase – with the space group P4mm – in all samples. X-ray photoelectron spectroscopy shows the formation of oxygen vacancies with a variable concentration that depends on the site preference of Gd ions. Fourier – Transform infrared analysis shows the presence of the most prominent peak between 544 cm−1 and 588 cm−1. Raman spectroscopy shows the tetragonal phase, with a most prominent peak around 514 cm−1 due to A1(TO3)E(TO4) mode. Shifting of this peak suggests the formation of GdBa defects. UV measurement suggests an increase in bandgap from 2.928 eV to 3.047 eV with Gd doping. Photoluminescence shows the presence of multiple level emission mechanisms for all samples. The dielectric constant increases while dielectric loss decreased with increasing dopant concentration, which is attributed to the self-compensation mechanism and defect dipole formation. Impedance spectra, Z ′ and Z ′ ′ vs frequency, suggest the presence of space charge polarization. Modulus spectra, M ′ and M ′ ′ vs frequency indicates the presence of short-range mobility at low frequency and long-range mobility at high frequency. AC conductivity shows almost negligible change with variable dopants concentration. Thus, electrical properties were observed to improve with Gd and Nb co-doping on BT ceramic oxides.

Recently, investigation on two-dimensional (2D) metal dichalcogenides has attracted significant attention owing to their impressive electronic structure and optical properties for optoelectronics and photocatalytic applications. Nevertheless, the higher rate of the photo-generated carriers and the electron-hole recombination process limits their technological applications. A promising strategy may consist of constructing 2D heterostructures that could potentially enhance their photocatalytic activities. This work reports the structure, electronic structure, optical, interfacial, and photocatalytic properties of MoSe2/InN heterostructure nanosheet. The interfacial interaction between the MoSe2 and the InN layers was the van der Waals bonding type. The valence band edge and conduction band edge positions of consecutive layers were altered near the Fermi level and formed type-II band orientation. The electronic structure and work function results confirmed that heterojunction potentially possesses improved photocatalytic activity. This work provides the basics for the future development of various enhanced heterostructures for photocatalytic applications.

Polyethylene plastic is a threat to the environment because of its enormous usage and limited recycling options. Herewith, the study reports the synthesis of Kish graphite from polyethylene waste. These wastes was mixed with molten iron and cooled into a rod-shaped mold. The molded iron ingots contain precipitated carbon material in 2D graphitic nature, which was obtained as Kish graphite after several acid treatments. The tafel studies show the anticorrosive nature of the sample with the corrosion potential of −1.6 V. Kish graphite and manganese oxide in the ratio 40:9 exhibited higher catalytic activity towards oxygen reduction reaction. Discharge studies of Mg-air battery with graphite (80%) air cathode recorded the highest capacity of 1226.51 mAh g−1, discharge life of 73.6 h and enhanced performance characteristics. Thus, waste polyethylene was effectively used as an supportive electrocatalyst in the Mg-air battery system.

Properties of materials greatly differ in nanoparticle form compared to their bulk counterpart. Strain mechanism, elastic properties and cation distribution play a major role as particle size decreased to nanoscale level and therefore it is necessary to evaluate these properties precisely through reliable methodology. In the present work, a detailed investigation has been carried out on nanocrystalline particles of Mg–Mn co-substituted CdFe2O4 to estimate intrinsic strain through Williamson-Hall (W–H) analysis. The results were compared with those obtained from Scherrer equation and Rietveld refinement. Bertuat method was used to estimate the cation distribution of spinel ferrite. Elastic properties such as, stiffness constant, Young's modulus, bulk modulus, rigidity modulus, Poisson's ratio and Debye temperature were studied by using the band positions of tetrahedral – A and octahedral – B sites observed through infrared spectra. The obtained results were discussed in the light of strain mechanism, elastic constants and substitution of Mg–Mn ions in the CdFe2O4.

Radio over Fiber is a promising technology for the 5G Cloud Radio Access Network. We demonstrate experimentally Sigma Delta Radio over Fiber by means of Sigma Delta Modulator (SDM) subsequently replacing expensive digital to analog converters. A second order SDM is proposed for LTE 20 MHz signal having 256 QAM modulation on a carrier frequency of 3.5 GHz for 10 Km of fiber length. The performance is reported in terms of error vector magnitude, adjacent channel leakage ratio and eye-opening penalty. The results show that the proposed architecture performance is cost and power efficient solution for next-generation wireless networks. Keywords: Radio over fiber, Sigma delta modulation, 5G C-RAN, EVM, ACPR

To decrease cost and consumption of future wireless infrastructures, radio-over fibre systems utilising 850 nm vertical cavity surface emitting lasers and standard single-mode fibre (SSMF) are deserving particular attention in replacing the typical use of graded-index multimode fibre (GI-MMF). In the present work, a characterisation of noise and non-linearities of these links is performed, followed by an estimation of their impact on the system dynamics and the quality of the received signal. This allows to show that very good and similar performances can be obtained through the utilisation of SSMF and GI-MMF for the transmission of five long-term evolution channels with 20 MHz bandwidth, confirming that the former, by the higher diffusion and lower cost per metre of the SSMF, can be put among the leading candidates for the realisation of fourth-generation (4G) and 5G wireless networks.

Machine learning (ML) methodologies gave an innovative and realistic direction to cope up with nonlinearity issues in fiber optics communication. In this paper, a 40-Gb/s 128-quadrature amplitude modulation (QAM) signal based Radio over Fiber (RoF) system is experimentally evaluated for 70 km of standard single mode fiber length which utilizes support vector machine (SVM) decision method to indicate an effective nonlinearity mitigation. The influence of different impairments in the system is evaluated that includes the influences of Mach-Zehnder Modulator nonlinearities, in-phase and quadrature phase skew of the modulator, input signal power and noise due to amplified spontaneous emission. By employing SVM, the results demonstrated in terms of bit error rate and eye linearity suggest that impairments are significantly reduced and licit input signal power span of 5dBs is enlarged to 15 dBs.

Analog Radio-over-Fiber (A-RoF) communication technology constitutes a promising technique for next generation radio access networks thanks to its relatively low bandwidth requirements. Within this context, an efficient predistortion technique is proposed, which can be applied to reduce the impairments of A-RoF systems due to the combined effects of frequency chirp of the laser source and chromatic dispersion of the optical channel. The radio frequency signal is firstly put in digital form through an analog to digital converter, then the predistortion operation is realized, and finally the resulting signal is put again into analog form. A comprehensive analysis on the theoretical basis of the proposed approach is presented, together with the approximations introduced, which makes it practically realizable. The improvements on the quality of the received signal due to the proposed solution are illustrated with reference to scenarios of applicative interest. The performance of proposed technique is evaluated in terms of adjacent channel leakage ratio and error vector magnitude when long term evolution signal is applied at the input.

In this paper, we report the synthesis of vanadium (V)-doped Ba0.9Ca0.1Ti0.9−xVxZr0.1O3 (BCZT) ceramic oxides prepared using conventional solid-state reaction methods. The X-ray diffraction (XRD) pattern confirmed the formation of the tetragonal phase—with the space group P4mm—in all samples. A barium vanadate (Ba3V2O8) impurity phase was observed in the doped samples, which suggests that the solubility limit of V was reached in the BCZT ceramics. X-ray photoelectron spectroscopy shows the formation of oxygen vacancies, which attain a maximum value at a concentration x = 0.02, i.e., 38.65%. Fourier-transform infrared analysis shows prominent peaks between 560 cm−1 to 558.1 cm−1, with a secondary-phase peak around 1017 ± 2 cm−1, as suggested by XRD. Photoluminescence (PL) spectra suggest that oxygen vacancies play important roles in promoting luminescence by trapping the excited photoelectrons. Oxygen vacancies also reduce the recombination rate of photo-generated electrons and holes. Ultraviolet–visible analysis agreed with PL studies, with comparable bandgap energy. Raman spectroscopy also shows the tetragonal phase, with the most-prominent peak around 520 cm−1 due to the A1(TO3)/E(TO) mode. We attribute two peaks observed around 330 cm−1 and 780 cm−1 to the Eg and A1g modes, respectively, of the secondary phase. Electrical studies performed for all samples reveal that variable oxidation states of Vin the presence of oxygen vacancies readily influence the resistivity—and thus the activation energy—of each sample. We obtained a maximum DC resistivity ρDC (max.) = 1.653 × 10−11(Ω cm) and a corresponding minimum DC conductivity σDC (min.) = 8.581 × 10−12 for x = 0.02, which is due to the presence of only an acceptor (V3+) concentration for this sample. The Curie temperature (Tc) also decreased from 71.8 °C to 31 °C with increasing V-ion concentration. The drift mobilities observed for all samples are in accordance with the Verwey–de Boer mechanism. Thus, the substitution of V ions at Ti sites can significantly influence the optical and electrical properties of BCZT ceramics.

The influence of Ag+ substitution on copper nanoferrites was reported. The single spinel phase within the synthesized nanoferrites was revealed from XRD analysis. The estimated crystallite sizes are showing variation within 18–27 nm. The FE-SEM micrographs exhibit the presence of nanoparticles with agglomeration at few places. The TEM profiles exhibit the nano-spheres with a mean diameter of 27 nm. The elemental compositions within the stoichiometry were confirmed from the EDS analysis. The presence of functional groups of spinel ferrites were exhibited by FTIR spectra of the ferrites. The VSM study shows decrease in the saturation magnetization with increasing Ag+ composition.

Passive bistatic radar (PBR) systems using different communication signals can only offer low-resolution target detection due to their inherent low bandwidth. In this paper, compressive sensing (CS) is applied to multichannel FM and GSM PBR to achieve improved range-Doppler resolutions and avoid some limitations of classical multiband PBR processing. In CS context, block-structured time-domain dictionary which is formed from multichannel signals suffers from coherence when fine range resolution is employed. To overcome such a pitfall, this work first transforms the dictionary to spectral domain where only the most important spectral components are retained. Principle component analysis followed by a whitening method are then applied to this spectrally transformed data in order to reduce the dimensionality of problem, thereby reducing the dictionary size and most importantly fulfilling the required condition of dictionary incoherence for better CS-based recovery. Two different block-structured dictionary formations are tested. The performance of the recovery of spatially close targets, in both FM and GSM PBR setups, are reported.

Radio over fiber (RoF) is an empowering technology for the next-generation wireless networks including fifth generation cloud radio access networks. In this paper, we propose a new fronthaul interface which has been demonstrated for a 20-MHz LTE signal having 64-Quadrature amplitude modulation (QAM) modulation over 50 km of standard single-mode fiber. The proposed methodology potentially reduces the overall bandwidth requirement of the link. The performance analysis has been demonstrated for conventional analog RoF (A-RoF) and proposed digital RoF (D-RoF). As a figure of merit, the performance evaluation of the two architectures is reported by analyzing error vector magnitude (EVM), signal-to-noise ratio and eye-opening penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 50 km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog-to–digital-converter resolution bits. For the D-RoF link, the EVM was measured to be less than 2 % at 50 km. This is within the LTE specifications, proving it as a cost and power effective solution for next-generation wireless networks.

The article proposes a Digital Predistortion (DPD) methodology that substantially meliorates the linearity of limited range Mobile Front Haul links for the extant Long-Term Evolution (LTE) and future (5G) networks. Specifically, the DPD is employed to Radio over Fiber links that contrive of Vertical Cavity Surface Emitting Lasers (VCSELs) working at 850 nm. Both, Memory and Generalized Memory Polynomial models are implied to Single Mode (SM) and Multi-Mode (MM) VCSELs respectively. The effectiveness of the proposed DPD methodology is analyzed in terms of Normalized Mean Square Error, Normalized Magnitude, Normalized phase and Adjacent Channel Power Ratio. The demonstration has been carried out with a complete (Long Term Evolution) LTE frame of 10 ms having 5 MHz bandwidth with 64-QAM modulation configuration. Additionally, the effectuality of the proposed DPD technique is evaluated for varying levels of input power and link lengths. The experimental outcomes signify the novel capability of the implied DPD methodology for different link lengths to achieve higher system linearization.

A Multi-channel LTE transmission on a Radio-over-Fibre (RoF) system realized with low cost and low consumption 850nm Vertical Cavity Surface Emitting Laser (VCSEL) and Standard Single Mode Fibre (SSMF) is proposed in the framework of wireless networks fronthaul links. The performances are evaluated through the Error Vector Magnitude (EVM) comparing different distances, channels employed and modulation formats using the carrier aggregation nominal channel spacing for 20 MHz bandwidth LTE signals. The potentiality of this link is then highlighted by the maximum length achievable according to the LTE standard for 64-QAM, 256-QAM and 1024-QAM modulation formats, for which the maximum length results to be greater than 2 km, 1 km and 100 m, respectively.

Sigma Delta Radio over Fiber (S-DRoF) systems are looked upon as an enabling technology due to their advantages that comes due to combination of analog and digital radio over fiber (RoF) systems. In this paper, we have proposed and experimentally demonstrated a Multi-stAge-noise-SHaping (MASH) based Sigma Delta Modulated RoF system targeting 5G C-RAN (cloud/centralized radio access network) fronthaul applications. The evaluation has been done for LTE 20 MHz signal having 256 quadrature amplitude modulation with a carrier frequency of 3.5 GHz up to 5 Km of Standard Single Mode Fiber (SSMF). Furthermore, a comprehensive analysis of the design is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude (EVM) and adjacent channel leakage ratio. It is concluded that S-DRoF substantiates the desired range of the 5G C-RAN fronthaul networks.

This letter unfolds a digital predistortion (DPD) technique that improves the linearity of limited range mobile front haul links for the contemporary long-term evolution (LTE) and future (5G) networks. In particular, the proposed technique is applied to radio-over-fiber links based on single-mode (SM) vertical cavity surface emitting lasers emitting at 850 nm and standard SM fibers. Both the memory and generalized memory polynomial models are exploited for the predistorter and identified by utilizing indirect learning architecture. The impact of the DPD technique is observed by the link performance improvement in terms of normalized mean square error and adjacent channel power ratio, referring to complete LTE frames of 10 ms occupying 5-MHz bandwidth and having 64-quadrature amplitude modulation format. Furthermore, the effectiveness of the DPD approach, when varying input power levels, is investigated. The experimental results demonstrate the capability of the proposed DPD technique to achieve promising linearization performance.

Passive bistatic radar (PBR) systems use existing RF broad − 1 cast and communication signals in the environment for surveillance and tracking applications. GSM mobile com − 1 munication signal based PBR systems are suitable for short-range surveillance systems, but the low-bandwidth of the signal results in low range resolutions when classical cross-correlation based processing is used for target detection. An alternative and more robust approach based on compressive sensing (CS) is proposed here to achieve high range resolution 1 by performing fine gridding for the target scene. To avoid the 1 increased coherence and computational load associated with the fine gridding, preprocessing steps are introduced in this paper, which involve choosing a suitable CS basis by application of spectral and subspace transformations. By so doing, resolution improvement is achieved when a single channel GSM signal and CS are employed for target detection.

Due to their inherent capillary distribution properties, Radio over Fiber (RoF) systems are expected to play a major role within future fifth generation wireless networks. However, significant bounds on the technology usability are set by the nonlinear generation of spurious frequencies, which, in the case of RoF links exploiting Directly Modulated Lasers (DML), has the combined effect of laser chirp and optical fiber dispersion among its prevailing causes. In this paper, a signal digital predistortion system, which can lower these detrimental effects, is proposed in two different versions. A detailed description of its functional model is given, and its attractive features in terms of quality improvement of the received signal is illustrated.

Wireless sensor networks (WSNs), built from many battery-operated sensor nodes are distributed in the environment for monitoring and data acquisition. Subsequent to the deployment of sensor nodes, the most challenging and daunting task is to enhance the energy resources for the lifetime performance of the entire WSN. In this study, we have attempted an approach based on the shortest path algorithm and grid clustering to save and renew power in a way that minimizes energy consumption and prolongs the overall network lifetime of WSNs. Initially, a wireless portable charging device (WPCD) is assumed which periodically travels on our proposed routing path among the nodes of the WSN to decrease their charge cycle time and recharge them with the help of wireless power transfer (WPT). Further, a scheduling scheme is proposed which creates clusters of WSNs. These clusters elect a cluster head among them based on the residual energy, buffer size, and distance of the head from each node of the cluster. The cluster head performs all data routing duties for all its member nodes to conserve the energy supposed to be consumed by member nodes. Furthermore, we compare our technique with the available literature by simulation, and the results showed a significant increase in the vacation time of the nodes of WSNs.