High Data Rate Communication Links Research Articles

High data-rate communication link supported through the exploitation of optical channels in a characterized turbulent underwater environment.

Underwater turbulence presents a myriad of challenges for underwater optical systems through wavefront distortion and beam deflection. In this work, an underwater turbulence emulator is developed and thoroughly characterized to experimentally test the proposed underwater turbulence mitigation technique. This technique applies a modified HOBBIT system introduced in atmospheric turbulence to the relatively unknown underwater turbulence domain. By varying a beam's spatial position and relative phase gradient, a volume of turbulence is rapidly probed to determine the beam state for optimal propagation. This probe and control method is applied in multiple facets, including improved optical power transmission as well as supporting a 25-Gbps communication link through a dynamic environment.

Analysis on the performance of reconfigurable intelligent surface-aided free-space optical link under atmospheric turbulence and pointing errors

<span lang="EN-US">Free-space optical (FSO) communication can provide the cost-efficient, secure, high data-rate communication links required for applications. For example, it provides broadband internet access and backhauling for the fifth-generation (5G) and the sixth-generation (6G) communication networks. However, previous solutions to deal with signal loss caused by obstructions and atmospheric turbulence. In these solutions, reconfigurable intelligent surfaces (RISs) are considered hardware technology to improve the performance of optical wireless communication systems. This study investigates the pointing error effects for RIS-aided FSO links under atmospheric turbulence channels. We analyze the performance of RIS-aided FSO links influenced by pointing errors, atmospheric attenuation, and turbulence for the subcarrier quadrature amplitude modulation (SC-QAM) technique. Atmospheric turbulence is modeled using log-normal distribution for weak atmospheric turbulence. Several numerical outcomes obtained for different transmitter beam waist radius and pointing error displacement standard deviation are shown to quantitatively illustrate the average symbol error rate (ASER).</span>

Highly anisotropic microwave third-harmonic generation due to mobile carriers in a graphene superlattice

We use a microscopic semiclassical approach based on the Boltzmann transport equation to explore the microwave third-harmonic generation (THG) due to mobile carriers in a one-dimensional graphene superlattice on a SiC substrate. As a model of the periodic potential of the superlattice, we adopt the piecewise constant Kronig–Penney potential. For the case of microwave radiation normally incident on the graphene superlattice, we calculate the THG conductivity of the superlattice both in the direction of its periodicity and in the perpendicular direction, and then evaluate the corresponding output THG powers from the superlattice in the reflected direction. The results obtained testify to a very strong dependence of this power on the polarization direction of the incident radiation (along or across the superlattice period) and, in addition, show that the superlattice potential applied to graphene can significantly enhance the microwave THG in graphene, which offers additional technological potentials for the design of graphene-based microwave frequency multipliers and up-converters needed for high data rate communication links.

A hybrid acoustic-RF communication framework for networked control of autonomous underwater vehicles: design and cosimulation

Underwater control applications, especially ones using autonomous underwater vehicles (AUVs) have become very popular for industrial and military underwater exploration missions. This has led to the requirement of establishing a high data rate communication link between base stations and AUVs, while underwater systems mostly rely on acoustic communications. However, limited data rate and considerable propagation delay are the major challenges for employing acoustic communication in missions requiring high control gains. In this paper, we propose a hybrid acoustic and RF communication framework for establishing a networked control system, in which, for long distance communication and control the acoustic link is used, and in the short range, the RF link is employed. Our scenario for testing implements a docking maneuver application, where a docking station determines the positions of the AUVs via acoustic or RF communication, and different medium access schemes are used for coordinating the transmission of the nodes according to the communication mode. Considering the full dynamics of the entire system for controlling the AUVs, the real-time behavior of the underwater networked control system is evaluated realistically using our proposed integrated cosimulation environment, which includes different simulators. Our performance results indicate that under calm water conditions, our proposed hybrid system reduces the docking time by 33% compared to the acoustic-only.

Lithium Niobate Piezoelectric Micromachined Ultrasonic Transducers for high data-rate intrabody communication

In recent years, there has been an increased interest in continuous monitoring of patients and their Implanted Medical Devices (IMDs) with different wireless technologies such as ultrasounds. This paper demonstrates a high data-rate intrabody communication link based on Lithium Niobate (LN) Piezoelectric Micromachined Ultrasonic Transducers (pMUTs). The properties of the LN allow to activate multiple flexural mode of vibration with only top electrodes. When operating in materials like the human tissue, these modes are merging and forming a large communication bandwidth. Such large bandwidth, up to 400 kHz, allows for a high-data rate communication link for IMDs. Here we demonstrate a full communication link in a tissue phantom with a fabricated LN pMUT array of 225 elements with an area of just 3 by 3 mm square, showing data-rates up to 800 kbits/s, starting from 3.5 cm and going up to 13.5 cm, which covers the vast majority of IMDs.

Unusual anisotropic behavior of free-carrier-induced third-harmonic generation in phosphorene at microwave frequencies

We theoretically investigate the microwave third-harmonic generation (THG) produced by free carriers in the conduction band of electrostatically doped phosphorene. It is assumed that a plane polarized microwave of frequency ω is incident normally on the phosphorene layer deposited on a dielectric substrate. Using an extremely simple model for the phosphorene’s anisotropic electronic structure, we calculate the power P(3ω) of the third harmonic wave generated in the reflected direction for the two principal cases of polarization of the incident radiation either along the ‘armchair’ () direction or along the ‘zigzag’ () one. Our results for and reveal an unusual anisotropy in the output THG power: the ratio varies from values less than 1 to values greater than 1 with an increase in the frequency ω at a fixed value of the electron density n S controlled by an external gate voltage. The effect predicted may be useful in providing a THG functionality in microwave devices, such as frequency multipliers and up-convertors, needed for developing high data rate communication links.

Spectral efficiency enhancement using an antenna‐based orthogonal frequency division multiaccess technique

An approach to enhance antenna spectral efficiency is proposed based on combining spacetime electromagnetic (EM) models of Tx/Rx antennas with orthogonal frequency division multiaccess (OFDM), leading to the EM-OFDM, a technology capable of removing intersymbol interference (ISI) in high-data rate communication links caused by the EM-induced distortion antenna effects. The proposed approach differs from traditional OFDM in wireless communication in several aspects. First, the technique suggests a new decoupling approach by treating each given antenna transreceive device pair as a “stand-alone channel” with its own distortion mechanisms considered separately from the propagation channel. Moreover, the deterministic distortion caused by the nonflat pure antenna EM filtration effects is exploited to carefully design a specialized OFDM transmission techniques based on the antenna parameters, not the multipath fading channels often invoked in conventional uses of OFDM methods. (The EM-OFDM, however, can be combined with a traditional OFDM later if fading channels are present.) In this manner, a more efficient implementation of the wireless link equalization strategy may be enacted since the EM antenna origin of ISI is very different from the traditional propagation channel one. As a proof of concept, the proposed EM-OFDM method is implemented for a single-input-single-output link comprised of half-wavelength linear wire antennas. A careful use of finite difference time-domain to provide EM data allowed the construction of 64 decoupled “pure antenna OFDM subchannels.” Simulation results suggests that the antenna-based OFDM system is capable of completely neutralizing all ISI effects caused by the limited antenna matching bandwidth of the transreceive wires, therefore, supporting considerably higher data rates with low symbol error rate (SER). A concrete evaluation of the SER using quadrature phase-shift keying (QPSK) digital carrier modulation resulted in an increase of the effective antenna digital communication spectral efficiency by ratios up to 300%. Moreover, the EM-OFDM error rate was found to be close to the ideal QPSK level or the maximum possible theoretical limit. Thus, combining detailed EM knowledge with standard signal processing methods can lead to considerable improvement in system design without modifying the antenna physical layout. The proposed approach is expected to play a role in the forthcoming 5G/6G and millimetre wave technology systems currently under development where there is a trend toward integration of EM and digital signal processing at the physical layer level.

G2A Communication Channel Modeling and Characterization Using Confocal Prolates

Characterization of radio environment is an important field of research that helps to analyze the limiting features of the propagation environment and leads to develop a realistic channel model. This paper proposes an appropriate multipath channel model for various ground-to-air (G2A) communication scenarios. An intensive review of the existing literature on A2G/G2A channel models is presented along with a critical analysis with appropriate comments wherever needed. It is observed that most of the research literature supposedly model G2A channels interchangeably in the same manner as that of land mobile communication links. G2A communications systems are generally equipped with directional antennas for dedicated coverage to flying aircrafts that benefits in increasing range and signal strength while restraining interfering signals coming through scattering objects around ground station (G). This research analyzes G2A multipath channel and thus proposes a geometrically-based physical G2A multipath channel model. The proposed channel model clearly justifies the existence of multipath environment in G2A communication due to the existence of aircrafts in the vicinity of the intended aircraft. This model is based on a three-dimensional confocal prolate spheroids and uses the principle of single-bounce multipath geometry. Moreover, the model gives an insight to analyze multipath multiuser G2A communication in wide-beam and narrow-beam communication link scenarios. This model is equally applicable to the networks of passenger aircrafts, flocks of jet fighters and mesh of UAV drones. This model can be used to analyze the performance of high data-rate communication links with high mobile speeds over sparsely distributed multipath channels.

Design of a novel wideband microstrip diplexer using artificial neural network

In this paper, we use an artificial neural network (ANN) to design a compact microstrip diplexer with wide fractional bandwidths (FBW) for wideband applications. For this purpose, a multilayer perceptron neural network model trained with the back-propagation algorithm is used. First, a novel resonator consists of coupled lines loaded by similar patch cells is proposed. Then, using the proposed ANN model, two mathematical equations for S11 and S21 are obtained to achieve the best configuration of the proposed bandpass filters and tune their resonant frequencies. Finally, using the obtained bandpass filters, a high-performance microstrip diplexer is created. The first channel of the diplexer is from 1.47 GHz up to 1.74 GHz with a wide FBW of 16.8%. The second channel is expanded from 2 to 2.23 GHz with a fractional bandwidth of 11%. In comparison with the previous designs, our diplexer has the most compact size. Moreover, the insertion losses at both channels are improved so that they are 0.1 dB and 0.16 dB at the lower and upper channels, respectively. Both channels are flat with a maximum group delay of 2.6 ns, which makes it suitable for high data rate communication links. To validate the designing method and simulation results, the presented diplexer is fabricated and measured.

A 60-GHz Ultra-Thin and Flexible Metasurface for Frequency-Selective Wireless Applications

This paper demonstrates a design, fabrication and performance evaluation of a frequency selective 60-GHz flexible metasurface in order to facilitate an unobstructed, secure, and low-loss high-frequency signal propagation. The high-attenuation 60 GHz millimeter-wave (MMW) band is selected for the design of a broadband metasurface. The symmetric metasurface unit-cell structure comprises of an assembly of a circular metallic ring embedded with a square-shaped ring. The screen printing process is deployed to perform fabrication of the metasurface on flexible films by means of highly-conductive nanoparticle copper pastes. Electromagnetic (EM) characteristics of the proposed structure are examined by using the quasi-optic bench testing facility in order to validate its potential contribution in the high data-rate communication links. The proposed ultra-thin and flexible metasurface can be integrated on walls and windows as wallpaper to enhance the wireless signal propagation in highly-dense indoor scenarios.

Design and characterisation of a screen-printed millimetre-wave flexible metasurface using copper ink for communication applications

In this paper, the design, fabrication and characterisation of metasurfaces with the anisotropic response for millimetre waves (MMW) has been presented for seamless, secure and low-loss high-frequency communication. Two frequency bands, 29 GHz and 60 GHz, have been selected for the development of efficient, cost-effective and broadband metasurfaces constituting an octa-armed star-shaped structure and a symmetric dual orthogonally I-shaped structure, respectively. Low-cost and high-performance nanoscale printing inks and pastes have been deployed in the screen-printing technique to perform the fabrication of designed metasurfaces on flexible films. Electromagnetic (EM) characteristics of the proposed metasurfaces are evaluated using state-of-the-art testing facilities to demonstrate their potential performance attributes in wave-propagation at MMW for high data rate communication links.

BER-Optimal Analog-to-Digital Converters for Communication Links

In this paper, we propose low precision BER-optimal analog-to-digital converters (ADC) where quantization levels and thresholds are set nonuniformly to minimize the bit-error rate (BER ) in a high data rate communication link. This is in contrast to how ADCs are used today, in which they act as transparent waveform preservers. Simulations for various communication channels show that for 2-PAM modulation, the BER-optimal ADC achieves shaping gains that range from 2.5 dB for channels with low intersymbol interference (ISI) to more than 30 dB for channels with high levels of ISI. Moreover, a 3-bit BER -optimal ADC achieves the same or even lower BER than a 4-bit uniform ADC. With a DFE and a high-ISI channel, a 3-bit BER -optimal ADC achieves lower BER than a 5-bit uniform ADC.