Transmission Of RF Signals Research Articles

Understanding Wireless ChannelsThrough NeRF2

Despite Maxwell's formulation of the electromagnetic wave laws over a century and a half ago, accurately modeling the transmission of RF signals within electrically complex environments continues to be a formidable challenge. This complexity arises from intricate interactions of RF signals with various obstacles, such as reflections and diffractions. Inspired by the effective utilization of neural networks in computer vision for representing optical fields, this paper introduces NeRF2, a novel neural radio-frequency radiance field. NeRF2 conceptualizes a continuous, volumetric scene function to interpret RF signal propagation. Uniquely, NeRF2, once trained with limited signal measurements, can predict the characteristics and reception of a signal at an arbitrary point, given the transmitter's location. Functioning as a physical-layer neural network, NeRF2 amalgamates learned statistical models with physical ray tracing to create synthetic datasets, tailored for the training needs of application-layer artificial neural networks (ANNs). This integration, termed "turbo-learning," combines authentic and synthetic datasets, significantly augmenting ANNs' training efficacy. Experimental results illustrate that turbo-learning can substantially improve performance, with an estimated 50% enhancement. The efficacy of NeRF2 is further underscored in its applications in indoor localization and 5G MIMO systems.

Stable Transmission of RF Signals With Low-Delay Passive Method Over Fiber Link

Stable Transmission of RF Signals With Low-Delay Passive Method Over Fiber Link

Study and Simulation of Transporting Radio Frequency Signals over Free Space Optics for Achieving High Data Rate and Power Saving

The remarkable technology for seamless integration of wireless and optical networks is radio frequency signals over Free Space Optics (FSO). This research study and simulation examine the design and evaluation performance of Radio Frequency over FSO (RF-FSO) wireless communication technology. These systems are implemented through medium communication link ranges to overcome excessive sensitivity of atmosphere medium and meet the requirements of a wide variety of optical wireless applications. There are two ways to achieve the application of the design mentioned above. The first way is the application of the Three modulation schemes of technology that is Amplitude shift keying (ASK), Quadrature amplitude modulation (QAM), and Quadrature phase-shift keying (QPSK) of digital modulation. The design of these modulation schemes is realized by using optiwave software to study the transmission of RF signals over the FSO channel and compare the three modulation techniques into the RF-FSO system. RF signals with the frequency range from (20 to 60) GHz is used in RF-FSO system and many carrier optical signals where the higher RF has a wider bandwidth to carrying larger information. To increase the transmission of data rates Wavelength Division Multiplexing (WDM) technology is used. The second way is based on a mathematical model which has been proposed for this study. This mathematical model calculates optimal beacon period (BI), and optimal listen interval (LI) to preventing the overlapping of time between the signals and the decrease in the required power. Using different weather conditions samples, the simulation results revealed that the best performance of the RF-FSO system is from link range, and the receiver is more sensitive. The simulation results are as follows: Two independent channels are transmitted 20 Gbps over ranges from (263 m to 6.55 km), while four channels are transmitted 40 Gbps over ranges from (257 m to 5.95 km), and eight independent channels transmit 80 Gbps over distance from (203 m to 5.2 km)

Analysis and impact of digital modulation techniques on LTE over fibre for 5G systems applications.

The impact of digital modulation techniques used in Long Term Evolution (LTE) when applied to radio over fibre for fifth-generation systems has been analysed and evaluated in this paper. The analyses are based on the measured BER and the observed eye-diagram with quality factors for the different modulation techniques such as QPSK, 16 QAM, 64 QAM, and 256 QAM. A fibre length between 5 km and 100 km is adopted to showcase the best configuration at a particular length that can support 5G systems. Huge bandwidth and low latency with high spectral efficiency are needed to accommodate 5G applications in areas of critical surgery, home automation, smart transportation, security, and smart cities via IoT among others. Recent researches are focusing on a synergy between the wireless systems and optical network systems to enhance the transmission of RF signals from a central location to a separate unit of the radio element known as the remote radio head (radio over fibre). This technology merges the optical networks and microwaves to provide a possible solution to increase channel capacity, mobility, and reduced the cost of the access network for customers’ comfort. The whole system link is simulated using a commercial optical simulator Optisystem 17.

A Low-Complexity Distributed-MIMO Testbed Based on High-Speed Sigma–Delta-Over-Fiber

Distributed multiple-input-multiple-output (DMIMO) is a very promising technique to improve capacity and quality of service for emerging 5G systems. In this paper, we propose a flexible and low-cost testbed for D-MIMO systems, where a sigma-delta over fiber (SDoF) solution is proposed to address the fundamental challenge of phase-coherent transmission between multiple distributed access points (APs) from a central unit (CU). Employing low-cost standardized optical data interconnects, SDoF, brings a very flexible and software controlled transmission of RF signals over optical fiber. An SDoF-based D-MIMO testbed with a CU feeding 12 distributed APs has been realized and experimentally evaluated. Initial experiments of D-MIMO and conventional colocated MIMO systems at 2.365 GHz have been performed to demonstrate the flexibility and potential of the proposed testbed as a new powerful tool in the design and analysis of emerging communication system concepts.

Simple and robust ternary pulse‐encoding and reconstruction of narrowband RF signals over low‐cost fibre‐optic links

An existing ternary pulse-coding scheme for bandpass signals, whereby a timing code specifies positive and negative rectangular pulses as well as a third zero state formed by skipping pulses, is adapted to transmission and reconstruction of narrowband RF signals over inexpensive fibre-optic links. The main feature of this technique is that reconstruction of the narrowband analog signal is particularly simple, requiring only a bandpass filter. Simulations using a complex band-limited Gaussian baseband input to represent a 20-MHz LTE-A signal establish the ideal theoretical performance, which is then compared to experimental results obtained by transmission on a 1.6-GHz carrier over a fibre-optic link consisting of an electro-absorption modulated laser, 10 km of standard single-mode fibre (SSMF), and avalanche photodiode detector. The experimental results are only slightly impaired from ideal performance, even for only 6 dB signal-to-noise ratio, thereby demonstrating the viability and robustness of the proposed technique.

Millimeter-Wave Radio Over Fiber Optical Upconversion Techniques Relying on Link Nonlinearity

A study of advanced upconversion techniques used in radio over fiber (ROF) is provided. With the huge increase in both the number of wireless communication subscribers and the bandwidth required per customer, migrating to higher frequencies, i.e., from lower radio frequency to millimeter-wave carriers, is an essential solution. However, due to the short propagation range of millimeter waves, a large number of radio access points are required for providing reliable coverage, which would increase the infrastructure costs. Hence, the transmission of RF signals between the central (or control) points and radio access points (or remote antenna units) using optical fibers is one of the major access network solutions that have been proposed for future high-bandwidth wireless communication systems. In this paper, we introduce the basics of ROF communication, including optical modulation, the optical channel, and the optical detection techniques. Then we survey the family of advanced optical upconversion techniques that exploit the nonlinearity of the ROF link. Specifically, we describe how optical upconversion can be achieved by exploiting the Mach–Zehnder modulator's nonlinearity, wavelength conversion techniques, or the photodetector's nonlinearity. The wavelength conversion techniques rely on the nonlinearities present in the fiber, in the optical amplifier, or in the electroabsorption modulator.

Low Cost E/O and O/E Modules for Radio Over Fibre Link

ABSTRACTIn this article low cost and low complexity E/O and O/E modules for radio over fibre link have been presented. The modules are built based on pigtail coaxial laser diode and photodiode available on the market. In the designs special attention has been focused on achieving flat transmission characteristics in the frequency range of 1‐3 GHz. The modules have been equipped with signalization of the proper supply and generation of optical carrier. The devices have been dedicated to transmission of modulated RF signals through optical fibre in radio over fibre link. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2423–2425, 2013

Duplex Digitized Transmission of 64-QAM Signals over a Single Fiber Using a Single Pulsed Laser Source

We demonstrate digitized duplex transmission of 64-QAM signals using pulsed optical communications. Bidirectional data transmission is achieved over a single 25 km optical fibre using a single optical pulsed source. The choice of suitable parameters for bandpass sampling technique used for the digitization of the 16 MSamples/s 64-QAM signal are discussed. It is demonstrated that using digitized transmission of RF signals, long distance transmission can be supported at a performance close to that of the back-to-back analogue benchmarker.

The FDM-A and FAM-C Methods with Regard to Effects Associated with Transmission of RF Signals

The FDM-A and FAM-C Methods with Regard to Effects Associated with Transmission of RF Signals

Studies on characterizing the transmission of RF signals over a turbulent FSO link

In this paper, we present an experimental study on transmission of RF signals over turbulent free-space optics (FSO) channel by using off-the-shelf Radio Frequency - FSO (RF-FSO) antennas. The results demonstrate potential of utilizing FSO links for transmission of RF signals and are used as a guideline in the design, prediction and evaluation of an advanced Dense Wavelength Division Multiplexing (DWDM) RoFSO system we are developing capable of transmitting multiple RF signals. An analytical modeling of the system is also conducted to identify key parameters in evaluating the performance of RF signal transmission using FSO links. The results confirm that the effect of scintillation on RF-FSO system performance can be estimated by using a simple estimation equation and satisfactory result are obtained from comparing the experimental and theoretical derived data under weak to strong turbulence condition.

Direct high-frequency modulation of VCSELs and applications in fibre optic RF and microwave links

With the rapid development of wireless communication networks there is an increasing demand for efficient and cost-effective transmission and distribution of RF signals. Fibre optic RF links, employing directly modulated semiconductor lasers, provide many of the desired characteristics for such distribution systems and in the search for cost-effective solutions, the vertical cavity surface emitting laser (VCSEL) is of interest. It has therefore been the purpose of this work to investigate whether 850 nm VCSELs fulfil basic performance requirements for fibre optic RF links operating in the low-GHz range. The performance of single- and multimode oxide confined VCSELs has been compared, in order to pin-point limitations and to find the optimum design. Fibre optic RF links using VCSELs and multimode fibres have been assembled and evaluated with respect to performance characteristics of importance for wireless communication systems. We have found that optimized single-mode VCSELs provide the highest performance and that links using such VCSELs and high-bandwidth multimode fibres satisfy the requirements in a number of applications, including cellular systems for mobile communication and wireless local area networks.

Focus on Analytical Instruments

Focus on Analytical Instruments

Compression and Transmission of RF Signals for Telediagnosis

Health care is a critical issue nowadays. Much emphasis is given to quality care for all people. Telediagnosis has attracted public attention. We propose a new method of ultrasound image transmission for telediagnosis. In conventional methods, video image signals are transmitted. In our method, the RF signals which are acquired by an ultrasound probe, are transmitted. The RF signals can be transformed to color Doppler images or high-resolution images by a receiver. Because a stored form is adopted, the proposed system can be realized with existent technology such as hyper text transfer protocol (HTTP) and file transfer protocol (FTP). In this paper, we describe two lossless compression methods which specialize in the transmission of RF signals. One of the methods uses the characteristics of the RF signal. In the other method, the amount of the data is reduced. Measurements were performed in water targeting an iron block and triangular Styrofoam. Additionally, abdominal fat measurement was performed. Our method achieved a compression rate of 13% with 8 bit data.

Multiplexing and transmission of RF signals using an optical fiber

Ultrasonic non-destructive testing systems designed to control huge structures normally use several transducers in the reception stage. To avoid increasing the cost of electronics, a multiplexer is used to send all received signals to the same processing module. Traditionally, transmission of such signals is carried out using copper cables. For special applications (i.e. continuous monitoring of nuclear plants) metallic cables are not suitable because of their high sensitivity to electromagnetic perturbations. Moreover, the multiplexing is made electronically. When the distance between the transducers and the reception unit is large and/or electromagnetic noise is important, signal degradation takes place. The proposed system implements the transmission and multiplexing of ultrasonic electrical signals obtained by means of broadband transducers (up to 1 MHz), using an optical fiber. Optical fibers are made of dielectric materials (silica or plastic) so they are inherently passive to electromagnetic noise. Wavelength division multiplexing is utilized for adding channels to the system by means of fiber optic couplers and different light sources. The wavelengths of the optical signals utilized are located far apart in the optical spectrum in order to avoid serious crosstalk in transmission. The limit to the number of multiplexed channels depends on the optical fiber selected, the spectrum of the light sources and the wavelength division multiplexers or couplers utilized.