Microwave Communication Networks Research Articles

Bayesian Networks based approach to enhance GO methodology for reliability modeling of multi-state consecutive-k-out-of-n: F system

As a success-oriented system reliability and safety analysis technique, GO methodology is widely used in the modeling and analysis scenarios of critical safety engineering systems with signal flow, such as nuclear, chemical industry, electric power transportation, wireless network and microwave communication network. Consecutive-k-out-of-n systems are also widely applied in these fields, but due to their relatively complex logic, there are no corresponding graphical modeling and calculation methods. In this paper, the basic GO methodology is extended to support the modeling and analysis of multi-state linear and circular consecutive-k-out-of-n: F system (MLC(k,n) &MCC(k,n)) models. Two new operators are defined in graphical modeling to represent the two types of complex system logic. The multi-state logic semantics of the new operators and mapping rules to Bayesian networks (BN) are given. And the programmable process is presented to transform the extended GO model into BN, and the reliability of the MLC(k,n)/MCC(k,n) is calculated. Finally, three cases are used to verify i) the correctness of the method supporting multi-state model, ii) the efficiency and ability of the algorithm, and iii) the forward calculation and reverse diagnosis of the MLC(k,n) and MCC(k,n) systems with external shared components.

Numerical Analysis of the Fractional-Order Telegraph Equations

This paper studied the fractional-order telegraph equations via the natural transform decomposition method with nonsingular kernel derivatives. The fractional result considered in the Caputo-Fabrizio derivative is Caputo sense. Currently, the communication system plays a vital role in a global society. High-frequency telecommunications continuously receive significant attention in the industry due to a slew of radiofrequency and microwave communication networks. These technologies use transmission media to move information-carrying signals from one location to another. We used natural transformation on fractional telegraph equations followed by inverse natural transformation to achieve the solution of the equation. To validate the technique, we have considered a few problems and compared them with the exact solutions.

Analysis of Microwave Communication Network Planning on Ocean Topography Using Space Diversity

One of the challenges often met by planners of the telecommunications network using microwave radio is surface conditions, especially when passing through the ocean. Propagation conditions above sea surface often result in increasing fading, which significantly affects the reliability of the microwave network. On the other hand, considering that Indonesia is an archipelago, ocean topography is unavoidable, and the use of microwave networks generally considered to be the most efficient among other technologies, especially in Eastern Indonesia. This research aims to respond to such a challenge by planning a microwave communication network using a space diversity technique. The type of microwave network used is a point to point, which links Bali and Lombok islands. The results showed that the use of space diversity techniques could increase fading margins from 34.42 dB to 35.15 dB and availability value from 99.99667% to 99.99873%. Therefore, this technique recommends implementing by telecommunications network providers in accelerating the deployment of connecting networks in areas that have ocean topography.

User Association for Millimeter-Wave Networks: A Machine Learning Approach

Millimeter-wave (mmWave) communication has been regarded as one of the most promising means to improve the cellular system capacity in the fifth-generation (5G) era. Compared with the conventional microwave communication networks, mmWave terminals should connect with multiple base stations (BSs) simultaneously to prevent the signal blockage. Meanwhile, the accurate instantaneous channel state information (CSI) is difficult to estimate and collect due to the densification of mmWave BSs. These unique characteristics pose stiff challenges to user association in mmWave networks. To deal with these issues, we develop a novel machine learning based user association approach to support multi-connectivity in mmWave networks. Specifically, we first formulate the mmWave user association problem as a multi-label classification problem, which is then transformed into a series of single-label classification problems through efficient multi-label classification algorithms. To further reduce the requirement on the amount of training samples, we utilize graphical model to represent the user association scenario and adopt novel feature extraction methods to obtain appropriate features from both geographical location information and topological information. With appropriate features, each single-label classification problem can be trained in a supervised manner. Test results show that the proposed approach can achieve a good performance with only a few training samples and without the need of CSI.

Reliability analysis of the PMU microwave communication networks using generalised stochastic Petri nets

The phasor measurement units (PMUs) have evolved as powerful extrapolations of the supervisory control and data acquisition (SCADA) systems due to their profound application in the real time monitoring of the smart grid (SG). In the SG several such PMUs continuously generate the time tagged phasor measurements which are communicated to a central monitoring station known as the phasor data concentrator (PDC). The communication system plays a pivotal role in the transfer of the phasor measurements to the PDC and thus should be highly reliable. This article presents a detailed approach for the construction of the generalised stochastic Petri nets (GSPNs) for the reliability analysis of the synchrophasor microwave communication networks. These communication networks are optimally planned to achieve maximum reliability without compromising the system observability. Results from the case studies for the North Eastern power grid of India are presented to demonstrate the efficacy of the proposed approach.

Reliability analysis of the PMU microwave communication networks using generalised stochastic Petri nets

Reliability analysis of the PMU microwave communication networks using generalised stochastic Petri nets

Ultra-broadband microwave metasurfaces for polarizer and beam splitting

Realization of ultra-broadband transmission-type functional metasurfaces is of high priority for the development of modern electromagnetic systems. In this paper, we propose a new strategy to design highly efficient ultra-broadband microwave metasurfaces with ultra-thin profiles that enable linear polarization and asymmetric transmission by merging two differently sized meta-atoms operating in neighbour frequency bands into a meta-molecule featuring an extended bandwidth. Capitalizing on the meta-molecule approach, we realize a transmission-type beam splitter based on the coding concept, which can, at higher frequencies, divide a normally incident wave into two beams propagating along symmetrical oblique directions and, at lower frequencies, couple the incident wave into two surface waves propagating away from the splitter in opposite directions. Our findings demonstrate thereby a flexible and robust approach for the realization of efficient ultra-broadband transmission-type metasurfaces that can readily be integrated into complex systems in order to implement multiple functionalities in microwave communication networks for diverse applications.

Gaussian Mixture Model for Millimeter-Wave Cellular Communication Networks

As compared to the microwave communication networks, the theoretical analyses of system performances such as the cell coverage and the cell average data rate are more difficult due to the unique propagation path loss model for mmWave cellular communication networks. In this paper, based on the unique transmission states of the distance-dependent piecewise propagation probability functions, the analytical six-state analytical mixture distribution of the propagation loss including the distance-dependent path loss, shadowing and small-scale fading is obtained. For each state, a novel Kullback–Leibler divergence based Gaussian approximation method is proposed to model the distribution of the propagation loss. The distribution of the propagation loss including the large-scale fading and small-scale fading is approximated via a six-state Gaussian mixture model, then the closed-form expression for the signal-to-noise ratio can be easily obtained. The cell coverage is expressed as the weighted sum of the error functions, and the cell average data rate is expressed as the weighted sum of the moments of the propagation loss for the six different states. Numerical results show that the cell coverage mainly depends on the none line-of-sight transmission and the cell average data rate mainly depends on the line-of-sight transmission.

Utilizing microwave communication data for detecting fog where satellite retrievals are challenged

This study shows the potential of microwave communication networks for the detection of fog in challenging conditions where satellite systems are often limited. In a first event, the ability to detect fog using commercial microwave links, at a time when the satellite cannot detect the phenomena due to high-level cloud cover obscuring the ground-level fog, is demonstrated. The ability of the microwave system to rule out ground-level fog at times when the satellite detects a low-lying stratus cloud, but cannot identify whether it is adjacent to the ground or at higher elevations above it, is demonstrated in a second event. The results indicate the operative potential of this technique to assist end users in reliable decision making that have highly important economic and safety implications.

A two-stage Markov model–aided frequency-duration technique for reliability analysis of phasor measurement unit microwave communication networks

The necessity for effective real-time monitoring and control, coupled with the developments in the fields of communication and sensor technologies, led to the emergence of the smart grid. The phasor measurement unit has emerged as an important sensor for the smart grid. The phasor measurement unit communication network is another crucial component which transfers the real-time sensor data measured by the phasor measurement unit to the phasor data concentrator for subsequent monitoring and control. Thus, its reliable operation is essential. The key parameters for assessment of reliability are the failure rate and the steady-state availability. This article presents a two-stage Markov model–aided frequency-duration technique for the reliability analysis of the phasor measurement unit microwave communication networks. Microwave communication network is a complex system as it requires several intermediate relaying towers or the microwave repeaters for communication feasibility. The Markov model explores the transition to the different system states and the frequency-duration approach estimates the frequency and duration of each of these states, thereby providing a simple and elegant means to compute the failure rates of a complex system. It provides a generalized expression for evaluating the systems availability and aids in diagnosing the components that are more prone to failure. Subsequently, this approach is used for the optimal placement of the phasor measurement units such that their resultant microwave communication networks are maximally available. Case study results for the Eastern power grid of India are presented to validate the credibility of the proposed approach.

Accumulated Mixed Precipitation Estimation Using Measurements from Multiple Microwave Links

Recently, microwave communication networks have been shown to be valuable tools for rainfall monitoring, based on the well-known Power-Law which relates rain-rate to attenuation in microwave frequencies. However, once precipitation other than pure rain exists (e.g., snow), the Power-Law relation is no longer accurate. In this paper we propose a model which relates the induced attenuation to rain, snow, and sleet. Based on this model we propose estimating the total accumulated precipitation, regardless of the precipitation type, using measurements from multiple microwave links. Our technique takes advantage of the commercial communication networks, need for redundancy, which dictates the use of multiple microwave links at the same area. We show that by using measurements from at least three microwave links better estimation of the total accumulated precipitation fall can be provided, when rain, snow, sleet, or a mixture of them coexists. To demonstrate the proposed approach, it has been applied on actual microwave links attenuation measurements, which were provided by a cellular carrier. The estimation results were compared with Rain-Gauges and disdrometer measurements and show very good agreement and improved accuracy.

Frontal Rainfall Observation by a Commercial Microwave Communication Network

Abstract A novel approach for reconstruction of rainfall spatial–temporal dynamics from a wireless microwave network is presented. It employs a stochastic space–time model based on a rainfall advection model, assimilated using a Kalman filter. The technique aggregates the data in time and space along the direction of motion of the rainfall field, which is recovered from the simultaneous observation of a multitude of microwave links. The technique is applied on a standard microwave communication network used by a cellular communication system, comprising 23 microwave links, and it allows for observation of near-surface rainfall at the temporal resolutions of 1 min. The accuracy of the method is demonstrated by comparing instantaneous rainfall estimates with measurements from five rain gauges, reaching correlations of up to 0.85 at the 1-min time interval with a bias and RMSE of −0.2 and 4.2 mm h−1, respectively, and up to 0.96 with RMSE of 1.6 mm h−1 at the 10-min time interval for a 22-h intensive rainstorm with an average rain rate of 3.0 mm h−1 and a peak rain rate of 84 mm h−1. The results are compared with those of other spatial reconstruction techniques. The proposed dynamic rainfall reconstruction approach can be applied to larger-scale dynamic rainfall assimilation methods, enabling interpolation over data-void regions and straightforward incorporation of data from other sources, for example, rain gauge networks and radars.

Estimation of rainfall fields using commercial microwave communication networks of variable density

The use of commercial microwave radio networks which are a part of cellular communication infrastructure for mapping of the near-the-ground rainfall is challenging for many reasons: the network geometry in space is irregular, the distribution of links by frequencies and polarizations is inhomogeneous, and measurements of rain-induced attenuation are distorted by quantization. A non-linear tomographic model over a variable density grid is formulated, and its applicability and performance limits are studied by means of a simulated experiment using a model of a real microwave network. It is shown that the proposed technique is capable to accurately measure integrated near-the-ground rainfall amounts over the area of 3200 km 2 with a bias smaller than 10%. In urban area, where the density of microwave links is high, the average correlation in space between the simulated model and reconstructed rainfall fields reaches 0.89 over the variable density grid with average cell size of 5.7 km 2 and 0.74 when interpolated into the rectangular grid with pixel size 0.775 × 0.775 km 2, for the quantization interval of 0.1 dB.

Millimeter-wave printed antenna arrays for covering various sector widths - [Antenna Designer's Notebook

We introduce new millimeter-wave corner antenna arrays (MWCA) with eight axially placed printed dipoles fed by an integrated symphase network. The antenna array is placed between two metal plates that make the corner reflector. The antennas were simulated and realized in the frequency range about 26 GHz, which is popular for microwave communication networks. Three antennas, with different H-plane beamwidths (intended for azimuth) of 55', 1100, and 1800, were investigated, simulated, and realized. The bandwidths of all of the antennas were wider than 12%. The losses in all of the antennas were less than 1 dB. The agreement between simulated and measured results was very good. Millimeter-wave corner antenna arrays are low in cost and very simple to realize, and are also suitable for integration.

Telepresence technology in medicine: principles and applications

Telepresence systems can improve surgeons' performance in minimally invasive surgery (MIS) and microsurgery and also enable them to operate on patients remotely over great distances. In MIS, telepresence technology allows surgeons to experiment surgery as if their hands and eyes were effectively inside the patient's closed abdomen, enabling them to work with improved skill and dexterity. In microsurgery, the technology can scale down the surgeons' motions, forces, and field of view, allowing them to skillfully operate on microscopic anatomy with relative ease. The systems also enable surgeons to treat patients remotely in inaccessible or hazardous locations with great effectiveness, allowing them to operate as if they were present at the remote site. The means for conveying human presence in such systems is through force-reflecting manipulators with digital servo controllers, stereo viewing systems, and communication links. Depending on the application, the surgeon at the telepresence workstation may be across the room from the patient or across the state, connected by a microwave link or communication network.

Interference aspects of off-shore terrestrial microwave networks

In an off-shore environment, as a general rule, communications need to be established directly between terminals with no provision for intervening repeaters. In planning terrestrial microwave communication networks, this imposes a requirement to use trans-horizon links to a greater extent than in land-based communications.The attendant problems of interference and practical methods for reducing such interference in terms of frequency planning, equipment design, and network power control are discussed.

Resmac: The New Mexican array

A new seismic array is currently being installed throughout Mexico. Resmac, which stands for Red Sismica Mexicana de Apertura Continental, or Mexican continental aperture seismic array, will use a nationwide microwave communication network as a vital element in a modern, all‐digital, integrated system of seismic data acquisition and processing.The Mexican microwave network spans the country from Tijuana to Cozumel and from coast to coast: hence it is called a ‘continental aperture array.’ Eventual cooperative projects now under the consideration of the Central American nations make a southward extension to Panama a possibility. At present, however, the Resmac project is sponsored exclusively by five agencies of the Mexican federal government, there being no financial or technical contribution from outside sources. The executive agency is the National University of Mexico, which is in close cooperation with the Department of Communications and Transportation of the federal government.

Microwave propagation and communication networks

Recent evolution of telecommunication networks has been strongly influenced by two main trends: an increase of radio (microwave radio links, satellite links, and mobile services) with respect to cable communication, and a rapidly progressing development of digital transmission techniques compared with analogic techniques. The first tendency leads to saturation of the frequency bands presently used for radioelectric systems and hence the need of going to higher as well as yet unused bands. Digital systems on the other hand are particularly prone to interruptions even of very short duration and such cuts can only be tolerated for extremely low time percentages. The object of this communication is to study the role of propagation conditions in the future solution of these problems, imposing a limit on the distance between repeaters or using diversity techniques.