Misalignment fading effects on the ACC performance of relay-assisted MIMO/FSO systems over atmospheric turbulence channels

<span>The continuous development of internet of things (IoT) technology enables many devices to be interconnected through the external environment. Meanwhile, 5G technology provides an enhanced quality of services with high data transmission rates, requiring IoT implementation in the 5G architecture. Free-space optical communication (FSO) is considered a promising technique that can provide high-speed communication links, so FSO is an optimal choice for wireless networks to fulfill the full potential of 5G technology, providing speeds of 100 Gb/s or more. By implementing 5G features in IoT, IoT coverage and performance will be enhanced by using FSO models. Therefore, the paper proposed and investigated the multiple-input and multiple-output/free-space optical communication (MIMO/FSO) model using subcarrier quadrature amplitude modulation (SC-QAM) and relay stations over atmospheric turbulence channels by log-normal and gamma-gamma distribution under different turbulence conditions. The performance is examined based on the average channel capacity (ACC), which is expressed in terms of average spectral efficiency (ASE) parameters while changing the different parameters of the model. The mathematical formulas of ACC for atmospheric turbulence cases are calculated and discussed the influence of turbulence strength, the different number of relay stations, misalignment effects, and different MIMO configurations.</span>

Extending the Quality of Secure Service Model to Multi-Hop Networks

Rarely are communications networks point-to-point. In most cases, transceiver relay stations exist between transmitter and receiver end-points. These relay stations, while essential for controlling cost and adding flexibility to network architectures, reduce the overall security of the respective network. In an effort to quantify that reduction, we extend the Quality of Secure Service (QoSS) model to these complex networks, specifically multi-hop networks. In this approach, the quantification of security is based upon probabilities that adversarial listeners and disruptors gain access to or manipulate transmitted data on one or more of these multi-hop channels. Message fragmentation and duplication across available channels provides a security performance trade-space, with its consequent QoSS. This work explores that trade-space and the corresponding QoSS model to describe it.

An Improved Cooperative Control Method for Hybrid Unmanned Aerial-Ground System in Multitasks

The cooperative control in complex multitasks using unmanned aerial vehicle and unmanned ground vehicle (UAV/UGV) is an important and challenging issue in the multirobot cooperative field. The main goal of the task studied in this paper is to minimize the time and energy consumed by the system to complete the assigned tasks. In this paper, a complex multitask problem using the hybrid UAV/UGV system is studied, which is divided into three stages, namely, the stage of finding the optimal locations of the relay stations for the UGV; the stage of solving the path planning problem for the UGV; and the stage of the task assignment for multi-UAVs. Furthermore, an improved integrated method is proposed to deal with the cooperative control problems in these three stages. Firstly, an adaptive clustering method is proposed to determine the locations of the UGV relay stations, and then an improved cuckoo search algorithm is used to find the shortest path for the UGV. Finally, a grouping method is presented to solve the multitask allocation problem of UAVs, based on an improved dynamic programming algorithm. In addition, some simulations are carried out and the results show that the proposed method has better performance when it comes to the time and energy consumption and can effectively guide the hybrid UAV/UGV system to carry out the complex multitasks.

Subcortical structures: The cerebellum, basal ganglia, and thalamus

Less is known of the function of the cerebellum, thalamus, and basal ganglia than of other structures in the brain, but there is an increasing appreciation of their complex role in motor and non-motor functions of the entire nervous system. These structures exercise functions that far exceed their previously assumed supporting parts as simple ‘relay stations’ between cortex and spinal cord. The subcortical structures receive massive different inputs from the cerebral cortex and peripheral sense organs and stretch receptors. Through recurrent feedback loops this information is integrated and shaped to provide output which contributes to scaling, sequencing, and timing of movement, as well as learning and automatization of motor and non-motor behaviours.

Reliability Model of Fuzzy Consecutive k-out-of-n: F System

Redundancy can be used to increase system reliability. The most popular type of redundancy, k-out-of-n system structure, finds wide applications in both industrial and military systems. Aspecial type of this system is the consecutive k-out-of-n:F system C(k,n:F) which have been proposed for reliability evaluation and integrated circuits design, microwave relay stations in telecommunication system, oil pipelines systems, vacuum systems in accelerators, computer ring networks, and spacecraft relay stations. In this paper, we will discuss a new algorithm for evaluating the fuzzy reliability of any fuzzy linear consecutive k-out-of-n:Fsystem (Lin/C(k,n:F)) with independent, unrepairable, and non-identical components.Later,we will introduce a model of unrepairable system consists of parallel subsystems if each subsystem is Lin/C(k,n:F). Due to uncertainty and insufficient data, failure time of each component follows fuzzy Rayleigh distribution with one fuzzy parameter. This fuzzy parameter is represented by triangular membership function and estimated from statistical data taken from random samples of each component. Furthermore, a numerical example for a fuzzy unrepairable parallel system with three subsystems is given while eachsystem is represented by Lin/C(k,n:F).Also, the failure time of each component follows fuzzy Rayleigh distribution to get analytically and represents the fuzzy reliability function of this fuzzy system graphically.

BER analysis of amplify-and-forward relaying FSO systems using APD receiver over strong atmospheric turbulence channels

<span lang="EN-US">In this paper, we theoretically analyze the performance of amplify-and-forward (AF) serial relaying free-space optical (FSO) systems using avalanche photodiodes (APD) and subcarrier quadrature amplitude modulation (SC-QAM) over strong atmospheric turbulence channels modelled by gamma-gamma distribution. Closed-form expression for average bit error rate (BER) of system is theoretically derived talking into account APD shot noise, thermal noise as well as the impact of atmospheric loss and turbulence. The numerical results show that using AF relay stations can extend the transmission distance and help to improve performance of FSO system significantly when compared with the direct transmission. Moreover, the selection of APD gain value is indispensable to the system performance. The proposed system could be achieved the best performance by selecting an optimal APD gain value. In addition, the optimal value of APD gain also significantly depends on various conditions, such as link distance, the number of relay stations and APD receiver noise.</span>

STEERABLE TOROIDAL BIFOCAL LENS-ARRAY ANTENNA IN 57–64 GHZ RANGE

Introduction. Currently, one of the most promising approaches of the 5th generation mobile wireless systems development is the deployment of heterogeneous networks based on existing LTE cellular systems with large and small cells. The main elements of such networks can be small low cost relay stations equipped with highly directional steerable antenna systems to connect small cells with LTE base station serving macrocell. Objective. Existing solutions are either too expensive or not allowing flexible rearrangement of current information transmission lines. The objective of this work is to develop antenna equipment for low cost relay stations based on simple steerable antenna systems of millimetre wavelength (57-64 GHz), which allow beamsteering in both azimuth and elevation planes. Methods and materials. The developed steerable bifocal lens antenna system is a lens of a special shape made of a high molecular weight polyethylene and integrated with a phased array antenna. A key feature of the designed antenna system is a wide-angle beamsteering in the azimuth plane and ability to adjust the beam in the elevation plane. The calculation of the lens profiles was carried out by means of an approximation of geometrical optics in Matlab, and the main technical characteristics of the lens antenna system were obtained by direct electromagnetic modelling in CST Microwave Studio. Results. The prototype of the steerable bifocal lens-array antenna system is developed and its characteristics are studied. The following technical characteristics are achieved in the 57–64 GHz range: beamsteering in the elevation plane is ±3º, beamsteering in the azimuth plane is ±40º, and antenna gain is from 20 to 27.5 dBi for all angles. Conclusion. It was shown that the developed antenna system can be successfully used as receiving and transmission antenna equipment of small relay stations that transmit information in the frequency range of 57-64 GHz over a distance of 100-300 m.