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Smart things & femtocells : from hype to reality
This book provides a comprehensive overview for the use of femtocells in smart Internet of Things (IoT) environments. Femtocells will help mobile operators to provide a basis for the next generation of services which are a combination of voice, video, and data services to mobile users. This book discusses modelling traffic and deployment strategies in femtocells and provides a review for the use of femtocells and their applications in IoT environments. Moreover, it highlights the efficient real-time medium access, data delivery, caching and security aspects in smart spaces. It concludes by presenting open research issues associated with smart IoT-femtocell based applications-- Provided by publisher.
Book
The Design and Evaluation of a Direction Sensor System Using Color Marker Patterns Onboard Small Fixed-Wing UAVs in a Wireless Relay System
Among the several usages of unmanned aerial vehicles (UAVs), a wireless relay system is one of the most promising applications. Specifically, a small fixed-wing UAV is suitable to establish the system promptly. In the system, an antenna pointing control system directs an onboard antenna to a ground station in order to form and maintain a communication link between the UAV and the ground station. In this paper, we propose a sensor system to detect the direction of the ground station from the UAV by using color marker patterns for the antenna pointing control system. The sensor detects the difference between the antenna pointing direction and the ground station direction. The sensor is characterized by the usage of both the color information of multiple color markers and color marker pattern matching. These enable the detection of distant, low-resolution markers, a high accuracy of marker detection, and robust marker detection against motion blur. In this paper, we describe the detailed algorithm of the sensor, and its performance is evaluated by using the prototype sensor system. Experimental performance evaluation results showed that the proposed method had a minimum detectable drawing size of 10.2 pixels, a motion blur tolerance of 0.0175, and a detection accuracy error of less than 0.12 deg. This performance indicates that the method has a minimum detectable draw size that is half that of the ArUco marker (a common AR marker), is 15.9 times more tolerant of motion blur than the ArUco marker, and has a detection accuracy error twice that of the ArUco marker. The color markers in the proposed method can be placed farther away or be smaller in size than ArUco markers, and they can be detected by the onboard camera even if the aircraft’s attitude changes significantly. The proposed method using color marker patterns has the potential to improve the operational flexibility of radio relay systems utilizing UAVs and is expected to be further developed in the future.
Journal Article
Performance Optimization of Multipair Massive MIMO Polarized Relay Systems
In this paper, we analyze the challenges faced by multipair massive Multiple-input-multiple-output (MIMO) relay channels in 5G wireless communication systems, where high path loss and severe shadow fading between different user nodes can cause poor channel quality. To overcome these limitations, we propose a polarization selection scheme for antenna arrays combining multipair massive MIMO relay and beamforming to improve MIMO relay channel quality. Specifically, our main goal is to exploit the potential of polarization diversity to maintain and improve the link quality while maintaining the compact size of the MIMO antenna array. To achieve this goal, we introduce a dynamic weighted particle swarm optimization algorithm with contraction factor (CF-DWPSO) to select the polarization direction. In addition, we employ distributed beamforming to effectively suppress or eliminate inter-pair interference. The performance of the simulation analysis shows that CF-DWPSO combined with beamforming provides significant performance improvement of the multipair massive MIMO polarized relay channels, which further indicates that it is of great necessity for improving the performance of this system to optimize the polarization selection by combining beamforming techniques.
Journal Article
Multi-antenna relay based cyber-physical systems in smart-healthcare NTNs: an explainable AI approach
In a generic modern multi-antenna relay system, the incremental cooperative networks use the neighbor nodes to assist the source by sending the source message to the destination for achieving spatial diversity. Therefore, the involvement of cyber-physical Systems (CPS) in smart healthcare has proportionately improved in terms of the relaying schemes. These schemes are equally implicated to terrestrial and non-terrestrial networks. For any non-terrestrial-networks (NTN), the computational intelligence in terms of artificial intelligence (AI) plays a viral role, the work have introduced a novel paradigm of NTN applications using Explainable-artificial intelligence (X-AI) approach. Initially, we propose and analyze a new cooperative relaying scheme for the incremental multi-antenna relays system; namely, incremental multi-antenna relays cooperation with a hybrid relaying scheme (IMARC-H). The IMARC-H, either Amplify-and-forward (AF) or Decode-and-forward (DF) uses relaying scheme based on the X-AI approach. Mathematical formulations have been deducted to support an optimal relationship between signal-to-noise ratio (SNR) and neighbour nodes in the physical layer. The simulations are presented to showcase the validation of the work. The analysis of the obtained simulation results shows that the proposed scheme outperforms in minimizing Bit-Error-Rate (BER) and outage probability as compared to the existing CPS-based relaying schemes such as IMARC-AF, IMARC-DF, etc.
Journal Article
Calculation of dynamic processes in relay systems of automatic control based on graph models
This article discusses the construction of a graph model of a relay system of automatic control. Based on the graph model, relations are derived for calculating transients in a relay system. To describe and analyse relay systems of automatic control, a specific feature of the relay element is used, consisting in the fact that its output value can take only certain constant values. The maximum possible set of structural states for relay elements is three. Accordingly, the relay element introduces a structure discretization effect into the system. This feature makes it possible to study relay systems with relatively simple means and makes it possible to develop methods for their calculation to a certain extent similar to methods for calculating linear systems. In developing the graph method for the description and analysis of relay automatic systems, this position was primarily taken as a basis. This method can be successfully used in any of the typical relay elements are included in the system. A two-dimensional relay system is considered as an example. Based on the graph model, the output coordinates of the system are calculated and their graphs are constructed.
Journal Article
Design and Evaluation on Onboard Antenna Pointing Control System for a Wireless Relay System Using Fixed-Wing UAV
Among several usages of unmanned aerial vehicles (UAV), wireless relay systems for high altitudes using fixed-wing UAVs, or high-altitude platform stations (HAPS), are some of the most promising applications. To realize the systems by making the most of advantages of the long flight duration and endurance of fixed-wing airplanes, this paper proposes an antenna pointing control system using mechanical gimbals onboard a fixed-wing UAV continuously turning midair and describes results of the blocking analysis of the antenna driving angles of the gimbal directed to a ground station, the design of the antenna pointing control system, and the evaluation of its performance. It is confirmed by the evaluation that, though the antenna pointing control accuracy is greatly influenced by the noisy antenna pointing direction command, its accuracy is greatly improved by using the highly accurate RF sensor to detect antenna pointing direction.
Journal Article
Throughput Maximization for the Full-Duplex Two-Way Relay System with Energy Harvesting
The full-duplex technique can improve the transmission capacity of the communication systems, and energy harvesting (EH) is a promising operation to prolong the lifespan of a wireless node by utilizing the radio-frequency signals. In this paper, the throughput performance of a full-duplex two-way energy EH capable relay system is investigated. In particular, a practical EH protocol, named the time-switching-based relaying (TSR) protocol, is used for EH and the decode-and-forward (DF) policy for information transmission. The outage probability is successfully obtained, and the corresponding system throughput for TSR protocol can be derived by it. The derived throughput is a function of different system parameters, including the time-switching (TS) ratio, power allocation ratio, and the length of the communication time slot. Meanwhile, the throughput is used to characterize a joint time and power allocation scheme for the system, and we aim to find the optimal time and power allocation to achieve the optimal throughput. Due to the existence of three variables and the integral form of throughput expression, an optimization for the throughput is difficult. However, a modified simulated annealing-based search (SABS) algorithm can be used to optimize the throughput. The modified SABS algorithm overcomes being highly impacted by the initial point, and derives the optimal solution fast. Simulation results show that the analytical throughput expression is related with the TS ratio, power allocation ratio, and the length of the communication time slot. The analytical curve of the throughput matches with the simulated one well, which shows that the obtained analytical system throughput for the TSR protocol is valid. Meanwhile, the proposed modified SABS algorithm could be used to derive accurate throughput when SNR is higher than 10 dB.
Journal Article
A multi-UAV assisted non-orthogonal multiple access based relay system for minimal average receiving rate maximization
In this paper, we proposed a data relay system consisting of multiple unmanned aerial vehicles (UAVs) and acess point (AP) with the aim of maximizing the minimum receiving rate of Internet of things devices (IoTDs) as the optimization objective. To enhance the utilization of communication resources, we employed non-orthogonal multiple access (NOMA) and successive interference cancellation (SIC) techniques at the AP side. In addition, we used the Wireless power transmission (WPT) technique on the UAV side to charge the IoTDs and prolong their operational lifetime. We formulated the problem as a mixed integer nonlinear programming (MINLP). To solve the MINLP problem, it was decomposed into four subproblems: connection scheduling between UAVs and IoTDs, time slot allocation, UAV trajectory, and AP’s power distribution. Finally, we solved all subproblems by using convex optimization techniques, such as successive convex approximations (SCA), and proposed an iterative algorithm. In the simulation, we compared our proposed algorithm with different optimization schemes. The results indicated that our scheme outperforms the others.
Journal Article
Development and Field Testing of a Wireless Data Relay System for Amphibious Drones
Amphibious (air and water) drones, capable of both aerial and aquatic operations, have the potential to provide valuable drone applications in aquatic environments. However, the limited range of wireless data transmission caused by the low antenna height on water and reflection from the water surface (e.g., 45 m for vertical half-wave dipole antennas with the XBee S2CTM, estimated using the two-ray ground reflection model) persists as a formidable challenge for amphibious systems. To overcome this difficulty, we developed a wireless data relay system for amphibious drones using the mesh-type networking functions of the XBeeTM. We then conducted field tests of the developed system in a large marsh pond to provide experimental evidence of the efficiency of the multiple-drone network in amphibious settings. In these tests, hovering relaying over water was attempted for extension and bypassing obstacles using the XBee S2CTM (6.3 mW, 2.4 GHz). During testing, the hovering drone (<10 m height from the drone controller) successfully relayed water quality data from the transmitter to the receiver located approximately 757 m away, but shoreline vegetation decreased the reachable distance. A bypassing relay test for vegetation indicated the need to confirm a connected path formed by pair(s) of mutually observable drones.
Journal Article
Guaranteeing Zero Secrecy Outage in Relaying Systems under Eavesdropper’s Arbitrary Location and Unlimited Number of Antennas
This paper proposes a three-phase transmission scheme to ensure zero secrecy outage in decode-and-forward relay systems by using the strategies of artificial noise (AN) injection and channel state information (CSI) leakage avoidance. The zero-outage secrecy spectral efficiency (ZOSSE) and energy efficiency (ZOSEE) of the scheme are then analyzed. Finally, the paper demonstrates that the scheme can always achieve zero secrecy outage even when the eavesdropper has an unlimited number of antennas or is in an arbitrary location, which shows its practical applicability. The paper also shows that the ZOSSE increases with the transmit power and that both the ZOSSE and the ZOSEE are maximized when the relay is halfway between the transmitter and the receiver. This suggests that the placement of the helper node is important in securing the communication of two distant nodes.
Journal Article