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This research paper deals with a directional high gain PCB 1 × 8 antenna array for 2.4 ISM band utilizations. To achieve this antenna array, a well-matched equal-split 9 dB-power splitter is designed and integrated with the suggested antenna array. It exhibits a wide operating range of 506 MHz (2.022–2.528 GHz) and splits the feed power to 8 equal-in-phase output quantities. Then eight identical patch elements with good reflection coefficient, high gain and excellent radiation efficiency are connected at the eight-output ports of the 1 × 8-power divider in order to obtain an array antenna consisting of eight radiating elements. A quarter-wave impedance adapter is utilized to obtain a perfect matching of impedance between patches and the power divider. The suggested directional antenna resonates at 2.4 GHz with good impedance matching via offering reflection coefficient S 1 1 = − 2 4. 3 4 dB and voltage standing wave ratio (VSWR) of 1.16. Moreover, it offers good radiation traits like the enhanced gain of 14.76 dB, an excellent radiating efficiency equals about 98.86% and a directional radiation pattern. Initially, the proposed planar directional antenna array has been designed and simulated utilizing high-frequency structure simulator (HFSS) EM simulation tool, the results are validated with another simulation tool via computer simulation technology (CST) software. This printed antenna array is a potential candidate to operate at around 2.4 GHz for RFID reader utilizations due to its outstanding impedance and radiation characteristics. [ABSTRACT FROM AUTHOR]

The continuous telemetry transmission between unmanned aerial vehicles (UAVs) and ground control stations is important particularly in scenarios lacking global positioning system (GPS) data. This paper proposes an adaptive novel elliptic trajectory formula-based tracking algorithm for received signal strength indicator (ANETF-RSSI) which dynamically optimizes model parameters based on energy-associated RSSI measurement errors. ANETF-RSSI generates a variable two-dimensional (2D) RSSI map to identify optimal paths, even under challenging conditions like circular flight paths, varying operating ranges, and accelerated maneuvering, which causes uncertainty into RSSI measurements during flight. In contrast to previous methods, the proposed approach eliminates the reliance on telemetry data such as GPS or complex multiantenna configurations, ensuring robust UAV communication continuity across routes ranging from 100 m to 100 km, even as the UAV rotates around the antenna. This method offers substantial contributions, including enhanced monitoring precision, simplified hardware configurations, continuous tracking with superior accuracy, and adaptability to diverse range routes without the need for preflight parameter tuning. Performance evaluations demonstrate that the proposed ANETF-RSSI method consistently outperforms existing technique, improving nominal performance by 32.02% in the most challenging operational scenarios and achieving a remarkable 48.76% improvement in minimum RSSI values. Consequently, this research provides a versatile and adaptive tracking solution for unexpected UAV flight trajectories. [ABSTRACT FROM AUTHOR]

The article discusses the need to create active protection of a mobile radio communication channel in the UHF/VHF band using a radio interference generator in the conditions of action of enemy ground-based radio monitoring means. The problem of determining the boundaries of the location area of a directional radio interference generator is formulated, at each point of which the protection of a mobile radio communication channel is provided. An algorithm for determining the boundaries of the radio interference generator location zone is proposed. The dependence of the shape and size of the obtained location zone of the radio interference generator on the current parameters of the mobile radio communication channel model is analyzed. [ABSTRACT FROM AUTHOR]

AbstractBackground Despite the theoretical advantages of treating metastatic bone disease with microwave ablation (MWA), there are few reports characterizing microwave absorption and bioheat transfer in bone. This report describes a computational modeling-based approach to simulate directional microwave ablation (dMWA) in spine, supported by ex vivo and pilot in vivo experiments in porcine vertebral bodies.Materials and methods A 3D computational model of microwave ablation within porcine vertebral bodies was developed. Ex vivo porcine vertebra experiments using a dMWA applicator measured temperatures approximately 10.1 mm radially from the applicator in the direction of MW radiation (T1) and approximately 2.4 mm in the contra-lateral direction (T2). Histologic assessment of ablated ex vivo tissue was conducted and experimental results compared to simulations. Pilot in vivo experiments in porcine vertebral bodies assessed ablation zones histologically and with CT and MRI.Results Experimental T1 and T2 temperatures were within 3–7% and 11–33% of simulated temperature values. Visible ablation zones, as indicated by grayed tissue, were smaller than those typical in other soft tissues. Posthumous MRI images of in vivo ablations showed hyperintensity. In vivo experiments illustrated the technical feasibility of creating directional microwave ablation zones in porcine vertebral body.Conclusion Computational models and experimental studies illustrate the feasibility of controlled dMWA in bone tissue.

Microwave medical imaging (MMI) is experiencing a surge in research interest, with antenna performance emerging as a key area for improvement. This work addresses this need by enhancing the directivity of a compact UWB antenna using a Yagi-Uda-inspired reflector antenna. The proposed reflector-loaded antenna (RLA) exhibited significant gain and directivity improvements compared to a non-directional reference antenna. When analyzed for MMI applications, the RLA showed a maximum increase of 4 dBi in the realized gain and of 14.26 dB in the transmitted field strength within a human breast model. Moreover, it preserved the shape of time-domain input signals with a high correlation factor of 94.86%. To further validate our approach, another non-directional antenna with proven head imaging capabilities was modified with a reflector, achieving similar directivity enhancements. The combined results demonstrate the feasibility of RLAs for improved performance in MMI systems. [ABSTRACT FROM AUTHOR]

Adhoc network expansion to FANET has attracted researchers and different companies to think of it as a trade and let users use it as per their needs. Mobility, in contrast to the mobile revolution, has led to its implementation on different networks. FANET is a case where mobility is inculcated with flying nodes where UAVs are deployed in real-time scenarios linked together-operating cooperatively in the best possible coordination for successful data transmission to a base station. The operational efficiency of such networks is in different rapidly changing missions, from line-of-sight to beyond-line-of-sight. Mission applicability ranging from rescue, disaster relief, army, surveillance, delivery of goods, agriculture, 3D mapping, and many others necessitates the development of a competent routing protocol that takes into account the nature of the application and amenities for positioning UAVs. Routing in UAVs has serious questions owing to its fast mobility, sometimes static and, at the same time, static with dynamic. According to recent studies, directed transmission and reception can achieve significant throughput improvements over omnidirectional transmission and reception. Numerous routing protocols are proposed, but each has its pros and cons for such dynamic flying networks. This paper presents the simulation-based performance of the OLSR routing protocol in various propagation models for FANET with directional antenna in different scenarios and considerations (parameters). [ABSTRACT FROM AUTHOR]

Wireless rechargeable sensor networks (WRSNs) are widely used in many fields. However, the limited battery capacity of sensor nodes (SNs) prevents its development. To extend the battery life of SNs, they can be charged by a mobile charger (MC) equipped with radio frequency-based wireless power transfer (WPT). The paper addressed the issue of optimizing route planning and charging based on an MC with directional charging in on-demand networks. A mixed integer linear programming model (MILP) is proposed to obtain the appropriate stopping points (SPs) and orientation charging angles to respond to input requests in the shortest possible time and with minimum energy consumption. First, to select the SPs and the orientation charging direction, we utilize a clustering and discretization technique while minimizing the number of SPs and maximizing the charging cover. Then, to decrease the charging time of the required SNs as well as the MC's energy consumption, we propose a heuristic search algorithm for adjusting the moving path for the directional mobile charger. Finally, experimental simulations are performed to evaluate the performance of the proposed directional charging scheduling algorithm, and the results reveal that the suggested approach outperforms existing studies in terms of MC energy consumption, charging delay, and distance traveled.

In this study, a novel received signal strength indicator (RSSI)-based tracking algorithm for antenna tracker systems utilizing directional antennas is proposed. This system has two sequential phases, which are the "Full Area Scan Phase" and the "Active RSSI-Based Tracking Phase" with a unique elliptic trajectory formula for generating an original two-dimensional (2D) RSSI map to detect the maximum signal. An elliptic trajectory paves the way for splitting RSSI measurements into specific regions equally on this map in which any disturbance and noises are eliminated. The proposed method do not require any telemetry data or multiple receivers for antennas. The simulation results showed that the algorithm attained to 98 % accuracy with respect to the Global Positioning System (GPS)-based ones. In real-world experiments, it captures the first handshake signal within 6 seconds even when the unmanned aerial vehicle (UAV) positions are uncertain. Furthermore, it is demonstrated that this novel technique can provide a continuous tracking at high resolution with the error value of 0. 135 ° and 0. 148 ° in the elevation and azimuth axes, respectively, compared with the GPS-based one. In conclusion, the simulation and test studies indicated that the proposed method could achieve a higher precision tracking with its advantages against the former methods. [ABSTRACT FROM AUTHOR]

With the rapid development of the Internet of Things, the number of wireless devices is increasing rapidly. Because of the limited battery capacity, these devices may suffer from the issue of power depletion. Radio frequency (RF) energy harvesting technology can wirelessly charge devices to prolong their lifespan. With the technology of beamforming, the beams generated by an antenna array can select the direction for wireless charging. Although a good charging-time schedule should be short, energy efficiency should also be considered. In this work, we propose two algorithms to optimize the time consumption for charging devices. We first present a greedy algorithm to minimize the total charging time. Then, a differential evolution (DE) algorithm is proposed to minimize the energy overflow and improve energy efficiency. The DE algorithm can also gradually increase fully charged devices. The experimental results show that both the proposed greedy and DE algorithms can find a schedule of a short charging time with the lowest energy overflow. The DE algorithm can further improve the performance of data transmission to promote the feasibility of potential wireless sensing and charging applications by reducing the number of fully charged devices at the same time. [ABSTRACT FROM AUTHOR]

In this paper, the directional antenna is developed to construct the printed dual‐frequency directional antenna for a 1‐GHz/2.3‐GHz dual‐frequency sensor application. An auxiliary dipole element generating the higher resonant mode is set on a primary dipole element introducing the lower resonant mode. The feed balance is also designed to cover the desired frequency between two resonance frequencies, which is based on the microstrip line (MS) to coplanar stripline (CPS) transition. To realize the directional antenna, two reflector elements are utilized, and one of them is a stepped‐width reflector on reducing the size of the antenna. In addition, the parasitic strip works as the lumped element used to obtain good impedance matching. A series of simulations are performed on the MS‐to‐CPS transition, the dual dipole element, the reflectors, and the parasitic strip to determine the optimal antenna design. A prototype is fabricated based on the optimal results of the simulation. Concerning the measured results, the proposed antenna has well unidirectional radiations, good radiation efficiencies, and low cross‐polarization levels at any operating frequencies. Key Points: The impedance matching of dual‐frequency directional antenna can be achieved by using the dual‐parasitic stripThe feed balance is also designed to cover the desired frequency between two resonance frequencies, which is based on the MS‐to‐CPS transitionA stepped‐width reflector is used for reducing the size of the antenna [ABSTRACT FROM AUTHOR]

In this paper, a novel low profile planar inverted-F antenna (PIFA) with high gain and low specific absorption rate (SAR) using a miniaturized artificial magnetic conductor (AMC) is investigated. The performance of the PIFA antenna is analyzed with AMC to understand the contribution of AMC. The gain enhancement of the PIFA antenna is achieved by applying AMC below the antenna. Furthermore, the placement of AMC also reduces the SAR of the antenna and improves the antenna front-to-back ratio (FBR). The proposed antenna when measured has an impedance bandwidth of 4.8–6.7 GHz (33% with center frequency at 5.75 GHz) which is suitable for Wireless Local Area Network (WLAN), satellite uplink C-band, and sub-6 5G applications with the maximum gain of 7.6 dBi. The performance of the proposed antenna is analyzed by full-wave commercial electromagnetic software and verified by measurements. [ABSTRACT FROM AUTHOR]

The fare payment system for public transportation has developed from coins, paper tickets, magnetic strips, and pre-paid cards to new technologies such as Radio-Frequency Identification (RFID) and Near Field Communication (NFC). Most fare payment systems are a fusion of NFC and mobile payment. As the latest fare payment system, the studies on gate-free technology without tag action are in progress. The gate-free system has several advantages, such as improving user convenience, eliminating congestion, and preventing the spread of infectious diseases. We introduce a gate-free system using Bluetooth Low Energy (BLE) technology as the next-generation fare payment system for public transportation. We propose a smart block structure for a gate-free system and analyze the antenna for this structure. A directional antenna is required for location detection of multiple mobile terminals in the gate-free zone, and an antenna to satisfy the requirements is analyzed. A stacked air-gap patch array that satisfies BLE performance and has high directivity has been proposed within the limited smart block size. To compensate for the low bandwidth of the patch antenna, an air gap is added between the patch radiator and the ground, and the antenna gain is increased by applying a stacked patch on the patch radiator. Based on the proposed antenna and smart block, a gate-free system testbed is installed, and the testing results are presented.

Microwave ablation (MWA) is becoming an increasingly important minimally invasive treatment option for localized tumors in many organ systems due to recent advancements in microwave technology that have conferred many advantages over other tumor ablation modalities. Despite these improvements in technology and development of applicators for site-specific tumor applications, the vast majority of commercially available MWA applicators are generally designed to create large-volume, symmetric, ellipsoid or spherically-shaped treatment zones and often lack the consistency, predictability, and spatial control needed to treat tumor targets near critical structures that are vulnerable to inadvertent thermal injury. The relatively new development and ongoing translation of directional microwave ablation (DMWA) technology, however, has the potential to confer an added level of control over the treatment zone shape relative to applicator position, and shows great promise to expand MWA’s clinical applicability in treating tumors in challenging locations. This paper presents a review of the industry-standard commercially available MWA technology, its clinical applications, and its limitations when used for minimally-invasive tumor treatment in medical practice followed by discussion of new advancements in experimental directional microwave ablation (DMWA) technology, various techniques and approaches to its use, and examples of how this technology may be used to treat tumors in challenging locations that may otherwise preclude safe treatment by conventional omni-directional MWA devices.

Recent advances in wireless sensor networks (WSNs) allow directional antennas to be used instead of omni-directional antennas. However, the problem of maintaining (symmetric) connectivity in directional wireless sensor networks is significantly harder. Contributing to this field of research, in this paper, we study two problems in WSNs equipped with k directional antennas ( 3 ≤ k ≤ 4 ). The first problem, called antenna orientation (AO) is that given a set S of nodes equipped with omni-directional antennas of unit range, the goal is to replace omni-directional antennas by directional antennas with beam-width θ ≥ 0 and to find a way to orient them such that the required range to yield a symmetric connected communication graph (SCCG) is minimized. For this problem, we propose an O (n log n) time algorithm yielding r = 2 s i n 180 ∘ k . The second problem, called antenna orientation and power assignment (AOPA) is to determine for each node u an orientation of its antennas and a range r u in order to induce an SCCG such that the total power assignment ∑ u r u β is minimized, where β is a distant-power gradient. We show that our solution for the AO problem also induces an O(1)-approximation algorithm for the AOPA problem. Simulation results demonstrate that our algorithms have better performance than previous approaches, especially in case k = 3 . [ABSTRACT FROM AUTHOR]

Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microwave medical imaging (MMI) is experiencing a surge in research interest, with antenna performance emerging as a key area for improvement. This work addresses this need by enhancing the directivity of a compact UWB antenna using a Yagi-Uda-inspired reflector antenna. The proposed reflector-loaded antenna (RLA) exhibited significant gain and directivity improvements compared to a non-directional reference antenna. When analyzed for MMI applications, the RLA showed a maximum increase of 4 dBi in the realized gain and of 14.26 dB in the transmitted field strength within a human breast model. Moreover, it preserved the shape of time-domain input signals with a high correlation factor of 94.86%. To further validate our approach, another non-directional antenna with proven head imaging capabilities was modified with a reflector, achieving similar directivity enhancements. The combined results demonstrate the feasibility of RLAs for improved performance in MMI systems.

In this work, a meta-surface (frequency selective surface) loaded high gain directional antenna system is presented. The antenna system is developed using ultra-wideband (UWB) antenna element and meta-surface reflector. The UWB antenna element is designed and simulated without meta-surface reflector. The UWB antenna element has poor impedance bandwidth and directivity. A meta-surface is created using unit cell and equal in the size of the antenna substrate. The meta-surface is placed over the UWB antenna element at optimized height (H=30 mm). The impedance bandwidth, directivity and gain of the proposed antenna are improved by the meta-surface reflector. The proposed antenna is fabricated and experimentally validated by the comparison of the simulated and measured results. The antenna has 3 to 6 GHz wide impedance bandwidth, more than 5 dBi gain and maximum 4.6 dBi directivity at 3.5 GHz frequency. Performance of the proposed antenna is also compared with existing carried out work. Comparatively, the proposed antenna with high directivity is most suitable for IEEE 802.15.4a UWB wireless sensor network (WSN) security application. [ABSTRACT FROM AUTHOR]

The use of mmWaves for achieving 5G networks is increasingly being seen as a necessity due to the vastly improved bandwidth and data rates at these frequencies. These waves suffer from severe attenuation and their use may, however, be restricted, in the immediate future, to short-range networks, such as personal area networks (IEEE 802.11ad) or vehicular and mobile adhoc networks operating in proximity. MmWaves require directional antennas which have the added advantage of allowing spatial reuse. Even though the high gain in a given direction in such antennas allows us to extend the range, there are several factors, such as error in antenna orientation, fading, blockage which show that an optimum beamwidth can be obtained to maximize the network throughput. The treatment of transmissions, during Line-of-Sight transmission conditions and during Non-Line-of-Sight, is completely different. The paper has evaluated the optimum beamwidth for successful mmWave transmissions in mmWave adhoc networks at 60 Ghz in short-range mmWave networks (IEEE 802.11ad). [ABSTRACT FROM AUTHOR]

Studying the geometry of electromagnetic band gap (EBG) structures in 1 and 3 dimensions is useful for achieving effective directional radiation, high gain, and side-lobe attenuation of antennae. This paper presents an EBG antenna, whose radiating source is a rectangular notched patch, which can be used for applications around 20 GHz. Two conventional woodpile dielectric structures with a triangular lattice are presented in a comparative study to extract the best physical and electromagnetic performance in terms of directivity, bandwidth, and gain; these are the square and the cylindrical rods. These two structures' electromagnetic and geometrical limits allow the design of a 3D EBG structure called an icosahedral structure. The proposed antenna is composed of different ceramic substrates (the Arlon AR 450, (h = 0.48 mm, ɛr = 4.5, El Tand = 0.0035) on which the radiating element is placed, the Rogers TMM 13i, (ɛr = 12.85, El Tand = 0.0019) for the 3D icosahedral structure; and the Taconic TLY-5A, (ɛr = 2.17, El Tand = 0.0009) for the 1D lateral walls). With a substrate-plated radiation source coupled with a 3D icosahedral structure and surrounded by a vertically mounted 1D structure, a directivity of 19 dBi was obtained with a realized gain of 17.7 dB and an optimal coupling (antenna–EBG material) at 19.8 GHz. These results are encouraging given the antenna size of 33.41 × 27.87 × 37.36 mm3. [ABSTRACT FROM AUTHOR]

The process of obtaining the positions of neighbors in narrow beam width directional MANET is important in both blind and semi-blind situations, and the process of which is called neighbor discovery. In this article, a semiblind neighbor discovery algorithm based the Chinese Remainder Theorem was proposed and designed. Firstly, the node model of directional antennas for sector distributions was constructed and evaluated. Then, the corresponding receiving and sending ID sequence was designed. Finally, the performance of the CRT semi-blind algorithm was evaluated and compared with the scan based algorithm-deterministic and the semi-blind completed randomized algorithm using MATLAB. The simulation results shows that the proposed algorithm has better overall performance than that of the other two algorithms. [ABSTRACT FROM AUTHOR]

Achieving neighbor discovery for a directional flying ad hoc network (FANET) with multiple channels poses challenges for media access control (MAC) protocol design, as it requires simultaneous main lobe and channel rendezvous while dealing with the high UAV mobility. In order to achieve fast neighbor discovery for initial access without coordination or prior information, we first establish the theoretical supremum for the directional main lobe. Then, to achieve the supremum, we introduce the BR-DA and BR-DA-FANET algorithms to respectively establish the supremum on rendezvous between a pair of UAVs’ main lobes and rendezvous of main lobes for all UAVs in the FANET. To further accelerate the neighbor discovery process, we propose the neighbor discovery with location prediction protocol (ND-LP) and the avoiding communication interruption with location prediction (ACI-LP) protocol. ND-LP enables quick main lobe rendezvous and channel rendezvous, while ACI-LP enables beam tracking and channel rendezvous together with the avoidance of communication interruptions. The simulation results demonstrate that the proposed protocols outperform the state-of-the-art works in terms of neighbor discovery delay.

With the rapid development of the Internet of Things, the number of wireless devices is increasing rapidly. Because of the limited battery capacity, these devices may suffer from the issue of power depletion. Radio frequency (RF) energy harvesting technology can wirelessly charge devices to prolong their lifespan. With the technology of beamforming, the beams generated by an antenna array can select the direction for wireless charging. Although a good charging-time schedule should be short, energy efficiency should also be considered. In this work, we propose two algorithms to optimize the time consumption for charging devices. We first present a greedy algorithm to minimize the total charging time. Then, a differential evolution (DE) algorithm is proposed to minimize the energy overflow and improve energy efficiency. The DE algorithm can also gradually increase fully charged devices. The experimental results show that both the proposed greedy and DE algorithms can find a schedule of a short charging time with the lowest energy overflow. The DE algorithm can further improve the performance of data transmission to promote the feasibility of potential wireless sensing and charging applications by reducing the number of fully charged devices at the same time.

The entrance of the underground personnel in coal mine should be equipped with a device to detect whether the identification card is working properly and uniquely. There are problems in the use of uniqueness detection technology based on palm prints and fingerprints, facial images, gait and other biological characteristics to detect the person carrying this card. The recognition accuracy is low due to the impact of the environment. The existing mine uniqueness detection device is interfered by the identification card outside the detection area, and the detection effect is not ideal when the person carries multiple identification card, carries wrong identification card, and does not carry the identification card. In order to solve the above problems, a mine uniqueness detection device based on 433 MHz wireless communication and iris recognition is designed. Firstly, by adjusting the transmission power of the directional antenna, real-time configuration of the detection area is realized. The 433 MHz wireless communication module configures the detection area identifier to the identification cards in the detection area through the directional antenna. The card reader base station reads the message data of the identification cards, and detects whether the detection area identifier of the message data is equal to the configured detection area identifier. In order to eliminate the interference of identification cards outside the area, the number of identification cards in the detection area is detected, and the detection results are written into the result table of the intermediate database. Secondly, the iris information of the personnel to be inspected is collected, and the identification card information of the personnel is queried by identifying the iris information. Finally, by judging whether the identification card information queried according to the iris information matches with the result table information of the intermediate database, the uniqueness detection of the identification card is realized. The test results show that the detection accuracy of the device is 100% for the cases of carrying multiple identification cards, carrying wrong identification cards, not carrying identification cards and carrying right identification cards. The average detection time does not exceed 2 s.

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a narrowband and compact antenna resonating at 6.1 GHz with a peak realized gain of 3.3 dBi is proposed to monitor the glucose concentration in the blood without taking invasive blood samples. The proposed antenna is fabricated using a low-cost FR-4 substrate with compact dimensions of 30 mm × 30 mm × 1.6 mm. The impedance bandwidth of this antenna ranges from 5.2 to 7.1 GHz. For measuring blood glucose levels, a human finger phantom model with dimensions of 15 mm × 12 mm × 10 mm is constructed using the EM simulation (HFSS) environment. The finger phantom consists of different layers such as skin, fat, muscle, blood, and bone modeled at 6.1 GHz using various dielectric materials for various glucose concentrations. The finger phantom model is placed at different locations around the antenna to measure the frequency shift for monitoring glucose concentration in blood samples. The proposed finger phantom model is validated by conducting an experimental study by placing a real human finger around the fabricated antenna and measuring the frequency shift. This study shows a very good agreement with the results obtained by the simulated phantom model. The advantages and outperformance of the proposed sensor are highlighted in terms of the sensitivity obtained and compared with other techniques given in the literature. [ABSTRACT FROM AUTHOR]

With innovative applications of unmanned aerial vehicle (UAV) ad hoc networks in various areas, their demands on broad bandwidth, large capacity and low latency become prominent. The combination of millimeter wave, directional antenna and time division multiple access techniques, which enables concurrent transmissions, is promising to deal with it. In this paper, we study the resource allocation problem in UAV ad hoc networks. Specifically, the slot assignment, antenna boresight and transmit power are jointly optimized to promote the network capacity. First, we formulate the optimization problem as the maximization of the fairness-weighted network capacity, subject to the constraint on priority guarantee. Then, because the formulated problem is a mixed integer non-linear programming problem (MINLP), which is NP-hard, two algorithms called dual-based iterative search algorithm (DISA) and sequential exhausted allocation algorithm (SEAA) are respectively proposed to efficiently solve it with acceptable complexity. DISA slacks the MINLP into a continuous-variable optimization problem and solves it with the Lagrangian dual method in an iterative manner. As a heuristic method, SEAA schedules links sequentially, i.e., from high-priority to low-priority ones. Numerical results demonstrate that both DISA and SEAA can efficiently allocate resources for UAVs, while guaranteeing the fairness and priority of links. [ABSTRACT FROM AUTHOR]

The adoption of abundant millimeter-wave (mmWave) spectrum offers higher capacity for short-range connectivity in various Unmanned Aerial Vehicle (UAV)-centric communications scenarios. In contrast to the conventional cellular paradigm, where the coordination of connected nodes is highly centralized, the distributed deployments, such as those operating over unlicensed frequency bands, maintain robust interactions in the absence of central control. These agile decentralized systems are being naturally created by dynamic UAV swarms that form a temporary 3D structure without reliance on remote management or pre-established network infrastructures. While much effort has been invested in the performance assessment of distributed, directional, and 3D systems individually, a combination of these three angles allows capturing more realistic UAV swarm scenarios and produces a novel research perspective. This work addresses one of the fundamental challenges in mmWave-based 3D networks– directional deafness– which is known to adversely affect the overall system performance. Particularly, we develop a mathematical framework by taking into account the peculiarities of 3D directional and distributed deployments. We provide a holistic analytical assessment of directional deafness and propose several powerful approximations that capture realistic antenna patterns. [ABSTRACT FROM AUTHOR]

The need of highly directional communications at mmWave band introduces high overhead for beam training and alignment, which also makes the medium access control (MAC) a grand challenge. However, the need of supporting highly directional multiple beams between transmitters and receivers makes the MAC design even harder. To harvest the gain of multi-beam mmWave communications, which benefits not only from the large bandwidth of mmWave spectrum but also the diversity of concurrent multi-user multi-beam transmissions, this paper studies the medium access control (MAC) layer related issues in multi-beam mmWave networks, including (1) efficient multi-beam training schemes to enable lower overhead thus faster AP association and beam alignment, (2) block-sparse mmWave channel estimation in different beam resolutions, and (3) effective concurrent radio resource allocation to facilitate better multi-user multi-beam transmissions. Simulation results demonstrate that the proposed schemes outperform existing techniques in improving the efficiency of mmWave communications thus achieving significantly higher network performances. To our best knowledge, we are the first to comprehensively consider both efficient training for beam alignment and resource scheduling in the MAC design to enable highly directional multi-user multi-beam concurrent transmissions in a mmWave network. [ABSTRACT FROM AUTHOR]

In this paper, blockage effects on high-frequency antennas are studied and their influence on the voltage standing wave ratio, gain, and radiation patterns is analysed. By simulating different blockage effects, the relationship between the antenna and the size of the blockage is clarified. It finds that radiation patterns are usually affected more seriously than other coefficients. The impact on the pattern is greater if the size or height of the blockage is larger than half of the wavelength. Two methods relating to the modification of the angle and height of the antenna are proposed that can reduce the influence of blockage effects. These are verified using a simulation and one is further demonstrated using a practical application. [ABSTRACT FROM AUTHOR]

Maintaining high system performance is critical for a multi-hop flying mesh network (FlyMesh) to perform missions in different environments. Although the Poisson point process (PPP) has been widely used for the performance analysis of FlyMesh, it still has flaws in describing the spatial distribution of the UAVs since it does not restrict the minimum distance between them. The spatial deployment of FlyMesh varies depending on the environment. Considering the relevance and practicality, we modeled the multi-hop FlyMesh using the β-Ginibre point process (β-GPP) and equipped each UAV with a directional antenna. Under the condition of the decode-and-forward protocol, we derived the connection probability and ergodic capacity of a multi-hop FlyMesh utilizing the Laplace transform of interference. Then, we calculated an approximate expression for the interference Laplace transform based on the diagonal approximation and further obtained the coverage probability. Finally, the numerical simulation results verified the correctness of the theoretical derivation, indicating that it is possible to optimize the system’s performance based on the expressions derived in this paper.

In this paper, a geometric single-bounce scattering channel model for mobile-to-mobile (M2M) communication is proposed that incorporates directional antennas at both mobile stations (MSs). The directional antennas are implemented to reduce the degree of non-stationarity for M2M communication channels and for safety-related M2M scenarios. Furthermore, using the confined scattering objects in the effective vicinity of the directional antennas, we derive statistical-based expressions for the probability density function (pdf) of angle-of-arrival (AoA). The derived AoA statistical distribution depends upon the spatial relationships between the scatterers and MSs. The proposed model employs scatterers uniformly distributed within the sectoral regions of circles around the MSs. Results for the proposed model are compared with those for the circular model of M2M communication as well as fixed-to-mobile (F2M) communication environments. Besides employing directivity, with an appropriate choice of scattering regions, the proposed model can be made suitable for both macrocellular and M2M communication scenarios. [ABSTRACT FROM AUTHOR]