Airborne Communication Networks: A Survey Cao, Xianbin; Yang, Peng; Alzenad, Mohamed ...
IEEE journal on selected areas in communications,
09/2018, Letnik:
36, Številka:
9
Journal Article
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Owing to the explosive growth of requirements of rapid emergency communication response and accurate observation services, airborne communication networks (ACNs) have received much attention from ...both industry and academia. ACNs are subject to heterogeneous networks that are engineered to utilize satellites, high-altitude platforms (HAPs), and low-altitude platforms (LAPs) to build communication access platforms. Compared to terrestrial wireless networks, ACNs are characterized by frequently changed network topologies and more vulnerable communication connections. Furthermore, ACNs have the demand for the seamless integration of heterogeneous networks such that the network quality-of-service (QoS) can be improved. Thus, designing mechanisms and protocols for ACNs poses many challenges. To solve these challenges, extensive research has been conducted. The objective of this special issue is to disseminate the contributions in the field of ACNs. To present this special issue with the necessary background and offer an overall view of this field, three key areas of ACNs are covered. Specifically, this paper covers LAP-based communication networks, HAP-based communication networks, and integrated ACNs. For each area, this paper addresses the particular issues and reviews major mechanisms. This paper also points out future research directions and challenges.
Liquid chromatography-high-resolution mass spectrometry (LC-MS)-based metabolomics aims to identify and quantify all metabolites, but most LC-MS peaks remain unidentified. Here we present a global ...network optimization approach, NetID, to annotate untargeted LC-MS metabolomics data. The approach aims to generate, for all experimentally observed ion peaks, annotations that match the measured masses, retention times and (when available) tandem mass spectrometry fragmentation patterns. Peaks are connected based on mass differences reflecting adduction, fragmentation, isotopes, or feasible biochemical transformations. Global optimization generates a single network linking most observed ion peaks, enhances peak assignment accuracy, and produces chemically informative peak-peak relationships, including for peaks lacking tandem mass spectrometry spectra. Applying this approach to yeast and mouse data, we identified five previously unrecognized metabolites (thiamine derivatives and N-glucosyl-taurine). Isotope tracer studies indicate active flux through these metabolites. Thus, NetID applies existing metabolomic knowledge and global optimization to substantially improve annotation coverage and accuracy in untargeted metabolomics datasets, facilitating metabolite discovery.
As descendants of social cockroaches, termites have an intriguing biology that makes them highly suitable study subjects in a wide variety of fields, such as eusocial evolution, ageing mechanisms, ...wood decomposition, ecosystem engineering, and pest management. This special section presents four studies ranging from the role of chemical compounds in foraging behaviour and food digestion to genetics and physiology of reproduction. Taken together, these studies offer new insights and ample suggestions for future work on these fascinating insects.
As descendants of social cockroaches, termites have an intriguing biology that makes them highly suitable study subjects in a wide variety of fields, such as eusocial evolution, ageing mechanisms, wood decomposition, ecosystem engineering, and pest management. This special section presents four studies ranging from the role of chemical compounds in foraging behaviour and food digestion to genetics and physiology of reproduction. Taken together, these studies offer new insights and ample suggestions for future work on these fascinating insects.
This paper is concerned with providing radio access network (RAN) elements (supply) for flash crowd traffic demands. The concept of multi-tier cells heterogeneous networks (HetNets) has been ...introduced in 5G network proposals to alleviate the erratic supply-demand mismatch. However, since the locations of the RAN elements are determined mainly based on the long-term traffic behavior in 5G networks, even the HetNet architecture will have difficulty in coping up with the cell overload induced by flash crowd traffic. In this paper, we propose a proactive drone-cell deployment framework to alleviate overload conditions caused by flash crowd traffic in 5G networks. First, a hybrid distribution and three kinds of flash crowd traffic are developed in this framework. Second, we propose a prediction scheme and an operation control scheme to solve the deployment problem of drone cells according to the information collected from the sensor network. Third, the software-defined networking technology is employed to seamlessly integrate and disintegrate drone cells by reconfiguring the network. Our experimental results have shown that the proposed framework can effectively address the overload caused by flash crowd traffic.
Autophagy is an important mechanism for cellular self‐digestion and basal homeostasis. This gene‐ and modulator‐regulated pathway is conserved in cells. Recently, several studies have shown that ...autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy‐related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins. The effects of other autophagy‐related drugs, such as chloroquine, 3‐methyladenine, rapamycin, and other potential therapeutic drugs and targets, in PH are also described.
Autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy‐related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins.
Nutritional support using exclusive enteral nutrition (EEN) has been studied as primary therapy for the management of liver diseases, Crohn's disease, and cancers. EEN can also increase the number of ...beneficial microbiotas in the gut, improve bile acid and lipid metabolism, and decrease the number of harmful dietary micro-particles, possibly by influencing disease occurrence and increasing immunity. This study investigated the effects of EEN-n-3 polyunsaturated fatty acids (3PUFAs) (EEN-3PUFAs) on the gut microbiome, intestinal barrier, and lipid or bile acid metabolism in mice. Metagenomic sequencing technology was used to analyze the effects of EEN-3PUFAs on the composition of gut microbiome signatures. The contents of short-chain fatty acids (SCFAs) and bile acids in the feces and liver of the mice were assayed by gas chromatography and ultra-high-pressure liquid chromatography/high-resolution tandem mass spectrometry, respectively. The levels of lipopolysaccharide (LPS) and D-lactic acid in the blood were used to assess intestinal permeability. The results indicated that EEN-3PUFAs could improve the composition of gut microbiome signatures and increase the abundance of Barnesiella and Lactobacillus (genus), Porphyromonadaceae, and Bacteroidia (species), and Bacteroidetes (phylum) after EEN-3PUFAs initiation. In addition, EEN-3PUFAs induced the formation of SCFAs (mainly including acetic acid, propionic acid, and butyric acid) and increased the intestinal wall compared to the control group. In conclusion, EEN-3PUFAs modulate the alterations in gut microbiome signatures, enhanced intestinal barrier, and regulated the fatty acid composition and lipid metabolism shifts and the putative mechanisms underlying these effects.
The unmanned aerial vehicle (UAV) network that is convinced as a significant component of 5G and emerging 6G wireless networks is desired to accommodate multiple types of service requirements ...simultaneously. However, how to converge different types of services onto a common UAV network without deploying an individual network solution for each type of service is challenging. We tackle this challenge in this paper through slicing the UAV network, i.e., creating logical UAV networks customized for specific requirements. To this end, we formulate the UAV network slicing problem as a sequential decision problem to provide mobile broadband (MBB) services for ground mobile users while satisfying ultra-reliable and low-latency requirements of UAV control and non-payload signal delivery. This problem, however, is difficult to be directly solved mainly due to the sequence-dependent characteristic and the lack of accurate location information of mobile users and accurate and tractable channel gain models in practice. To overcome these difficulties, we propose a novel solution approach based on learning and optimization methods. Particularly, we develop a distributed learning method to predict mobile users' locations, where partial user location information stored on each UAV is utilized to train user location prediction networks. To achieve accurate channel gain models, we design deep neural networks (DNNs) that are trained by signal measurements at each UAV. To cope with the challenging sequence-dependent characteristic of the problem, we develop a Lyapunov-based optimization framework with provable performance guarantees to decompose the original problem into a sequence of separate optimization subproblems based on the learned results. Finally, an iterative optimization scheme joint with a successive convex approximation technique is exploited to solve these subproblems. Simulation results demonstrate the accuracy of the learning methods as well as the effectiveness of the Lyapunov-based optimization framework.
Unmanned aerial vehicle (UAV) relay networks are convinced to be a significant complement to terrestrial infrastructures to provide robust network capacity. However, most of the existing works either ...considered enhanced mobile broadband (eMBB) payload communication or ultra-reliable and low latency communications (URLLC) control information communication. In this paper, we investigate resource allocation for the eMBB payload and URLLC control information communication multiplexing in a multi-UAV relay network. We firstly propose a multi-UAV relay model comprehensively considering path loss, small-scale channel fading and different quality of service requirements of eMBB and URLLC communications. Then we formulate the multiplexing problem as a joint user association, bandwidth and transmit power optimization problem to improve total transmission data rate and reduce power consumption. The solution of this problem is challenging due to different capacity characteristics of eMBB and URLLC communications, the coupling of continuous variables and integer variables, and the non-convexity. To mitigate these challenges, we equivalently decompose the original optimization problem into a URLLC problem and an eMBB problem. For the URLLC problem, we derive closed-form expressions of the optimal bandwidth and transmit power. For the eMBB problem, we develop an iterative solution framework of alternatively optimizing user association, bandwidth and transmit power.
This letter is concerned with investigating a joint user association and unmanned aerial vehicle (UAV) location optimization problem for UAV-aided communications. Different from the majority of ...existing studies, this letter aims at deriving solutions to the joint optimization problem that is modeled as a mixed-integer non-convex optimization problem (MINCOP) with a goal of maximizing users' total achievable data rates. A novel iterative optimization scheme is proposed to handle the MINCOP. Specifically, the MINCOP is first decomposed into an integer optimization subproblem and a non-convex optimization subproblem. An iterative algorithm is then developed to optimize these two separated subproblems alternatively. Besides, the non-convexity of the non-convex subproblem is handled via successive convex approximation. Based on approximate results, Karush-Kuhn-Tucker (KKT) conditions are leveraged to obtain the evolutionary-form solution to the joint optimization problem. The comparison with the state-of-the-art verifies that the developed algorithm is convergent and is able to achieve good performance.
Abstract
Background
Aging and diabetes can impair the balance function of the elderly and diabetic patients and increase their fall risk. This study aimed to assess the shaking amplitude of the ...center-of-pressure (CoP) during static standing, to analyze the effects of aging and diabetes on the balance control.
Materials and methods
This cross-sectional observational study, compared the balance performance of 20 healthy younger adults (27.65 ± 5.60 years), 16 healthy older adults (58.88 ± 3.54 years) and 15 diabetic patients (58.33 ± 5.33 years) in four static standing conditions on a force plate: horizontal, anteroposterior (AP), left and right slope planes (5° angles on AP, left and right directions, respectively). The trajectory coordinates of the CoP over time were recorded and analyzed by principal components analysis to obtain the 95% confidence ellipse and its parameters: angle, major and minor axes lengths, and area. The balance indicators were compared among the three groups using one-way analysis of variance (ANOVA), Brown–Forsythe test or Kruskal–Wallis H test, depending on the normality and homogeneity of variance assumptions.
Results
The diabetic group had a significantly larger confidence ellipse area than the healthy younger adults on the horizontal plane (
P
= 0.032) and than the healthy older adults on the horizontal (
P
= 0.036), AP slope (
P
= 0.023), and right ML slope (
P
= 0.037) planes. There were no significant differences in the major axis length of the confidence ellipse among the three groups. The diabetic group had a significantly longer minor axis length than the healthy younger adults on the AP slope (
P
= 0.039), left ML slope (
P
= 0.045) and right ML slope (
P
= 0.016) planes and than the healthy older adults on the AP slope (
P
= 0.007), left ML slope (
P
= 0.035) and right ML slope (
P
= 0.012) planes.
Conclusions
The balance control of diabetic patients is decreased compared with healthy younger and older people, and the body swing amplitude increases mainly in the direction of minor axis of confidence ellipse during static standing, while the swing amplitude in the direction of the major axis has no significant change. Evaluating the balance function of diabetic patients can help clinicians identify people with fall risk early and intervene early, thereby reducing the occurrence of fall events in this population.
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