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Effects of Aerobic Exercise on Patients with Mental Illness in a Veterans Inpatient Psychiatric Unit: A Review of the Literature <s> Methods and Designs of Studies <s> This study investigated qualitatively the experiences of men who took part in a 10 week integrated exercise/psychosocial mental health promotion program... | The findings from the review focused on 10 peer-reviewed articles. Frameworks of the reviewed articles were not specifically listed in the literature. However, the articles were found to be a collection of different methods and designs. Designs ranging from qualitative studies BIB005 BIB001 to quantitative (Bonsaksen &... |
Effects of Aerobic Exercise on Patients with Mental Illness in a Veterans Inpatient Psychiatric Unit: A Review of the Literature <s> Settings of Studies <s> This study investigated qualitatively the experiences of men who took part in a 10 week integrated exercise/psychosocial mental health promotion programme, “Back o... | The settings took place in multiple countries around the world. Studies were based in Norway (Bonsaksen & Lerdal, 2012) , United States (Brown et al., 2015; Powers et al., 2015; BIB003 BIB007 , Canada BIB005 , Australia BIB002 , Germany (Oretel-Knochel et al., 2014) , Ireland (McArdle et al., 2012) , and the United Kin... |
Effects of Aerobic Exercise on Patients with Mental Illness in a Veterans Inpatient Psychiatric Unit: A Review of the Literature <s> Sample Sizes of Studies <s> This study investigated qualitatively the experiences of men who took part in a 10 week integrated exercise/psychosocial mental health promotion programme, “Ba... | Studies included sample sizes from (N = 9) the smallest sample (Powers et al., 2015) to (N = 200) the largest sample of subjects BIB002 ) giving a mean sample size for the review of 64.2. Some studies had an even representation of male and female subjects while others had skewed numbers of males BIB001 and females (Pow... |
Effects of Aerobic Exercise on Patients with Mental Illness in a Veterans Inpatient Psychiatric Unit: A Review of the Literature <s> Other Themes of Studies <s> This study investigated qualitatively the experiences of men who took part in a 10 week integrated exercise/psychosocial mental health promotion programme, “Ba... | Other major themes found in the reviews were preference such as exercise choice, exercise structure, and exercise length BIB003 BIB001 BIB005 , which helped improve compliance in one study BIB001 . Another theme found is symptom severity (Bonsaksen & Lerdal, 2012; BIB006 BIB001 BIB002 Powers et al., 2015) and exercise ... |
Effects of Aerobic Exercise on Patients with Mental Illness in a Veterans Inpatient Psychiatric Unit: A Review of the Literature <s> Measurement Tools Used in Studies <s> This study investigated qualitatively the experiences of men who took part in a 10 week integrated exercise/psychosocial mental health promotion prog... | Measurements of major variables were completed with some strategies that included multiple measurement tools. The Diagnostic and Statistical Manual is a tool that was used to measure the severity of depression BIB002 Measures of cognitive training and performance were captured by using the brief assessment of cognition... |
Effects of Aerobic Exercise on Patients with Mental Illness in a Veterans Inpatient Psychiatric Unit: A Review of the Literature <s> Discussion <s> Involvement in warfare can have dramatic consequences for the mental health and well-being of military personnel. During the 20th century, US military psychiatrists tried t... | Aerobic exercise is a beneficial intervention for people who suffer from mental illness and veterans are prone to mental health disorders with exposure to combat situations and high-stress environments BIB001 . Aerobic exercise was shown to have improvements in cognition and symptom management. Exercise as an intervent... |
English as an International Language: A Review of the Literature <s> Speaker and ELT practitioners' attitudes towards EIL <s> In this paper, the author argues that when teaching English as an international language, educators should recognize the value of including topics that deal with the local culture, support the s... | One of the main challenges the EIL model seems to face is the way it is perceived, not by students or authorities, but by teachers themselves. , in a research study of the attitudes of forty-seven pre-service teachers in Turkey, found that, although these pre-service teachers considered intelligibility to be the centr... |
Ambient Backscatter Communications: A Contemporary Survey <s> <s> This paper surveys recent technical research on the problems of privacy and security for radio frequency identification (RFID). RFID tags are small, wireless devices that help identify objects and people. Thanks to dropping cost, they are likely to prol... | a result, this technique has found many useful applications in practice such as radio-frequency identification (RFID), tracking devices, remote switches, medical telemetry, and low-cost sensor networks BIB003 , BIB004 . However, due to some limitations BIB001 BIB002 BIB005 , conventional backscatter communications can... |
Ambient Backscatter Communications: A Contemporary Survey <s> A. Energy Harvesting for Green Communications Networks <s> Wireless power transfer (WPT) technologies have been widely used in many areas, e.g., the charging of electric toothbrush, mobile phones, and electric vehicles. This paper introduces fundamental prin... | Recently, energy harvesting (EH) technique has gained a lot of attention from both academia and industry due to its promising features for green communications networks, e.g., WSNs and IoT. The key principle of EH is that it allows wireless devices to harvest energy from RF signals to support their operations. There ar... |
Ambient Backscatter Communications: A Contemporary Survey <s> B. Backscatter Communications Systems <s> Scatter radio achieves communication by reflection and requires low-cost and low-power RF front-ends. However, its use in wireless sensor networks (WSNs) is limited, since commercial scatter radio (e.g. RFID) offers ... | Backscatter communications systems can be classified into three major types based on their architectures: monostatic backscatter communications systems (MBCSs), BBCSs, and ABCSs as shown in Fig. 2. 1) Monostatic Backscatter Communications Systems: In an MBCS, e.g., an RFID system, there are two main components: a backs... |
Ambient Backscatter Communications: A Contemporary Survey <s> C. Fundamentals of Modulated Backscatter Communications <s> Analog-to-digital converters (ADCs) are ubiquitous, critical components of software radio and other signal processing systems. This paper surveys the state-of-the-art of ADCs, including experimental... | Despite differences in configurations, MBCSs, BBCSs, and ABCSs share the same fundamentals. In particular, instead of initiating their own RF transmissions as conventional wireless systems, a backscatter transmitter can send data to a backscatter receiver just by tuning its antenna impedance to reflect the received RF ... |
Ambient Backscatter Communications: A Contemporary Survey <s> D. Antenna Design <s> RF modulated backscatter (RFMB), also known as modulated radar cross section or sigma modulation, is a RF transmission technique useful for short-range, low-data-rate applications, such as nonstop toll collection, electronic shelf tags,... | In a backscatter communications system, an antenna is an essential component used to receive and backscatter signals. Thus, the design of the antenna can significantly affect the performance of the backscatter communications system. The maximum practical distance between the backscatter transmitter and the RF source, 1... |
Ambient Backscatter Communications: A Contemporary Survey <s> 3) Antenna Gain: <s> The most-up-to-date resource available on antenna theory and design. Expanded coverage of design procedures and equations makes meeting ABET design requirements easy and prepares readers for authentic situations in industry. New coverage... | Antenna gain is the amount of power transmitted in the direction of peak radiation to an isotropic source [40] . In general, the higher antenna gain leads to the longer range of transmission. Thus, it is important to calculate the antenna gain based on the target communication distance when designing the antenna [41] .... |
Ambient Backscatter Communications: A Contemporary Survey <s> E. Channel Coding and Decoding <s> Basic Principles of Radiofrequency Identification Antennas for RFID Transponders Transponders Antennas for Interrogators Interrogators Interrogator Communication and Control The Air Communication Link Commands for Transpond... | Channel coding, i.e., coding in the baseband, is a process that matches a message and its signal representation to the characteristics of the transmission channel. The main purpose of the coding process is to ensure reliable transmissions by protecting the message from interference, collision, and intentional modificat... |
Ambient Backscatter Communications: A Contemporary Survey <s> F. Modulation and Demodulation <s> We provide an overview of our experimental system, testing in practice a sensor communicating through backscatter at a range of approximately 15 meters indoors, with 5 mW transmission power at 10 bits per second. Our system... | Modulation is a process of varying one or more properties, i.e., frequency, amplitude, and phase, of carrier signals. At a backscatter receiver, by analyzing the characteristics of the received signals, we can reconstruct the original data by measuring the changes in reception phase, amplitude, or frequency, i.e., demo... |
Ambient Backscatter Communications: A Contemporary Survey <s> G. Backscatter Communications Channels <s> A new multi-antenna or multiple-input-multiple-output (MIMO) configuration is introduced for RF modulated backscatter in a multipath environment. RF modulated backscatter is used by semipassive RF tags to transmit w... | In the following, we describe general models of backscatter communication channels. Then, theoretical analyses and experimental measurements for the backscatter channels are discussed. 1) Backscatter Communications Channels: a) Basic backscatter channel: A general system model of a backscatter communications system con... |
Ambient Backscatter Communications: A Contemporary Survey <s> A. Overview of Bistatic Backscatter Communications Systems <s> This work examines the idea of dislocating the carrier transmission from the tag-modulated carrier reception, i.e. bi-static rather than mono-static backscatter radio. In that way, more than one ... | BBCSs have been introduced for low-cost, low-power, and large-scale wireless networks. Due to the prominent characteristics, BBCSs have been adopted in many applications such as wireless sensor networks, IoT, and smart agriculture BIB001 , BIB003 , BIB007 . As shown in Fig. 5 , there are three major components in the B... |
Ambient Backscatter Communications: A Contemporary Survey <s> B. Performance Improvement for Bistatic Backscatter Communications Systems <s> This work examines the idea of dislocating the carrier transmission from the tag-modulated carrier reception, i.e. bi-static rather than mono-static backscatter radio. In that way... | 1) Communication Improvement: As mentioned above, a bistatic backscatter offers better communication range and transmission rate than those of MBCSs. Nevertheless, the performances need to be further improved to meet requirements of future wireless systems and their applications. Kimionis et al. BIB001 propose a backsc... |
Ambient Backscatter Communications: A Contemporary Survey <s> 3) Energy Consumption Reduction: <s> We introduce inter-technology backscatter, a novel approach that transforms wireless transmissions from one technology to another, on the air. Specifically, we show for the first time that Bluetooth transmissions can be u... | The backscatter transmitters in BBCSs use energy harvested from the surrounding environment for their internal operations such as modulating and transmitting. However, the amount of the harvested energy is typically small. Therefore, several designs are proposed to use energy efficiently in BBCSs. Iyer et al. BIB001 de... |
Ambient Backscatter Communications: A Contemporary Survey <s> A. Overview of Ambient Backscatter Communications Systems 1) Definition and Architecture: <s> This paper presents the wireless identification and sensing platform (WISP), which is a programmable battery-free sensing and computational platform designed to exp... | The first ABCS is introduced in , and it has quickly become an effective communication solution which can be adopted in many wireless applications and systems. Unlike BBCSs, ABCSs allow backscatter transmitters to communicate by using signals from ambient RF sources, e.g., TV towers, cellular and FM base stations, and... |
Ambient Backscatter Communications: A Contemporary Survey <s> B. Performance Improvement for Ambient Backscatter Communications Systems <s> This paper provides analyses of three types of diversity combining systems in practical use. These are: selection diversity, maximal-ratio diversity, and equal-gain diversity syste... | 1) Communication Improvement: Although ABCSs possess many advantages as mentioned above, their communication ranges and bitrates are very limited. In particular, for the first ABCS introduced in , to achieve a target BER of 10 −2 , the backscatter receiver can receive at a rate of 1 kbps at distance up to 2.5 feet for... |
Ambient Backscatter Communications: A Contemporary Survey <s> C. Potential Applications <s> This paper argues for a clean-slate redesign of wireless sensor systems to take advantage of the extremely low power consumption of backscatter communication and emerging ultra-low power sensor modalities. We make the case that ... | The development of ambient backscatter techniques opens considerable opportunities for D2D communications. Thus, ABCSs can be adopted in many applications such as smart life, logistics, and medical biology , BIB003 , BIB004 , , BIB002 , . ABCSs allow devices, i.e., backscatter transmitters, to operate independently ... |
Ambient Backscatter Communications: A Contemporary Survey <s> A. Tag-to-Tag Communication RFID Systems <s> In this paper we propose and discuss an optimized link state routing protocol, named OLSR, for mobile wireless networks. The protocol is based on the link state algorithm and it is proactive (or table-driven) in n... | RFID systems are mainly used for tracking and identifying objects, e.g., in supply chain applications. However, RFID systems are only reliable at a range of few meters as the tags rely on RFID readers to backscatter their data. The studies have shown that even if a dense infrastructure of RFID readers is deployed, stil... |
Ambient Backscatter Communications: A Contemporary Survey <s> B. RF-Powered Cognitive Radio Networks and Backscatter Communications <s> Wireless networks can be self-sustaining by harvesting energy from ambient radio-frequency (RF) signals. Recently, researchers have made progress on designing efficient circuits and de... | Cognitive Radio Networks (CRNs) are first introduced in to utilize the spectrum more efficiently. Specifically, in CRNs, a radio can dynamically reconfigure its transmitter parameters, e.g., waveform, protocol, frequency, and transmit power, according to the conditions of its operating environment. In this way, CRNs e... |
Ambient Backscatter Communications: A Contemporary Survey <s> C. Wireless-Powered Communication Networks and Backscatter Communication <s> This paper studies the newly emerging wireless powered communication network in which one hybrid access point (H-AP) with constant power supply coordinates the wireless energy/infor... | WPCNs allow devices to use energy from dedicated or ambient RF sources to actively transmit data to their receivers. However, in WPCNs, a wireless-powered transmitter may require a long time to acquire enough energy for active transmissions, and thus the performance of the system is significantly sub-optimal. Therefore... |
Ambient Backscatter Communications: A Contemporary Survey <s> D. Backscatter Relay Networks <s> This paper introduces the first design that enables full-duplex communication on battery-free backscatter devices. Specifically, it gives receivers a way to provide low-rate feedback to the transmitter on the same frequency ... | Although many designs and solutions are introduced to improve the performance of backscatter networks, the singlehop communication range is still limited. One of the practical solutions recently proposed is to use relay nodes. Ma et al. BIB002 introduce an RFID system, named "RFly", that leverages drones as relays to e... |
Ambient Backscatter Communications: A Contemporary Survey <s> E. Visible Light Backscatter Communications <s> The ubiquity of the lighting infrastructure makes the visible light communication (VLC) well suited for mobile and Internet of Things (IoT) applications in the indoor environment. However, existing VLC systems ... | Visible light backscatter communications system (VLBCS) is proposed to enable efficient data transmissions in RF limited environments, e.g., in hospitals or on planes. In general, the principles of VLBCSs are similar to backscatter RF systems. Specifically, Li et al. BIB001 design a backscatter transmitter, namely ViTa... |
Ambient Backscatter Communications: A Contemporary Survey <s> D. Security and Jamming Issues <s> Backscatter wireless communication lies at the heart of many practical low-cost, low-power, distributed passive sensing systems. The inherent cost restrictions coupled with the modest computational and storage capabilities ... | Due to the simple coding and modulation schemes adopted, backscatter communications are vulnerable to security attacks such as eavesdropping and jamming. The passive nature of backscatter communications making it challenging to secure backscatter secrecy. On one hand, any attacker that uses active RF transmitters can b... |
Ambient Backscatter Communications: A Contemporary Survey <s> E. Millimeter-Wave-Based Ambient Backscatter <s> Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamform... | Utilizing high-frequency millimeter waves (mmWave) for high speed communication has been deemed as one of the enabling technologies for the fifth-generation cellular networks. Due to different physical characteristics from UHF waves, mmWave requires LOS communication channels and miniaturized high-gain antennas and ant... |
Ambient Backscatter Communications: A Contemporary Survey <s> F. Full-Duplex Based Ambient Backscatter <s> This paper introduces the first design that enables full-duplex communication on battery-free backscatter devices. Specifically, it gives receivers a way to provide low-rate feedback to the transmitter on the same... | As ambient backscatter devices can communicate with each other, the full-duplex technique can be adopted to improve the performance of ABCSs. For example, Liu et al. BIB001 introduce an ambient backscattering system in which the backscatter receiver can send feedback to the backscatter transmitter to inform any error a... |
Ambient Backscatter Communications: A Contemporary Survey <s> G. Wireless Body Area Networks and Ambient Backscatter Communications <s> A new tag for pervasive sensing applications consists of a custom integrated circuit, an antenna for radio frequency energy harvesting, and sensors for monitoring physiological paramet... | Having many prominent features, ambient backscatter can be adopted to facilitate many practical applications for wireless body area networks (WBANs). The recent work in BIB002 designs smart shoes supported by ambient backscatter to count steps or heart rate. Wang et al. BIB003 successfully implement smart fabric applic... |
Ambient Backscatter Communications: A Contemporary Survey <s> H. Backscatter Communications for Internet of Things <s> Powering the massive number of small computing devices in the Internet of Things (IoT) is a major challenge because replacing their batteries or powering them with wires is very expensive and impractic... | With many prominent features, backscatter communications pave the way for empowering IoTs. However, the system performance can be significantly limited due to interference and double fading effects in large network architectures in which the backscatter devices and RF sources are located randomly, e.g., as points of in... |
A Survey of Deep Facial Attribute Analysis <s> Introduction <s> Computer vision applications for mobile phones are gaining increasing attention due to several practical needs resulting from the popularity of digital cameras in today's mobile phones. In this work, we consider the task of face detection and authenticatio... | Facial attributes represent intuitive semantic features that describe human-understandable visual properties of face images, such as smiling, eyeglasses, and mustache. Therefore, as vital information of faces, facial attributes have contributed to numerous real-world applications, e.g., face verification (Kumar et al. ... |
A Survey of Deep Facial Attribute Analysis <s> Face Detection and Alignment <s> We have created the first image search engine based entirely on faces. Using simple text queries such as "smiling men with blond hair and mustaches," users can search through over 3.1 million faces which have been automatically labeled on t... | Before the databases with more facial attribute annotations were released, most of the attribute prediction methods BIB001 BIB003 took whole human images (faces and torsos) as inputs. Only several well-marked facial attributes could be estimated, i.e., smile, gender, and has glasses. However, torso regions contain cons... |
A Survey of Deep Facial Attribute Analysis <s> Feature Extraction <s> The goal of this paper is face recognition – from either a single photograph or from a set of faces tracked in a video. Recent progress in this area has been due to two factors: (i) end to end learning for the task using a convolutional neural networ... | Deep convolutional neural networks (CNNs) play significant roles in learning discriminative representations and have achieved attractive performance in deep FAE. In general, arbitrary classical CNN networks, such as VGG BIB001 and ResNet BIB002 , can be used to extract deep facial attribute features. For example, BIB00... |
A Survey of Deep Facial Attribute Analysis <s> Attribute Classification <s> Thesupport-vector network is a new learning machine for two-group classification problems. The machine conceptually implements the following idea: input vectors are non-linearly mapped to a very high-dimension feature space. In this feature spa... | Early methods learn feature representations with deep networks but make the prediction with traditional classifiers, such as support vector machines (SVMs) BIB001 BIB002 , decision trees BIB003 , and k-nearest neighbor (kNN) classifier BIB004 BIB008 . For example, Kumar et al. (2009) train multiple SVMs BIB001 with rad... |
A Survey of Deep Facial Attribute Analysis <s> Facial Attribute Analysis Datasets <s> We introduce the use of describable visual attributes for face verification and image search. Describable visual attributes are labels that can be given to an image to describe its appearance. This paper focuses on images of faces and... | We present an overview of publicly available facial attribute analysis datasets for both FAE and FAM, including data sources, sample sizes, and test protocols. More details of these datasets are listed in Table 1 . FaceTracer dataset is an extensive collection of realworld face images collected from the internet. There... |
A Survey of Deep Facial Attribute Analysis <s> • mean Average Precision (mAP) <s> Machine learning is commonly used to improve ranked retrieval systems. Due to computational difficulties, few learning techniques have been developed to directly optimize for mean average precision (MAP), despite its widespread use in eva... | As there is more than one label in multi-label image classification, the mean Average Precision (mAP) becomes a prevalent metric BIB001 BIB002 ), which computes the average of the precision-recall curve from the recall 0 to recall 1. Moreover, mAP is the mean of Average Precision (AP) for a set of categories, while AP ... |
A Survey of Deep Facial Attribute Analysis <s> • Qualitative Metrics <s> Recent studies have shown remarkable success in image-to-image translation for two domains. However, existing approaches have limited scalability and robustness in handling more than two domains, since different models should be built independentl... | Statistical survey is the most intuitive way to qualitatively evaluate the quality of generated images in most generative tasks. By establishing specific rules in advance, subjects vote for generated images with appealing visual fidelity, and then, researchers draw conclusions according to the statistical analysis of v... |
A Survey of Deep Facial Attribute Analysis <s> • Quantitative Metrics <s> Objective methods for assessing perceptual image quality traditionally attempted to quantify the visibility of errors (differences) between a distorted image and a reference image using a variety of known properties of the human visual system. Un... | Distribution difference measure calculates the differences between real images and generated face images. BIB009 achieve this goal by the Fréchet inception distance BIB008 ) (FID) with the means and covariance matrices of two distributions before and after editing facial attributes. BIB010 compute the peak signal to no... |
A Survey of Deep Facial Attribute Analysis <s> Separate Auxiliary Localization based Methods <s> We address the classic problems of detection, segmentation and pose estimation of people in images with a novel definition of a part, a poselet. We postulate two criteria (1) It should be easy to find a poselet given an inp... | Since facial attributes describe subtle details of face representations based on human vision, locating the positions of facial attributes enforces subsequent feature extractors and attribute classifiers to focus more on attribute-relevant regions. The most intuitive approach is to take existing face part detectors as ... |
A Survey of Deep Facial Attribute Analysis <s> End-to-End Localization Based Methods <s> Predicting face attributes in the wild is challenging due to complex face variations. We propose a novel deep learning framework for attribute prediction in the wild. It cascades two CNNs, LNet and ANet, which are fine-tuned jointl... | Compared with the separate auxiliary localization based methods that locate attribute regions and make the attribute prediction separately and independently, end-to-end localization based methods jointly exploit location cues where facial attributes appear and predict their presence in a unified framework. BIB001 first... |
A Survey of Deep Facial Attribute Analysis <s> Holistic Deep FAE Methods <s> Predicting facial attributes from faces in the wild is very challenging due to pose and lighting variations in the real world. The key to this problem is to build proper feature representations to cope with these unfavourable conditions. Given... | In contrast to part-based FAE approaches that detect and utilize facial components, holistic deep FAE methods focus more on exploring the attribute relationships and extracting features from entire face images rather than facial parts. A schematic diagram of holistic FAE models is provided in Fig. 8 . As shown in Fig. ... |
A Survey of Deep Facial Attribute Analysis <s> Model-Based Deep FAM Methods <s> This paper presents a Deep convolutional network model for Identity-Aware Transfer (DIAT) of facial attributes. Given the source input image and the reference attribute, DIAT aims to generate a facial image that owns the reference attribute... | Model-based methods map an image in the source domain to the target domain and then distinguish the generated target distribution with the real target distribution under the constraint of an adversarial loss. Therefore, model-based methods are greatly task-specific and have excellent performance in yielding photorealis... |
A Survey of Deep Facial Attribute Analysis <s> Extra Condition-Based Deep FAM Methods <s> Generative Adversarial Nets [8] were recently introduced as a novel way to train generative models. In this work we introduce the conditional version of generative adversarial nets, which can be constructed by simply feeding the d... | Deep FAM methods conditioned on extra attribute vectors alter desired attributes with given conditional attribute vectors, such as one-hot vectors indicating the presence of corresponding facial attributes. During the training process, the conditional vectors are concatenated with the to-bemanipulated images in latent ... |
A Survey of Deep Facial Attribute Analysis <s> Imbalance Learning in Facial Attribute Analysis <s> Data in vision domain often exhibit highly-skewed class distribution, i.e., most data belong to a few majority classes, while the minority classes only contain a scarce amount of instances. To mitigate this issue, contemp... | Face attribute data exhibits an imbalanced distribution in terms of different categories. It is normally called the classimbalance issue, which means in a dataset, some of the facial attribute classes have a much higher number of samples than others, corresponding to the majority class and minority class ), respective... |
A Survey of Deep Facial Attribute Analysis <s> Relative Attribute Ranking in Facial Attribute Analysis <s> We study the problem of object classification when training and test classes are disjoint, i.e. no training examples of the target classes are available. This setup has hardly been studied in computer vision resea... | Relative attribute learning aims to formulate functions to rank the relative strength of attributes , which can be widely applied in object detection BIB004 ), finegrained visual comparison , and facial attribute estimation BIB009 ). The general insight in this line of work is learning global image representations in ... |
A Survey of Deep Facial Attribute Analysis <s> Adversarial Robustness in Facial Attribute Analysis <s> Deep neural networks are highly expressive models that have recently achieved state of the art performance on speech and visual recognition tasks. While their expressiveness is the reason they succeed, it also causes ... | Adversarial images, which are generated from the network topology, training process, and hyperparameter variation by adding slight artificial perturbations, can be used as inputs of deep facial attribute analysis models. By classifying the original inputs correctly and misclassifying the adversarial inputs, the robustn... |
A Survey of Deep Facial Attribute Analysis <s> Data <s> The way people look in terms of facial attributes (ethnicity, hair color, facial hair, etc.) and the clothes or accessories they wear (sunglasses, hat, hoodies, etc.) is highly dependent on geo-location and weather condition, respectively. This work explores, for ... | The development of deep neural networks makes FAE a data-driven task. That means large numbers of samples are required for training deep models to capture attributerelevant facial details. However, contemporary studies suffer from insufficient training data. In this case, deep neural networks would easily fit the data ... |
A Survey of Deep Facial Attribute Analysis <s> Algorithms <s> Attribute recognition, particularly facial, extracts many labels for each image. While some multi-task vision problems can be decomposed into separate tasks and stages, e.g., training independent models for each task, for a growing set of problems joint opti... | As mentioned before, part-based deep FAE methods and holistic deep FAE methods develop in parallel. The former pays more attention to locating attributes, and the latter concentrates more on modeling attribute relationships. Below, we provide the main challenges from the perspective of algorithms and analyze the future... |
A Survey of Deep Facial Attribute Analysis <s> Applications <s> Computer vision applications for mobile phones are gaining increasing attention due to several practical needs resulting from the popularity of digital cameras in today's mobile phones. In this work, we consider the task of face detection and authenticatio... | Various viewpoints of the same person are difficult challenges for maintaining the identity-attribute consistency in deep FAE methods. On the one hand, such viewpoint diversification helps to learn richer features from the same person. On the other hand, images of different viewpoints might differ in attributes even fr... |
A Survey on Star Identification Algorithms <s> The Beginning <s> AbstractIn this paper, we discuss an attitude determination approach for autonomous,on-board, near-real-timedetermination of spacecraft attitude with sub-ten-arc-secondprecision. The method employs a systematic pattern recognition procedure foridentifying... | After the first CCD-based star tracker was developed by Salomon in 1976 at JPL , Junkins, Turner, Strikwerda BIB001 , and others began work on implementing an algorithm that could identify stars in real-time. While they realized the benefit of using the easily-computable sine of inter-star angles as a pattern feature... |
A Survey on Star Identification Algorithms <s> ). <s> Abstract : A new strapped-down system for on-board, real-time spacecraft attitude determination is discussed. The electro-optical system is capable of sub-ten-arc second precision with no moving parts. The light-sensitive element is an array-type Charged Coupled Dev... | In 1986, Groth suggested that a faster way to search the sub-catalogs would be to sort the triangles sides in order based on permutation-invariant values such as the logarithm of the perimeter of a triangle. BIB001 ). He admits, however, that his algorithm runs at high polynomial power of n, much as Junkins' has. Grot... |
A Survey on Star Identification Algorithms <s> Search Process Acceleration <s> A software system for a star imager for on-line satellite attitude determination is described. The system works with a single standard commercial CCD-camera with a high aperture lens and an onboard star catalogue. It is capable of both an in... | The next year, Liebe BIB001 made the critical connection of the feature selection process to the database search time, making the Lost-In-Space problem tractable. Liebe suggested the use of the two closest stars to a selected star as components of the star pattern, and the angular separations from the two closest stars... |
A Survey on Star Identification Algorithms <s> Search Time Reduced Much Further <s> A software system for a star imager for on-line satellite attitude determination is described. The system works with a single standard commercial CCD-camera with a high aperture lens and an onboard star catalogue. It is capable of both ... | Later in 1997, Mortari proposed an even faster database search technique, the "Search-Less Algorithm," (SLA). Mortari retained the approach of selecting any pair of stars in the field of view, O(b)-time, but he proposed using a "k-vector" to search the database in an amount of time independent of the size of the data... |
A Survey on Star Identification Algorithms <s> Non-dimensional Algorithms <s> An efficient star pattern recognition algorithm is presented. The purpose of this algorithm is to make sure of the compatibility of the software and the imaging sensor noise level. The new CMOS APS sensors have not currently reached the same ... | In 2003 Samaan, along with Junkins and Mortari BIB002 , presented a new Star-ID technique that was robust to calibration errors. For flight systems in which temperature variations would cause cyclic variations in the accuracy of the calibration, the new technique would promise to eliminate the ambiguity in matching sta... |
A Survey on Star Identification Algorithms <s> Recursive Star Identification <s> Star identification can be accomplished by several different available algorithms that identify the stars observed by a star tracker. However, efficiency and reliability remain key issues and the availability of new active pixel cameras re... | Samaan made other advances for recursive Star-ID in 2005 BIB001 . His key to reducing the recursive mode time was to speed the selection of stars that ought to be visible given some other visible stars. He presented two methods, one which used the Mortari's Spherical Polygon-Search (SP-Search) BIB002 BIB003 , which in ... |
A Survey on Star Identification Algorithms <s> Star Trackers for Different Applications <s> An approach to star identification based on comparing observed pattern statistics with the precomputed star cataloged statistics is suggested. The identification criterion is based on evaluating a posteriori probabilities of des... | Although Star-ID is predominantly used for attitude determination, it can be used for other spacecraft related tasks. Here are some examples: 1. Star Gyros. With appropriate algorithms, images from star cameras may also be used for estimating the angular velocity of the spacecraft BIB004 . 2. Space Surveillance. It can... |
A Survey on Security Metrics <s> Security metrics is <s> An organized record of actual flaws can be useful to computer system designers, programmers, analysts, administrators, and users. This survey provides a taxonomy for computer program security flaws, with an Appendix that documents 50 actual security flaws. These ... | . The security metrics problem certainly has received a lot of attention, including government and industry bodies [Chew et al. ; (IATAC) 2009; Institute ; for Internet Security 2010] . For example, the United States National Institute of Standards and Technology proposed three categories of security metrics-implementa... |
A Survey on Security Metrics <s> Scope <s> A metric is proposed for quantifying leakage of information about secrets and about how secrets change over time. The metric is used with a model of information flow for probabilistic, interactive systems with adaptive adversaries. The model and metric are implemented in a pro... | We have to limit the scope of the literature that is surveyed in the present paper. This is because every security paper that improves upon a previous result-be it a better defense or more powerful attack-would be considered relevant in terms of security metrics. However, most security publications did not address the ... |
A Survey on Security Metrics <s> Measuring system users' vulnerabilities <s> In this paper we present the results of a roleplay survey instrument administered to 1001 online survey respondents to study both the relationship between demographics and phishing susceptibility and the effectiveness of several anti-phishing ... | One metric is user's susceptibility to phishing attacks BIB001 . This online study of 1,001 users shows that phishing education can reduce the user's susceptibility to phishing attacks and that young people (18 to 25 years old) are more susceptible to phishing attacks. This metric is measured via the false-positive rat... |
A Survey on Security Metrics <s> Measuring password vulnerabilities <s> In this paper we attempt to determine the effectiveness of using entropy, as defined in NIST SP800-63, as a measurement of the security provided by various password creation policies. This is accomplished by modeling the success rate of current pas... | The parameterized password guessability metric measures the number of guesses an attacker with a particular cracking algorithm (i.e., a particular threat model) needs to make before recovering a password BIB001 BIB002 BIB003 BIB005 . This metric is easier to use than earlier metrics such as password entropy , which ca... |
A Survey on Security Metrics <s> Measuring software vulnerability temporal characteristics. Temporal characteristics of software vulnerabilities include their evolution and lifetime. <s> Targeted attacks on civil society and nongovernmental organizations have gone underreported despite the fact that these organizations... | Measuring evolution of software vulnerabilities. The historical vulnerability metric measures the degree that a system is vulnerable, or the number of vulnerabilities, in the past ]. The future vulnerability metric measures the number of vulnerabilities that will be discovered during a future period of time . Interesti... |
A Survey on Security Metrics <s> Measuring software vulnerability severity. <s> The automatic patch-based exploit generation problem is: given a program P and a patched version of the program P', automatically generate an exploit for the potentially unknown vulnerability present in P but fixed in P'. In this paper, we ... | This metric measures the degree of damage that can be caused by the exploitation of a vulnerability. A popular example is the CVSS score, which considers the following three factors [of Incident Response and (FIRST) ]. The base score reflects the vulnerability's timeand environment-invariant characteristics, such as it... |
A Survey on Security Metrics <s> Measuring cryptographic key vulnerabilities <s> RSA and DSA can fail catastrophically when used with malfunctioning random number generators, but the extent to which these problems arise in practice has never been comprehensively studied at Internet scale. We perform the largest ever ne... | Cryptographic keys are vulnerable when the underlying random number generators are weak, as witnessed by the pseudorandom-number-generation vulnerability in Debian Linux's OpenSSL [Yilek et al. ] . Here we highlight the weak cryptographic keys caused by using the fast /dev/urandom as a replacement of the slow /dev/rand... |
A Survey on Security Metrics <s> Measuring the individual detection power. <s> We present a method of analysis for evaluating intrusion detection systems. The method can be used to compare the performance of intrusion detectors, to evaluate performance goals for intrusion detectors, and to determine the best configurat... | For instrument-based attack detection, the detection time metric measures the delay between the time t 0 at which a compro-mised computer sends its first scan packet and the time t that a scan packet is observed by the instrument . This metric depends on several factors, including malware spreading model, the distribu... |
A Survey on Security Metrics <s> Measuring the collective detection power. <s> Attackers continually innovate and craft attacks that penetrate existing defenses. New security product purchasing decisions are key in order to keep organizations as secure as possible. Current information available to inform these decision... | This metric has been proposed for measuring the collective effectiveness of intrusion detection systems and anti-malware programs BIB001 BIB002 . Let A denote a set of attacks, D = {d 1 , . . . , d n } denote the set of n defense tools, X d denote the set of attacks that are detected by defense tool d ∈ D. The collec... |
A Survey on Security Metrics <s> Measuring the effectiveness of Address Space Layout Randomization (ASLR) <s> Address-space randomization is a technique used to fortify systems against buffer overflow attacks. The idea is to introduce artificial diversity by randomizing the memory location of certain system components.... | Code injection was a popular attack that aims to inject some malicious code into a running program and direct the processor to execute it. The attack requires the presence of a memory region that is both executable and writable, which was possible because operating systems used to not distinguish programs and data. The... |
A Survey on Security Metrics <s> Measuring the effectiveness of enforcing Control-Flow Integrity (CFI) <s> Alias analysis is a prerequisite for performing most of the common program analyses such as reaching-definitions analysis or live-variables analysis. Landi [1992] recently established that it is impossible to comp... | Despite the employment of defenses such as the aforementioned DEP and ASLR, control-flow hijacking remains to be a big threat BIB002 BIB003 . Enforcing CFI has a great potential in assuring security. The basic idea underlying CFI is to extract a program's Control-Flow Graph (CFG), typically from its source code via sta... |
A Survey on Security Metrics <s> Measuring the threat landscape <s> For many years, online criminals have been able to conduct their illicit activities by masquerading behind disreputable Internet Service Providers (ISPs). For example, organizations such as the Russian Business Network (RBN), Atrivo (a.k.a., Intercage)... | The threat landscape can be characterized via multiple attributes. One attribute is the attack vector. The number of exploit kits metric describes the number of automated attack tools that are available in the black market BIB002 . This metric can be extended to accommodate, for example, the vulnerabilities that the ex... |
A Survey on Security Metrics <s> Measuring the attack power of botnets. <s> The emergence of order in natural systems is a constant source of inspiration for both physical and biological sciences. While the spatial order characterizing for example the crystals has been the basis of many advances in contemporary physics... | The threat of botnets can be characterized by several metrics. The first metric is botnet size. It is natural to count the number x of bots belonging to a botnet. It is important to count the number of bots that can be instructed to launch attacks (e.g., distributed denial-of-service attacks) at a point in time t, deno... |
A Survey on Security Metrics <s> Measuring the power of attacks that exploit multiple vulnerabilities. <s> This paper presents a graph-based approach to network vulnerability analysis. The method is flexible, allowing analysis of attacks from both outside and inside the network. It can analyze risks to a specific netwo... | Vulnerabilities can be exploited in a chaining fashion. There is a large body of literature in this field, including attack graphs (see, e.g., BIB001 BIB003 BIB004 BIB005 BIB006 ), attack trees , and privilege trees BIB002 . At a high level, these models accommodate system vulnerabilities, vulnerability dependencies ... |
A Survey on Security Metrics <s> Measuring the power of evasion against learning-based detection. <s> Many classification tasks, such as spam filtering, intrusion detection, and terrorism detection, are complicated by an adversary who wishes to avoid detection. Previous work on adversarial classification has made the u... | Sophisticated attacks can evade the defense system by, for example, manipulating some features that are used in the detection models (e.g., classifiers). This problem is generally known as adversarial machine learning [Dalvi et al. 2004; BIB001 BIB002 Srndic and Laskov 2014] . There is a spectrum of evasion scenarios, ... |
A Survey on Security Metrics <s> Measuring obfuscation sophistication <s> The first steps in analyzing defensive malware are understanding what obfuscations are present in real-world malware binaries, how these obfuscations hinder analysis, and how they can be overcome. While some obfuscations have been reported indepe... | Obfuscation based on tools such as run-time packers have been widely used by malware-writers to defeat static analysis. Despite the numerous studies that have been surveyed elsewhere BIB001 BIB002 , we understand very little about how to quantify the obfuscation capability of malware. Nevertheless, there have been some... |
A Survey on Security Metrics <s> Measuring the evolution of security state <s> System architects need quantitative security metrics to make informed trade-off decisions involving system security. The security metrics need to provide insight on weak points in the system defense, considering characteristics of both the s... | As illustrated in Figures 1-2 , the security state vector of an enterprise system S(t) = (s 1 (t), . . . , s n (t)) and the security state s i (t) of computer c i (t) both dynamically evolve as a outcome of attack-defense interactions. These metrics aim to measure the dynamic security states. However, the measurement p... |
A Survey on Security Metrics <s> Measuring temporal characteristics of security incidents. <s> The paper is based on a conceptual framework in which security can be split into two generic types of characteristics, behavioral and preventive. Here, preventive security denotes the system's ability to protect itself from e... | The temporal characteristic of incidents can be described by the delay in incident detection [for Internet Security 2010] , which measures the time between when an incident occurred and when the incident is discovered. Another metric is the time between incidents [for Internet Security 2010; , which measures the perio... |
A Survey on Security Metrics <s> What should we measure? <s> This paper presents the results of an experiment in security evaluation. The system is modeled as a privilege graph that exhibits its security vulnerabilities. Quantitative measures that estimate the effort an attacker might expend to exploit these vulnerabil... | First, Table 7 shows that there are big gaps between the state-of-the-art metrics (i.e., second column) and the desirable metrics (i.e., third column). For example, we used the thickness of blue bars and red arrows in Figures 1 and 2 to reflect the defense power and attack power, respectively. However, the existing sec... |
A Survey on Security Metrics <s> What are the desirable properties of security metrics? <s> The Definitive Guide to Quantifying, Classifying, and Measuring Enterprise IT Security OperationsSecurity Metrics is the first comprehensive best-practice guide to defining, creating, and utilizing security metrics in the enterp... | There have been proposals for characterizing "good" metrics, such as the following. From a conceptual perspective, a good metric should be easy to understand not only to researchers, but also to defense operators BIB002 . From a measurement perspective, a good metric should be relatively easy to measure, consistently a... |
A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks <s> Table-Driven Routing Protocols <s> An ad-hoc network is the cooperative engagement of a collection of Mobile Hosts without the required intervention of any centralized Access Point. In this paper we present an innovative design for the operat... | Table-driven routing protocols attempt to maintain consistent, up-to-date routing information from each node to every other node in the network. These protocols require each node to maintain one or more tables to store routing information, and they respond to changes in network topology by propagating updates throughou... |
A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks <s> Source-Initiated On-Demand Routing <s> In this paper we describe the current state of the DARPA packet radio network. Fully automated algorithms and protocols to organize, control, maintain, and move traffic through the packet radio network h... | A different approach from table-driven routing is source-initiated on-demand routing. This type of routing creates routes only when desired by the source node. When a node requires a route to a destination, it initiates a route discovery process within the network. This process is completed once a route is found or all... |
A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks <s> Comparisons <s> We present a loop-free, distributed routing protocol for mobile packet radio networks. The protocol is intended for use in networks where the rate of topological change is not so fast as to make “flooding” the only possible ro... | The following sections provide comparisons of the previously described routing algorithms. The next section compares table-driven protocols, and another section compares ondemand protocols. A later section presents a discussion of the two classes of algorithms. In Tables 1 and 2 , time complexity is defined as the numb... |
A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks <s> Source-Initiated On-Demand Routing Protocols <s> We present a new distributed routing protocol for mobile, multihop, wireless networks. The protocol is one of a family of protocols which we term "link reversal" algorithms. The protocol's reac... | AODV employs a route discovery procedure similar to DSR; however, there are a couple of important distinctions. The most notable of these is that the overhead of DSR is potentially larger than that of AODV since each DSR packet must carry full routing information, whereas in AODV packets need only contain the destinati... |
A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks <s> Applications and Challenges <s> b this paper we present a case for using new power-aware metn.cs for determining routes in wireless ad hoc networks. We present five ~erent metriw based on battery power consumption at nodw. We show that using ... | Akin to packet radio networks, ad hoc wireless networks have an important role to play in military applications. Soldiers equipped with multimode mobile communicators can now communicate in an ad hoc manner without the need for fixed wireless base stations. In addition, small vehicular devices equipped with audio senso... |
Overview of Structural Reliability Analysis Methods — Part II: Sampling Methods <s> Importance Sampling <s> From the Publisher: ::: Provides the first simultaneous coverage of the statistical aspects of simulation and Monte Carlo methods, their commonalities and their differences for the solution of a wide spectrum of ... | The basic idea of importance sampling (IS) is to focus on the region(s) of "importance" so as to save computational resources BIB002 . The importance region(s) in reliability problem can be seen as the failure region. The concept underlying the importance sampling (IS) method is to replace the original PDF ( ) X f x wi... |
Overview of Structural Reliability Analysis Methods — Part II: Sampling Methods <s> Latin Hypercube Sampling (LHS) <s> From the Publisher: ::: Provides the first simultaneous coverage of the statistical aspects of simulation and Monte Carlo methods, their commonalities and their differences for the solution of a wide s... | Generally, in simulation methods, the random sampling method is adopted to generate samples. In order to improve the efficiency of basic MCS, another sampling method called Latin Hypercube Sampling (LHS) was developed . Latin hypercube sampling is a widely-used method to generate controlled random samples and its basi... |
Overview of Structural Reliability Analysis Methods — Part II: Sampling Methods <s> Directional Simulation <s> Probability computation methods for structural and mechanical reliability analysis are presented. Methods for random variable, random process and random field reliability models are included, with special emph... | Directional Simulation (DS) reduces the dimension of probability integral by identifying a set of directions for integration and estimating the probability as a weight average of the directional integrals BIB004 . It is based on the concept of conditional probability and it also exploits the symmetry of the standard no... |
Embodied Evolution in Collective Robotics: A Review <s> Introduction <s> The pitfalls of naive robot simulations have been recognised for areas such as evolutionary robotics. It has been suggested that carefully validated simulations with a proper treatment of noise may overcome these problems. This paper reports the r... | This paper provides an overview of evolutionary robotics research where evolution takes place in a population of robots in a continuous manner. coined the phrase embodied evolution for evolutionary processes that are distributed over the robots in the population to allow them to adapt autonomously and continuously. Em... |
Embodied Evolution in Collective Robotics: A Review <s> Off-line Design of Behaviours in Collective Robotics <s> The term swarm has been applied to many systems (in biology, engineering, computation, etc.) as they have some of the qualities that the English-language term swarm denotes. With the growth of the various ar... | Decentralised decision-making is a central theme in collective robotics research: when the robot collective cannot be centrally controlled, the individual robots' behaviour must be carefully designed so that global coordination occurs through local interactions. Seminal works from the 1990s such as Mataric's Nerd Herd ... |
Embodied Evolution in Collective Robotics: A Review <s> Lifelong Learning in Evolutionary Robotics <s> This paper is concerned with adaptation capabilities of evolved neural controllers. We propose to evolve mechanisms for parameter self-organization instead of evolving the parameters themselves. The method consists of... | It has long been argued that deploying robots in the real world may benefit from continuing to acquire new capabilities after initial deployment BIB003 , especially if the environment is not known beforehand. Therefore, the question we are concerned with in this paper is how to endow a collective robotics system with ... |
Embodied Evolution in Collective Robotics: A Review <s> Replacement <s> We introduce Embodied Evolution (EE) as a new methodology for evolutionary robotics (ER). EE uses a population of physical robots that autonomously reproduce with one another while situated in their task environment. This constitutes a fully distri... | The currently active genome is replaced by a new individual (the offspring), implying the removal of the current genome. This event can be triggered by a robot's internal conditions (e.g. running out of time or virtual energy, reaching a given performance level) or through interactions with other robots (e.g., receivin... |
Embodied Evolution in Collective Robotics: A Review <s> Local Selection <s> In this paper we present an evolutionary method that can deal with the specific problem requirements of adaptivity, scalability and robustness. These requirements are increasingly observed in the areas of pervasive and autonomic computing, and ... | In embodied evolution, the evolutionary process is generally implemented through local interactions between the robots, i.e., the mating operation introduced above. This implies the concept of a neighbourhood from which mates are selected. One common way to define neighbourhood is to consider robots within communicatio... |
Embodied Evolution in Collective Robotics: A Review <s> Objective Functions vs Selection Pressure <s> Embodied evolutionary robotics is a sub-field of evolutionary robotics that employs evolutionary algorithms on the robotic hardware itself, during the operational period, i.e., in an on-line fashion. This enables robot... | In traditional evolutionary algorithms, the optimisation process is guided by a (set of) objective function(s) . Evaluation of the candidate solutions, i.e., of the genomes in the population, allows for (typically numerical) comparison of their performance. Beyond its relevance for performance assessment, the evaluati... |
Embodied Evolution in Collective Robotics: A Review <s> Autonomous Performance Evaluation <s> We present a novel evolutionary approach to robotic control of a real robot based on genetic programming (GP). Our approach uses GP techniques that manipulate machine code to evolve control programs for robots. This variant of... | The decentralised nature of the evolutionary process implies that there is no omniscient presence who knows (let alone determines) the fitness values of all individuals. Consequently, when an objective function is defined, it is the robots themselves that must gauge their performance, and share it with other robots whe... |
Embodied Evolution in Collective Robotics: A Review <s> Research Agenda <s> In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ fem... | We identify a number of open issues that need to be addressed so that embodied evolution can develop into a relevant technique to enable on-line adaptivity of robot collectives. Some of these issues have been researched in other fields (e.g., credit assignment is a well-known and often considered topic in reinforcement... |
Embodied Evolution in Collective Robotics: A Review <s> Evolution of Social Complexity <s> This article lists fourteen open problems in artificial life, each of which is a grand challenge requiring a major advance on a fundamental issue for its solution. Each problem is briefly explained, and, where deemed helpful, som... | Nature abounds with examples of social complexity: from cooperation to division of labour, from signalling to social organisation BIB003 . As shown in Section 4, embodied evolution demonstrated so far only a limited set of social organisation: simple cooperative and division of labour behaviours. In order to address mo... |
Embodied Evolution in Collective Robotics: A Review <s> Evolutionary biology <s> Our concepts of biology, evolution, and complexity are constrained by having observed only a single instance of life, life on earth. A truly comparative biology is needed to extend these concepts. Because we cannot observe life on other pl... | In the last 100 years, evolutionary biology benefited from both experimental and theoretical advances. It is now possible, for instance, to study evolutionary mechanisms through methods such as gene sequencing BIB005 BIB007 . However, in vitro experimental evolution has its own limitations: with evolution in "real" sub... |
A Review of High Gain and High Efficiency Reflectarrays for 5G Communications <s> I. INTRODUCTION <s> The Letter derives and verifies the concept of antenna focusing by planar ‘microstrip reflectarray’ antenna. Experimental results from schematically distributed patch radiators with microstrip delay lines are consisten... | The high data rate precision in the order of Gbps is required for current communication systems to evolve into future 5th Generation (5G) technology. These high data rates will mainly be supported by fast switching mechanisms which are possible to achieve at short wavelengths of millimeter waves. Additionally, the enha... |
A Review of High Gain and High Efficiency Reflectarrays for 5G Communications <s> A. REFLECTARRAY STRUCTURES <s> A class of antennas that utilizes arrays of elementary antennas as reflecting surfaces has been investigated. An antenna of this type is here called a Reflectarray. It has been found that the Reflectarray co... | The nature and the type of the elements of a reflectarray antenna also defines its performance characteristics based on its classification. The response of the reflectarray antenna mainly depends on the type of material used to develop its resonant elements. Figure 2 classifies four different types of commonly used ref... |
A Review of High Gain and High Efficiency Reflectarrays for 5G Communications <s> B. ANTENNAS IN 5G COMMUNICATIONS <s> A technique for the measurement of scattering parameters ::: of an infinite reflectarray is presented which takes into account effects of mutual coupling. Infinite reflectarrays designed at 10 GHz with dif... | The main candidates for 5G communications are massive MIMO systems due to their possible integrity with small cells BIB003 , BIB002 , BIB004 , . However, their design complexity and less adaptability with shorter wavelengths restrict them to attain the level of array antennas. Some types of antennas have already been ... |
A Review of High Gain and High Efficiency Reflectarrays for 5G Communications <s> II. HIGH GAIN REFLECTARRAY DESIGN TECHNIQUES <s> This paper discusses the theoretical modeling and practical design of millimeter wave reflectarrays using microstrip patch elements of variable size. A full-wave treatment of plane wave ref... | Along with bandwidth, the gain of a reflectarray antenna is also an important factor when a higher data rate with large throughput for wider coverage area is required. The reflectarray is a directional antenna therefore, its gain in a particular direction is normally higher than an ideal isotropic radiator. Its gain de... |
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