Beamforming

The noise produced by complex systems such as automobiles, airplanes, machines, etc. contributes to overall noise of an environment. In the way to reduce these levels, the identification of the prominent sources is necessary. In many cases the beamforming technique is capable to carry out this task creating a visual map of the sound source. The goal of this work will be to give a basic understanding of beamforming techniques including software, hardware and to illustrate its wide applicability to common noise control and vibration problems. Resumo Os ruidos produzidos por sistemas complexos como automoveis, aeronaves, maquinas, etc. contribuem para o ruido global de um ambiente. De modo a reduzir estes niveis, a identificacao das fontes proeminentes se faz necessaria. Em muitos casos, a tecnica de beamforming e capaz de realizar esta tarefa criando um mapa visual da fonte sonora. Este trabalho objetiva fornecer o entendimento basico sobre a tecnica de beamforming, incluindo software...

The millimeter wave (mmWave) frequency band is seen as a key enabler of multi-gigabit wireless access in future cellular networks. In order to overcome the propagation challenges, mmWave systems use a large number of antenna elements both at the base station and at the user equipment, which lead to high directivity gains, fully-directional communications, and possible noise-limited operations. The fundamental differences between mmWave networks and traditional ones challenge the classical design constraints, objectives, and available degrees of freedom. This paper addresses the implications that highly directional communication has on the design of an efficient medium access control (MAC) layer. The paper discusses key MAC layer issues, such as synchronization, random access, handover, channelization, interference management, scheduling, and association. The paper provides an integrated view on MAC layer issues for cellular networks, identifies new challenges and tradeoffs, and provides novel insights and solution approaches.

Viscoelastic material is commonly used in the passive treatment of structural vibration of the vehicle structure, to introduce damping and reduce vibration level at resonance frequencies. In a passenger vehicle chassis it is usual to add around 10 kg of these viscoelasctic patches. The effectiveness of such damping treatment depends on design parameters such as application location, area, thickness, and choice of the type of damping material. This paper describes an experimental procedure implemented to evaluate the performance of two different layers of damping material, when they are applied to a passenger vehicle chassis (white body). Results are presented for the white body chassis: 1) without damping added, 2) with asphalt pad added and 3) with liquid applied sprayable damper. The results are discussed through a comparison with adequated mapping of the responses and by results from beamforming tests in a chassis prototype, in terms of its efficiency for the damping of vibrations.

Resumen – En el presente trabajo se expone el diseño de un arreglo lineal de parlantes con control de directividad utilizando procesamiento digital. Se desarrollaron los conceptos teóricos pertinentes al problema y se diseñó y planteó un modelo para futuras pruebas del sistema, a fin de comprobar conceptos teóricos y llevarlos a la práctica. Por otro lado, se implementó una modalidad distinta de reducción de lóbulos secundarios basada en un algoritmo de optimización, proponiendo una opción que difiere de métodos previos empleando " shading " derivado de ventanas o polinomios de Legendre.

Nel presente lavoro sono analizzati alcuni risultati sperimentali di una misura del coefficiente di assorbimento acustico, a inci-denza quasi normale, effettuata sulla superficie assorbente di una barriera antirumore utilizzando un’antenna Beamforming a basso costo. Viene descritta la metodologia di misura e il risultato è confrontato con dati di riferimento misurati con un adattamento del metodo EN 1793-5 (evoluzione del metodo “Adrienne”), dai quali è stato calcolato il coefficiente di assorbimento acustico.

Beam forming is the process of combining the weighted signals received on an array of sensors to improve the directionality. Adaptive beamforming is the ability of the beamformer to receive the signal only from the desired direction and to reject all other signals from undesired directions. The weight vector for the adaptive beamformer continuously changes based on some adaptive algorithm. Therefore, adaptive digital beam formers can point the antenna to the signal direction without changing the physical architecture of the array antenna. The beam pointing direction can be varied electronically with this technique. This paper focuses on Least Mean Square (LMS) adaptive algorithm. Index Terms— Beamformer, Digital Beamformer (DBF) Receiver, Direction of Arrival (DoA), Least Mean Square (LMS) algorithm

Physical layer protection, which protects data confidentiality using information-theoretic methods, has recently attracted a lot of research attention. Using the inherent randomness of the transmission channel to ensure protection in the physical layer is the core concept behind physical layer security. In 5G wireless communication, new challenges have arisen in terms of physical layer security. This paper introduces the most recent survey on various 5G technologies, including millimeter-Wave, massive multi-input multiple outputs, microcells, beamforming, full-duplex technology, etc. The mentioned technologies have been used to solve this technology, such as attenuation, millimeter-Wave penetration, antenna array architecture, security, coverage, scalability, etc. Besides, the author has used descriptions of the techniques/algorithms, goals, problems, and meaningful outcomes, and the results obtained related to this approach were demonstrated.

This paper deals with the study of various types of Beamforming algorithms. A beam former is a processor used in conjunction with an array of sensors to provide a versatile form of spatial filtering. The sensor array collects spatial samples of propagating wave fields, which are processed by the beam former. The objective is to estimate the signal arriving from a desired direction in the presence of noise and interfering signals. A beam former performs spatial filtering to separate signals that have over lapping frequency content but originate from different spatial locations.

This paper describes recent work on the topic of multi-dimensional (MD) spatio-temporal noise and distortion shaping for radio-frequency (RF) antenna arrays with applications in wireless communications, phased-array radar sensing, microwave/mm-wave imaging, and radio astronomy instrumentation. The MD spectral properties of propagating plane-waves that arise from electromagnetics are combined with MD circuits and signal processing theory based on passive resistive terminated 2-D filters. The result, for the first time in the literature, is MD multi-port extensions of the analog and digital electronics found within wireless transceivers, including RF amplifiers, mixers, and data converters. In particular, a multi-port extension of conventional analog-to-digital converters (ADCs) is proposed in which the distortion that is generated from non-linear operations (such as quantization) is spectrally shaped in multiple spatio-temporal dimensions such that the region of support (ROS) of the desired RF signals corresponding to desired planar waves is ideally mutually exclusive with that of these undesired components. Because of spectral shaping, both distortion and noise are non-overlapping with the signal of interest and can be filtered out after sampling by using an MD digital filter. This theoretical advance in MD noise and distortion shaping across both space and time domains ensures that both electronic noise and non-linear distortion arising from coarse low-complexity quantization do not appreciably reduce the signal to noise and distortion ratio (SNDR) of antenna array receivers. The proposed method is an extension of ∆ − Σ modulation that is commonly used in conventional single-input single-output ADCs but does not require either temporal or spatial over-sampling. Moreover, to the best of our knowledge this paper is the first to combine 2-D analog filters derived from resistively-terminated classical passive low-pass filter prototypes with active analog feedback control in multiple dimensions (space, time) to realize 2-D analog-digital mixed-signal electronics for RF array processing applications.

Hybrid cars have become more important due to increasing fuel costs and the goal of reducing CO2 emissions. In this talk, the noise producing mechanisms of a Honda Civic Hybrid will be studied using a phased array and a range of beamforming techniques. The importance of multiple propagation paths, incoherent and coherent source distributions, tone and broadband noise, and array focus distance will be illustrated. Frequencies to be considered run from 100 Hz to 30 kHz. Methods to be discussed and compared include classical beamforming in 2D and 3D, beamforming with enhanced resolution, CLEAN-SC, and DAMAS2. Emphasis will be given to exterior sounds, with some treatment of the interior case. The goal of the presentation will be to give a basic understanding of beamforming techniques including software and hardware and to illustrate their wide applicability to common noise control problems and the implications of the choice of method for different types of noise sources.

The  next  generation  of  wireless  local  area  networks (WLANs),  currently  standardized  within  IEEE  S02.11ac,  will
surely  adopt  multiuser  multiple-input  multiple-output  (MU­
MIMO)  technology.  This  paper  addresses  the  design  of  a  mul­
tiuser  proportional  fair  scheduling  scheme,  based  on  MU-MIMO orthogonal  frequency  division  multiplexing  (OFDM),  that  is  able to  schedule  simultaneous  transmissions  to  various  users  while providing  a  high  degree  of  fairness.  The  proposed  scheme  is complemented  by  a  fast  link  adaptation  (FLA)  strategy  that,  in light  of  the available channel  state information  (CSI), determines the  most  appropriate  transmission  parameters  for  each  selected user.  Simulation  results  generated  using  specifi cations  envisaged for  IEEE  S02.11ac demonstrate the gains off ered by  the proposed
technique  with  practical  modulation  and  coding  schemes.

Listening tests are essential for optimising and evaluating novel signal processing concepts
for hearing devices. When they are performed inside the laboratory they are
highly controlled, but typically lack ecological validity. On the other hand, field-studies
provide high ecological validity, but are difficult to control, time-consuming and costly.
Even though field-studies may ultimately be required, there still is a necessity for more
realistic laboratory-based listening tests.
This thesis focuses on creating and validating realistic virtual sound environments (VSEs),
primarily based on the method of higher-order Ambisonics (HOA), for testing hearing
aids (HAs). Particular emphasis has been given on how the VSE limitations affect the
output of multi-microphone directional HAs. To systematically and objectively analyse
the errors incurred by such VSEs, we developed and verified a framework that consists
of: (1) the simulation of a reverberant acoustic scene; (2) the coding of that scene using
HOA; (3) the reconstruction of the VSE via a loudspeaker array; and (4) the evaluation
of the SNR benefit and output pressure of directional HAs worn on an acoustic
manikin placed inside the VSE. A listening experiment was additionally designed to
test the simulation results. For that purpose, a real-room ‘cocktail-party’ acoustic scene
was created and acoustically modelled. Ambisonics was then applied to reproduce that
scene inside a loudspeaker array. Listening tests involving hearing-impaired subjects,
fitted with directional HAs, were next conducted inside the real and the virtual sound
environments. The intelligibility and acceptable-noise-level benefits of the directional
HAs were thereby estimated.
The above evaluation illustrated that most of the real-environment properties can be
faithfully reconstructed by the considered VSEs. Moreover, directional HA algorithms
were shown to behave and adapt in a similar way as in real environments. However,
sound-field reconstruction deviations were noticeable. For the case of highly directional
schemes, such as the considered bilateral beamformer, such deviations may result in a
reduced benefit estimation. Hence, we can conclude that although the described VSEs
illustrated a reduced sensitivity in demonstrating real-life benefits, they are nonetheless
suitable for evaluating directional HA processing schemes.

In this study, we propose an implementation of the cross-pattern coherence (CroPaC) spatial- filtering technique. This parametric algorithm utilizes the normalized cross-spectral density be- tween signals from microphones of different orders as a criterion for focusing in specific direc- tions and is implemented by using directional microphones placed in the same look direction and have the same magnitude and phase response. A spatial-filter is calculated from a multichan- nel input and is used to assign attenuation values to a coincidentally captured audio signal. The proposed algorithm is simple to implement and offers the capability of coping with interfering sources at different azimuthal locations with or without the presence of diffuse sound. In con- trary to previous techniques, which rely on the performance of the beamformer for source focusing, CroPaC provides additional beamforming capabilities with increased performance at low frequen- cies. Significant improvement is demonstrated over traditional beamforming techniques in terms of noise reduction and focusing capabilities. Sound examples of the algorithm can be fond online in http://www.acoustics.hut.fi/projects/cropac/soundExamples/

Classical Beamforming is a signal processing technique capable of creating acoustic images. The algorithm utilized is the simple delay-and-sum over the sampled sound waves in the time domain. One important tool in the application of the technique is the array (or antenna), which is composed of a set of microphones, organized in a specific geometry. Depending on its construction, the resulting acoustic images will have different patterns. For this reason, a research has to be performed on the array's specifications to and for the best performance depending on the application. The way to test the performance is to evaluate the PSFs (Point Spread Functions) of the geometries, which is dependent on the width of the analysis' bandwidth. Hence, this work will compare and discuss some aspects of bandwidth on PSFs simulations regarding four different array geometries.

► A kind of Elastic Composite, Reinforced Lightweight Concrete (ECRL.C) with the mentioned specifics is a type of "Resilient Composite Systems (RCS)" in which, contrary to the basic geometrical assumption of the flexure theory in Solid Mechanics, "the strain changes in the beam height during bending" is typically "Nonlinear". (The RCS could be counted as "The Methodically Reinforced Nonlinear Porous Materials", also having the high specific modulus of resilience in flexure.)

♦ Through employing this integrated structure, with significantly high strain capability and modulus of resilience in bending, we can achieve the high bearing capacities in beams with the secure fracture pattern, in less weight.

♦ Due to the system particulars and its behavior in bending, the usual calculation of the necessary equilibrium steel amount to attain the low-steel bending sections with the secure fracture pattern in the beams and its related limitations do not become propounded. Thereby, the strategic deadlock of the high possibility of the brittle fracture pattern in the bending elements made of the usual reinforced lightweight concretes, especially about the low-thickness bending elements as slabs, is unlocked.

♦ This simple, applied technology and the related components and systems can have several applications in the road and building industries. (It can also be used in making the resilient pieces and constructions "with appropriate behavior and high resistance against severe blasts and shocks.)

♦ Regarding the "strategic importance of Lightweight and Integrated Construction in the practical increase of the resistance and safety against earthquake" and considering the appropriate behavior of this "resilient", durable structure against the dynamic loads, shakes, impacts, blasts, and shocks and the possibility of making some lightweight and insulating, non-brittle, reinforced sandwich panels and pieces, this resilient system and its components can especially be useful in the "seismic areas".

♦ This system can also be employed in constructing the vibration and impact absorber bearing pieces & slabs, which can be used in the "Railroad & Subway Structures" too.

♦ Here, the "Resilient Composite Systems (RCS)" and particularly, the ECRLC as a type of the RCS have been concisely presented. [By the way, an instance of the said new structure and its components and the results of some performed experiments (as bending loading and compressive loading of the slabs made of this structure, similar to ASTM E 72 Standard) have been shown in the related pictures & figures.]
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/ ● Key Words: Strength of materials (solid mechanics), Civil (construction), Materials, Earthquake (resistance and safety), Resilient concrete (flexible concrete, bendable concrete, elastic concrete), Composite concrete, Lightweight concrete, Reinforced concrete, Fibered concrete, Lightweight and integrated construction, Rail (railroad, railway), Subway, Road, Bridge, Resilience, Energy absorption, Fracture pattern, Non-linear, Strain changes, Beam, Ductility, Toughness, Insulating (insulation), Thin, Slab, Roof, Ceiling, Wall (partition), Building, Tower, Plan of mixture, Insulating reinforced lightweight pieces, 3d, Sandwich panel, Dry mix, Plaster, Foam, Expanded polystyrene (EPS), Polypropylene, Pozzolan, Porous matrix (Pored matrix), Mesh (lattice), Cement, RCS, ECRLC
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/ ► Contents:
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* ABSTRACT
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* I. INTRODUCTION
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* II. WHAT ARE THE RESILIENT COMPOSITE SYSTEMS
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- A. General Review
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- B. Components
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. - 1) Mesh or Lattice
. - 2) Fibers or Strands
. - 3) "Matrix" With the Suitable Hollow "Pores (Voids)" and/or "Lightweight Aggregates" in its Context
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- C. More Explanations About the RCS
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- D. Why Are These Systems Called "Composite"?
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- E. The General Structural Particulars and Functional Criteria as the Necessary Specifications of the Compound Materials Generally Called "Resilient Composite Systems"
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. - 1) General Structural Criteria
. - 2) Functional Criteria (Required Specifications)
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* III. "ELASTIC COMPOSITE REINFORCED LIGHTWEIGHT CONCRETE (ECRLC)" AS A TYPE OF THE RESILIENT COMPOSITE SYSTEMS (RCS)
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- An Instance of the Lightweight Concrete That Could be Used in Making the ECRLC
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* IV. REVIEW OF SOME EXPERIMENTS, AND MORE DESCRIPTION ABOUT ECRLC
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* V. SUPPLEMENTARY ELEMENTS
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* VI. APPLICATIONS
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* VII. FINAL REVIEW
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* ACKNOWLEDGEMENTS
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* REFERENCES 
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***
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/ ● General Review:
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• A kind of "Elastic Composite, Reinforced Lightweight Concrete" with the said specifics is a type of the "Resilient Composite Systems (R.C.S.)" in which, contrary to the basic geometrical assumption of flexure theory in the Solid Mechanics, the strain changes in the beam height during bending is typically "Non-linear".
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• Indeed, the RCS, as the Elastic Composite, Reinforced Lightweight Concrete (ECRLC), do not behave as most of the solid materials in bending.
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• In the "Resilient Composite Systems", distributed pores and/or appropriate lightweight aggregates or beads, accompanied by the reticular structure of the strengthened conjoined matrix, bring about the expedient internal shape changes during bending and continuing the elasticity in bending with the said nonlinearly pattern. This means better distribution of the stresses and strains and better utilizing the potential capacities of the employed reinforcements in bending and tension; whereas, in the usual lightweight concretes for instance, distributed hollow pores (such as the gas bulbs in the cellular concretes) or lightweight aggregates (such as Plastic, Rubber or polystyrene beads or any other kind of lightweight aggregates such as Perlite and Vermiculite) decrease the modulus of resilience in bending and could increase "the possibility of beam fracture of brittle and primary compressive type" in bending (compared to the concrete with higher density) according to the case.
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• In this way, by using the mentioned method to make the said particular composite systems, we could considerably increase the modulus of resilience and bearing capacity in bending "together with" significant decrease of the weight and also the possibility of beam fracture of primary compressive type. Through making these particular integrated functioning systems, for the first time, the said (paradoxical) properties have been concomitantly fulfilled in "one functioning unit" altogether.
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• Respect to the special pattern of the strain changes during bending in the particular Resilient Composite System termed ECRLC, this system as an integrated functioning unit with the reticular arrangement and texture has more strain capability (particularly within the elastic limit), energy absorption and load bearing capacities in bending compared to the usual reinforced concrete beams.
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• Thereby, through employing this applied structure, solving some of the main problems in lightweight concretes application, especially the deadlock of brittle and insecure being of fracture pattern in many of the usual reinforced lightweight concrete structures, is provided; reaching to the high bearing capacities in bending elements (even with low dimensions & weights) is to hand, and getting access to a simple and practical opportunity for "qualitative development of possibilities of using lightweight concretes" (especially with oven-dry densities of < 1350-1400kg/m3 and compressive strengths of <14-17mpa, and even with oven-dry densities of < 800kg/m3) is conceivable.
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• Naturally, by more studies in the field, these structures and their applications in various fields could be developed more.
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/ ► FULL TEXT (Open Access):
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- http://arxiv.org/abs/1510.03933 
( https://arxiv.org/ftp/arxiv/papers/1510/1510.03933.pdf ) ;
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. Kamyar Esmaeili: "Elastic Composite Reinforced Lightweight Concrete as a Type of Resilient Composite Systems";
The Internet Journal of Innovative Technology and Creative Engineering (IJITCE); 2012; 2(8): 1-22.
- http://ia800305.us.archive.org/34/items/IJITCE/vol2no801.pdf [Also archived at: http://www.webcitation.org/6B2pFPpBh ] ;
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- https://www.scribd.com/doc/11530978/Elastic-Composite-Reinforced-Lightweight-Concrete-ECRLC-as-a-type-of-Resilient-Composite-Systems-RCS-http-arxiv-org-abs-1510-03933 ; 
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- https://sites.google.com/site/NEWSTRUCTURE1 ;
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- https://sites.google.com/site/newstructure1/publications-page/ELASTIC%20COMPOSITE%2C%20REINFORCED%20LIGHTWEIGHT%20CONCRETE%20AS%20A%20TYPE%20OF%20RESILIENT%20COMPOSITE%20SYSTEMS.pdf ;
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- http://www.pdf-archive.com/2015/09/22/elasticcomposite-reinforcedlightweightconcreteasatypeofrcs/elasticcomposite-reinforcedlightweightconcreteasatypeofrcs.pdf ;
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- The link to the document in PDF format on this site:
file:///C:/Users/pc5/Downloads/ELASTIC_COMPOSITE_REINFORCED_LIGHTWEIGHT.pdf ;
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- ...

This paper concerns the eavesdropping attacks in wireless
ad hoc networks under a shadow fading environment. Most of previous
studies have only concentrated on protecting the confidential communications
at both the transmitters and the receivers and little attention
has been paid on investigating the eavesdropping behaviors done by the
malicious nodes. We therefore investigate the eavesdropping success rate
of eavesdroppers equipped with various antenna models under various
channels conditions, such as the path loss effect and the shadow fading
effect. In particular, we formulate the eavesdropping attack problem with
consideration of both simplistic directional antenna models and realistic
antenna models. We then conduct extensive simulations to evaluate the
eavesdropping success rate with different eavesdroppers. Our simulation
results show that the eavesdropping success rate heavily depends on both
the antenna models and the channel conditions.

Compared with omni-directional antennas, directional antennas have many merits, such as lower
interference, better spatial reuse, longer transmission range and the improved network capacity. Directional
antennas enable numerous emerging outdoor and indoor applications, which have been addressed in many
recent studies. Despite the advances in wireless networks with directional antennas (DAWNs), there are
many research challenges in all layers of DAWNs. This paper presents a detailed study on recent advances
and open research issues on DAWNs. Firstly, we briefly introduce the classification of directional antennas,
antenna radiation patterns, antenna modes as well as the challenges in the physical layer of DAWNs. Then,
we present research issues on the MAC layer, followed by the current solutions as well as open research
problems. We also discuss the research issues on the routing layer, the transport layer and the performance
evaluation of DAWNs. A brief introduction of indoor DAWNs is given in this paper as well.

This paper presents an experimental investigation of the flow-induced noise created by a wall-mounted finite airfoil at low-to-moderate Reynolds number and zero angle of attack. Far-field noise measurements have been taken at a single observer location and with two perpendicular microphone arrays in an anechoic wind tunnel at Reynolds numbers of Rec=9.2×104–1.6×105, based on chord, and for a variety of airfoil aspect ratios (length to chord ratio of L/C=0.2–2, corresponding to length to thickness ratio of L/T=1.7–16.7). Additionally, surface oil-film visualisation images and unsteady velocity measurements taken in the near trailing edge wake are related to far-field noise measurements to determine the flow mechanisms responsible for noise generation. The results show that the wall-mounted finite airfoil radiates noise similar to a two-dimensional airfoil when L/T>8.3. Despite the incoming boundary layer height at the junction being 1.30≤δ/T≤1.46, junction and tip flow suppresses tonal noise production for airfoil׳s up to L/T=8.3 at Rec=9.2×104–1.2×105. Trailing edge noise is found to be the dominant airfoil noise generation mechanism at frequencies above 1 kHz with the position of the noise source along the trailing edge determined by the proportion of the airfoil span influenced by flow at the airfoil–wall junction.

This paper describes preliminary research results on enhancement of loudspeaker impulse response measurement in small room. Proposed enhancement is a combination of MLS (Maximum Length Sequence) algorithm and Delay-Sum Beamforming in order to measure frequency response of loudspeakers even in very small and poorly suppressed rooms. Application of the beamforming algorithm allows the extension measure of impulse response by damping reflections from walls, floor and ceiling.