22 research outputs found
Evaluation of CupCarbon Network Simulator for Wireless Sensor Networks
[EN] Wireless sensor networks (WSNs) are a technology in continuous evolution with great future and a huge quantity of applications. The implementation and deployment of a WSN imply important expenses, so it is interesting to simulate the operation of our design before deploying it. In addition, WSNs are limited by a set of parameters such as the low processing capacity, low storing capacity or limited energy. Energy consumption is the most limiting parameter since the network stability and availability depends on the survival of the nodes. To check the correct operation of a network, currently, there are several network simulators and day by day new proposals are launched. This paper presents the evaluation of a new network simulator called CupCarbon. Along the document, we present the main characteristics of this simulator and check its operation by an example. To evaluate the ease of use of this new network simulator, we propose a modified version of Dijkstra algorithm. In addition of considering the cost route to calculate the best route, it considers the remaining energy in nodes as an additional parameter to evaluate the best route. CupCarbon allows implementing our proposal and the results show that our proposal is able to offer a more stable network with an increase of the network lifetime of the 20%. Finally, to extract some conclusions from our experiences, we compare the characteristics and results of CupCarbon with the most common network simulators currently used by researchers. Our conclusions point out that CupCarbon can be used as a complementary tool for those simulators that are not able to monitor the energy consumption in nodes. However, it needs some improvements to reach the level of functionality of the most used simulators. CupCarbon could be an interesting option for academic environments.López-Pavón, C.; Sendra, S.; Valenzuela-Valdés, JF. (2018). Evaluation of CupCarbon Network Simulator for Wireless Sensor Networks. Network Protocols and Algorithms. 10(2):1-27. https://doi.org/10.5296/npa.v10i2.13201S12710
Empirical Validation of a Class of Ray-Based Fading Models
As new wireless standards are developed, the use of higher operation
frequencies comes in hand with new use cases and propagation effects that
differ from the well-established state of the art. Numerous stochastic fading
models have recently emerged under the umbrella of generalized fading
conditions, to provide a fine-grain characterization of propagation channels in
the mmWave and sub-THz bands. For the first time in literature, this work
carries out an experimental validation of a class of such ray-based models, in
a wide range of propagation conditions (anechoic, reverberation and indoor) at
mmWave bands. We show that the independently fluctuating two-ray (IFTR) model
has good capabilities to recreate rather dissimilar environments with high
accuracy. We also put forth that the key limitations of the IFTR model arise in
the presence of reduced diffuse propagation, and also due to a limited phase
variability for the dominant specular components.Comment: 9 pages, 13 figure
Joint Direction-of-Arrival and Time-of-Arrival Estimation with Ultra-wideband Elliptical Arrays
This paper presents a general technique for the joint Direction-of-Arrival
(DoA) and Time-of-Arrival (ToA) estimation in multipath environments. The
proposed ultra-wideband technique is based on phase-mode expansions and the use
of nearly frequency-invariant elliptical arrays. New possibilities open with
the present approach, as not only elliptical, but also circular and linear
(highly flattened) arrays can be considered with the same implementation.
Systematic selection/rejection of signals-of-interest/signals-not-of-interest
in smart wireless environments is possible, unlike with previous approaches
based on circular arrays. Concentric elliptical arrays of many sizes and
eccentricities can be jointly considered, with the subsequent improvement that
entails in DoA and ToA detection. This leads to the realization of
pseudo-random array patterns; namely, quasi-arbitrary geometries created from
the superposition of multiple elliptical arrays. Some simulation and
experimental tests (measurements in an anechoic chamber) are carried out for
several frequency bands to check the correct performance of the method. The
method is proven to give accurate estimations in all tested scenarios, and to
be robust against noise and position uncertainty in sensor placement.Comment: Published in IEEE Transactions on Wireless Communication
Time-periodic Metallic Metamaterials defined by Floquet Circuits
In this paper, we study the scattering and diffraction phenomena in
time-modulated metamaterials of metallic nature by means of Floquet equivalent
circuits. Concretely, we focus on a time-periodic screen that alternates
between "metal" and "air" states. We generalize our previous approaches by
introducing the concepts of "macroperiod" and "duty cycle" to the time
modulation. This allows to analyze time-periodic metallic metamaterials whose
modulation ratios are, in general, rational numbers. Furthermore, with the
introduction of the duty cycle, perfect temporal symmetry is broken within the
time modulation as the time screen could remain a different amount of time in
metal and air states. Previous statements lead to an enrichment of the
diffraction phenomenon and to new degrees of freedom that can be exploited in
engineering to control the reflection and transmission of electromagnetic
waves. Finally, we present some analytical results that are validated with a
self-implemented finite-difference time-domain (FDTD) approach. Results show
that the scattering level and diffraction angles can be controlled
independently by means of the duty cycle and the modulation ratio,
respectively. Thus, novel time-based pulsed sources and beamformers can be
efficiently designe
Joint Ultra-wideband Characterization of Azimuth, Elevation and Time of Arrival with Toric Arrays
In this paper, we present an analytical framework for the joint
characterization of the 3D direction of arrival (DoA), i.e., azimuth and
elevation components, and time of arrival (ToA) in multipath environments. The
analytical framework is based on the use of nearly frequency-invariant
beamformers (FIB) formed by toric arrays. The frequency response of the toric
array is expanded as a series of phase modes, which leads to azimuth-time and
elevation-time diagrams from which the 3D DoA and the ToA of the incoming waves
can be extracted over a wide bandwidth. Firstly, we discuss some practical
considerations, advantages and limitations of using the analytical method.
Subsequently, we perform a parametric study to analyze the influence of the
method parameters on the quality of the estimation. The method is tested in
single-path and multipath mm-wave environments over a large bandwidth. The
results show that the proposed method improves the quality of the estimation,
i.e., decreases the level of the artifacts, compared to other state-of-art FIB
approaches based on the use of single/concentric circular and elliptical
arrays.Comment: 10 pages, 8 figure
Analytical Equivalent Circuits for Three-dimensional Metamaterials and Metagratings
In recent times, three-dimensional (3D) metamaterials have undergone a
revolution driven mainly by the popularization of 3D-printing techniques, which
has enabled the implementation of modern microwave and photonic devices with
advanced functionalities. However, the analysis of 3D metamaterials is complex
and computationally costly in comparison to their 1D and 2D counterparts due to
the intricate geometries involved. In this paper, we present a fully-analytical
framework based on Floquet-Bloch modal expansions of the electromagnetic fields
and integral-equation methods for the analysis of 3D metamaterials and
metagratings. Concretely, we focus on 3D configurations formed by periodic
arrangements of rectangular waveguides with longitudinal slot insertions. The
analytical framework is computationally efficient compared to full-wave
solutions and also works under oblique incidence conditions. Furthermore, it
comes associated with an equivalent circuit that allows to gain physical
insight into the scattering and diffraction phenomena. The analytical
equivalent circuit is tested against full-wave simulations in commercial
software CST. Simulation results show that the proposed 3D structures provide
independent polarization control of the two orthogonal polarizations states.
This key property is of potential interest for the production of full-metal
polarizers, such as the one illustrated
Design rules for antenna placement on MIMO systems
In recent works, it is demonstrated that, depending on the different spatial distributions and distance between elements, there exists a different true polarization diversity (TPD) configuration that provides a high improvement in terms of capacity. This means that it is necessary to choose the appropriate TPD configuration to maximize the multiple-input-multiple-output (MIMO) capacity. In this work, a genetic algorithm is used to optimize the element positions for four new different configurations in combination with the TPD technique. It is shown that, for some configurations, the same polarization option is always found to reach the maximum capacity. Based on this, some novel design rules are provided to maximize MIMO capacity when the area for placing the antennas is very small. This is the case for most of the wireless devices, where the antenna design and location is one of the latest design constraints to be taken into consideration in the device design
Electronically controllable phase shifter with progressive impedance transformation at K band
This communication presents the design of a two-port electronically tunable phase shifter at K band. The phase shifter consists of a 3 dB hybrid coupler loaded with reflective phase-controllable circuits. The reflective circuits are formed by varactors and non-sequential impedance transformers which increase the operational bandwidth and the provided phase shift. The final phase shifter design is formed by two loaded-coupler stages of phase shifting to guarantee a complete phase turn. An 18 GHz phase shifter design with dynamic range of 600 degrees of phase shift is depicted in this document. The prototype is manufactured and validated through measurements showing good agreement with the simulation results
Circularly polarised broadband planar lightweight reflectarray with eligible pattern for satellite communications in Ku-Band
This study presents a lightweight planar patch-array reflectarray at Ku-band for satellite communications. The reflectarray is composed of two separate planar structures: the radiating interface formed by a planar multi-layered broadband patch array, and a phase shifting device formed by 3 dB/90° couplers. The radiating element is a multi-layered patch structure, designed to provide circular polarisation (CP). Each array cell phase is controlled by open-ended shifting lines of variable length connected to the 3 dB/90° couplers. The use of this kind of couplers maintains the same CP received/transmitted: the design imposes that if a right-hand CP (RHCP) [or left-hand CP (LHCP)] is received coming from the feeder, the same RHCP (or LHCP) configuration is re-radiated by the reflectarray. Additionally, the feeding horn can be moved in the x or y axes, so that the feeder angular position let re-define the radiation pattern and its pointing direction. Finally, measurements of a lightweight portable planar reflectarray prototype are provided and very good agreement is observed when compared with theoretical result
Broadband electronically tunable reflectionbased phase shifter for active-steering microwave reflectarray systems in Ku-band
This document provides the design of an electronically reconfigurable microwave phase shifter for reflectarray systems. The phase shifter is based on a hybrid coupler with reflective circuits in three ports. Each reflective circuit introduces a phase variation that can be modified due to the variable capacity value of a varactor inserted in it. The phase shifting process includes three different stages of phase shifting for the incoming signal in its way through the phase shifter: the signal is conducted through the device towards the reflective circuits in four different ways. The input port of the device is also the output one, providing the desired reflective phase shifting effect. This device is of great interest in reflectarray applications in order to provide more than 360° of controllable phase shifting at each array element. The document includes the complete design of the phase shifter along with its design parameters and circuital behaviour