97 research outputs found
Phase Shifter for Millimeter-Wave Frequency Range Based on Glide Symmetric Structures
The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we propose a mm-wave phase shifter whose elements have a glide-symmetric configuration to achieve a greater phase shift in the same waveguide space than the non-glide-symmetric case. The glide-symmetric phase shifter is implemented in waveguide technology and is formed by rows of metallic pins that produce the desired phase shift. To assess the better performance of the glide-symmetric phase shifter, it is compared to its non-glide-symmetric version whose metallic pins are located only in one of the broad sides of the waveguide. The operating frequency range of the phase shifter is 67 to 75 GHz. Results show a 180 degree phase shift in regard to the reference waveguide without pins, and 50 degrees more than the non-glide-symmetric version.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Addressing the 5G cell switch-off problem with a multi-objective cellular genetic algorithm
© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The power consumption foreseen for 5G networks is expected to be substantially greater than that of 4G systems, mainly because of the ultra-dense deployments required to meet the upcoming traffic demands. This paper deals with a multi- objective formulation of the Cell Switch-Off (CSO) problem, a well-known and effective approach to save energy in such dense scenarios, which is addressed with an accurate, yet rather unknown multi-objective metaheuristic called MOCell (multi- objective cellular genetic algorithm). It has been evaluated over a different set of networks of increasing densification levels. The results have shown that MOCell is able to reach major energy savings when compared to a widely used multi-objective algorithm.TIN2016-75097-P
Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
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
Optimization of massive connections in 5G networks for IoT
The expected traffic demands for the coming years requires a major technology development. Indeed, from 2017 to 2022, the global annual traffic growth is estimated to reach 220%. This annual growth leads in turn to an increase in the number of users connected to IP networks, going from 2.4 to 3.6 devices connected per person. Currently, 4G networks are capable of handling this load, but the irruption of the 5G breakthroughs, expected to be at full operation by 2020, is visible. However, 5G technologies may come along with a considerable power consumption if they are not devised properly. As a consequence, a key issue in the developing of these networks is to make them energetically sustainable. In this work, a preliminary study of the optimization of various aspects of the 5G system is presented. It addresses the configuration of the different basic parameters of the system and optimizes the power transmitted by the base stations to obtain simultaneous improvements in system capacity and its power consumption for a massive connections scenario. To the best of our knowledge, this is the very first time this type of 5G scenario is optimized with these two performance criteria.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Sample selection method for arbitrary fading emulation using mode-stirred chambers
Mode-stirred chambers (MSC) consist on one or more resonant cavities coupled in some way in order to allow the measurement of different antenna parameters such as antenna efficiency, correlation, diversity gain or MIMO capacity, among others. In a single-cavity mode-stirred chamber, also known as a reverberation chamber (RC), the environment is isotropic and the amplitude of the signal is Rayleigh distributed. Real environments, however, rarely follow an isotropic Rayleigh-fading scenario. Previous results have shown that a Rician-fading emulation can be obtained via hardware modification using an RC. The different methods lack from an accurate emulation performance and are strongly dependent upon chamber size and antenna configurations. With the innate complexity of more-than-one cavity MSC, the coupling structure generates sample sets which are complex enough so as to contain different clusters with diverse fading characteristics. This paper presents a novel method to accurately emulate a more realistic Rician-fading distribution from a Rayleigh-fading distribution by selecting parts of the sample set that forms different statistical ensembles using a complex two-cavity multi-iris-coupled MSC. Sample selection is performed using a genetic algorithm. Results demonstrate the potential of MSCs for versatile MIMO fading emulation and OTA testing. The method is patent protected by EMITE Ing.This work was supported in
part by the Spanish National R&D Programme through TEC2008-05811
and by Fundación Séneca, the R&D coordinating agency for the Region of
Murcia (Spain) under the 11783/PI/09 project
Emulation of MIMO nonisotropic fading environments with reverberation chambers
Some recent publications have extended the emulating
capabilities of reverberation chambers. While polarization
imbalance has been removed and Ricean-fading environments
are now properly emulated, these chambers are still limited to
isotropic nonline of sight (NLOS) scattering. By controlling the
power received, number of resolvable multipath components
(MPC), angular spread (AS), and angle of arrival (AoA), the emulation
of real-propagating environments with both isotropic and
nonisotropic scattering are demonstrated in this letter using a reverberation
chamber with several multiple-input–multiple-output
(MIMO) arrays.This work was supported in part by the Fundación Séneca,
the R&D unit of the Autonomous Region of Murcia (Spain) under project references
TIC-TEC 07/02-0005 and by the Spanish National R&D Programme
through TEC2007/63470/TCM
Effect of user presence on receive diversity and MIMO capacity for rayleigh-fading channels
The effects of the presence of the user on multipleinput–
multiple-output (MIMO) performance for wireless communications
systems is investigated through measurements in a reverberation
chamber. Measured results have demonstrated that despite
a decrement on the envelope correlation coefficient, a degradation
of both diversity gain and MIMO capacity are expected
when the user is present. While the validity of the correlation coefficients
for predicting MIMO performance is limited in the presence
of the user, the effects have also been found to be strongly dependent
upon frequency, antenna topology, and user characteristics.This work
was supported in part by the Fundación Séneca, the R&D coordinating unit
of the Autonomous Region of Murcia (Spain) under Projects 2I05SU0033 and
TIC-TEC 06/01-0003
Accurate Estimation of Correlation and Capacity for Hybrid Spatial-Angular MIMO Systems
In this paper, several novel functions for accurately
estimating the correlation and the multiple-input–multiple-output
(MIMO) capacity of combined spatial and true polarization diversity
(TPD) schemes are proposed for the first time. Minimum
error estimation of the correlation for a hybrid spatial–TPD linear
scheme previously reported cannot be obtained by simple nonlinear
least-square estimators, and the use of genetic algorithms
(GAs) provides an accurate solution. Channel matrix coefficients
and MIMO capacities are analyzed for the diverse optimization
strategies employed, which aim to identify the best prediction of
MIMO performance. The novel functions are used with previously
reported results and validated for Rayleigh fading scenarios with
isotropic scattering using a multimode-stirred chamber (MIMO
Analyzer). An accurate prediction of high correlation values is
concluded to be of extreme importance for the final MIMO
performance estimation. This has been found to be particularly
important for estimating MIMO capacity with achieved prediction
accuracies of 1.1% at SNR = 15 dB. In contrast, the accurate
prediction of low correlation values has been found to have a
less-important effect on the final capacity-predicting performance.This work was supported in part by the Spanish National R&D Program under Grant TEC2008-05811
Optimized Varactor Parasitic Modelling in the Millimeter-Wave Band.
This work explores the utilization of varactors in the millimeter-wave (mm-wave) band, specifically focusing on their application in voltage-controlled reconfigurable devices. Varactors, or variable capacitors, can adjust capacitance through voltage control, making them ideal for creating rapidly variable systems for radiofrequency (RF) applications. However, parasitic elements in varactors can significantly affect their performance when moving up to the millimeter-wave band and limit their efficiency. Therefore, this work aims to present an optimization approach that accurately calculates the parasitic model for these varactors.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Human Head Natural Protection Against Electromagnetic Fields
In this paper we provide concluding evidence that the human skull acts as a dynamic barrier to electromagnetic fields (EMF) and temperature flow at 1800 MHz. This natural helmet e®ectively and dynamically protects brain tissue against safety-de¯ned threshold temperature increase due to external EMF induction. A half-wavelength dipole antenna has been employed as the EMF source. The human head is modelled by several coronal planes extracted from the Visible Human Project. Results described here have a great importance should thermal e®ects be directly used to derive basic restrictions to EM fields safety limits for human exposure.FUNDACIÓN SENECA. Plan de
Ciencia y Tecnología de la Región de Murcia. Código: 05746/PI/07
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