51 research outputs found
On the energy efficiency of spatial modulation concepts
No full textSpatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique
which realizes low complexity implementations in wireless communication systems. Due the
transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter.
Therefore, the complexity of the transmitter is lower compared to the complexity of
traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the
single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter.
Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At
the receiver side, due to the SM transmission mechanism, detection is conducted using a low
complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a
single stream detector, SM achieves a multiplexing gain.
A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation,
the concept of SMis extended at the receiver side, using linear precoding with Channel
State Information at the Transmitter (CSIT). Even though receive space modulation does not
preserve the single RF chain configuration of SM, due to the deployed linear precoding, it
can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual
Multiple-Input Multiple-Output (VMIMO) architecture.
Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of
SM and its extension in different forms of MIMO communication. In particular, a realistic
power model for the power consumption of a Base Station (BS) is deployed in order to assess
the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and
considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that
SM is significantly more energy efficient compared to the traditional MIMO techniques. In
the considered system setup, it is shown that SM is up to 67% more energy efficient compared
to the benchmark systems. In addition, the concept of space modulation is researched at the
receiver side. Specifically, based on the union bound technique, a framework for the evaluation
of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space
modulation is developed. Because receive space modulation deploys linear precoding with
CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in
this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of
the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided.
It is concluded that receive space modulation is able to outperform the corresponding traditional
MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order
to form a novel virtual MIMO architecture. It is shown that the new architecture practically
eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO
space modulation architectures. This is undertaken by using precoding in a novel fashion. The
evaluation of the new architecture is conducted using simulation and theoretical results
The Slavic Homer: From Grigorios Stavridis to Grigor Prličev
No full textIn 1860 Stavridis/Prličev’s poem Armatol unexpectedly won him the University of Athens poetry competition, which met with opposition from part of the Greek community and a smear campaign in the press. Despite his declarations of having a “Hellenic heart”, the author from Ohrid was not well received by Athenian society. He took part in the competition once more two years later, this time trying to match Homer himself and presenting an extensive though unfinished epic poem with Gjergj Kastrioti Skanderbeg as the protagonist. The paper, which serves as an introduction to the Polish translation of Skanderbeg, contains extensive excerpts from the reports of both competition committees, chaired by Alexandros Rangavis, especially the second one, when the judges justified why they could not award Stavridis the prize despite being impressed with his poem. His disappointment at his cool reception and his failure in the competition most likely contributed to a radical change in the attitude of the Slavic Homer, who not only stopped “serving Greece” but began vigorously eliminating any Greek influences in his native Ohrid
Multi-user spatial modulation MIMO
No full textSpatial Modulation (SM) is a recently proposed single-RF multiple-input-multiple-output (MIMO) technique, which is capable of outperforming many conventional MIMO transmission schemes with low implementation and computational complexity. Recently, there have been some attempts in understanding the performance of SM in multi-user environments. However, most of the work has been oriented towards uplink multi-access scenarios. Also, conventional downlink/broadcast MIMO precoding techniques such as Zero Forcing (ZF) or Minimum Mean Square Error (MMSE) cannot be used in Multi-User SM (MU-SM), as part of the data in SM is also encoded into the Channel Impulse Responses (CIRs). In this paper, a novel precoding scheme for single-cell downlink MU-SM systems is proposed with a two-fold objective: i) the precoder needs to be able to completely eliminate the Multi-User Interference (MUI) by taking advantage of the Channel State Information (CSI) at the transmitter and ii) it needs to allow the users to use a single-user Maximum Likelihood (ML) optimum detector while achieving the same performance as interference-free point-to-point SM transmission. Finally, we also develop an interference-aware multi-user detection scheme, which does not require any CSI at the transmitter, and compare its performance with that of single-user detection schemes based on precoding
Performance Evaluation of Space Modulation Techniques in VLC Systems
No full textIn this paper, the Bit Error Rate (BER) performanceof three major space modulation techniques in a Multiple-InputMultiple-Output (MIMO) Visible Light Communication (VLC)system is studied. The considered space modulation techniquesare Optical Spatial Modulation (OSM); Optical GeneralizedSpatial Modulation (OGeSM); and Optical Multi-Stream SpatialModulation (OMS-SM). The space modulation techniques areevaluated against two benchmark systems: Optical Spatial MultipleXing(OSMX) and Optical Repetition Coding (ORC). Theperformance assessment, for both the space modulation schemesand the benchmark systems, is undertaken using simulation andanalytical results. For the considered system setup, it is concludedthat, in relative low Signal-to-Noise Ratio (SNR), OSM offers thebest performance. Whereas, in relative high SNR and for highspectral efficiency, OMS-SM is the most efficient scheme in termsof BER
O LABORATÓRIO DE CIÊNCIAS DA ESCOLA DO FUTURO - TECNOLOGIAS E CONTEÚDOS EMERGENTES
No full textEste artigo investiga as tendências atuais na transformação de laboratórios STEM na era da digitalização devido à integração de tecnologias digitais e ao reconhecimento da importância do desenvolvimento de habilidades metacognitivas. O artigo examina o papel da metacognição e seu impacto no processo de aprendizagem, bem como o uso de tecnologias digitais, como laboratórios remotos, laboratórios virtuais, realidade aumentada, realidade virtual e dispositivos móveis na educação STEM. Os resultados desta pesquisa sugerem que o uso dessas tecnologias digitais pode ser benéfico para a aprendizagem de ciências no ensino superior e secundário. Além disso, essas tecnologias podem ser usadas para promover o engajamento, a colaboração e o acesso dos alunos ao conhecimento científico. Além disso, a metacognição é uma habilidade importante para professores e alunos, e pode ser desenvolvida através do uso da pirâmide do conhecimento, pirâmide de inteligência emocional, pirâmide metacognitiva e modelos de pirâmide de superdotação.Este artículo investiga las tendencias actuales en la transformación de los laboratorios STEM en la era de la digitalización debido a la integración de tecnologías digitales y al reconocimiento de la importancia del desarrollo de habilidades metacognitivas. El documento examina el papel de la metacognición y su impacto en el proceso de aprendizaje, así como el uso de tecnologías digitales como laboratorios remotos, laboratorios virtuales, realidad aumentada, realidad virtual y dispositivos móviles en la educación STEM. Los resultados de esta investigación sugieren que el uso de estas tecnologías digitales puede ser beneficioso para el aprendizaje de las ciencias tanto en la educación superior como en la secundaria. Además, estas tecnologías pueden utilizarse para promover la participación, colaboración y acceso al conocimiento científico por parte de los estudiantes. Además, la metacognición es una habilidad importante tanto para profesores como para estudiantes y puede desarrollarse mediante el uso de los modelos de pirámide del conocimiento, pirámide de inteligencia emocional, pirámide metacognitiva y pirámide de talento.This paper investigates the current trends in the transformation of STEM laboratories in the age of digitization due to the integration of digital technologies and the recognition of the importance of developing metacognitive skills. The paper examines the role of metacognition and its impact on the learning process, as well as the use of digital technologies such as remote labs, virtual labs, augmented reality, virtual reality, and mobile devices in STEM education. Results from this research suggest that the use of these digital technologies can be beneficial for science learning in both higher and secondary education. Additionally, these technologies can be used to promote student engagement, collaboration, and access to scientific knowledge. Furthermore, metacognition is an important skill for both teachers and students, and can be developed through the use of the knowledge pyramid, emotional intelligence pyramid, metacognitive pyramid, and giftedness pyramid models.Este artigo investiga as tendências atuais na transformação de laboratórios STEM na era da digitalização devido à integração de tecnologias digitais e ao reconhecimento da importância do desenvolvimento de habilidades metacognitivas. O artigo examina o papel da metacognição e seu impacto no processo de aprendizagem, bem como o uso de tecnologias digitais, como laboratórios remotos, laboratórios virtuais, realidade aumentada, realidade virtual e dispositivos móveis na educação STEM. Os resultados desta pesquisa sugerem que o uso dessas tecnologias digitais pode ser benéfico para a aprendizagem de ciências no ensino superior e secundário. Além disso, essas tecnologias podem ser usadas para promover o engajamento, a colaboração e o acesso dos alunos ao conhecimento científico. Além disso, a metacognição é uma habilidade importante para professores e alunos, e pode ser desenvolvida através do uso da pirâmide do conhecimento, pirâmide de inteligência emocional, pirâmide metacognitiva e modelos de pirâmide de superdotação
Bezout-Based Robust Precoding for MIMO Frequency Selective Channel Using Imperfect Channel Knowledge
No full textPublication in the conference proceedings of EUSIPCO, Barcelona, Spain, 201
Color-Based Time Synchronization for Future Networks: Advantages, System Architecture, and Potential Use Cases
No full textGiven its relevance to industrial applications, over-the-air time synchronization (TS) is anticipated to play a crucial role in future communication networks. Thus, we investigate the potential of optical wireless signals for TS in various applications, including high-precision manufacturing and power distribution. More specifically, in this article, we propose the use of color-based encoded timestamps for TS. In the proposed technique, the master node transmits timestamps to the existing slave nodes encoded in optical signals. To do this, we introduce the implementation of the color-based TS technique and highlight its merits. It is concluded that color-based optical signals can be efficiently used for TS in future networks.</p
Partnership for the Americas: Western Hemisphere strategy and U. S. Southern Command
No full textEn el texto se exploran los enlaces geográficos, culturales, económicos y geopolíticos, que Estados Unidos comparte con América Latina y el Caribe. Se describe asimismo algunas de las difíciles condiciones que afectan a la región – pobreza y desigual distribución de las riquezas – y como estas influyen en desafíos específicos como: el crimen, la violencia y el tráfico ilícito de drogas, gente y armamento. The text explores the links geographic, cultural, economic and geopolitical, which the U.S. shares with Latin America and the Caribbean. It describes some of the difficult conditions facing the region - poverty and unequal distribution of wealth - and how are you influencing specific challenges such as crime, violence and drug trafficking, people and weapons.National Defense University PressÍNDICE | Foreword xi | Preface xiii | Introduction xvii | Chapter 1 We're All in This Together 1 | Chapter 2 Have a Plan 23 | Chapter 3 Pulling the Oar Together 49 | Chapter 4 Trafficking 73 | Chapter 5 People First, Human Rights Always 103 | Chapter 6 Health Engagement and Humanitarianism 135 | Chapter 7 Innovation 171 | Chapter 8 Youth Matters 205 | Chapter 9 Looking to the Future 229 | About the Author 263
Energy Evaluation of Spatial Modulation at a Multi-Antenna Base Station
No full textInternational audienceIn this paper, we aim to study the Energy Efficiency (EE) of Spatial Modulation (SM) at different Base Stations (BSs) taking into account the total power consumption. Compared to conventional Multiple-Input Multiple-Output (MIMO) schemes, SM benefits from a single Radio Frequency (RF) chain which results in decreased power supply (W), higher EE (Mbits/J), and reduced complexity. Using the fundamental limits of Shannon capacity, we show that SM achieves a range of average data rates with only a fraction, which can be as low as 24% for four transmit antennas, of the total power supply of conventional MIMO. In addition, we demonstrate that the EE of the studied schemes is maximized for a certain average data rate and that SM achieves the highest EE among them. Finally, we note that a BS employing SM can be up to 67% more energy efficient compared to a BS under a conventional MIMO transmission scheme, for four transmit antennas
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