199 research outputs found
Orthogonal Codes for Robust Low-Cost Communication
Orthogonal coding schemes, known to asymptotically achieve the capacity per
unit cost (CPUC) for single-user ergodic memoryless channels with a zero-cost
input symbol, are investigated for single-user compound memoryless channels,
which exhibit uncertainties in their input-output statistical relationships. A
minimax formulation is adopted to attain robustness. First, a class of
achievable rates per unit cost (ARPUC) is derived, and its utility is
demonstrated through several representative case studies. Second, when the
uncertainty set of channel transition statistics satisfies a convexity
property, optimization is performed over the class of ARPUC through utilizing
results of minimax robustness. The resulting CPUC lower bound indicates the
ultimate performance of the orthogonal coding scheme, and coincides with the
CPUC under certain restrictive conditions. Finally, still under the convexity
property, it is shown that the CPUC can generally be achieved, through
utilizing a so-called mixed strategy in which an orthogonal code contains an
appropriate composition of different nonzero-cost input symbols.Comment: 2nd revision, accepted for publicatio
Compact Multi-Coil Inductive Power Transfer System with a Dynamic Receiver Position Estimation
Inductive power transfer (IPT) systems with tolerance to the lateral misalignment are
advantageous for enhancing the transmitted power, usability and security of the system. In this
thesis, a misalignment tolerant multi-coil design is proposed to supply stationary and dynamic
battery-free wireless devices. A compact architecture composed of individually switchable 3
layers of printed coils arranged with overlap for excellent surface coverage. A hybrid architecture
based on three compact AC supply modules reduces the supply circuit complexity on the sending
Seite 2 von 4side. It detects the position of the receiver coil quickly, controls the activation of the transmitting
coils and estimates the next receiver position. The proposed architecture reduces the circuit
footprint by a factor of 62% compared to common architectures.
A transmitter coil activation strategy is proposed based on the detection of the transmitting coils
voltage and communication between sending side and receiving side to detect devices to supply
nature and position and to differentiate them from other conductive objects in the sending area
to the supplying security. The experimental results prove that the proposed architecture has a
good performance for different trajectories when the device speed does not exceed 15 mm/s.
Besides, the maximum detection time for the initial device position is about 1.6 s. The maximal
time interval to check the transmitter coils is around 0.7 s.:1. INTRODUCTION
2. THEORETICAL BACKGROUND
3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS
4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM
5. MULTI-COIL ACTIVATION PROCEDURE
6. EXPERIMENTAL INVESTIGATIONS
7. CONCLUSION AND OUTLOOKInduktive Energieübertragungssysteme (IPT) mit Toleranz gegenüber seitlichem Versatz sind
vorteilhaft, um die übertragene Leistung, die Nutzbarkeit und die Sicherheit des Systems zu
verbessern. In dieser Arbeit wird ein versatztolerantes Multispulen-Design vorgeschlagen, um
stationäre und dynamische batterielose drahtlose Geräte zu versorgen. Die kompakte Architektur
besteht aus 3 einzeln schaltbaren Schichten gedruckter Spulen, die überlappend angeordnet sind,
um eine hervorragende Oberflächenabdeckung zu gewährleisten. Eine hybride Architektur, die auf
drei kompakten AC-Versorgungsmodulen basiert, reduziert die Komplexität der
Versorgungsschaltung auf der Senderseite. Sie erkennt die Position der Empfängerspule schnell,
steuert die Aktivierung der Sendespulen und schätzt die nächste Empfängerposition. Die
vorgeschlagene Architektur reduziert den Platzbedarf der Schaltung um einen Faktor von 62 % im
Vergleich zu herkömmlichen Architekturen.
Es wird eine Aktivierungsstrategie für die Sendespulen vorgeschlagen, die auf der Erkennung der
Spannung der Sendespulen und der Kommunikation zwischen Sende- und Empfangsseite basiert,
um die Art und Position der zu versorgenden Geräte zu erkennen und sie von anderen leitfähigen
Objekten im Sendebereich zu unterscheiden. Die experimentellen Ergebnisse zeigen, dass die
vorgeschlagene Architektur eine gute Leistung für verschiedene Trajektorien hat, wenn die
Geschwindigkeit der Geräte 15 mm/s nicht überschreitet. Außerdem beträgt die maximale
Erkennungszeit für die anfängliche Geräteposition etwa 1,6 s. Das maximale Zeitintervall für die
Überprüfung der Senderspulen beträgt etwa 0,7 s.:1. INTRODUCTION
2. THEORETICAL BACKGROUND
3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS
4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM
5. MULTI-COIL ACTIVATION PROCEDURE
6. EXPERIMENTAL INVESTIGATIONS
7. CONCLUSION AND OUTLOO
Optimization of Spectrum Management in Massive Array Antenna Systems with MIMO
Fifth generation (5G), is being considered as a revolutionary technology in the telecommunication
domain whose the challenges are mainly to achieve signal quality and great ability to
work with free spectrum in the millimetre waves. Besides, other important innovations are the
introduction of a more current architecture and the use of multiple antennas in transmission
and reception. Digital communication using multiple input and multiple output (MIMO) wireless
links has recently emerged as one of the most significant technical advances in modern communications.
MIMO technology is able to offer a large increase in the capacity of these systems,
without requiring a considerable increase in bandwidth or power required for transmission.
This dissertation presents an overview of theoretical concepts of MIMO systems. With such a
system a spatial diversity gain can be obtained by using space-time codes, which simultaneously
exploit the spatial domain and the time domain. SISO, SIMO and MISO systems are differentiated
by their channel capacity and their configuration in relation to the number of antennas in the
transmitter/receiver. To verify the effectiveness of the MIMO systems a comparison between the
capacity of SISO and MIMO systems has been performed using the Shannon’s principles. In the
MIMO system some variations in the number of antennas arrays have been considered, and the
superiority of transmission gains of the MIMO systems have been demonstrated. Combined with
millimetre waves (mmWaves) technology, massive MIMO systems, where the number of antennas
in the base station and the number of users are large, is a promising solution.
SDR implementations have been performed considering a platform with Matlab code applied to
MIMO 2x2 Radio and Universal Software Peripheral Radio (USRP). A detailed study was initially
conducted to analyze the architecture of the USRP. Complex structures of MIMO systems can
be simplified by using mathematical methods implemented in Matlab for the synchronization of
the USRP in the receiver side. SISO transmission and reception techniques have been considered
to refine the synchronization (with 16-QAM), thus facilitating the future implementation of the
MIMO system. OpenAirInterface has been considered for 4G and 5G implementations of actual
mobile radio communication systems. Together with the practical MIMO, this type of solution is
the starting point for future hardware building blocks involving massive MIMO systems.A quinta geração (5G) está sendo considerada uma tecnologia revolucionária no setor de telecomunicações,
cujos desafios são principalmente a obtenção de qualidade de sinal e grande capacidade
de trabalhar com espectro livre nas ondas milimétricas. Além disso, outras inovações
importantes são a introdução de uma arquitetura mais atual e o uso de múltiplas antenas em
transmissão e recepção. A comunicação digital usando ligaçõe sem fio de múltiplas entradas e
múltiplas saídas (MIMO) emergiu recentemente como um dos avanços técnicos mais significativos
nas comunicações modernas. A tecnologia MIMO é capaz de oferecer um elevado aumento na
capacidade, sem exigir um aumento considerável na largura de banda ou potência transmitida.
Esta dissertação apresenta uma visão geral dos conceitos teóricos dos sistemas MIMO. Com esses
sistemas, um ganho de diversidade espacial pode ser obtido utilizando códigos espaço-tempo
reais. Os sistemas SISO, SIMO e MISO são diferenciados pela capacidade de seus canais e a sua
configuração em relação ao número de antenas no emissor/receptor. Para verificar a eficiência
dos sistemas MIMO, realizou-se uma comparação entre a capacidade dos sistemas SISO e MIMO
utilizado os princípios de Shannon. Nos sistemas MIMO condecideraram-se algumas variações no
número de agregados de antenas, e a superioridade dos ganhos de transmissão dos sistemas MIMO
foi demonstrada. Combinado com a tecnologia de ondas milimétricas (mmWaves), os sistemas
massivos MIMO, onde o número de antenas na estação base e o número de usuários são grandes,
são uma solução promissora.
As implementações do SDR foram realizadas considerando uma plataforma com código Matlab
aplicado aos rádios MIMO 2x2 e Universal Software Peripheral Radio (USRP). Um estudo detalhado
foi inicialmente conduzido para analisar a arquitetura da USRP. Estruturas complexas de sistemas
MIMO podem ser simplificadas usando métodos matemáticos implementados no Matlab para a
sincronização do USRP no lado do receptor. Consideraram-se técnicas de transmissão e recepção
SISO para refinar a sincronização (com 16-QAM), facilitando assim a implementação futura do
sistema MIMO . Considerou-se o OpenAirInterface para implementações 4G e 5G de sistemas
reais de comunicações móveis. Juntamente com o MIMO na pratica, este tipo de solução é
o ponto de partida para futuros blocos de construção de hardware envolvendo sistemas MIMO
massivos
Vector sensors for underwater : acoustic communications
Acoustic vector sensors measure acoustic pressure and directional components separately.
A claimed advantage of vector sensors over pressure-only arrays is the directional information
in a collocated device, making it an attractive option for size-restricted applications.
The employment of vector sensors as a receiver for underwater communications is relatively
new, where the inherent directionality, usually related to particle velocity, is used
for signal-to-noise gain and intersymbol interference mitigation. The fundamental question
is how to use vector sensor directional components to bene t communications, which
this work seeks to answer and to which it contributes by performing: analysis of acoustic
pressure and particle velocity components; comparison of vector sensor receiver structures
exploring beamforming and diversity; quanti cation of adapted receiver structures in distinct
acoustic scenarios and using di erent types of vector sensors. Analytic expressions
are shown for pressure and particle velocity channels, revealing extreme cases of correlation
between vector sensors' components. Based on the correlation hypothesis, receiver
structures are tested with simulated and experimental data. In a rst approach, called
vector sensor passive time-reversal, we take advantage of the channel diversity provided
by the inherent directivity of vector sensors' components. In a second approach named
vector sensor beam steering, pressure and particle velocity components are combined, resulting
in a steered beam for a speci c direction. At last, a joint beam steering and
passive time-reversal is proposed, adapted for vector sensors. Tested with two distinct
experimental datasets, where vector sensors are either positioned on the bottom or tied
to a vessel, a broad performance comparison shows the potential of each receiver structure.
Analysis of results suggests that the beam steering structure is preferable for shorter
source-receiver ranges, whereas the passive time-reversal is preferable for longer ranges.
Results show that the joint beam steering and passive time-reversal is the best option to
reduce communication error with robustness along the range.Sensores vetoriais acústicos (em inglês, acoustic vector sensors) são dispositivos que
medem, alem da pressão acústica, a velocidade de partícula. Esta ultima, é uma medida que
se refere a um eixo, portando, esta associada a uma direção. Ao combinar pressão acústica
com componentes de velocidade de partícula pode-se estimar a direção de uma fonte sonora
utilizando apenas um sensor vetorial. Na realidade, \um" sensor vetorial é composto de um
sensor de pressão (hidrofone) e um ou mais sensores que medem componentes da velocidade
de partícula. Como podemos notar, o aspecto inovador está na medição da velocidade de
partícula, dado que os hidrofones já são conhecidos.(...)This PhD thesis was supported by the Brazilian Navy Postgraduate Study Abroad
Program Port. 227/MB-14/08/2019
Antenna Systems
This book offers an up-to-date and comprehensive review of modern antenna systems and their applications in the fields of contemporary wireless systems. It constitutes a useful resource of new material, including stochastic versus ray tracing wireless channel modeling for 5G and V2X applications and implantable devices. Chapters discuss modern metalens antennas in microwaves, terahertz, and optical domain. Moreover, the book presents new material on antenna arrays for 5G massive MIMO beamforming. Finally, it discusses new methods, devices, and technologies to enhance the performance of antenna systems
A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications
The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined
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