38 research outputs found
Millimeter-Wave Beam-Formed Array Antenna for Connected Driving Scenarios
Connected vehicles are the next frontier in massive mobile communications. The automotive industry is pursuing the exchange of essential information between vehicles, road infrastructure and all kind of external agents (V2X) for improving safety and traffic efficiency. Sharing data such as the position or kinematics, for example, can be used by other road participants to make a better prediction of hazardous situations. Even though, to meet the automotive-grade requirements, such as reliability during information exchange, or to support highly-automated applications such as platooning, high levels of reliability during information exchange are required. These cannot be sustained by the sub-6 GHz V2X band so it is therefore necessary to relocate to other bands such as the millimeter- Wave (mmWave) Frequency Range 2 (FR2) band, where larger bandwidths are available. The goal of this project is to develop a mmWave beam-formed array antenna for connected driving scenarios. With this framework, it will be possible to obtain metrics and understand how channel measurements can be used to improve V2X communications, by using for instance, di?erent antenna setups or combining di?erent beamforming strategies i.e. beam steering or beam shaping in diverse down-scaled urban scenarios. Based on this, it is largely intended to use physical layer measurements as a promising first barrier to improve the quality of V2X communications. MmWave communications for advanced connected and automated vehicle driving scenarios have drawn significant attention for their adaptability in a wide variety of applications. However, when Line-Of-Sight (LOS) and link stability cannot be assured in urban scenarios, the exchange of information between two vehicles becomes more complex and sometimes even dangerous if the information sent through the channel is not reliable. In this thesis, an improved mmWave beamforming method based on array antenna beam steering is presented. By using a channel-aware imaging algorithm, it aims to solve in large part the above-mentioned problematic by finding the most reliable path in non Line-Of- Sight (NLOS) scenarios. Thus, link stability over road infrastructures might be potentially improved besides enhancing safe-channel communications and traffic efficiency
Adaptive Multicell 3D Beamforming in Multi-Antenna Cellular Networks
We consider a cellular network with multi-antenna base stations (BSs) and
single-antenna users, multicell cooperation, imperfect channel state
information, and directional antennas each with a vertically adjustable beam.
We investigate the impact of the elevation angle of the BS antenna pattern,
denoted as tilt, on the performance of the considered network when employing
either a conventional single-cell transmission or a fully cooperative multicell
transmission. Using the results of this investigation, we propose a novel
hybrid multicell cooperation technique in which the intercell interference is
controlled via either cooperative beamforming in the horizontal plane or
coordinated beamfroming in the vertical plane of the wireless channel, denoted
as adaptive multicell 3D beamforming. The main idea is to divide the coverage
area into two disjoint vertical regions and adapt the multicell cooperation
strategy at the BSs when serving each region. A fair scheduler is used to share
the time-slots between the vertical regions. It is shown that the proposed
technique can achieve performance comparable to that of a fully cooperative
transmission but with a significantly lower complexity and signaling
requirements. To make the performance analysis computationally efficient,
analytical expressions for the user ergodic rates under different beamforming
strategies are also derived.Comment: Accepted for publication in IEEE Transaction on Vehicular Technolog
A Vision of Self-Evolving Network Management for Future Intelligent Vertical HetNet
Future integrated terrestrial-aerial-satellite networks will have to exhibit
some unprecedented characteristics for the provision of both communications and
computation services, and security for a tremendous number of devices with very
broad and demanding requirements in an almost-ubiquitous manner. Although 3GPP
introduced the concept of self-organization networks (SONs) in 4G and 5G
documents to automate network management, even this progressive concept will
face several challenges as it may not be sufficiently agile in coping with the
immense levels of complexity, heterogeneity, and mobility in the envisioned
beyond-5G integrated networks. In the presented vision, we discuss how future
integrated networks can be intelligently and autonomously managed to
efficiently utilize resources, reduce operational costs, and achieve the
targeted Quality of Experience (QoE). We introduce the novel concept of
self-evolving networks (SENs) framework, which utilizes artificial
intelligence, enabled by machine learning (ML) algorithms, to make future
integrated networks fully intelligent and automated with respect to the
provision, adaptation, optimization, and management aspects of networking,
communications, and computation. To envisage the concept of SEN in future
integrated networks, we use the Intelligent Vertical Heterogeneous Network
(I-VHetNet) architecture as our reference. The paper discusses five prominent
communications and computation scenarios where SEN plays the main role in
providing automated network management. Numerical results provide an insight on
how the SEN framework improves the performance of future integrated networks.
The paper presents the leading enablers and examines the challenges associated
with the application of SEN concept in future integrated networks
Ondas milimétricas e MIMO massivo para otimização da capacidade e cobertura de redes heterogeneas de 5G
Today's Long Term Evolution Advanced (LTE-A) networks cannot support
the exponential growth in mobile traffic forecast for the next decade. By
2020, according to Ericsson, 6 billion mobile subscribers worldwide are projected
to generate 46 exabytes of mobile data traffic monthly from 24 billion
connected devices, smartphones and short-range Internet of Things (IoT)
devices being the key prosumers. In response, 5G networks are foreseen
to markedly outperform legacy 4G systems. Triggered by the International
Telecommunication Union (ITU) under the IMT-2020 network initiative, 5G
will support three broad categories of use cases: enhanced mobile broadband
(eMBB) for multi-Gbps data rate applications; ultra-reliable and low latency
communications (URLLC) for critical scenarios; and massive machine
type communications (mMTC) for massive connectivity. Among the several
technology enablers being explored for 5G, millimeter-wave (mmWave)
communication, massive MIMO antenna arrays and ultra-dense small cell
networks (UDNs) feature as the dominant technologies. These technologies
in synergy are anticipated to provide the 1000_ capacity increase for 5G
networks (relative to 4G) through the combined impact of large additional
bandwidth, spectral efficiency (SE) enhancement and high frequency reuse,
respectively. However, although these technologies can pave the way towards
gigabit wireless, there are still several challenges to solve in terms of
how we can fully harness the available bandwidth efficiently through appropriate
beamforming and channel modeling approaches. In this thesis, we
investigate the system performance enhancements realizable with mmWave
massive MIMO in 5G UDN and cellular infrastructure-to-everything (C-I2X)
application scenarios involving pedestrian and vehicular users. As a critical
component of the system-level simulation approach adopted in this thesis,
we implemented 3D channel models for the accurate characterization of the
wireless channels in these scenarios and for realistic performance evaluation.
To address the hardware cost, complexity and power consumption of the
massive MIMO architectures, we propose a novel generalized framework for
hybrid beamforming (HBF) array structures. The generalized model reveals
the opportunities that can be harnessed with the overlapped subarray structures
for a balanced trade-o_ between SE and energy efficiently (EE) of 5G
networks. The key results in this investigation show that mmWave massive
MIMO can deliver multi-Gbps rates for 5G whilst maintaining energy-efficient operation of the network.As redes LTE-A atuais não são capazes de suportar o crescimento exponencial
de tráfego que está previsto para a próxima década. De acordo
com a previsão da Ericsson, espera-se que em 2020, a nível global, 6 mil
milhões de subscritores venham a gerar mensalmente 46 exa bytes de tráfego
de dados a partir de 24 mil milhões de dispositivos ligados à rede móvel,
sendo os telefones inteligentes e dispositivos IoT de curto alcance os principais
responsáveis por tal nível de tráfego. Em resposta a esta exigência,
espera-se que as redes de 5a geração (5G) tenham um desempenho substancialmente
superior às redes de 4a geração (4G) atuais. Desencadeado pelo
UIT (União Internacional das Telecomunicações) no âmbito da iniciativa
IMT-2020, o 5G irá suportar três grandes tipos de utilizações: banda larga
móvel capaz de suportar aplicações com débitos na ordem de vários Gbps;
comunicações de baixa latência e alta fiabilidade indispensáveis em cenários
de emergência; comunicações massivas máquina-a-máquina para conectividade
generalizada. Entre as várias tecnologias capacitadoras que estão a ser
exploradas pelo 5G, as comunicações através de ondas milimétricas, os agregados
MIMO massivo e as redes celulares ultradensas (RUD) apresentam-se
como sendo as tecnologias fundamentais. Antecipa-se que o conjunto
destas tecnologias venha a fornecer às redes 5G um aumento de capacidade
de 1000x através da utilização de maiores larguras de banda, melhoria da
eficiência espectral, e elevada reutilização de frequências respetivamente.
Embora estas tecnologias possam abrir caminho para as redes sem fios
com débitos na ordem dos gigabits, existem ainda vários desafios que têm
que ser resolvidos para que seja possível aproveitar totalmente a largura de
banda disponível de maneira eficiente utilizando abordagens de formatação
de feixe e de modelação de canal adequadas. Nesta tese investigamos a
melhoria de desempenho do sistema conseguida através da utilização de
ondas milimétricas e agregados MIMO massivo em cenários de redes celulares
ultradensas de 5a geração e em cenários 'infraestrutura celular-para-qualquer
coisa' (do inglês: cellular infrastructure-to-everything) envolvendo
utilizadores pedestres e veiculares. Como um componente fundamental das
simulações de sistema utilizadas nesta tese é o canal de propagação, implementamos modelos de canal tridimensional (3D) para caracterizar de
forma precisa o canal de propagação nestes cenários e assim conseguir uma
avaliação de desempenho mais condizente com a realidade. Para resolver os
problemas associados ao custo do equipamento, complexidade e consumo
de energia das arquiteturas MIMO massivo, propomos um modelo inovador
de agregados com formatação de feixe híbrida. Este modelo genérico revela
as oportunidades que podem ser aproveitadas através da sobreposição
de sub-agregados no sentido de obter um compromisso equilibrado entre
eficiência espectral (ES) e eficiência energética (EE) nas redes 5G. Os principais
resultados desta investigação mostram que a utilização conjunta de
ondas milimétricas e de agregados MIMO massivo possibilita a obtenção, em
simultâneo, de taxas de transmissão na ordem de vários Gbps e a operação
de rede de forma energeticamente eficiente.Programa Doutoral em Telecomunicaçõe
Analysis and performance improvement of consumer-grade millimeter wave wireless networks
Millimeter-wave (mmWave) networks are one of the main key components in next cellular
and WLANs (Wireless Local Area Networks). mmWave networks are capable of providing multi gigabit-per-second rates with very directional low-interference and high spatial reuse links. In 2013, the first 60 GHz wireless solution for WLAN appeared in the market. These were wireless docking stations under theWiGig protocol. Today, in 2019, 60 GHz communications have gained importance with the IEEE 802.11ad amendment with different products on the market, including routers, laptops and wireless Ethernet solutions. More importantly, mmWave networks are going to be used in next generation cellular networks, where smartphones will be using the 28 GHz band. For backbone links, 60 GHz communications have been proposed due to its higher directionality and unlicensed use. This thesis fits in this frame of constant development of themmWave bands to meet the needs of latency and throughput that will be necessary to support future communications. In this thesis, we first characterize the cost-effective design of COTS (commercial off-the-shelf) 60 GHz devices and later we improve their two main weaknesses, which are their low link distance and their non-ideal spatial reuse.
It is critical to take into consideration the cost-effective design of COTS devices when
designing networking mechanisms. This is why in this thesis we do the first-of-its-kind COTS analysis of 60 GHz devices, studying the D5000 WiGig Docking station and the TP-Link Talon IEEE 802.11ad router. We include static measurements such as the synthesized beam patterns of these devices or an analysis of the area-wide coverage that these devices can fulfill. We perform a spatial reuse analysis and study the performance of these devices under user mobility, showing how robust the link can be under user movement. We also study the feasibility of having flying mmWave links. We mount a 60 GHz COTS device into a drone and perform different measurement campaigns. In this first analysis, we see that these 60 GHz devices have a large performance gap for the achieved communication range as well as a very low spatial reuse. However, they are still suitable for low density WLANs and for next generation aerial micro cell stations.
Seeing that these COTS devices are not as directional as literature suggests, we analyze how channels are not as frequency stable as expected due to the large amount of reflected signals. Ideally, frequency selective techniques could be used in these frequency selective channels in order to enlarge the range of these 60 GHz devices. To validate this, we measure real-world 60 GHz indoor channels with a bandwidth of 2 GHz and study their behavior with respect to techniques such as bitloading, subcarrier switch-off, and waterfilling. To this end, we consider a Orthogonal Frequency-Division Multiplexing (OFDM) channel as defined in the IEEE 802.11ad standard and show that in point of fact, these techniques are highly beneficial in mmWave networks allowing for a range extension of up to 50%, equivalent to power savings of up to 7 dB. In order to increase the very limited spatial reuse of these wireless networks, we propose a centralized system that allows the network to carry out the beam training process not only to maximize power but also taking into account other stations in order to minimize interference. This system is designed to work with unmodified clients. We implement and validate our system on commercial off-the-shelf IEEE 802.11ad hardware, achieving an average throughput gain of 24.67% for TCP traffic, and up to a twofold throughput gain in specific cases.Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan CarlosPresidente: Andrés García Saavedra.- Secretario: Matilde Pilar Sánchez Fernández.- Vocal: Ljiljana Simi
DYNAMIC USER-CENTRIC CAPACITY MAXIMIZATION BY OPTIMIZING ANTENNA PARAMETERS
Cellular network has become the primary means of voice as well as data communication. With sophisticated but affordable end user devices e.g. smartphones, tablet PCs etc. and ubiquity of mobile connectivity, users are able to access a range of multimedia services requiring low to high data rate and with desired quality of experience everywhere and all the times. However, mobile network operators (MNOs) always have limited bandwidth resources as compared to users’ demand, as bandwidth is the most expensive resource in the network. Thus MNOs always seek new tools and technologies to optimally utilize the available bandwidth to accommodate maximum number of users and provide high quality of services, maximizing the revenue in return. Especially, in the case of ultra-dense heterogeneous deployment of small cells equipped with massive-MIMO antenna configuration operating over mmWave spectrum in 5G, automated solution for dynamic spectrum optimization with respect to rapidly changing users and network requirement will be of critical importance.
This thesis presents a novel scheme for spectral efficiency (SE) optimization through clustering of users. By clustering users with respect to their geographical concentration we propose a solution for dynamic steering of antenna beam by dynamically adjusting antenna azimuth and tilt angles with respect to the most focal point in every cell that would maximize overall SE in the system. The proposed framework thus introduces the notion of elastic cells that can be potential component of 5G networks. The proposed scheme decomposes large-scale system-wide optimization problem into small-scale local sub-problems and thus provides a low complexity solution for dynamic system wide optimization. Every sub-problem involves clustering of users to determine focal point of the cell for given user distribution in time and space, and determining new values of azimuth and tilt that would optimize the overall system SE performance. To this end, we proposed three user clustering algorithms to transform a given user distribution into the focal points that can be used in optimization process: the first is based on received signal to interference ratio (SIR) at the user; the second is based on received signal level (RSL) at the user; the third and final one is based on relative distances of users from the base stations. We also formulate and solve an optimization problem to determine optimal radii of clusters. The performances of proposed algorithms and framework are evaluated through system level simulations. Performance comparison against benchmark where no elastic cell deployed, shows that a gain in spectral efficiency of up to 26% is achievable depending upon user distribution in each cell
Evaluation of mmWave 5G Performance by Advanced Ray Tracing Techniques
Technological progress leads to the emergence of new concepts, which can change people’s everyday lives and accelerate the transformation of many industries. Among the more recent of these revolutionary concepts are big data analysis, artificial intelligence, augmented/virtual reality, quantum computing, and autonomous vehicles. However, this list would be incomplete without referring to fifth-generation (5G) technology, which is driven by several trends. First, the exponential growth of the worldwide monthly smartphone traffic up to 50 petabytes during the next three years will require the development of mobile networks supporting high datasharing capabilities, excellent spectral efficiency, and gigabits per second of throughput. Another trend is Industry 4.0/5.0 (also called the smart factory), which refers to advanced levels of automation requiring millions of distributed sensors/devices connected into a scalable and smart network. Finally, the automation of critical industrial processes, as well as communication between autonomous vehicles, will require 99.999% reliability and under 1 ms latency as they also become the drivers for the emergence of 5G.
Besides traditional sub-6 GHz microwave spectrum, the 5G communication encompasses the novel millimeter-wave bands to mitigate spectrum scarcity and provide large bandwidth of up to several GHz. However, there are challenges to be overcome with the millimeter-wave band. The band suffers from higher pathloss, more atmospheric attenuation, and higher diffraction losses than microwave signals. Because the millimeter-wave band has such a small wavelength (< 1 cm), it is now feasible to implement compact antenna arrays. This enables the use of beamforming and multi-input and multi-output techniques. In this thesis, advanced ray tracing methodology is developed and utilized to simulate the propagation mechanisms and their effect on the system-level metrics. The main novelty of this work is in the introduction of typical millimeter-wave 5G technologies into channel modelling and propagation specifics into the system-level simulation, as well as the adaptation of the ray tracing methods to support extensive simulations with multiple antennas
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DISTRIBUTED PHASED ARRAY ANTENNAS IN WIDE AREA RFID
Ultra High Frequency (UHF) Radio Frequency Identification (RFID) has gained importance over the past two decades in many applications such as stock management, asset
tracking and access control. For wide area applications, Distributed Antenna Systems
(DAS) have been used to obtain good coverage with few antennas by making use of
multiple spatially distributed antennas and phase dithering. This implements a far-field
beamforming that maximises the instantaneous power at a tag. Separately, phased array
antennas have also been used to increase the read range by increasing the effective field
of view of an antenna and overcoming multipath fading through beam steering. This
dissertation explores a combination of both approaches to improve RFID read ranges in
wide interrogation zones.
Distributed antenna arrays are explored in the context of delivering high tag detection
probabilities in a multi-cell RFID system, while maximising inter-antenna separations.
A Distributed Antenna Array System (DAAS) is designed and shown to be capable of
providing comparable performance to a fixed DAS system with fewer antennas. The properties of the system are further studied and its upper performance limit is explored by
modelling a hypothetical perfectly steerable antenna array. The concept of using perfectly
steerable arrays is further explored to propose a cell-less RFID system, in which cell allocation in wide area RFID is replaced with a tag location-based interrogation requiring the
global reader antenna population to be used for interrogation of all tags, leading to significant potential increases in inter-antenna separation, and consequently good coverage
with fewer antennas. It is also argued that this system leads to the avoidance of complex
reader anti-collision policies, since only a single central reader is now required. Finally,
the design of a wide-scan-angle antenna array is presented as a compromise solution for
perfectly steerable antennas, whist still keeping the desired property of being flat panel.
A 3D RFID multi-antenna model is presented and used for simulating and analysing the
various described systems and for system planning