1,816 research outputs found
Conformação de pulso de formas de onda OFDM para a interface aérea 5G
Orientador: Luís Geraldo Pedroso MeloniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: As formas de onda com multiplexação ortogonal por divisão de freqüência (OFDM) foram utilizadas com sucesso na interface aérea 3GPP LTE para superar a seletividade do canal e proporcionar uma boa eficiência espectral e altas taxas de transmissão de dados. O próximo sistema de comunicações 5G tem como objetivo oferecer suporte a mais serviços do que o antecessor, como comunicações de banda larga móveis, comunicações de tipo máquina e comunicações de baixa latência, e considera muitos outros cenários de aplicação, como o uso de espectro fragmentado. Esta diversidade de serviços com diferentes requisitos não pode ser suportada pela OFDM convencional, pois OFDM configura toda a largura de banda com parâmetros que atendem a um serviço em particular. Além disso, pode ocorrer interferência interportadora (ICI) quando a OFDM convencional é usada com multiplexação assíncrona de múltiplos usuários e isso é devido às altas emissões fora de banda (OOB) das subportadoras e à violação da condição de ortogonalidade do sinal. Portanto, para atender aos requisitos das futuras aplicações sem fio 5G, o desenvolvimento de uma interface aérea inovadora com novas capacidades torna-se necessário, em particular, uma nova forma de onda mais espectralmente ágil do que OFDM capaz de suportar múltiplas configurações, suprimindo efetivamente a interferência entre usuários, e com integração direta com as camadas superiores. Este trabalho centra-se em duas técnicas de conformação de pulsos para reduzir a emissões fora de banda e melhorar o desempenho de formas de onda baseadas em OFDM. A conformação de pulsos pode permitir o uso de parametrizações múltiplas dentro da forma de onda e abandonar os paradigmas rígidos de ortogonalidade e sincronismo com uma degradação de desempenho causada por interferência intersymbol (ISI) e ICI relativamente baixa. A primeira parte aborda um método de modelagem de pulso baseado na filtragem por subportadora para reduzir a emissão fora de banda no transmissor e interferência de canal adjacente (ACI) no receptor. Ele pode ser implementado usando funções de janela e alguns formatos de janela são apresentados nesta parte. O primeiro usa o prefixo cíclico (CP) existente dos símbolos para suavizar as transições abruptas do sinal, portanto, os grandes lóbulos espectrais sinc causados pelos filtros retangulares. Isso garante a compatibilidade retroativa em sistemas que usam OFDM com prefixo cíclico (CP-OFDM). O formato da segunda janela estende o comprimento do CP para reter a capacidade da forma de onda para combater a propagação do atraso do canal. Os efeitos no desempenho do ISI e ICI são estudados em termos de relação de sinal para interferência (SIR) e taxa de erro de bit (BER) usando formas de onda LTE em um cenário de espectro fragmentado multi-usuário. A segunda parte deste trabalho aborda o desenho e análise de filtros para a contenção espectral flexível em transceptores com filtragem baseada em sub-banda. Este filtro, chamado aqui semi-equiripple, exibe melhor atenuação na banda de rejeição para reduzir as interferências entre subbandas do que os filtros equiripple e filtros sinc baseados em janelamento e também possui boas características de resposta ao impulso para reduzir o ISI. O projeto de filtros baseia-se no algoritmo Parks-McClellan para obter diferentes taxas de decaimento da banda de parada e atende a especificações arbitrárias de máscaras de emissão de espectro (SEM) com baixa distorção dentro da banda. Portanto, pode ser útil para obter baixas emissões fora da banda e configurar sub-bandas com parâmetros independentes, uma vez que a interferência assíncrona é contida pelos filtros. São estudadas três distorções de ISI no filtro: espalhamento de símbolos relacionado à causalidade do filtro, ecos de símbolos devido a ondulações na banda e amplificação de ISI devido a amostras de valores anômalas nas caudas de sua resposta de impulso. O desempenho do filtro é avaliado em termos de densidade de espectro de potência (PSD) e conformidade com SEMs, taxa de erro de modulação (MER) e operação em um esquema assíncrono multi-serviço usando uma única forma de onda. O SIR e o efeito da filtragem na precisão da modulação são avaliados usando formas de onda OFDM ISDB-T e LTE. Estruturas de hardware flexíveis também são propostas para implementações reais. Os resultados mostram que esses métodos de conformação de pulso permitem que a forma de onda explore os fragmentos de espectro disponíveis e ofereça suporte a múltiplos serviços sem uma penalidade de desempenho significativa, o que pode permitir uma interface aérea mais flexívelAbstract: Orthogonal frequency division multiplexing (OFDM) waveforms have been used successfully in the 3GPP Long Term Evolution (LTE) air interface to overcome the channel selectivity and to provide good spectrum efficiency and high transmission data rates. The forthcoming 5G communication system aims to support more services than its predecessor, such as enhanced mobile broadband, machine-type communications and low latency communications, and considers many other application scenarios such as the fragmented spectrum use. This diversity of services with different requirements cannot be supported by conventional OFDM since OFDM configures the entire bandwidth with parameters attending one service in particular. Also, substantial intercarrier interference (ICI) can occur when conventional OFDM is used with asynchronous multiuser multiplexing and this is due to the high out-of-band (OOB) emissions of the subcarriers and the violation of the signal orthogonality constraint. Therefore, to meet the requirements of future 5G wireless applications, the development of an innovative air interface with new capabilities becomes necessary, in particular, a new waveform more spectrally agile than OFDM capable of supporting multiple configurations, suppressing the inter-user interference effectively, and with straightforward integration with the upper layers. This work focuses on two pulse shaping techniques to reduce the OOB emission and improve the in-band and OOB performances of OFDM-based waveforms. Pulse shaping can enable the use of multiple parameterizations within the waveform and abandon the strict paradigms of orthogonality and synchronism with relatively low performance degradation caused by intersymbol interference (ISI) and ICI. The first part addresses a pulse shaping method based on per-subcarrier filtering to reduce both OOB emission in the transmitter and adjacent channel interference (ACI) in the receiver. It can be implemented using window functions and some window formats are presented in this part. The first uses the existing cyclic prefix (CP) of OFDM symbols to smooth abrupt transitions of the signal, thus the large sinc spectral sidelobes caused by the rectangular filters. This guarantees backwards compatibility in systems using conventional cyclic prefixed OFDM (CP-OFDM). The second window format extends the CP length to retain the waveform ability to combat channel delay spread. The effects on performance of ISI and ICI are studied in terms of the signal to interference ratio (SIR) and bit error rate (BER) using LTE waveforms in a multi-user fragmented spectrum scenario. The second part of this work addresses the design and analysis of a filters for flexible spectral containment in subband-based filtering transceivers. This filter, called here semi-equiripple, exhibits better stopband attenuation to reduce the inter-subband interferences than equiripple and windowed truncated sinc filters and also has good impulse response characteristics to reduce ISI. The design is based on the Parks-McClellan algorithm to obtain different stopband decay rates and meet arbitrary spectrum emission masks (SEM) specifications with low in-band distortion. Therefore, it can be useful to achieve low OOB emission and configure subbands with independent parameters since the asynchronous interference is contained by the filters. Three ISI distortions in the filter are studied: symbol spreading related to the filter causality, symbol echoes due to in-band ripples, and ISI amplification due to outlier samples in the tails of its impulse response. The performance of the filter is assessed in terms of the power spectrum density (PSD) and compliance with tight SEMs, modulation error rate (MER) and operation in a multi-service asynchronous scheme using a single waveform. The SIR and the effect of filtering on the modulation accuracy are evaluated using OFDM ISDB-T and LTE waveforms. Flexible hardware structures are also proposed for actual implementations. The results show that these pulse shaping methods enable the waveform to exploit the available spectrum fragments and support multiple services without significant performance penalty, which can allow a more flexible air interfaceMestradoTelecomunicações e TelemáticaMestre em Engenharia ElétricaCAPE
Waveform Advancements and Synchronization Techniques for Generalized Frequency Division Multiplexing
To enable a new level of connectivity among machines as well as between people and machines, future wireless applications will demand higher requirements on data rates, response time, and reliability from the communication system. This will lead to a different system design, comprising a wide range of deployment scenarios. One important aspect is the evolution of physical layer (PHY), specifically the waveform modulation. The novel generalized frequency division multiplexing (GFDM) technique is a prominent proposal for a flexible block filtered multicarrier modulation.
This thesis introduces an advanced GFDM concept that enables the emulation of other prominent waveform candidates in scenarios where they perform best. Hence, a unique modulation framework is presented that is capable of addressing a wide range of scenarios and to upgrade the PHY for 5G networks. In particular, for a subset of system parameters of the modulation framework, the problem of symbol time offset (STO) and carrier frequency offset (CFO) estimation is investigated and synchronization approaches, which can operate in burst and continuous transmissions, are designed.
The first part of this work presents the modulation principles of prominent 5G candidate waveforms and then focuses on the GFDM basic and advanced attributes. The GFDM concept is extended towards the use of OQAM, introducing the novel frequency-shift OQAM-GFDM, and a new low complexity model based on signal processing carried out in the time domain. A new prototype filter proposal highlights the benefits obtained in terms of a reduced out-of-band (OOB) radiation and more attractive hardware implementation cost. With proper parameterization of the advanced GFDM, the achieved gains are applicable to other filtered OFDM waveforms.
In the second part, a search approach for estimating STO and CFO in GFDM is evaluated. A self-interference metric is proposed to quantify the effective SNR penalty caused by the residual time and frequency misalignment or intrinsic inter-symbol interference (ISI) and inter-carrier interference (ICI) for arbitrary pulse shape design in GFDM. In particular, the ICI can be used as a non-data aided approach for frequency estimation. Then, GFDM training sequences, defined either as an isolated preamble or embedded as a midamble or pseudo-circular pre/post-amble, are designed. Simulations show better OOB emission and good estimation results, either comparable or superior, to state-of-the-art OFDM system in wireless channels
Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives
© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements
Performance Comparison of Dual Connectivity and Hard Handover for LTE-5G Tight Integration in mmWave Cellular Networks
MmWave communications are expected to play a major role in the Fifth
generation of mobile networks. They offer a potential multi-gigabit throughput
and an ultra-low radio latency, but at the same time suffer from high isotropic
pathloss, and a coverage area much smaller than the one of LTE macrocells. In
order to address these issues, highly directional beamforming and a very
high-density deployment of mmWave base stations were proposed. This Thesis aims
to improve the reliability and performance of the 5G network by studying its
tight and seamless integration with the current LTE cellular network. In
particular, the LTE base stations can provide a coverage layer for 5G mobile
terminals, because they operate on microWave frequencies, which are less
sensitive to blockage and have a lower pathloss. This document is a copy of the
Master's Thesis carried out by Mr. Michele Polese under the supervision of Dr.
Marco Mezzavilla and Prof. Michele Zorzi. It will propose an LTE-5G tight
integration architecture, based on mobile terminals' dual connectivity to LTE
and 5G radio access networks, and will evaluate which are the new network
procedures that will be needed to support it. Moreover, this new architecture
will be implemented in the ns-3 simulator, and a thorough simulation campaign
will be conducted in order to evaluate its performance, with respect to the
baseline of handover between LTE and 5G.Comment: Master's Thesis carried out by Mr. Michele Polese under the
supervision of Dr. Marco Mezzavilla and Prof. Michele Zorz
Sensing Integrated DFT-Spread OFDM Waveform and Deep Learning-powered Receiver Design for Terahertz Integrated Sensing and Communication Systems
Terahertz (THz) communications are envisioned as a key technology of
next-generation wireless systems due to its ultra-broad bandwidth. One step
forward, THz integrated sensing and communication (ISAC) system can realize
both unprecedented data rates and millimeter-level accurate sensing. However,
THz ISAC meets stringent challenges on waveform and receiver design to fully
exploit the peculiarities of THz channel and transceivers. In this work, a
sensing integrated discrete Fourier transform spread orthogonal frequency
division multiplexing (SI-DFT-s-OFDM) system is proposed for THz ISAC, which
can provide lower peak-to-average power ratio than OFDM and is adaptive to
flexible delay spread of the THz channel. Without compromising communication
capabilities, the proposed SI-DFT-s-OFDM realizes millimeter-level range
estimation and decimeter-per-second-level velocity estimation accuracy. In
addition, the bit error rate (BER) performance is improved by 5 dB gain at the
BER level compared with OFDM. At the receiver, a deep learning based
ISAC receiver with two neural networks is developed to recover transmitted data
and estimate target range and velocity, while mitigating the imperfections and
non-linearities of THz systems. Extensive simulation results demonstrate that
the proposed deep learning methods can realize mutually enhanced performance
for communication and sensing, and is robust against Doppler effects, phase
noise, and multi-target estimation
D4.1 Draft air interface harmonization and user plane design
The METIS-II project envisions the design of a new air interface in order to fulfil all the performance requirements of the envisioned 5G use cases including some extreme low latency use cases and ultra-reliable transmission, xMBB requiring additional capacity that is only available in very high frequencies, as well as mMTC with extremely densely distributed sensors and very long battery life requirements. Designing an adaptable and flexible 5G Air Interface (AI), which will tackle these use cases while offering native multi-service support, is one of the key tasks of METIS-II WP4. This deliverable will highlight the challenges of designing an AI required to operate in a wide range of spectrum bands and cell sizes, capable of addressing the diverse services with often diverging requirements, and propose a design and suitability assessment framework for 5G AI candidates.Aydin, O.; Gebert, J.; Belschner, J.; Bazzi, J.; Weitkemper, P.; Kilinc, C.; Leonardo Da Silva, I.... (2016). D4.1 Draft air interface harmonization and user plane design. https://doi.org/10.13140/RG.2.2.24542.0288
Filtered Multicarrier Transmission
Orthogonal frequency‐division multiplexing (OFDM) has been adopted as the waveform of choice in the existing and emerging broadband wireless communication systems for a number of advantages it can offer. Nevertheless, investigations of more advanced multicarrier transmission schemes have continued with the aim of eliminating or mitigating its essential limitations. This article discusses multicarrier schemes with enhanced spectrum localization, which manage to reduce the spectral sidelobes of plain OFDM that are problematic in various advanced communication scenarios. These include schemes for enhancing the OFDM waveform characteristics through additional signal processing as well as filter‐bank multicarrier (FBMC) waveforms utilizing frequency‐selective filter banks instead of plain (inverse) discrete Fourier transform processing for waveform generation and demodulation.acceptedVersionPeer reviewe
Estudo de formas de onda e conceção de algoritmos para operação conjunta de sistemas de comunicação e radar
The focus of this thesis is the processing of signals and design of algorithms
that can be used to enable radar functions in communications systems.
Orthogonal frequency division multiplexing (OFDM) is a popular multicarrier
modulation waveform in communication systems. As a wideband
signal, OFDM improves resolution and enables spectral efficiency in radar
systems, while also improving detection performance thanks to its inherent
frequency diversity. This thesis aims to use multicarrier waveforms for radar
systems, to enable the simultaneous operation of radar and communication
functions on the same device. The thesis is divided in two parts. The first
part, studies the adaptation and application of other multicarrier waveforms
to radar functions. At the present time many studies have been carried out
to jointly use the OFDM signal for communication and radar functions, but
other waveforms have shown to be possible candidates for communication
applications. Therefore, studies on the evaluation of the application of these
same signals to radar functions are necessary. In this thesis, to demonstrate
that other multicarrier waveforms can overcome the OFDM waveform
in radar/communication (RadCom) systems, we propose the adaptation of
the filter bank multicarrier (FBMC), generalized frequency division multiplexing
(GFDM) and universal filtering multicarrier (UFMC) waveforms for radar
functions. These alternative waveforms were compared performance-wise
regarding achievable target parameter estimation performance, amount of
residual background noise in the radar image, impact of intersystem interference
and flexibility of parameterization. In the second part of the thesis,
signal processing techniques are explored to solve some of the limitations
of the use of multicarrier waveforms for RadCom systems. Radar systems
based on OFDM are promising candidates for future intelligent transport networks.
Exploring the dual functionality enabled by OFDM, we presents cooperative
methods for high-resolution delay-Doppler and direction-of-arrival
estimation. High-resolution parameter estimation is an important requirement
for automotive radar systems, especially in multi-target scenarios that
require reliable target separation performance. By exploring the cooperation
between vehicles, the studies presented in this thesis also enable the distributed
tracking of targets. The result is a highly accurate multi-target tracking
across the entire cooperative vehicle network, leading to improvements
in transport reliability and safety.O foco desta tese é o processamento de sinais e desenvolvimento de algoritmos
que podem ser utilizados para a habilitar a função de radar nos sistemas
de comunicação. OFDM (Orthogonal Frequency Division Multiplexing)
é uma forma de onda com modulação multi-portadora, popular em sistemas
de comunicação. Para sistemas de radar, O OFDM melhora a resolução e
fornece eficiência espectral, além disso sua diversidade de frequências melhora
o desempenho na detecção do radar. Essa tese tem como objetivo
utilizar formas de onda multi-portadoras para sistemas de radar, possibilitando
a operação simultânea de funções de radar e de comunicação num
mesmo dispositivo. A tese esta dividida em duas partes. Na primeira parte
da tese são realizados estudos da adaptabilidade de outras formas de onda
multi-portadora para funções de radar. Nos dias atuais, muitos estudos sobre
o uso do sinal OFDM para funções de comunicação e radar vêm sendo
realizados, no entanto, outras formas de onda mostram-se possíveis candidatas
a aplicações em sistemas de comunicação, e assim, avaliações para
funções de sistema de radar se tornam necessárias. Nesta tese, com a
intenção de demonstrar que formas de onda multi-portadoras alternativas
podem superar o OFDM nos sistemas de Radar/comunicação (RadCom),
propomos a adaptação das seguintes formas de onda: FBMC (Filter Bank
Multicarrier); GFDM (Generalized Frequency Division Multiplexing); e UFMC
(Universal Filtering Multicarrier) para funções de radar. Também produzimos
uma análise de desempenho dessas formas de onda sobre o aspecto
da estimativa de parâmetros-alvo, ruído de fundo, interferência entre sistemas
e parametrização do sistema. Na segunda parte da tese serão explorados
técnicas de processamento de sinal de forma a solucionar algumas
das limitações do uso de formas de ondas multi-portadora para sistemas
RadCom. Os sistemas de radar baseados no OFDM são candidatos
promissores para futuras redes de transporte inteligentes, porque combinam
funções de estimativa de alvo com funções de rede de comunicação
em um único sistema. Explorando a funcionalidade dupla habilitada pelo
OFDM, nesta tese, apresentamos métodos cooperativos de alta resolução
para estimar o posição, velocidade e direção dos alvos. A estimativa de
parâmetros de alta resolução é um requisito importante para sistemas de
radar automotivo, especialmente em cenários de múltiplos alvos que exigem
melhor desempenho de separação de alvos. Ao explorar a cooperação entre
veículos, os estudos apresentados nesta tese também permitem o rastreamento
distribuído de alvos. O resultado é um rastreamento multi-alvo altamente
preciso em toda a rede de veículos cooperativos, levando a melhorias
na confiabilidade e segurança do transporte.Programa Doutoral em Telecomunicaçõe
A reduced reference video quality assessment method for provision as a service over SDN/NFV-enabled networks
139 p.The proliferation of multimedia applications and services has generarted a noteworthy upsurge in network traffic regarding video content and has created the need for trustworthy service quality assessment methods. Currently, predominent position among the technological trends in telecommunication networkds are Network Function Virtualization (NFV), Software Defined Networking (SDN) and 5G mobile networks equipped with small cells. Additionally Video Quality Assessment (VQA) methods are a very useful tool for both content providers and network operators, to understand of how users perceive quality and this study the feasibility of potential services and adapt the network available resources to satisfy the user requirements
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