115 research outputs found
On Investigations of Machine Learning and Deep Learning Techniques for MIMO Detection
This paper reviews in detail the various types of multiple input multiple output (MIMO) detector algorithms. The current MIMO detectors are not suitable for massive MIMO (mMIMO) scenarios where there are a large number of antennas. Their performance degrades with the increase in number of antennas in the MIMO system. For combatting the issues, machine learning (ML) and deep learning (DL) based detection algorithms are being researched and developed. An extensive survey of these detectors is provided in this paper, alongwith their advantages and challenges. The issues discussed have to be resolved before using them for final deployment
Performance Analysis of Massive MIMO-OFDM System Incorporated with Various Transforms for Image Communication in 5G Systems
Modern-day applications of fifth-generation (5G) and sixth-generation (6G) systems require fast, efficient, and robust transmission of multimedia information over wireless communication medium for both mobile and fixed users. The hybrid amalgamation of massive multiple input multiple output (mMIMO) and orthogonal frequency division multiplexing (OFDM) proves to be an impressive methodology for fulfilling the needs of 5G and 6G users. In this paper, the performance of the hybrid combination of massive MIMO and OFDM schemes augmented with fast Fourier transform (FFT), fractional Fourier transform (FrFT) or discrete wavelet transform (DWT) is evaluated to study their potential for reliable image communication. The analysis is carried over the Rayleigh fading channels and M-ary phase-shift keying (M-PSK) modulation schemes. The parameters used in our analysis to assess the outcome of proposed versions of OFDM-mMIMO include signal-to-noise ratio (SNR) vs. peak signal-to-noise ratio (PSNR) and SNR vs. structural similarity index measure (SSIM) at the receiver. Our results indicate that massive MIMO systems incorporating FrFT and DWT can lead to higher PSNR and SSIM values for a given SNR and number of users, when compared with in contrast to FFT-based massive MIMO-OFDM systems under the same conditions.publishersversionpublishe
Massive Access in Media Modulation Based Massive Machine-Type Communications
The massive machine-type communications (mMTC) paradigm based on media
modulation in conjunction with massive MIMO base stations (BSs) is emerging as
a viable solution to support the massive connectivity for the future
Internet-of-Things, in which the inherent massive access at the BSs poses
significant challenges for device activity and data detection (DADD). This
paper considers the DADD problem for both uncoded and coded media modulation
based mMTC with a slotted access frame structure, where the device activity
remains unchanged within one frame. Specifically, due to the slotted access
frame structure and the adopted media modulated symbols, the access signals
exhibit a doubly structured sparsity in both the time domain and the modulation
domain. Inspired by this, a doubly structured approximate message passing
(DS-AMP) algorithm is proposed for reliable DADD in the uncoded case. Also, we
derive the state evolution of the DS-AMP algorithm to theoretically
characterize its performance. As for the coded case, we develop a
bit-interleaved coded media modulation scheme and propose an iterative DS-AMP
(IDS-AMP) algorithm based on successive inference cancellation (SIC), where the
signal components associated with the detected active devices are successively
subtracted to improve the data decoding performance. In addition, the channel
estimation problem for media modulation based mMTC is discussed and an
efficient data-aided channel state information (CSI) update strategy is
developed to reduce the training overhead in block fading channels. Finally,
simulation results and computational complexity analysis verify the superiority
of the proposed algorithms in both uncoded and coded cases. Also, our results
verify the validity of the proposed data-aided CSI update strategy.Comment: Accepted by IEEE Transactions on Wireless Communications. The codes
and some other materials about this work may be available at
https://gaozhen16.github.i
Cooperative multiterminal radar and communication: a new paradigm for 6G mobile networks
The impending spectrum congestion imposed by the emergence of new
bandwidth-thirsty applications may be mitigated by the integration of radar and
classic communications functionalities in a common system. Furthermore, the
merger of a sensing component into wireless communication networks has raised
interest in recent years and it may become a compelling design objective for
6G. This article presents the evolution of the hitherto separate radar and
communication systems towards their amalgam known as a joint radar and
communication (RADCOM) system. Explicitly, we propose to integrate a radio
sensing component into 6G. We consider an ultra-dense network (UDN) scenario
relying on an active multistatic radar configuration and on cooperation between
the access points across the entire coverage area. The technological trends
required to reach a feasible integration, the applications anticipated and the
open research challenges are identified, with an emphasis on high-accuracy
network synchronization. The successful integration of these technologies would
facilitate centimeter-level resolution, hence supporting compelling
high-resolution applications for next-generation networks, such as robotic cars
and industrial assembly lines.publishe
Equalizador híbrido na banda das ondas milimétricas para sistemas GFDM
Wireless communication using very-large multiple-input multiple-output
(MIMO) antennas has been regarded as one of the enabling technologies
for the future mobile communication. It refers to the idea of equipping
cellular base stations (BSs) with a very large number of antennas giving the
possibility to focusing the transmitted signal energy into very short-range
areas, which will provide huge improvements in the capacity, in addition
to the spectral and energy efficiency. Concurrently, this demand for high
data rates and capacity led to the necessity of exploiting the enormous
amount of spectrum in the millimeter wave (mmWave) bands. However,
the combination of millimeter-wave communications arrays with a massive
number of antennas has the potential to dramatically enhance the features
of wireless communication. This combination implies high cost and power
consumption in the conventional full digital architecture, where each RF chain
is dedicated to one antenna. The solution is the use of a hybrid architecture,
where a small number of RF chains are connected to a large number of
antennas through a network of phase shifters.
On the other hand, another important factor that affect the transmission
quality is the modulation technique, which plays an important role in the
performance of the transmission process, for instance, GFDM is a flexible
non-orthogonal multicarrier modulation concept, that introduces additional
degrees of freedom when compared to other multicarrier techniques. This
flexibility makes GFDM a promising solution for the future cellular generations,
because it can achieve different requirements, such as higher spectrum
efficiency, better control of out-of-band (OOB) emissions, as well as achieving
low peak to average power ratio (PAPR).
In this work, we present an analog-digital transmitter and receiver structures.
Considering a GFDM modulation technique to be implemented in the digital
part, while in the analog part, we propose a full connected hybrid multiuser
linear equalizer, combined with low complexity hybrid precoder for wideband
millimeter-wave massive MIMO systems. The hybrid equalizer is optimized by
minimizing the mean square error between the hybrid approach and the full
digital counterpart.
The results show that the performance of the proposed hybrid scheme is very
close to the full digital counterpart and the gap reduces as the number of RF
chains increases.O uso de um número elevado de antenas, também designado por MIMO
massivo, tem sido considerada uma das tecnologias mais promissoras para
os futuros sistemas de comunicação sem fios. Esta tecnologia, refere-se à
ideia de equipar as estações base (BSs) com um número muito grande de
antenas, dando a possibilidade de focar a energia do sinal transmitido em
áreas de alcance muito restritas, o que proporcionará grandes melhorias na
capacidade, além das espectrais e eficiência energética. Simultaneamente,
a exigência por taxas de dados elevadas e capacidade levou à necessidade
de explorar uma enorme quantidade de espectro nas bandas de ondas
milimétricas (mmWave). A combinação de comunicação na banda das ondas
milimétricas com terminais equipados com um grande número de antenas
tem o potencial de melhorar drasticamente os recursos da comunicação sem
fios. Considerando no entanto uma arquitetura digital, usada em sistemas
MIMO convencionais, em que cada cadeia de RF é dedicada a uma antena,
implica um custo e um consumo de energia elevados. A solução é o uso
de uma arquitetura híbrida, na qual um pequeno número de cadeias de
RF é conectado a um grande número de antenas através de um conjunto
de deslocadores de fase. Outro fator importante que afeta a qualidade da
transmissão é a técnica de modulação usada, que desempenha um papel
importante no desempenho do processo de transmissão. O GFDM é um
conceito de modulação de portadora múltipla, não ortogonal e flexível, que
introduz graus de liberdade adicionais, quando comparado a outras técnicas
de portadora múltipla, como o OFDM. Essa flexibilidade faz do GFDM uma
solução promissora para as futuras gerações celulares, pois pode atender
a diferentes requisitos, como maior eficiência de espectro, melhor controle
das emissões fora de banda (OOB), além de atingir baixo rácio de potência
média / pico ( PAPR).
Neste trabalho, é assumido uma arquitetura hibrida no transmissor e
recetor. Considera-se uma técnica de modulação GFDM a ser implementada
na parte digital, enquanto na parte analógica, é proposto um equalizador
linear híbrido multiutilizador totalmente conectado, i.e., cada cadeia RF
está ligada a todas as antenas, combinado com um pré-codificador híbrido,
de baixa complexidade para sistemas MIMO massivo de banda larga. O
equalizador híbrido é otimizado, minimizando o erro quadrático médio entre a
abordagem híbrida e a contraparte totalmente digital. Os resultados mostram
que o desempenho do esquema híbrido proposto está muito próximo do
equivalente digital, à medida que o número de cadeias de RF aumenta.Mestrado em Engenharia Eletrónica e Telecomunicaçõe
Towards a new cloud-based planning and optimization methodology for mobile communication networks
The great concern of telecommunication operators to offer high-quality services
to their customers requires a constant care with the state of the networks. These
networks can present some problems that imply that the experience offered to customers is unsatisfactory. In order to monitor these situations, operators collect, on
a fairly regular basis, data, like drive tests, that allow them to monitor and correct
minor issues. This thesis takes advantage of the data collected and uses it in network planning in order to precisely obtain the coverage estimation of a network. In
order to automate failure correction mechanisms, a totally automatic propagation
model is presented, which precisely describes the state of the network, allowing it
to be used for network planning and optimisation. After its implementation, the
model was compared to a second model, generated through Artificial Intelligence,
which is completely agnostic to all telecommunications knowledge. These models,
for the considered scenarios, reached average absolute errors between estimated
and actual values of 6.1 dB with a standard deviation of 4 dB.
The existence of several real telecommunication network measures and their
evolution to Multiple Input, Multiple Output (MIMO) systems motivated not only
the investigation on the coverage impact with the change from a Single Input, Single Output (SISO) to a MIMO system, but also the investigation on the reduction
of complexity of the receivers used in MIMO systems. The closer the Bit Error
Rate performance of the receiver is to the Matched Filter Bound, the smaller will
be the reduction in the coverage area with the transition from a SISO system to
a MIMO system.A grande preocupação dos operadores de telecomunicações em oferecerem serviços de alta qualidade aos seus clientes leva a um constante cuidado com o estado das redes. Estas redes podem apresentar alguns problemas que implicam que a
experiência oferecida aos clientes seja desagradável. De forma a monitorizar estas situações, os operadores recolhem, com bastante regularidade, dados, como "drive tests", que lhes permitem avaliar e corrigir pequenos problemas. Esta tese aproveita
os dados recolhidos e utiliza-os no planeamento da rede de forma a obter fielmente a estimativa de cobertura de uma rede. De forma a automatizar mecanismos de correção de falhas, é apresentado um modelo de propagação completamente automático, que descreve de forma precisa o estado da rede permitindo que seja aplicado em algoritmos de planeamento e otimização da rede. Após a sua implementação, este modelo foi comparado com um segundo modelo, gerado através de inteligência artificial, que é completamente agnóstico a todo o conhecimento de telecomunicações. Estes modelos, para os cenários estudados, atingiram erros absolutos médios entre os valores estimados e os valores reais de 6.1 dB com um desvio padrão de 4 dB.
A existência de diversos dados reais das redes de telecomunicações e a evolução para os sistemas "Multiple Input", "Multiple Output" (MIMO) motivou não só a investigação no impacto da cobertura com a mudança de um sistema "Single Input",
"Single Output" (SISO) para um sistema MIMO, mas também a investigação na redução de complexidade dos recetores utilizados em sistemas MIMO. Quanto mais próxima a "Bit Error Rate performance" do recetor estiver do "Matched Filter Bound",
menor será a redução na área de cobertura com a transição de um sistema SISO para um sistema MIMO
A Tutorial
Funding Information: This work is funded by FCT/MCTES through national funds and when applicable co-funded EU funds under the projects UIDB/EEA/50008/2020 and 2022.03897.PTDC. Funding Information: We acknowledge the support of FCT/MCTES, as described above in funding. We also acknowledge the support of Autonoma TechLab for providing an interesting environment to carry out this research. Publisher Copyright: © 2022 by the authors.This is a tutorial on current techniques that use a huge number of antennas in intelligent reflecting surfaces (IRS), large intelligent surfaces (LIS), and radio stripes (RS), highlighting the similarities, differences, advantages, and drawbacks. A comparison between IRS, LIS, and RS is performed in terms of the implementation and capabilities, in the form of a tutorial. We begin by introducing the IRS, LIS, and RS as promising technologies for 6 G wireless technology. Then, we will look at how the three notions are applied in wireless networks. We discuss various performance indicators and methodologies for characterizing and improving the performance of IRS, LIS, and RS-assisted wireless networks. We cover rate maximization, power consumption reduction, and cost implementation concerns in order to take advantage of the performance increase. Furthermore, we extend the discussion to some cases of emerging use. In the description of the three concepts, IRS-assisted communication was introduced as a passive system, considering the capacity/data rate, with power optimization being an advantage, while channel estimation was a challenge. LIS is an active component that goes beyond massive MIMO; a recent study found that channel estimation issues in IRS had improved. In comparison to IRS, capacity enhancement is a highlight, and user interference showed a trend of decreasing. However, power consumption due to utilizing power amplifiers has restrictions. The third technique for increasing coverage is cell-free massive MIMO with RS, with easy deployment in communication network structures. It is demonstrated to have suitable energy efficiency and power consumption. Finally, for future work, we further propose expanding the conversation to include some cases of new uses, such as complexity reduction; design and simulation with LDPC code could be a solution to decreasing complexity.publishersversionpublishe
Técnicas de gestão de feixe de onda para sistemas Massive MIMO nas redes 5G NR
The use of Millimeter wave (mmWave) spectrum frequencies is seen as a key enabler technology for the future wireless communication systems to overcome the bandwidth shortage of the sub 6GHz microwave spectrum band, enabling high speed data transmissions in the 5G/6G systems. Nevertheless, mmWave propagation characteristics are associated to significant free-path losses and many more attenuations that become even more harsher as the frequency increases, rendering the communication challenging at this frequencies.
To overcome these distinct disadvantages, multiple antenna arrays are employed to allow beamforming techniques for the transmission of narrower concentrated beams in more precise directions and less interference levels between them, consequently improving the link budget. Thus, to constantly assure that the communication with each device is done using the beam pair that allows the best possible connectivity, a set of Beam Management control procedures is necessary to assure an efficient beamformed connection establishment and its continuous maintenance between the device and the network.
This dissertation will address the description of the Initial Beam Establishment (IBE) BM procedure, focusing the selection of the most suitable transmit-receive beam pair available after completed beam sweeping techniques to measure the different power levels of the received signal. The main goal is to design a new 3GPP-standard compliant beam pair selection algorithm based on SSS angle estimation (BSAE), that makes use of multiple Synchronization Signal Blocks (SSBs) to maximize the Reference Signal Received Power (RSRP) value at the receiver, through the selected beam pair. This optimization is done using the Secondary Synchronization Signals (SSSs) present in each SSB to perform channel estimation in the digital domain (comprising the effects of the analog processing). Afterwards, the combination of those estimations were used to perform the equivalent channel propagation matrix estimation without the analog processing effects. Finally, through the channel propagation matrix, the angle that maximizes the RSRP was determined to compute the most suitable beam through the aggregated response vector.
The obtained results show that the proposed algorithm achieves better performance levels compared to a conventional beam pair selection algorithm. Furthermore, a comparison with an optimal case is also done, i.e., the situation where the channel is known, and the optimal beam pair angle can be determined. Therefore, the similar performance results compared to the optimal case indicates that the proposed algorithm is interesting for practical 5G mmWave mMIMO implementations, according to 3GPP-compliant standards.O uso de frequências na banda das ondas milimétricas é visto como uma tecnologia chave para os futuros sistemas de comunicação móveis, tendo em vista a ultrapassar o problema da escassez de banda a sub-6 GHz, e por permitir as elevadas taxas de dados requeridas para sistemas 5G/6G. Contudo, a propagação deste tipo de ondas está associado a perdas acentuadas em espaço livre e várias atenuações que se tornam cada vez mais significativas com o aumento do valor da frequência, impondo obstáculos à comunicação.
Para ultrapassar estas adversidades, agregados constituídos por múltiplos elementos de antena são implementados por forma a permitir técnicas de formação de feixe e possibilitar a transmissão de feixes mais estreitos e altamente direcionais, diminuindo os níveis de interferência e melhorando consequentemente o link budget. Deste modo, para assegurar constantemente que a comunicação efetuada em cada dispositivo ocorre utilizando o conjunto de feixes que proporciona o melhor nível de conectividade, é então necessário um conjunto de procedimentos de controlo de gestão de feixe, assegurando um estabelecimento eficiente da comunicação e a sua contínua manutenção entre um dispositivo e a rede.
Esta dissertação descreve o procedimento de gestão de feixe conhecido como estabelecimento inicial de feixe, focando o processo de seleção do melhor par de feixe de transmissão-receção disponível após o uso de técnicas de varrimento de feixe por fim a efetuar medições dos diferentes níveis de potência do sinal recebido. O principal objetivo passa pela conceção de um novo algoritmo de estabelecimento de par de feixes baseado em estimações de ângulo (BSAE), que explora o uso de múltiplos SSBs definidos pelo 3GPP, por forma a maximizar o RSRP no recetor, através do feixe selecionado. Esta otimização é feita usando os sinais de sincronização secundários (SSSs) presentes em cada SSB para efetuar uma estimação de canal no domínio digital (que contém o efeito do processamento analógico). Depois, combinando essas estimações, foi feita uma estimação da matriz do canal de propagação, sem o efeito desse processamento analógico. Finalmente, através da matriz do canal de propagação, foi determinado o ângulo que maximiza o RSRP, e calculado o feixe através do vetor de resposta do agregado.
Os resultados obtidos demonstram que o algoritmo proposto atinge melhor desempenho quando comparado com o algoritmo convencional de seleção de par de feixes. Foi feita ainda uma comparação com o caso ótimo, isto é, com o caso em que se conhece completamente o canal e se obtém um ângulo ótimo. Os resultados obtidos pelo algoritmo proposto foram muito próximos do caso ótimo, pelo que é bastante interessante para sistemas práticos 5G mmWave mMIMO, que estejam de acordo com o padrão 3GPP.Mestrado em Engenharia Eletrónica e Telecomunicaçõe
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