60 research outputs found
Energy Efficiency of Generalized Spatial Modulation Aided Massive MIMO Systems
One of focuses in green communication studies is the energy efficiency (EE)
of massive multiple-input multiple-output (MIMO) systems. Although the massive
MIMO technology can improve the spectral efficiency (SE) of cellular networks
by configuring a large number of antennas at base stations (BSs), the energy
consumption of radio frequency (RF) chains increases dramatically. The
increment of energy consumption is caused by the increase of RF chain number to
match the antenna number in massive MIMO communication systems. To overcome
this problem, a generalized spatial modulation (GSM) solution is presented to
simultaneously reduce the number of RF chains and maintain the SE of massive
MIMO communication systems. A EE model is proposed to estimate the transmission
and computation power of massive MIMO communication systems with GSM.
Simulation results demonstrate that the EE of massive MIMO communication
systems with GSM outperforms the massive MIMO communication systems without
GSM. Besides, the computation power consumed by massive MIMO communication
systems with GSM is effectively reduced
D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies
This document provides the most recent updates on the technical contributions and research
challenges focused in WP3. Each Technology Component (TeC) has been evaluated
under possible uniform assessment framework of WP3 which is based on the simulation guidelines
of WP6. The performance assessment is supported by the simulation results which are in their
mature and stable state. An update on the Most Promising Technology Approaches (MPTAs)
and their associated TeCs is the main focus of this document. Based on the input of all the TeCs in WP3, a consolidated view of WP3 on the role of multinode/multi-antenna transmission
technologies in 5G systems has also been provided. This consolidated view is further
supported in this document by the presentation of the impact of MPTAs on METIS scenarios
and the addressed METIS goals.Aziz, D.; Baracca, P.; De Carvalho, E.; Fantini, R.; Rajatheva, N.; Popovski, P.; Sørensen, JH.... (2015). D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675
Spectral and Energy Efficient Communication Systems and Networks
In this thesis, design and analysis of energy- and spectral-efficient communication and cellular systems in micro wave and millimeter wave bands are considered using the following system performance metrics: i) Energy efficiency; ii) Spectral efficiency; iii) Spatial spectral efficiency; iv) Spatial energy efficiency, and v) Bit error rate. Statistical channel distributions, Nakagami-m and Generalized-K, and path loss models, Line of Sight (LOS) and Non-Line of Sight (NLOS), are used to represent the propagation environment in these systems. Adaptive M-QAM and M-CPFSK communication systems are proposed to enhance their efficiency metrics as a function of Signal-to-Noise Ratio (SNR) over the channel. It is observed that in the adaptive M-QAM system energy efficiency can be improved by 0.214 bits/J whereas its spectral efficiency can be enhanced by 40%, for wide range of SNR compared to that of conventional M-QAM system. In case of adaptive M-CPFSK system, spectral and energy efficiencies can be increased by 33% and 76%, respectively. A framework for design and analysis of a cellular system, with omni and sectorized antenna systems at Base Station (BS), using its efficiency metrics and coverage probability is presented assuming wireless channel is Nakagami-m fading coupled with path loss and co-channel interference. It is noted that sectorized antenna system at BS enhances energy and spectral efficiencies by nearly 109% and 1.5 bits/s/Hz, respectively, compared to conventional omni antenna system. A Multi-User MIMO cellular system is then investigated and closed-form expressions for its uplink efficiency metrics are derived for fading and shadowing wireless channel environment. It is observed that increasing number of antennas in MIMO system at BS can significantly improve efficiency metrics of cellular system. Finally, a framework for design and analysis of dense mmWave cellular system, in 28 and 73 GHz bands, is presented for efficient utilization of spectrum and power of the system. The efficiency metrics of the system are evaluated for LOS and NLOS links. It is observed that while 28 GHz band is expedient for indoor cellular systems, the 73 GHz band is appropriate for outdoor systems
Performance analysis of NOMA-based land mobile satellite networks
Non-orthogonal multiple access (NOMA) scheme, which has the ability to superpose information in the power domain and serve multiple users on the same time/frequency resource, is regarded as an effective solution to increase transmit rate and fairness. In this paper, we introduce the NOMA scheme in a downlink land mobile satellite (LMS) network and present a comprehensive performance analysis for the considered system. Specifically, we first obtain the power allocation coefficients by maximizing the sum rate while meeting the predefined target rates of each NOMA user. Then, we derive the theoretical expressions for the ergodic capacity and the energy efficiency of the considered system. Moreover, the outage probability (OP) and average symbol error rate performances of NOMA users are derived analytically. To gain further insights, we derive the asymptotic OP at the high signal-to-noise ratio regime to characterize the diversity orders and coding gains of NOMA users. Finally, simulation results are provided to validate the theoretical analysis as well as the superiority of employing the NOMA scheme in the LMS system, and show the impact of key parameters, such as fading configurations and user selection strategy on the performance of NOMA users
6G Wireless Systems: Vision, Requirements, Challenges, Insights, and Opportunities
Mobile communications have been undergoing a generational change every ten
years or so. However, the time difference between the so-called "G's" is also
decreasing. While fifth-generation (5G) systems are becoming a commercial
reality, there is already significant interest in systems beyond 5G, which we
refer to as the sixth-generation (6G) of wireless systems. In contrast to the
already published papers on the topic, we take a top-down approach to 6G. We
present a holistic discussion of 6G systems beginning with lifestyle and
societal changes driving the need for next generation networks. This is
followed by a discussion into the technical requirements needed to enable 6G
applications, based on which we dissect key challenges, as well as
possibilities for practically realizable system solutions across all layers of
the Open Systems Interconnection stack. Since many of the 6G applications will
need access to an order-of-magnitude more spectrum, utilization of frequencies
between 100 GHz and 1 THz becomes of paramount importance. As such, the 6G
eco-system will feature a diverse range of frequency bands, ranging from below
6 GHz up to 1 THz. We comprehensively characterize the limitations that must be
overcome to realize working systems in these bands; and provide a unique
perspective on the physical, as well as higher layer challenges relating to the
design of next generation core networks, new modulation and coding methods,
novel multiple access techniques, antenna arrays, wave propagation,
radio-frequency transceiver design, as well as real-time signal processing. We
rigorously discuss the fundamental changes required in the core networks of the
future that serves as a major source of latency for time-sensitive
applications. While evaluating the strengths and weaknesses of key 6G
technologies, we differentiate what may be achievable over the next decade,
relative to what is possible.Comment: Accepted for Publication into the Proceedings of the IEEE; 32 pages,
10 figures, 5 table
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
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