137 research outputs found
Spectrum cartography techniques, challenges, opportunities, and applications: A survey
The spectrum cartography finds applications in several areas such as cognitive radios, spectrum aware communications, machine-type communications, Internet of Things, connected vehicles, wireless sensor networks, and radio frequency management systems, etc. This paper presents a survey on state-of-the-art of spectrum cartography techniques for the construction of various radio environment maps (REMs). Following a brief overview on spectrum cartography, various techniques considered to construct the REMs such as channel gain map, power spectral density map, power map, spectrum map, power propagation map, radio frequency map, and interference map are reviewed. In this paper, we compare the performance of the different spectrum cartography methods in terms of mean absolute error, mean square error, normalized mean square error, and root mean square error. The information presented in this paper aims to serve as a practical reference guide for various spectrum cartography methods for constructing different REMs. Finally, some of the open issues and challenges for future research and development are discussed.publishedVersio
Reconfigurable Intelligent Surface Assisted High-Speed Train Communications: Coverage Performance Analysis and Placement Optimization
Reconfigurable intelligent surface (RIS) emerges as an efficient and
promising technology for the next wireless generation networks and has
attracted a lot of attention owing to the capability of extending wireless
coverage by reflecting signals toward targeted receivers. In this paper, we
consider a RIS-assisted high-speed train (HST) communication system to enhance
wireless coverage and improve coverage probability. First, coverage performance
of the downlink single-input-single-output system is investigated, and the
closed-form expression of coverage probability is derived. Moreover, travel
distance maximization problem is formulated to facilitate RIS discrete phase
design and RIS placement optimization, which is subject to coverage probability
constraint. Simulation results validate that better coverage performance and
higher travel distance can be achieved with deployment of RIS. The impacts of
some key system parameters including transmission power, signal-to-noise ratio
threshold, number of RIS elements, number of RIS quantization bits, horizontal
distance between base station and RIS, and speed of HST on system performance
are investigated. In addition, it is found that RIS can well improve coverage
probability with limited power consumption for HST communications.Comment: 14 figures, accepted by IEEE Transactions on Vehicular Technolog
Performance Improvement of LeastSquares Adaptive Filter for High-Speed Train Communication Systems
The downlink communication channel from high-altitude platform (HAP) to high-speed train (HST) in the Ka-band is a slowly time-varying Rician distributed flat fading channel with 10-25 dB Rician K factor. In this respect, the received signal is mainly affected by the Doppler shift of the line-of-sight (LOS) link. In order to increase receiver performance, we propose to firstly compensate the Doppler shift of the received signal before least-squares (LS) adaptive filtering is pursued. Implementing the proposed method requires a priori knowledge of the time-varying phase of the LOS component. This is justified since signalling between the train and the controller exists such that the train velocity and location are predictable. Implementing the proposed method to the recursive LS (RLS) received beamforming algorithm shows reduction of mean square error (MSE) and bit error rate (BER)
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin
Diseño y evaluación de nuevas formas e onda para comunicaciones de alta movilidad
Programa Oficial de Doutoramento en Tecnoloxías da Información e Comunicación en Redes Móbiles. 553V01[Resumo]
Os servizos multimedia e de datos experimentaron un crecemento continuo nos últimos anos e espérase
que crezan aínda máis nos anos seguintes. A xente está a usar cada vez máis os seus dispositivos
móbiles para acceder a servizos baseados en datos para fins relacionados co traballo, entretemento ou
socialización en liña. Ademais, as comunicacións masivas de tipo máquina tamén están en ascenso
(por exemplo, as comunicacións en transporte e loxística, sensores, Internet das cousas, etc.), e serán
moi importantes para a nova xeración de sistemas de comunicacións sen fíos. Para afrontar o aumento
esperado no uso de servizos multimedia e baseado en datos, así como para soportar novos casos de uso
que hoxe non son posibles, unha nova xeración de redes sen fíos é necesaria. Para iso, espérase que
os sistemas de comunicación sen fíos 5G traian as melloras necesarias: maiores taxas de datos, baixas
latencias, mellor eficiencia enerxética, alta fiabilidade, etc.
O coñecemento das características da canle sen fíos é fundamental para a planificación das redes
de comunicación sen fíos e o deseño de transceptores. Como primeiro paso, centramos este traballo na
caracterización completa da canle para diferentes escenarios, como son os trens de alta velocidade, metro
e comunicacións vehículo a infraestrutura en estradas. A canle caracterizouse mediante a avaliación da
relación sinal a ruído, a perda de traxecto (path loss) e os chamados parámetros condensados da canle (por
exemplo, o factor K, o perfil potencia-retardo (power delay profile) e a densidade espectral de potencia Doppler. Ademais, para a nova interface aérea das redes 5G, unha das principais cuestións foi a forma de
onda a usar. Finalmente, o 3rd Generation Partnership Project (3GPP) decidiu usar a tecnoloxía de
multiplexación por división de frecuencias ortogonais (OFDM polas súas siglas en inglés). Isto semella
unha elección natural debido ás moitas vantaxes de OFDM e que tamén é a técnica de modulación
empregada nas redes 4G. Con todo, nos últimos anos, esquemas multiportadora baseados en bancos de
filtros (FBMC polas súas siglas en inglés) recibiron unha grande atención como alternativa a OFDM
debido ás súas vantaxes: non utilizan un prefixo cíclico (proporcionan unha maior eficiencia espectral),
os usuarios non precisan ser sincronizados no enlace ascendente, e un mellor rendemento teórico
en contornas de alta velocidade debido a unha menor interferencia entre portadoras. Neste traballo
comparamos experimentalmente o rendemento de FBMC e OFDM en contornas de alta velocidade.
Tamén analizamos o rendemento de FBMC e OFDM no caso de uso práctico dun vehículo aéreo
lixeiro pilotado remotamente. A maior parte do traballo realizado nesta tese requiriu o deseño e
desenvolvemento do chamado GTEC 5G Simulator, que foi usado en conxunto co GTEC Testbed para
realizar a maior parte das campañas de medicións e avaliacións de rendemento mediante transmisións
polo aire.[Resumen]
Los servicios multimedia y basados en datos experimentaron un crecimiento sin interrupciones en los
últimos años, y se espera que crezcan aún más en los años siguientes. Las personas utilizan cada
vez más sus dispositivos móviles para acceder a los servicios basados en datos con fines relacionados
con el trabajo, el entretenimiento o la socialización en línea. Además, las comunicaciones masivas
de tipo máquina también están en aumento (por ejemplo, comunicaciones en transporte y logística,
sensores, Internet de las cosas, etc.) y serán muy importantes para la nueva generación de sistemas de
comunicaciones inalámbricos. Para hacer frente al aumento esperado en el uso de servicios multimedia
y basados en datos, así como para soportar nuevos casos de uso que no son posibles hoy en día, se
requiere una nueva generación de sistemas inalámbricos. Para esto, se espera que los sistemas de
comunicación inalámbrica 5G aporten las mejoras necesarias: mayores tasas de datos, menores latencias,
mejor eficiencia energética, alta fiabilidad, etc.
El conocimiento de las características del canal inalámbrico es fundamental para la planificación de
redes de comunicación inalámbricas y el diseño de transceptores. Como primer paso, centramos este
trabajo en la caracterización completa del canal para diferentes escenarios, tales como trenes de alta
velocidad, metro y comunicaciones vehículo a infraestructura en carreteras. El canal se caracterizó por
medio de la evaluación de la relación señal a ruido, la pérdida de trayecto (path loss) y los llamados
parámetros condensados de canal (por ejemplo, el factor K, el perfil potencia-retardo (power delay
profile) y la densidad espectral de potencia Doppler).
Además, para la nueva interfaz aérea de las redes 5G, una de las preguntas principales ha sido
la forma de onda a usar. Finalmente, el 3rd Generation Partnership Project (3GPP) decidió usar
la tecnología de multiplexación por división de frecuencias ortogonales (OFDM por sus siglas en
inglés). Esta es una elección lógica, debido a las muchas ventajas exhibidas por OFDM y dado que
también es la técnica de modulación empleada en las redes 4G. Sin embargo, en los últimos años, los
esquemas multiportadora basados en bancos de filtros (FBMC por sus siglas en inglés) han recibido
una gran atención como una alternativa a OFDM debido a sus ventajas: no usan un prefijo cíclico (lo que proporciona una mayor eficiencia espectral), los usuarios no necesitan sincronizarse en el
enlace ascendente, y un mejor rendimiento teórico en escenarios de alta velocidad debido a una menor
interferencia entre subportadoras. En este trabajo comparamos experimentalmente el rendimiento de
FBMC y OFDM en entornos de alta velocidad. También analizamos el rendimiento de FBMC y OFDM
en el caso de uso práctico de un vehículo aéreo ligero tripulado remotamente. La mayor parte del trabajo
llevado a cabo en esta tesis requirió el diseño y desarrollo del denominado GTEC 5G Simulator, que se
utilizó junto con el GTEC Testbed para realizar la mayoría de las campañas de medidas y evaluaciones
de rendimiento por medio de transmisiones por aire.[Abstract]
Multimedia and data-based services experienced a non-stopping growth over the last few years and
are expected to grow even more in the following years. People are using more and more their mobile
devices to access data-based services for work-related purposes, entertainment or online socialization.
Moreover, massive machine-type communications are also on the rise (e.g., transport and logistics
communications, sensors, Internet of Things, etc.), and will be very important for the new generation
of wireless communication systems. To cope with the expected increase in the usage of multimedia and
data-based services, as well as to support new use cases which are not possible today, a new generation
of wireless systems is required. For this, 5G wireless communication systems are expected to bring the
necessary improvements: higher data rates, lower latencies, better energy efficiency, high reliability, etc.
Knowledge of the wireless channel characteristics is fundamental for the planning of wireless
communication networks and transceivers design. As a first step, this work centered in the channel
characterization for different scenarios such as high-speed trains, subways, and vehicle-to-infrastructure
in roads. The channel was characterized by means of assessing the signal-to-noise ratio, the path loss,
and the so-called channel condensed parameters (e.g., the K-factor, the power delay profile, and the
Doppler power spectral density).
Moreover, for the new air interface of 5G networks, one of the main questions was the waveform to
be used. Finally, the 3rd Generation Partnership Project (3GPP) decided to use orthogonal frequencydivision
multiplexing (OFDM). This seems a natural choice due to the many advantages exhibited by
OFDM and it is also the modulation technique employed by 4G networks. However, over the last few
years, schemes based on filter bank multicarrier (FBMC) using quadrature amplitude modulation have
received a great attention as an alternative to OFDM due to their advantages: they do not use a cyclic
prefix (thus providing a higher bandwidth efficiency), users do not need to be synchronized in the uplink,
and they achieve a theoretical better performance in high-speed scenarios due to a lower inter-carrier
interference. In this work, we have experimentally compared the performance of FBMC versus OFDM in high-speed scenarios. We have also analyzed the performance of FBMC versus OFDM in the practical
use case of a lightweight remotely piloted aircraft. The majority of the work carried out in this thesis
required the design and development of the so-called GTEC 5G Simulator, which was used in conjunction
with the GTEC Testbed to perform most of the measurement campaigns and performance evaluations by
means of over-the-air transmissions
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin
Channel Fading in Mobile Broadband Systems: Challenges and Opportunities
High-speed data signals transmitted over mobile broadband channels are seriously distorted by both time-varying effect and frequency-selective fading (FSF). These distortions introduce challenges since channel variances in both time-domain and frequency-domain form a two-dimensional channel matrix which is hard to estimate, but meanwhile provide opportunities for information security since all signals are directly encrypted by the channels which are adequately random over time, frequency and space. These challenges and opportunities are studied in this thesis as two parts. In the first part, we propose a novel time-varying channel estimation (TVCE) algorithm named piece-wise time-invariant approximation (PITIA) to estimate a typical type of mobile broadband channels - the high-speed train (HST) channels. PITIA customizes general time-varying channel models according to HST channels' specific features, and outperforms conventional TVCE algorithms by about 3-dB in terms of estimation error. In the second part, we propose the first physical-layer challenge-response authentication mechanism (PHY-CRAM) which uses the mobile broadband channels to prevent eavesdropping during authentication. Since pilots and reference signals are eliminated, eavesdroppers cannot demodulate credential information, while legitimate receivers use the channels' reciprocal property to cancel FSF. PITIA is evaluated by computer based simulations, and the effectiveness of PHY-CRAM is validated by prototyping and real-world experiments. Both pieces of works are built upon a unified system model and orthogonal frequency-division multiplexing (OFDM) modulation.Ph.D.College of Engineering and Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/106584/1/Dissertation_Dan_Shan.pd
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