290 research outputs found
On Random Sampling for Compliance Monitoring in Opportunistic Spectrum Access Networks
In the expanding spectrum marketplace, there has been a long term evolution towards more market€“oriented mechanisms, such as Opportunistic Spectrum Access (OSA), enabled through Cognitive Radio (CR) technology. However, the potential of CR technologies to revolutionize wireless communications, also introduces challenges based upon the potentially non€“deterministic CR behaviour in the Electrospace. While establishing and enforcing compliance to spectrum etiquette rules are essential to realization of successful OSA networks in the future, there has only been recent increased research activity into enforcement. This dissertation presents novel work on the spectrum monitoring aspect, which is crucial to effective enforcement of OSA. An overview of the challenges faced by current compliance monitoring methods is first presented. A framework is then proposed for the use of random spectral sampling techniques to reduce data collection complexity in wideband sensing scenarios. This approach is recommended as an alternative to Compressed Sensing (CS) techniques for wideband spectral occupancy estimation, which may be difficult to utilize in many practical congested scenarios where compliance monitoring is required. Next, a low€“cost computational approach to online randomized temporal sensing deployment is presented for characterization of temporal spectrum occupancy in cognitive radio scenarios. The random sensing approach is demonstrated and its performance is compared to CS€“based approach for occupancy estimation. A novel frame€“based sampling inversion technique is then presented for cases when it is necessary to track the temporal behaviour of individual CRs or CR networks. Parameters from randomly sampled Physical Layer Convergence Protocol (PLCP) data frames are used to reconstruct occupancy statistics, taking account of missed frames due to sampling design, sensor limitations and frame errors. Finally, investigations into the use of distributed and mobile spectrum sensing to collect spatial diversity to improve the above techniques are presented, for several common monitoring tasks in spectrum enforcement. Specifically, focus is upon techniques for achieving consensus in dynamic topologies such as in mobile sensing scenarios
Analysis, characterization and optimization of the energy efficiency on softwarized mobile platforms
Mención Internacional en el título de doctorLa inminente 5ª generación de sistemas móviles (5G) está a punto de revolucionar la industria, trayendo una nueva arquitectura orientada a los nuevos mercados verticales y servicios. Debido a esto, el 5G Infrastructure Public Private Partnership (5G-PPP) ha especificado una lista de Indicadores de Rendimiento Clave (KPI) que todo sistema 5G tiene que soportar, por ejemplo incrementar por 1000 el volumen de datos, de 10 a 100 veces m´as dispositivos conectados o consumos energéticos 10 veces inferiores. Con el fin de conseguir estos requisitos, se espera expandir los despligues actuales usando mas Puntos de Acceso (PoA) incrementando así su densidad con
múltiples tecnologías inalámbricas. Esta estrategia de despliegue masivo tiene una contrapartida en la eficiencia energética, generando un conflicto con el KPI de reducir por 10 el consumo energético. En este contexto, la comunidad investigadora ha propuesto nuevos paradigmas para alcanzar los requisitos impuestos para los sistemas 5G, siendo materializados en tecnologías como Redes Definidas por Software (SDN) y Virtualización de Funciones de Red (NFV). Estos nuevos paradigmas son el primer paso hacia la softwarización de los despliegues móviles, incorporando nuevos grados de flexibilidad y reconfigurabilidad de la Red de Acceso Radio (RAN). En esta tesis, presentamos primero un análisis detallado y caracterización de las redes móviles softwarizadas. Consideramos el software como la base de la nueva generación de redes celulares y, por lo tanto, analizaremos y caracterizaremos el impacto en la eficiencia energética de estos
sistemas. La primera meta de este trabajo es caracterizar las plataformas software disponibles para Radios Definidas por Software (SDR), centrándonos en las dos soluciones principales de código abierto: OpenAirInterface (OAI) y srsLTE. Como resultado, proveemos una metodología para analizar y caracterizar el rendimiento de estas soluciones en función del uso de la CPU, rendimiento de red, compatibilidad y extensibilidad de dicho software. Una vez hemos entendido
qué rendimiento podemos esperar de este tipo de soluciones, estudiamos un prototipo SDR construido con aceleración hardware, que emplea una plataformas basada en FPGA. Este prototipo está diseñado para incluir capacidad de ser consciente de la energía, permiento al sistema ser reconfigurado para minimizar la huella energética cuando sea posible. Con el fin de validar el diseño de nuestro sistema, más tarde presentamos una plataforma para caracterizar la energía que será empleada para medir experimentalmente el consumo energético de dispositivos reales. En nuestro enfoque, realizamos dos tipos de análisis: a pequeña escala de tiempo y a gran escala de tiempo. Por lo tanto, para validar nuestro entorno de medidas, caracterizamos a través de análisis numérico los algoritmos para la Adaptación de la Tasa (RA) en IEEE 802.11, para entonces comparar
nuestros resultados teóricos con los experimentales. A continuación extendemos nuestro
análisis a la plataforma SDR acelerada por hardware previamente mencionada. Nuestros resultados experimentales muestran que nuestra sistema puede en efecto reducir la huella energética reconfigurando el despligue del sistema.
Entonces, la escala de tiempos es elevada y presentamos los esquemas para Recursos bajo Demanda (RoD) en despliegues de red ultra-densos. Esta estrategia está basada en apagar/encender
dinámicamente los elementos que forman la red con el fin de reducir el total del consumo
energético. Por lo tanto, presentamos un modelo analítico en dos sabores, un modelo exacto que predice el comportamiento del sistema con precisión pero con un alto coste computacional y uno simplificado que es más ligero en complejidad mientras que mantiene la precisión. Nuestros resultados muestran que estos esquemas pueden efectivamente mejorar la eficiencia energética de
los despliegues y mantener la Calidad de Servicio (QoS). Con el fin de probar la plausibilidad
de los esquemas RoD, presentamos un plataforma softwarizada que sigue el paradigma SDN,
OFTEN (OpenFlow framework for Traffic Engineering in mobile Network with energy awareness).
Nuestro diseño está basado en OpenFlow con funcionalidades para hacerlo consciente de
la energía. Finalmente, un prototipo real con esta plataforma es presentando, probando así la plausibilidad de los RoD en despligues reales.The upcoming 5th Generation of mobile systems (5G) is about to revolutionize the industry,
bringing a new architecture oriented to new vertical markets and services. Due to this, the 5G-PPP
has specified a list of Key Performance Indicator (KPI) that 5G systems need to support e.g. increasing
the 1000 times higher data volume, 10 to 100 times more connected devices or 10 times
lower power consumption. In order to achieve these requirements, it is expected to expand the
current deployments using more Points of Attachment (PoA) by increasing their density and by
using multiple wireless technologies. This massive deployment strategy triggers a side effect in
the energy efficiency though, generating a conflict with the “10 times lower power consumption”
KPI. In this context, the research community has proposed novel paradigms to achieve the imposed
requirements for 5G systems, being materialized in technologies such as Software Defined
Networking (SDN) and Network Function Virtualization (NFV). These new paradigms are the
first step to softwarize the mobile network deployments, enabling new degrees of flexibility and
reconfigurability of the Radio Access Network (RAN).
In this thesis, we first present a detailed analysis and characterization of softwarized mobile
networking. We consider software as a basis for the next generation of cellular networks and
hence, we analyze and characterize the impact on the energy efficiency of these systems. The
first goal of this work is to characterize the available software platforms for Software Defined
Radio (SDR), focusing on the two main open source solutions: OAI and srsLTE. As result, we
provide a methodology to analyze and characterize the performance of these solutions in terms
of CPU usage, network performance, compatibility and extensibility of the software. Once we
have understood the expected performance for such platformsc, we study an SDR prototype built
with hardware acceleration, that employs a FPGA based platform. This prototype is designed
to include energy-awareness capabilites, allowing the system to be reconfigured to minimize the
energy footprint when possible. In order to validate our system design, we later present an energy
characterization platform that we will employ to experimentally measure the energy consumption
of real devices. In our approach, we perform two kind of analysis: at short time scale and large
time scale. Thus, to validate our approach in short time scale and the energy framework, we have
characterized though numerical analysis the Rate Adaptation (RA) algorithms in IEEE 802.11,
and then compare our theoretical results to the obtained ones through experimentation. Next
we extend our analysis to the hardware accelerated SDR prototype previously mentioned. Our experimental results show that our system can indeed reduce the energy footprint reconfiguring
the system deployment.
Then, the time scale of our analysis is elevated and we present Resource-on-Demand (RoD)
schemes for ultradense network deployments. This strategy is based on dynamically switch on/off
the elements that form the network to reduce the overall energy consumption. Hence, we present
a analytic model in two flavors, an exact model that accurately predicts the system behaviour
but high computational cost and a simplified one that is lighter in complexity while keeping the
accuracy. Our results show that these schemes can effectively enhance the energy efficiency of
the deployments and mantaining the Quality of Service (QoS). In order to prove the feasibility of
RoD, we present a softwarized platform that follows the SDN paradigm, the OFTEN (Open Flow
framework for Traffic Engineering in mobile Networks with energy awareness) framework. Our
design is based on OpenFlow with energy-awareness functionalities. Finally, a real prototype of
this framework is presented, proving the feasibility of the RoD in real deployments.FP7-CROWD (2013-2015) CROWD (Connectivity management for eneRgy Optimised Wireless Dense networks).-- H2020-Flex5GWare (2015-2017) Flex5GWare (Flexible and efficient hardware/software platforms for 5G network elements and devices).Programa de Doctorado en Ingeniería Telemática por la Universidad Carlos III de MadridPresidente: Gramaglia , Marco.- Secretario: José Nuñez.- Vocal: Fabrizio Giulian
Performance issues in hybrid fiber radio communication systems due to nonlinear distortion effects in laser transmitters
With the increasing demand for broadband services, it is expected that hybrid fiber radio systems may be employed to provide high capacity access networks for both mobile and fixed users. In these systems, the radio frequency data signals are modulated onto an optical carrier at a mobile switching centre and then sent over fiber to a number of base stations, before being transmitted over air to the users. A possible method of generating the optical radio frequency data signals for distribution over fiber is to directly modulate the electrical signal onto an optical carrier using a laser diode. The major problem with this technique is that nonlinearities in electncal-to-optical conversion may seriously degrade the system performance.
In this work we initially examined the distribution of a wideband code division multiple access signal (centered around 6 GHz) through an optically fed microwave system. Our results show that the adjacent channel leakage ratio is degraded from -52 to -32 dBc after passing through the optical system. We then examined the technique of externally injecting light into the directly modulated laser, to extend the bandwidth of the laser diode and hence, increase it’s linear region to beyond the frequency of interest With this technique an improvement of over 10 dB in the adjacent channel leakage ratio of the signal was achieved. We subsequently went on to examine the distribution of a 5-channel radio frequency signal (each channel carrying 10 Mbit/s) through a hybrid fiber system As in the previous work, we examined how external light injection into the directly modulated laser could be used to improve system performance, and our results show an improvement of up to 5 dB.
Finally a model was designed using Matlab, which simulated the 5-channel system mentioned above. It used the laser rate equations to mimic the nonlinear effects of the laser diode Good correlation was observed between experimental and simulated results
Self-Evaluation Applied Mathematics 2003-2008 University of Twente
This report contains the self-study for the research assessment of the Department of Applied Mathematics (AM) of the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) at the University of Twente (UT). The report provides the information for the Research Assessment Committee for Applied Mathematics, dealing with mathematical sciences at the three universities of technology in the Netherlands. It describes the state of affairs pertaining to the period 1 January 2003 to 31 December 2008
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