Context-Aware Adaptive Opportunistic Routing in Mobile Ad-hoc and Sensor Networks

Mobile ad-hoc networks (MANETs) and wireless sensor networks (WSNs) have been attracting increasing attention for decades due to their broad civilian and military applications. Basically, a MANET or WSN is a network of nodes connected by wireless communication links. Due to the limited transmission range of the radio, many pairs of nodes in MANETs or WSNs may not be able to communicate directly, hence they need other intermediate nodes to forward packets for them. Routing in such types of networks is an important issue and it poses great challenges due to the dynamic nature of MANETs or WSNs. On the one hand, the open-air nature of wireless environments brings many difficulties when an efficient routing solution is required. The wireless channel is unreliable due to fading and interferences, which makes it impossible to maintain a quality path from a source node to a destination node. Additionally, node mobility aggravates network dynamics, which causes frequent topology changes and brings significant overheads for maintaining and recalculating paths. Furthermore, mobile devices and sensors are usually constrained by battery capacity, computing and communication resources, which impose limitations on the functionalities of routing protocols. On the other hand, the wireless medium possesses inherent unique characteristics, which can be exploited to enhance transmission reliability and routing performance. Opportunistic routing (OR) is one promising technique that takes advantage of the spatial diversity and broadcast nature of the wireless medium to improve packet forwarding reliability in multihop wireless communication. OR combats the unreliable wireless links by involving multiple neighboring nodes (forwarding candidates) to choose packet forwarders. In opportunistic routing, a source node does not require an end-to-end path to transmit packets. The packet forwarding decision is made hop-by-hop in a fully distributed fashion. Motivated by the deficiencies of existing opportunistic routing protocols in dynamic environments such as mobile ad-hoc networks or wireless sensor networks, this thesis proposes a novel context-aware adaptive opportunistic routing scheme. Our proposal selects packet forwarders by simultaneously exploiting multiple types of cross-layer context information of nodes and environments. Our approach significantly outperforms other routing protocols that rely solely on a single metric. The adaptivity feature of our proposal enables network nodes to adjust their behaviors at run-time according to network conditions. To accommodate the strict energy constraints in WSNs, this thesis integrates adaptive duty-cycling mechanism to opportunistic routing for wireless sensor nodes. Our approach dynamically adjusts the sleeping intervals of sensor nodes according to the monitored traffic load and the estimated energy consumption rate. Through the integration of duty cycling of sensor nodes and opportunistic routing, our protocol is able to provide a satisfactory balance between good routing performance and energy efficiency for WSNs.

A Passive WiFi Source Localization System based on Fine-grained Power-based Trilateration

Indoor localization systems become more interesting for researchers because of the attractiveness of business cases in various application fields. A WiFi-based passive localization system can provide user location information to third-party providers of positioning services. However, indoor localization techniques are prone to multipath and Non-Line Of Sight (NLOS) propagation, which lead to significant performance degradation. To overcome these problems, we provide a passive localization system for WiFi targets with several improved algorithms for localization. Through Software Defined Radio (SDR) techniques, we extract Channel Impulse Response (CIR) information at the physical layer. CIR is later adopted to mitigate the multipath fading problem. We propose to use a Nonlinear Regression (NLR) method to relate the filtered power information to propagation distances, which significantly improves the ranging accuracy compared to the commonly used log-distance path loss model. To mitigate the influence of ranging errors, a new trilateration algorithm is designed as well by combining Weighted Centroid and Constrained Weighted Least Square (WC-CWLS) algorithms. Experiment results show that our algorithm is robust against ranging errors and outperforms the linear least square algorithm and weighted centroid algorithm.

La lectura de la ciudad a través de la literatura

El trabajo intenta acercar la mirada de la literatura hacia la ciudad. Se procura tomar esta mirada como un enfoque para poder "leer" la ciudad desde su "textualidad"; es decir, desde su recorrido para poder posicionarnos en lo que la sociedad va "escribiendo" en cada recorte espacial. Para ello, se indagó sobre la relación de la literatura con la geografía y se tomaron determinadas obras y autores, que desde la literatura han aportado miradas sobre la ciudad, la naturaleza y el paisaje. Encontramos que la literatura y los autores pueden alejarse de la mirada cotidiana y plasmar en papel la otra ciudad, la que la cotidianeidad, la vorágine y la superposición del espacio y el tiempo, nos terminan diluyendo

La lectura de la ciudad a través de la literatura

El trabajo intenta acercar la mirada de la literatura hacia la ciudad. Se procura tomar esta mirada como un enfoque para poder "leer" la ciudad desde su "textualidad"; es decir, desde su recorrido para poder posicionarnos en lo que la sociedad va "escribiendo" en cada recorte espacial. Para ello, se indagó sobre la relación de la literatura con la geografía y se tomaron determinadas obras y autores, que desde la literatura han aportado miradas sobre la ciudad, la naturaleza y el paisaje. Encontramos que la literatura y los autores pueden alejarse de la mirada cotidiana y plasmar en papel la otra ciudad, la que la cotidianeidad, la vorágine y la superposición del espacio y el tiempo, nos terminan diluyendo

La lectura de la ciudad a través de la literatura

El trabajo intenta acercar la mirada de la literatura hacia la ciudad. Se procura tomar esta mirada como un enfoque para poder "leer" la ciudad desde su "textualidad"; es decir, desde su recorrido para poder posicionarnos en lo que la sociedad va "escribiendo" en cada recorte espacial. Para ello, se indagó sobre la relación de la literatura con la geografía y se tomaron determinadas obras y autores, que desde la literatura han aportado miradas sobre la ciudad, la naturaleza y el paisaje. Encontramos que la literatura y los autores pueden alejarse de la mirada cotidiana y plasmar en papel la otra ciudad, la que la cotidianeidad, la vorágine y la superposición del espacio y el tiempo, nos terminan diluyendo

La lectura de la ciudad a través de la literatura

El trabajo intenta acercar la mirada de la literatura hacia la ciudad. Se procura tomar esta mirada como un enfoque para poder "leer" la ciudad desde su "textualidad"; es decir, desde su recorrido para poder posicionarnos en lo que la sociedad va "escribiendo" en cada recorte espacial. Para ello, se indagó sobre la relación de la literatura con la geografía y se tomaron determinadas obras y autores, que desde la literatura han aportado miradas sobre la ciudad, la naturaleza y el paisaje. Encontramos que la literatura y los autores pueden alejarse de la mirada cotidiana y plasmar en papel la otra ciudad, la que la cotidianeidad, la vorágine y la superposición del espacio y el tiempo, nos terminan diluyendo

Working on a baseline for the Kongsfjorden food web: production and properties of macroalgal particulate organic matter (POM), supplementary material

Macroalgae, in particular kelps, produce a large amount of biomass in Kongsfjorden, which is to a great extent released into the water in an annual cycle. As an example, the brown alga Alaria esculenta loses its blade gradually, 3 ± 0.8 % of the blade area per day (August 2012), thereby adding to the pool of particulate organic matter (POM) in the fjord. Upon release small thallus pieces are "aging" in that they are prone to leaching and serving as substrate for microorganisms, thus turning into palatable food for suspension and bottom feeders. In order to define a macroalgal baseline for the Kongsfjorden food web, stable isotopes d14C and d15N were measured in individuals of A. esculenta, Saccharina latissima and Laminaria digitata directly sampled after collection and in artificially produced POM (aPOM) of A. esculenta that was allowed to age under experimental conditions. In aPOM from this species sampled in August 2012 the C/N ratios decreased between d1 and d8 of a 14-day culture period in parallel to the fading photosynthetic activity of the algal fragments as demonstrated by use of an Imaging-PAM. Microscopic observations of the aPOM in August 2012 and 2013 revealed the frequent occurrence of small brown algal endo- and epiphytes. First feeding experiments with Mysis oculata (Mysids) and Hiatella arctica (Bivalves) showed that these species can ingest macroalgal POM. The importance of kelp-derived POM for the food web is subject of the current research.

Modulation-mode Assignment for SVD-assisted Multiuser MIMO Systems with Correlation.

Multiuser multiple-input multiple-output (MIMO) downlink (DL) transmission schemes experience both multiuser interference as well as inter-antenna interference. The singular value decomposition provides an appropriate mean to process channel information and allows us to take the individual user’s channel characteristics into account rather than treating all users channels jointly as in zero-forcing (ZF) multiuser transmission techniques. However, uncorrelated MIMO channels has attracted a lot of attention and reached a state of maturity. By contrast, the performance analysis in the presence of antenna fading correlation, which decreases the channel capacity, requires substantial further research. The joint optimization of the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers has to be activated in order to minimize the overall BER under the constraint of a given fixed data throughput.

Evaluación de las Prestaciones de una Red WiMAX Móvil en un Escenario de Alta Movilidad

The aim of this paper is to evaluate the performance of mobile WiMAX technology for users in a highly mobility scenario for an operating frequency of 3.5 GHz. By utilizing a modified version of the extended Erceg’s propagation model, based on the introduction of Rayleigh fading due to multipath, we have calculated the received desired power and the interference power to obtain the statistical signal-to-interference-plusnoise rate (as a function of mean value and variance of cochannel interference) and the user throughput. A rural scenario composed of a transmitting base station and users in moving vehicles along a cell sector is proposed. The obtained results about coverage and throughput have been simulated by a tool built in MATLAB

Measurement of Distributed Antenna Systems at 2.4 GHz in a Realistic Subway Tunnel Environment.

Accurate characterization of the radio channel in tunnels is of great importance for new signaling and train control communications systems. To model this environment, measurements have been taken at 2.4 GHz in a real environment in Madrid subway. The measurements were carried out with four base station transmitters installed in a 2-km tunnel and using a mobile receiver installed on a standard train. First, with an optimum antenna configuration, all the propagation characteristics of a complex subway environment, including near shadowing, path loss,shadow fading, fast fading, level crossing rate (LCR), and average fade duration (AFD), have been measured and computed. Thereafter, comparisons of propagation characteristics in a double-track tunnel (9.8-m width) and a single-track tunnel (4.8-m width) have been made. Finally, all the measurement results have been shown in a complete table for accurate statistical modeling.

Almost rejectionless sampling from Nakagami-m distributions (m ≥ 1)

The Nakagami-m distribution is widely used for the simulation of fading channels in wireless communications. A novel, simple and extremely efficient acceptance-rejection algorithm is introduced for the generation of independent Nakagami-m random variables. The proposed method uses another Nakagami density with a half-integer value of the fading parameter, mp ¼ n/2 ≤ m, as proposal function, from which samples can be drawn exactly and easily. This novel rejection technique is able to work with arbitrary values of m ≥ 1, average path energy, V, and provides a higher acceptance rate than all currently available methods. RESUMEN. Método extremadamente eficiente para generar variables aleatorias de Nakagami (utilizadas para modelar el desvanecimiento en canales de comunicaciones móviles) basado en "rejection sampling".

WHERE2 location aided communications

This paper presents an overview of preliminary results of investigations within the WHERE2 Project on identifying promising avenues for location aided enhancements to wireless communication systems. The wide ranging contributions are organized according to the following targeted systems: cellular networks, mobile ad hoc networks (MANETs) and cognitive radio. Location based approaches are found to alleviate significant signaling overhead in various forms of modern communication paradigms that are very information hungry in terms of channel state information at the transmitter(s). And this at a reasonable cost given the ubiquitous availability of location information in recent wireless standards or smart phones. Location tracking furthermore opens the new perspective of slow fading prediction.

Air Mines. Urban Space Station

Air Mines The sky over the city's port was the color of a faulty screen, only partly lit up. As the silhouette of nearby buildings became darker, but more clearly visible against the fading blur-filter of a background, the realization came about how persistent a change had been taking place. Slowly, old wooden water reservoirs and rattling HVAC systems stopped being the only inhabitants of roofs. Slightly trembling, milkish jellyfish-translucent air volumes had joined the show in multiples. A few years ago artists and architects seized upon the death of buildings as their life-saving media. Equipped with constructive atlases and instruments they started disemboweling their subjects, poking about their systems, dumping out on the street the battered ugliness of their embarrassing bits and pieces, so rightly hidden by facades and height from everyday view. But, would you believe it? Even ?old ladies?, investment bankers or small children failed to get upset. Of course, old ladies are not what they used to be. It was old ladies themselves that made it happen after years of fights with the town hall, imaginative proposals and factual arguments. An industry with little financial gains but lots of welcome externalities was not, in fact, the ground for investment bankers. But they too had to admit that having otherwise stately buildings make fine particulate pencils with their facades was not the worse that could happen. Yes, making soot pencils had been found an interesting and visible end product of the endeavor, a sort of mining the air for vintage writing tools one can actually touch. The new view from the street did not seem as solid or dignified as that of old, and they hated that the market for Fine Particulates Extraction (FPE, read efpee) had to be applied on a matrix of blocks and streets that prevented undue concentration of the best or worse solutions. It had to be an evenly distributed city policy in order for the city to apply for cleaning casino money. Once the first prototypes had been deployed in buildings siding Garden Avenue or Bulwark Street even fast movers appreciated the sidekick of flower and plant smell dripping down the Urban Space Stations (USS, read use; USSs, read uses) as air and walls cooled off for a few hours after sunset. Enough. It was all nice to remember, but it was now time to go up and start the lightweight afternoon maintenance of their USS. Coop discussions had taken place all through the planning and continued through the construction phase as to how maintenance was going to be organized. Fasters had voted for a pro, pay a small amount and let them use it for rent and produce. In the end some neighbors decided they were slow enough to take care and it was now the turn. Regret came periodically, sometimes a week before, and lasted until work actually started. But lately it had been replaced by anxiety when it needed to be passed over to the next caretaker. It did not look their shift was good enough and couldn?t wait to fix it. Today small preparations needed to be made for a class visit next day from a nearby cook school. They were frequenters. It had not been easy, but it shouldn?t have been that hard. In the end, even the easiest things are hard if they involve a city, buildings and neighbors. On the face of the data, the technicalities and the way final designs had been worked out for adaptation to the different settings, the decision of where to go was self evident, but organization issues and the ever-growing politics of taste in a city of already-gentrified-rodents almost put the project in the frozen orbit of timeless beautiful future possibilities. This is how it was. A series of designs by XClinic and OSS had made it possible to adapt to different building structures, leave in most cases the roof untouched and adapted a new technology of flexing fiberglass tubes that dissipated wind pressure in smooth bending.......

Desmaterialización de la envolvente estructural contemporánea : una secuencia de estrategias arquitectónicas en Toyo Ito, Herzog&de Meuron y Sanaa

La Tesis investiga aquellas obras en las que se ha producido un desplazamiento de la estructura portante hacia el perímetro del edificio para alcanzar su posterior desvanecimiento aplicando ciertos mecanismos arquitectónicos. En el proceso de la investigación se ha detectado cómo la rotundidad e inmediatez de la huella de lo estructural percibida en la arquitectura tradicional, tiende a desvanecerse, su desmaterialización queda patente en ciertas obras de la arquitectura contemporánea. La investigación comienza con la concordancia hallada entre tres edificios contemporáneos cuyo perímetro lo conforma una Envolvente Estructural: la tienda TODS, de Toyo Ito (2003); PRADA, de Herzog&de Meuron (2000) y DIOR, de SANAA (2001). Tres obras de fechas consecutivas, que, aun respondiendo a las mismas condiciones de ubicación, Omotesando (Tokio), uso, volumetría, altura y superficie, su Envolvente se configura de modo muy diverso, produciendo soluciones estructurales diferenciadas y heterogéneas. De estos tres modos de configurarse la envolvente, se desprenden las tres estrategias arquitectónicas empleadas en el desarrollo de la Tesis: figuración, abstracción y desmaterialización. Así pues, la investigación descubre, por una parte, un procedimiento figurativo que pone el acento en valores expresivos empleando códigos de significado como son los objetos de la naturaleza; por otra parte, un procedimiento abstracto, priorizando las reglas de construcción formal del propio objeto; y por último, como continuación de los anteriores, se descubre un procedimiento de desmaterialización planteado desde la delgadez de los muros, los materiales efímeros o una semitransparencia que pretende mayor conexión con el mundo exterior. Con el análisis de estas tres categorías secuenciales desveladas por los edificios citados de Omotesando, se han identificado otras obras clarividentes de Toyo Ito, Herzog&de Meuron y SANAA, por ser representativos de dichas nociones. Así pues, se han seleccionado veinticuatro casos de estudio y se han ordenado formando una colección de obras capaz de llegar a formular por sí misma un enunciado conclusivo sobre los procedimientos arquitectónicos capaces de velar la estructura mecánica. En la actualidad, el planteamiento de la Envolvente Estructural recurre a un nuevo modo de abordar la arquitectura. Esta ya no consiste en el juego sabio, correcto y magnífico, sino que adquiere una nueva dimensión poética desde la ausencia de la esencia resistente. Efectivamente, por un lado, se ha afirmado que ‘sin estructura no hay arquitectura’; y por otro lado, se trata de hacerla desaparecer. Así queda expresado en palabras de SANAA: “Para nosotros la estructura es muy importante, incluso su desaparición lo es”. Por otro lado, la Envolvente Estructural analizada en la Tesis recoge el legado de la historia, lo interpreta y se manifiesta con el lenguaje contemporáneo manteniendo aquella unidad entre las disciplinas de arquitectura e ingeniería comenzada en el siglo XIX. El contorno edilicio, conformado en un único elemento compacto e indiferenciado, resuelve diversas funciones habitualmente asignadas a otros elementos específicos: Encierra en un reducido espesor el cerramiento, la estructura resistente, el ornamento y el acondicionamiento térmico (en algunos casos); configura la forma arquitectónica y envuelve el espacio arquitectónico mostrando una libertad formal (cáscaras esculturales) y un lenguaje de liviandad (muros de espesores reducidos) sin precedentes. La tipología planteada condensa todo aquello que le permite expresar el enunciado más inmaterial de la estructura mecánica. Concluyendo, la Tesis verifica que una parte de la arquitectura contemporánea ya ha pasado del límite denso, corporeizado y mecánico tradicional, a un límite borroso, que se ha erosionado, se ha transmutado hasta su desmaterialización, su desvanecimiento o incluso su desaparición. ABSTRACT This thesis researches those buildings where the bearing structure has been moved towards the perimeter in order to reach its fading by means of architectural strategies. In the research development it has been detected how the clearness and immediacy of the footprint of the structure as noticed in the traditional architecture, tends to vanish, its dematerialization remains patent in certain contemporary architecture works. The research begins with the agreement found in three contemporary buildings whose perimeter is shaped by a structural envelope: TODS shop, by Toyo Ito (2003); PRADA, by Herzog&de Meuron (2000) and DIOR, by SANAA (2001). Three works in consecutive dates, that share the placement conditions, Omotesando (Tokio), use, volume, height and area, but its envelope is shaped in various ways, generating different and heterogeneous structural solutions. From these three ways of the envelope shape are deduced the three architectural strategies studied during the Thesis development: figuration, abstraction and dematerialization. Thus, the research discovers, on one hand, a figurative procedure that highlights the expressive values by using meaning codes such as the nature objects; on the other hand, an abstract procedure, prioritizing the formal construction rules typical of the object; at last, as a continuation of the others, a dematerialization procedure is shown, set out from the wall thinness, the ephemeral materials or the semitransparency that tries to increase the connection with the world around. With the analysis of these three categories in a sequence, shown in the Ometesando buildings, other works from Toyo Ito, Herzog&de Meuron and SANNAA have been identified because of being representative of those concepts. Therefore, twenty four case studies have been selected and have been ordered to set a collection of works that are able to formulate by themselves a conclusive statement about the architectural procedures that are able to veil the mechanical structure. Nowadays, the Structural envelope approach leads to a new way of dealing with architecture. This is not any more a wise game, correct and magnificent, but it acquires a new poetic dimension from the absence of the resistant essence. Indeed, on the one hand, it has been stated that ‘without structure there is no architecture’; and on the other hand, it tries to make it disappear. It is so stated in SANAA words: ‘The structure is very important for us, and even its disappearance” On the other hand, the Structural envelope analysed in this Thesis gathers the legacy of history, interprets it and it is expressed with a contemporary language, by keeping that unity between disciplines of architecture and engineering already started in the XIX century. The building boundary, shaped as a compacted and undifferentiated single element, solves several functions commonly assigned to other specific elements: keeps in a small thickness the envelope, the bearing structure, the ornament and the thermal conditioning (in same cases); it shapes the architectural form and envelopes the architectural space by showing a formal freedom (sculptural shells) and a lightness language (small thickness walls) with no precedents. This typology gathers all what lets to express the most immaterial statement of the mechanical structure. As a conclusion, the Thesis verifies that a part of the contemporary architecture has already gone over the dense limit, shaped and mechanical traditional to a blur limit that has been eroded, it has been changed until its dematerialization, its fading or event its disappearance.

CANDELS: The progenitors of compact quiescent galaxies at z ~ 2

We combine high-resolution Hubble Space Telescope/WFC3 images with multi-wavelength photometry to track the evolution of structure and activity of massive (M_*> 10^10 M_☉) galaxies at redshifts z = 1.4-3 in two fields of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We detect compact, star-forming galaxies (cSFGs) whose number densities, masses, sizes, and star formation rates (SFRs) qualify them as likely progenitors of compact, quiescent, massive galaxies (cQGs) at z = 1.5-3. At z≲2, cSFGs present SFR = 100-200 M_☉ yr^–1, yet their specific star formation rates (sSFR ~ 10^–9 yr^–1) are typically half that of other massive SFGs at the same epoch, and host X-ray luminous active galactic nuclei (AGNs) 30 times (~30%) more frequently. These properties suggest that cSFGs are formed by gas-rich processes (mergers or disk-instabilities) that induce a compact starburst and feed an AGN, which, in turn, quench the star formation on dynamical timescales (few 10^8 yr). The cSFGs are continuously being formed at z = 2-3 and fade to cQGs down to z ~ 1.5. After this epoch, cSFGs are rare, thereby truncating the formation of new cQGs. Meanwhile, down to z = 1, existing cQGs continue to enlarge to match local QGs in size, while less-gas-rich mergers and other secular mechanisms shepherd (larger) SFGs as later arrivals to the red sequence. In summary, we propose two evolutionary tracks of QG formation: an early (z≲2), formation path of rapidly quenched cSFGs fading into cQGs that later enlarge within the quiescent phase, and a late-arrival (z≳2) path in which larger SFGs form extended QGs without passing through a compact state.