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Resource Allocation and End-to-End Quality of Service for Cellular Communications Systems in Congested and Contested EnvironmentsGhorbanzadeh, Mohammad 09 December 2015 (has links)
This research addresses the concept of radio resource allocation for cellular communications systems operating in congested and contested environments with an emphasis on end-to-end quality of service (QoS). The radio resource allocation is cast under a proportional fairness formulation which translates to a convex optimization problem. Moreover, the resource allocation scheme considers subscription-based and traffic differentiation in order to meet the QoS requirements of the applications running on the user equipment in the system. The devised resource allocation scheme is realized through a centralized and a distributed architecture and solution algorithms for the aforementioned architectures is derived and implemented in the mobile devices and the base stations. The sensitivity of the resource allocation scheme to the temporal dynamics of the quantity of the users in the system is investigated. Furthermore, the sensitivity of the resource allocation scheme to the temporal dynamics in the application usage percentages is accounted for. In addition, a transmission overhead of the centralized and distributed architectures for the resource allocation schemes is performed. Furthermore, the resource allocation scheme is modified to account for a possible additive bandwidth done through spectrum sharing in congested and contested environments, in particular spectrally coexistent radar systems. The radar-spectrum additive portion is devised in a way to ensure fairness of the allocation, high bandwidth utilization, and interference avoidance. In order to justify the aforesaid modification, the interference from radar systems into the Long Term Evolution (LTE) as the predominant 4G technology is studies to confirm the possibility of the spectrum sharing. The preceding interference analysis contains a detailed simulation of radar systems, propagation path loss models, and a third generation partnership project compliant LTE system. The propagation models are Free Space Path Loss (FSPL) and Irregular Terrain Model (ITM). The LTE systems under consideration are macro cell, outdoor small cells, and indoor small cells. Furthermore, the resource allocation under channel consideration is formalized such that the resources are allocated under a congested environment and based on the quality of channel the users have in the network as well as the quality of service requirements of the applications running on the mobile devices. / Ph. D.
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Performance evaluation of low-cost GPS machine guidance systems for livestock production forage and pasture management applicationsWright, Conner Childress 10 May 2024 (has links) (PDF)
Global Positioning System (GPS) machine guidance aids in the precise navigation and piloting of farm machinery and serves to boost productivity and optimize farm operations. Characterization of low-cost GPS guidance systems for livestock production operations is necessary for return on investment (ROI) decision making. The objective of this research is to characterize the accuracy of four commercially available low-cost ($985 - $4,200) wide area augmentation system (WAAS) corrected GPS guidance systems. Testing procedures were designed in accordance with the ASABE/ISO standard 12188-2 for testing of satellite-based guidance systems during straight line travel. The vehicles lateral deviation of a planned path, characterized as cross-track error (XTE), was evaluated for short-term and long-term guidance for each system at speeds of 4.8, 9.6, and 14.5 kph (3, 6, and 9 mph).
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Stratégies de coopération dans les réseaux radio cognitif / Cooperation strategies in radio cognitive networksKouassi, Boris Rodrigue 25 October 2013 (has links)
Les réseaux radio actuelles utilisent le spectre inefficacement, car une bande de fréquence est allouée de façon permanente à une technologie spécifique. Vu que le spectre est une ressource limitée, cette attribution statique ne pourra bientôt plus combler les besoins des systèmes de transmission qui ne cessent de croître. On peut toutefois optimiser l'utilisation du spectre en permettant des transmissions secondaires (SU) dans les espaces libres du primaire (PU). Cette vision constitue l'objectif principal de la radio cognitive. Nous proposons d'évaluer les stratégies de transmission pour la coexistence des systèmes primaires (PU) et SU dans les mêmes réseaux. Plus concrètement, nous nous focalisons sur un scénario spatial interweave en émettant les signaux SU dans les espaces vides du PU à l'aide d'un précodeur linéaire. Néanmoins, ce précodage nécessite une connaissance a priori des canaux interférents. L'échange d'informations entre le PU et le SU étant proscrit, nous exploitons l'hypothèse de la réciprocité du canal. Cette hypothèse compense l'absence de coopération, mais elle n'est pas si évidente à exploiter en pratique à cause des perturbations des circuits radio fréquence. Nous suggérons de compenser ces perturbations par des méthodes de calibration relative. Nous proposons ensuite une implémentation temps-réel des solutions sur une plateforme LTE. Pour finir, nous généralisons l'approche RC à un système de transmission multi-utilisateurs, à travers une combinaison des techniques RC et massive MIMO, cette approche constitue s’établit comme une solution à la progression exponentielle du trafic. / The accelerated evolution of wireless transmission in recent years has dramatically increased the spectrum overcrowding. Indeed, the spectrum is inefficiently used in the conventional networks, since a frequency band is statically allocated to a specific technology called primary (PU). Whereas the radio spectrum is limited, this static frequency allocation will no longer be able to meet the increasing needs of bandwidth. However, the spectrum can be optimally used in enabling secondary (SU) transmissions, provided the latters do not harm the PU. This opportunistic vision of wireless transmissions is the main aim of Cognitive Radio (CR). CR enables smart use of wireless resources and is a key ingredient to perform high spectral efficiency. We focus on a spatial interweave (SIW) CR scenario which exploits the spatial white spaces to enable SU transmissions. The latter forms spatial beams using precoders, so that there is no interference towards the primary. Nevertheless, this precoding requires acquisition of the crosslink channel. However, due to the lack of cooperation between PU and SU, we acquire the channel thanks to channel reciprocity. Furthermore, the practical use of the reciprocity is not as straightforward as in theory, because it is is jeopardized by the nonreciprocal radio frequency front-ends. These perturbations are compensated in our study by relative calibration algorithms. Subsequently, we propose an implementation of our solutions in a real-time LTE platform. Eventually, we extend the CR model to a MU system in suggesting a combination of SIW and massive MIMO techniques. This scheme is an interesting candidate to overcome the exponential traffic growth.
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Antenna as a sensor for sensing available LTE networksKumar Sathish Kumar, Barath January 2022 (has links)
This thesis primarily deals with the concept of designing an antenna based device to harvest energy from Radio Frequency (RF) and using the harvested energy to sense the available Long Term Evolution (LTE) network in order for the Internet of Things (IoT) devices to connect to the network for the purpose of transmitting and receiving data. Secondarily the importance of this project is targeting how to conserve battery power in an IoT device and extend it’s lifetime. Research in the field of energy harvesting has been going on for a long time. Most of the researches concentrate on harvesting significant amount of energy to power up an entire device and so no one has ever thought of using the harvested RF energy to sense the availability of LTE network. This method of using antenna to sense network requires only a small amount of harvested energy. Due to this reason the proposed design works for a very low input received signal strength indicator (RSSI) as well, unlike higer RSSI required for other applications. The proposed design has three major sub-parts such as the (i) Antenna for the purpose of receiving the available ambient radio frequency. (ii) Matching circuit for the purpose of maximum power transfer between the antenna and the rectifier circuit. Finally (iii) rectifier which is used to convert the AC voltage into DC voltage. The device then measures the obtained voltage through the Analog to Digital Converter (ADC) pin in the Micro-Controlling Unit (MCU) available with the attached IoT device. The MCU then maps the harvested voltage into the corresponding analog voltage.Depending on the set threshold voltage the MCU can then advice whether or not to connect to the LTE network. The design implements matching circuit for the two LTE bands that are primarily in use in the European region i.e., band 3, 8 that work in 915, 1800 MHz frequency region respectively. In this way we can identify in which band the device is harvesting energy. The matching circuit also acts as a bandpass filter. For the design and production of the entire harvester device one needs adequate knowledge in the field of RF and Antennas and a high level knowledge in the field of electronics in order to run Simulations and to design Printed Circuit Boards (PCBs). Advanced Design Software (ADS) has been used to run all the simulations and Altium software for the design of PCBs. The final prototype is presented along with the casing and tested on the field in practical scenario. Antenna test chambers were used to test the performance of the antennas being used for the design. The prototype harvests RF energy and indicates whether or not to connect to the LTE network with the help of light emitting diode (LED). The uniqueness of the device is that it can detect signals as low as -110 dBm, this has been set as the threshold for the purpose of sensing LTE networks. / Denna avhandling behandlar primärt konceptet att använda antenner för att hämta energi från RF och att använda den insamlade energin för att känna av det tillgängliga LTE-nätverket för att IoT-enheterna ska kunna ansluta till nätverket för syftet med att överföra och ta emot data. Sekundärt Målet med av detta projekt är att spara batteri i en IoT-enhet och förlänga dess livslängd. Forskning inom området energiskörd har pågått under lång tid nu. De flesta av undersökningarna koncentrerar sig på att skörda betydande mängder energi för att driva en hel enhet och så ingen har någonsin tänkt på att använda den avkända RF-energin för att känna av tillgängligheten för LTE-nätverket. Denna metod för att använda antenn för att känna av nätverk kräver endast en liten mängd skördad energi. På grund av denna anledning fungerar den föreslagna designen även för en mycket låg ingång RSSI, till skillnad från högre RSSI som krävs för andra applikationer. Den föreslagna designen har tre huvuddelar, såsom (i) antennen för att ta emot den tillgängliga omgivande radiofrekvensen. (ii) Matchningskrets för maximal effektöverföring mellan antennen och likriktarkretsen. Slutligen (iii) likriktaren som används för att omvandla AC-spänningen till DC-spänning. Enheten mäter sedan den erhållna spänningen genom ADC-stiftet i MCU som finns tillgänglig med den anslutna IoT-enheten. MCU mappar sedan den genererade spänningen till motsvarande analoga spänning. Beroende på den inställda tröskelspänningen kan MCU sedan ge råd om att ansluta till LTE-nätverket eller inte. Konstruktionen implementerar matchningskrets för de två LTE-banden som primärt används i den europeiska regionen vilka är band 3, 7 som arbetar i 915 respektive 1800 MHz frekvensområdet. På så sätt kan vi identifiera i vilket band enheten hämtar energi i. Matchningskretsen fungerar också som ett bandpassfilter. För design och produktion av hela insamlingsenheten behöver man adekvat kunskap inom området RF och antenner och en hög nivå kunskap inom elektronikområdet för att kunna köra simuleringar och designa PCBs.ADS har använts för att köra alla simuleringar och Altium-mjukvara för design av PCBs. Den slutliga prototypen presenteras tillsammans med höljet och testas på fältet i praktiskt scenario. Antenntestkammare användes för att testa prestandan hos antennerna som användes för konstruktionen. Prototypen skördar RF-energi och indikerar om man ska ansluta till LTE-nätverket eller inte med hjälp av blinkande LED.Det unika med enheten är att den kan upptäcka signaler så låga som - 110 dBm, detta har satts som tröskel för avkänning LTE nätverk.
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Protocol design for machine-to-machine networksAijaz, Adnan January 2014 (has links)
Machine-to-Machine (M2M) communications is an emerging communication paradigm that provides ubiquitous connectivity between devices along with an ability to communicate autonomously without human intervention. M2M communications acts as an enabling technology for the practical realization of Internet-of-Things (IoT). However, M2M communications differs from conventional Human-to-Human (H2H) communications due to its unique features such as massive number of connected devices, small data transmissions, little or no mobility, requirements of high energy efficiency and reliability, etc. These features create various challenges for existing communication networks which are primarily optimized for H2H communications. Therefore, novel solutions are required to meet the key requirements of M2M communications. In addition, enhancements are required at different layers of the protocol stack to support co-existence of M2M devices and H2H users. The main objective of this research is to investigate the challenges of M2M communications in two broad types of M2M networks; capillary M2M and cellular M2M networks. The primary focus is on developing novel solutions, algorithms, and protocol enhancements for successfully enabling M2M communications. Since cognitive radio technology is very promising for M2M communications, special emphasis is on capillary M2M networks with cognitive radio based Physical layer. Besides, the focus is also on exploring new frontiers in M2M communications. This thesis covers different aspects of M2M communications. Considering the motivation for cognitive M2M and service requirements of M2M devices, two cognitive MAC protocols have been proposed. The first protocol is centralized in nature and utilizes a specialized frame structure for co-existence with the primary network as well as handling different Quality-of-Service (QoS) requirements of M2M devices. The second protocol is a distributed cognitive MAC protocol, which is specially designed to provide high energy efficiency and reliability for M2M devices operating in challenging wireless environments. Both protocols explicitly account for the peculiarities of cognitive radio environments. The protocols have been evaluated using analytical modeling and simulation studies. Recently IETF has standardized a specially designed routing protocol for capillary M2M networks, known as RPL (Routing for Low Power and Lossy Networks). RPL is emerging as the de facto routing protocol for many M2M applications including the smart grid. On the other hand, the application of cognitive radio for smart grid communication is under active investigation in the research community. Hence, it is important to investigate the applicability and adaptation of RPL in cognitive radio environments. In this regard, an enhanced RPL based routing protocol has been proposed for cognitive radio enabled smart grid networks. The enhanced protocol provides novel modifications to RPL for protecting the primary users along with meeting the utility requirements of the secondary network. An important challenge in LTE-based cellular networks with M2M communications is the uplink radio resource management as available resources are shared between M2M devices and H2H users, having different and often conflicting QoS requirements. Apart from this, energy efficiency requirements become critically important. Further, the specific constraints of Single Carrier Frequency Division Multiple Access (SC-FDMA) complicate the resource allocation problem. In this respect, an energy efficient resource allocation algorithm for the uplink of LTE networks with M2M/H2H co-existence under statistical QoS guarantees has been developed, that is based on canonical duality theory. The proposed algorithm outperforms classical algorithms in terms of energy efficiency while satisfying the QoS requirements of M2M devices and H2H users. A new frontier in M2M communications is the nano-M2M communications, which is envisioned to create the Internet-of-Nano-Things (IoNT). Molecular communication (MC) is a promising communication technique for nano-M2M communications. In literature, no model for error performance of MC exists. Therefore, an error performance model has been developed that explicitly accounts for noise and interference effects. Since relaying and network coding based solutions are gaining popularity for nano-M2M networks, the error performance of a network coded molecular nano-M2M network has been evaluated as well. Finally, the thesis is concluded based on the overall picture of the research conducted. In addition, some directions for future work are included as well.
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Conception de systèmes multi-antennaires pour techniques de diversité et MIMO : application aux petits objets nomades communicantsDioum, Ibra 12 December 2013 (has links) (PDF)
La demande de transmissions à débits de plus en plus élevés s'accentue davantage avec l'essor de nouveaux services dans les réseaux de communication sans fils. Pour répondre à cette demande, une solution consiste à augmenter la capacité de transmission du canal radiofréquence entre la station de base et le terminal portatif. Ceci peut être réalisé en augmentant le nombre d'éléments rayonnant impliqués à l'émission et à la réception de cette liaison radiofréquence : on parle alors de technique MIMO (Multiple Input, Multiple Output). Cette thèse porte principalement sur la conception, l'optimisation et la caractérisation de systèmes multi-antennaires pour techniques de diversité et MIMO en bandes LTE (Long Term Evolution). Trois prototypes multi-bandes sont proposés dont deux systèmes planaires et un système d'antennes IFAs compactes. De nouvelles solutions multi-bandes et l'influence de la position de l'antenne sur le plan de masse sont étudiées pour réaliser de la diversité spatiale, de polarisation et de diagramme de rayonnement avec une faible corrélation entre les signaux reçus sur chaque antenne mais surtout une bonne efficacité totale. Une ligne de neutralisation est utilisée pour isoler les antennes et un fonctionnement multi-bande est réalisé. L'impédance d'entrée des antennes est étudiée avec la méthode de Youla & Carlin afin d'améliorer la bande passante de la structure compacte de type IFA. Les performances en diversité et en MIMO de ces systèmes sont évaluées dans différents environnements de propagation. Elles montrent que ces systèmes peuvent être utilisés efficacement pour des applications en diversité et MIMO.
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La communication D2D dans le réseau LTE-AdvancedFeng, Junyi 19 December 2013 (has links) (PDF)
Device-to-device (D2D) communication is a promising new feature in LTE-Advanced networks. It is brought up to enable efficient discovery and communication between proximate devices. With D2D capability, devices in physical proximity could be able to discover each other using LTE radio technology and to communicate with each other via a direct data path. This thesis is concerned with the design, coordination and testing of a hybrid D2D and cellular network. Design requirements and choices in physical and MAC layer functions to support D2D discovery and communication underlaying LTE networks are analyzed. In addition, a centralized scheduling strategy in base station is proposed to coordinate D2D data communication operating in LTE spectrum. The scheduling strategy combines multiple techniques, including mode selection, resource and power allocation, to jointly achieve an overall user performance improvement in a cell. Finally the performances of D2D data communication underlaying LTE system are calibrated in a multi-link scenario via system-level simulation.
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Analyse et Optimisation du Partage de Spectre dans les Systèmes Mobiles Intégrés Satellite et Terrestre / Analysis and Optimization of Spectrum Sharing in Integrated Satellite and Terrestrial Mobile SystemsDeslandes, Vincent 27 June 2012 (has links)
Les technologies mobiles terrestre et satellite sont naturellement complémentaires. Les réseaux cellulaires terrestres sont adaptés aux villes où la densité d'utilisateurs est maximale mais perdent leur rentabilité dans les zones peu peuplées. A l'inverse, les systèmes mobile satellite permettent de couvrir de vastes zones à moindre coût mais n'assurent pas la couverture dans les zones urbaines car le signal est bloqué par les constructions. En les combinant pour assurer la couverture en ville par le réseau terrestre et dans les zones moins denses avec le satellite, on obtient un système à la couverture totale pour un coût optimal. Nous appelons un tel système intégrant une composante satellite et une composante terrestres un "système intégré" satellite/terrestre. Nul doute que d'ici quelques années, le rêve de la communauté satellite de rendre tous les terminaux mobiles capables de se connecter à un satellite sera accessible. Le satellite pourra ainsi être vu par les utilisateurs de terminaux portables comme une énième technologie d'accès à un système "intégré", aux côtés du Bluetooth, du Wifi et des technologies cellulaires (GSM, UMTS, LTE). La réutilisation du spectre satellite par les systèmes terrestres est un facteur déterminant dans le succès de cette intégration car elle permet de justifier les investissements dans le système satellite qui ne peut être rentabilisé par les abonnements seuls. Toutefois sa mise en œuvre pose de nombreux problèmes : règlementaires, commerciaux et bien entendu techniques. Cette thèse apporte des solutions sur ce dernier point et j'espère qu'elle contribuera ainsi à rendre possible ce rêve d'intégration. Nous avons adopté une approche descendante du problème du partage de spectre dans les systèmes mobiles satellite-terrestre. Nous avons tout d'abord établi une synthèse sur les aspects recouverts par l'intégration des systèmes mobiles satellite et terrestre. Nous avons ensuite dressé l'état de l'art sur la problématique de la réutilisation du spectre satellite par les systèmes terrestres, que nous avons complété par nos analyses. Nous avons décidé dans cette thèse de nous focaliser sur un des problèmes majeurs soulevés par cette réutilisation : les interférences co-fréquence du système terrestre sur le lien montant satellite. A partir de l'analyse d'une solution de partage statique de spectre par coordination des plans de fréquence (principe de zone d'exclusion), nous avons élaboré puis analysé les performances de mécanismes innovants d'allocation de ressources dans le système terrestre qui permettent de réduire de façon importante les interférences. De plus, nous proposons une méthode pour garantir au système satellite que les interférences subies sur son lien montant soient inférieures à une valeur limite. Enfin, nous définissons une architecture et les mécanismes associés qui permettent l'implantation des solutions proposées dans un système satellite-terrestre fondé sur la technologie LTE. L'étude du sujet de partage de spectre dans les systèmes mobiles satellite-terrestre est relativement nouvelle et cette thèse constitue donc un travail novateur important qui pourra être utilisé comme base à de futurs travaux. / Terrestrial and satellite mobile technologies are naturally complementary. Terrestrial cellular systems are adapted to urban areas where the user density is maximal but their cost-effectiveness is much lower in sparsely populated areas. On the contrary, mobile satellite systems cover large zones at a relatively low cost but they cannot ensure coverage in urban areas because of signal blockage due to buildings. By combining both systems for ensuring coverage in cities with terrestrial networks and in less dense areas with the satellite, we obtain a system with complete coverage for an optimal cost. Such a system is called mobile terrestrial and satellite "integrated system". It is likely that in a few years, the dream of enabling satellite connectivity on all mobile terminals will be within reach. The satellite will then be perceived for mobile terminal users as an additional access technology to an "integrated network" comparable to Wifi, Bluetooth or cellular technologies (GSM, UMTS, LTE). The spectrum reuse by terrestrial systems is a key for the success of this integration because it justifies part of the investments in the satellite systems that cannot be supported by user subscriptions only. However, implementation of spectrum sharing generates many issues: regulatory, commercial and obviously technical. This thesis brings answers on the latter and I hope it will contribute to make this dream of integration become reality. We used a descending approach of the issue of spectrum sharing in terrestrial and satellite mobile systems. First, we establish a synthesis of all the aspects covered by the integration of mobile satellite and terrestrial systems. Then, we made the state of the art on the issue of satellite spectrum reuse by terrestrial systems and we completed it with our analysis. We decided to focus our work on one of the major issues raised by this reuse: co-frequency interference generated by the terrestrial system on the satellite uplink. From the analysis of a solution proposing a static spectrum sharing by coordination of frequency plans (the exclusion zone principle), we elaborated and analyzed performances of innovative mechanisms of resources allocation in the terrestrial system that allows to reduce significantly the interferences. Moreover, we proposed a method for guaranteeing to the satellite system that interferences from the terrestrial system will not exceed a given threshold. At last, we define an architecture and the associated mechanism that allow the implementation of our solution in an integrated terrestrial-satellite systems based on LTE technology. The study of spectrum sharing in terrestrial-satellite mobile systems is rather new and this thesis represents an innovative work that may serve as a basis for future studies on this issue.
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Controle de potÃncia e estratÃgias de eficiÃncia energÃtica para comunicaÃÃes D2D subjacentes redes celulares / Power control and energy efficiency strategies for D2D communications underlying cellular networksYuri Victor Lima de Melo 14 July 2015 (has links)
Ericsson Brasil / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Em um mundo onde as pessoas contam com
smartphone, smartwatch, tablet e outros
dispositivos para mantÃ-las conectadas onde quer que vÃo, t
odos esperam que seus
aplicativos sejam executados sem problemas, tais como cham
adas abandonadas,
download
lento e vÃdeos com saltos.
Neste contexto, comunicaÃÃo dispositivo-a-dispositivo (
do inglÃs, Device-to-Device (D2D))
constitui uma tecnologia promissora, pois à um tipo de comun
icaÃÃo direta e utiliza baixa
potÃncia entre dispositivos prÃximos, permitindo-se desv
iar o trÃfego da rede mÃvel, aumentar
a eficiÃncia espectral e de potÃncia. Do ponto de vista do assi
nante, D2D significa usar
aplicaÃÃo sem problemas e aumentar o tempo de vida da bateria
do celular.
No entanto, a fim de realizar os ganhos potenciais das comunic
aÃÃes D2D, algumas
questÃes-chave devem ser abordadas, pois as comunicaÃÃes D
2D podem aumentar a
interferÃncia co-canal e comprometer a qualidade do enlace
das comunicaÃÃes celulares.
Esta dissertaÃÃo foca em tÃcnicas de Gerenciamento de Recur
sos de RÃdio (do inglÃs, Radio
Resource Management (RRM)) para mitigar a interferÃncia co
-canal para comunicaÃÃes D2D
que se baseiam na EvoluÃÃo de Longo Prazo (do inglÃs, Long Ter
m Evolution (LTE)), visando
a reduÃÃo da interferÃncia intra- e inter-celular e na melho
ria da eficiÃncia energÃtica. Os
principais esquemas de Controle de PotÃncia (do inglÃs, Pow
er Control (PC)) (e.g. OLPC,CLPC
e SDPC) e um esquema hÃbrido (CLSD) sÃo calibrados e utilizad
os no cenÃrio macro ou micro
multicelular, usando diferentes cargas e InformaÃÃo do Est
ado do Canal (do inglÃs, Channel
State Information (CSI)) perfeita ou imperfeita. AlÃm diss
o, o impacto da inclinaÃÃo da antena
(
downtilt
) à analisado, que à usada para ajustar o raio de cobertura de u
ma Evolved Node
B (eNB) e reduzir a interferÃncia co-canal, aumentando o iso
lamento de cÃlulas.
Os resultados numÃricos indicam que os regimes de controle d
e potÃncia e inclinaÃÃo
da antena, devidamente calibrados, podem fornecer ganhos p
ara a comunicaÃÃo celular e
D2D. Em outras palavras, a tecnologia D2D pode ser utilizada
para aumentar ainda mais
a eficiÃncia de espectro e a eficiÃncia energÃtica se algoritm
os de RRM forem utilizados
adequadamente / In a world where people count on their smartphone, smartwatch, tablet and other devices to keep them connected wherever they go, they expect its application to run without problems, such as dropped calls, slow download and choppy videos.
In this context, Device-to-Device (D2D) communication represents a promising technology, because it is a direct and low-power communication between devices close, allowing to offload the data transport network, increase spectral and power efficiency. From the subscriber point of view, D2D means to use applications without problem and increase battery life. However, in order to realize the potential gains of D2D communications, some key issues must be tackled, because D2D communications may increase the co-channel interference and compromise the link quality of cellular communications.
This masterâs thesis focuses on Radio Resource Management (RRM) techniques, especially Power Control (PC) schemes, to mitigate the co-channel interference for D2D communications
underlaying a Long Term Evolution (LTE) network, aiming at the reduction of the intra- and inter- cell interference and at the improvement of energy efficiency. The main PC schemes (e.g. OLPC, CLPC and SDPC) and a hybrid scheme (CLSD) are calibrated and used in macro- or micro- multicell scenario, using different loads and imperfect Channel State Information (CSI).
In addition, the impact of downtilt is analyzed, which is used to adjust the coverage radius of an Evolved Node B (eNB) and reduce co-channel interference by increasing cell isolation.
The numerical results indicate that PC schemes and downtilt, duly calibrated, can provide gains to cellular and D2D communications. In other words, D2D technology can be used to further increase the spectral and energy efficiency if RRM algorithms are used suitably.
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Controle de qualidade de experiência para disseminação de vídeos em tempo real sobre redes ad hoc veicularesQUADROS, Carlos Jean Ferreira de 24 March 2017 (has links)
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Previous issue date: 2017-03-24 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A disseminação de vídeos em tempo real sobre Redes Veiculares (do Inglês, Vehicular Ad hoc Networks - VANETs) é fundamental para inúmeros serviços, como: vídeos de emergência, anúncios, monitoramento inteligente etc. Essas aplicações enfrentam muitos desa
fios devido os requisitos de qualidade de vídeo, topologia dinâmica e ambiente das VANETs. Para lidar com esses desafios e reduzir a sobrecarga de roteamento na rede, protocolos de roteamento estatásticos (do Inglês, Statistical Routing Protocols - SRPs) tem sido propostos para a distribuição de fluxos de vídeo em VANETs, normalmente usando parâmetros de posicionamento e Qualidade de Serviço. Porém, além desses parâmetros, a disseminação de vídeo, considerando a perspectiva dos usuários, também exige a preocupação com questões relacionadas a aceitação pelo Sistema Visual Humano (SVH). Devido aos diferentes requisitos e a estrutura hierárquica de vídeos, apenas parâmetros de posição e do nível de rede não são sufi
cientes para disseminação de vídeo com níveis satisfatórios de Qualidade de Experiência (do Inglês Quality of Experience - QoE) e alcançabilidade. Esta tese foca na melhoria do QoE dos vídeos em tempo real disseminados em VANETs. Assim, propõe-se um mecanismo cross-layer para Broadcast baseado em Receptor dirigido a QoE (BRQ), modularmente acoplado em SRPs para oferecer parâmetros relacionados a vídeo no processo de seleção de nodos encaminhadores dos fluxos de vídeo e manutenção de rotas. A partir do BRQ, os nodos da rede decidem por eles mesmos, se devem retransmitir as sequências de vídeo ou não, melhorando a capacidade do sistema em distribuir vídeos com melhor QoE. No topo dessa arquitetura, uma técnica para Correção de Erros, nomeadamente Entrelaçamento (do Inglês, Interleaving), foi adicionada, permitindo mitigar ainda mais os efeitos de perdas em rajadas de quadros relativos ao ambiente de conexão inseguro de VANETs. Para validação, o mecanismo BRQ foi adicionado a um SRP projetado usando a estratégia de encaminhamento baseada em Distância, chamado de protocolo DBRQ (Distance BRQ). Os resultados mostram que os ganhos do protocolo DBRQ comparado a outros atuais SRPs, forneceram disseminação de vídeo com maior suporte da QoE, menos sobrecarga de roteamento e alcançabilidade satisfatória. / Live video dissemination over Vehicular Ad hoc Networks (VANETs) is fundamental for several services, e.g., roadside video emergency, advertisement's broadcast, and smart video surveillance. All these applications face many challenges due to stringent video quality level requirements, dynamic topologies, and broadcast environments. To deal with these challenges, as well as reduce network routing overhead, geographic Statistical Routing Protocols (SRPs) have been proposed as a suitable solution for the distribution of video flows in VANETs, usually by using positioning and Quality of Service (QoS) parameters. However, rather than only these parameters, a satisfactory video dissemination from the user's perspective also requires video and human-awareness issues. In real situations, due to different requirements and hierarchical structures of multimedia applications, network level and position parameters alone are not enough to select the best relay nodes and build up reliable routes to multi-hop video dissemination with satisfactory reachability and Quality of Experience (QoE) levels. This thesis focuses on improving the disseminated quality of on-road live videos in VANETs. Thus, we propose the cross-layer Broadcast Receiver-based and QoE-driven (BRQ) mechanism, which is modularly coupled to SRPs to offer QoE-aware and video-related parameters for the relay node selection and route maintenance. Thus, nodes decide for themselves to retransmit further the video sequences, enhancing the capacity of the system in delivering videos with better QoE assurance. On top of this, an application-level Error-Control (EC) scheme, namely Interleaving, allows mitigating the effects of frame loss. BRQ was added to a straightforward SRP built using the Distance method, named DBRQ protocol. Results show the gains of DBRQ compared to current SRPs, achieving video dissemination with QoE support, less routing overhead, and satisfactory reachability.
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