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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Resource allocation in energy cooperation enabled 5G cellular networks

Xu, Bingyu January 2018 (has links)
In fifth generation (5G) networks, more base stations (BSs) and antennas have been deployed to meet the high data rate and spectrum efficiency requirements. Heterogeneous and ultra dense networks not only pose substantial challenges to the resource allocation design, but also lead to unprecedented surge in energy consumption. Supplying BSs with renewable energy by utilising energy harvesting technology has became a favourable solution for cellular network operators to reduce the grid energy consumption. However, the harvested renewable energy is fluctuating in both time and space domains. The available energy for a particular BS at a particular time might be insufficient to meet the traffic demand which will lead to renewable energy waste or increased outage probability. To solve this problem, the concept of energy cooperation was introduced by Sennur Ulukus in 2012 as a means for transferring and sharing energy between the transmitter and the receiver. Nevertheless, resource allocation in energy cooperation enabled cellular networks is not fully investigated. This thesis investigates resource allocation schemes and resource allocation optimisation in energy cooperation enabled cellular networks that employed advanced 5G techniques, aiming at maximising the energy efficiency of the cellular network while ensuring the network performance. First, a power control algorithm is proposed for energy cooperation enabled millimetre wave (mmWave) HetNets. The aim is to maximise the time average network data rate while keeping the network stable such that the network backlog is bounded and the required battery capacity is finite. Simulation results show that the proposed power control scheme can reduce the required battery capacity and improve the network throughput. Second, resource allocation in energy cooperation enabled heterogeneous networks (Het- Nets) is investigated. User association and power control schemes are proposed to maximise the energy efficiency of the whole network respectively. The simulation results reveal that the implementation of energy cooperation in HetNets can improve the energy efficiency and the improvement is apparent when the energy transfer efficiency is high. Following on that, a novel resource allocation for energy cooperation enabled nonorthogonal multiple access (NOMA) HetNets is presented. Two user association schemes which have different complexities and performances are proposed and compared. Following on that, a joint user association and power control algorithm is proposed to maximise the energy efficiency of the network. It is confirmed from the simulation results that the proposed resource allocation schemes efficiently coordinate the intra-cell and inter-cell interference in NOMA HetNets with energy cooperation while exploiting the multiuser diversity and BS densification. Last but not least, a joint user association and power control scheme that considers the different content requirements of users is proposed for energy cooperation enabled caching HetNets. It shows that the proposed scheme significantly enhances the energy efficiency performance of caching HetNets.
12

A Study on Random Access Performance in Next Generation Mobile Network Systems / En studie i random access prestanda i nästa generations mobila nätverkssystem

Thalén, Magnus January 2015 (has links)
The next generation of mobile telecommunication, 5G, will be specified in the near future. One of the proposed changes relative to the previous generation, 4G,is the inclusion of a new system control plane (SCP). The purpose of the SCP is to improve system scalability, forward compatibility, peak performance and to enable a higher degree of support for advanced antenna techniques. This is done by logically separating data transmitted explicitly from and to the user, the dynamic transmissions, from the broadcasted transmissions that remain constant regardless of user activity, the static transmissions, and by then redesigning the static part to make it more lean. This is expected to have several positive effects such as considerably more free resources, resulting in energy savings and potentially increased usage of MIMO. Knowing what effect the SCP has upon aspects such as random access is of importance when designing the solution that will go into the standard. Simulations show that there is potential in the inclusion of the new SCP. While the simulated 5G candidate systems that include the SCP have an increased delay when running the random access procedure, some aspects of the procedure have been improved. The main differences relative to the simulated 4G system are the performance of the first message in the procedure, which increased, and the performance of the second message in the procedure, which decreased. The deficiencies found in the handling of the second message, however, can be alleviated by using a more proper algorithm and channel design than what was used in this study.
13

High Performance Reference Crystal Oscillator for 5G mmW Communications

Torabian Esfahani, Tahmineh, Stefanidis, Stefanos January 2014 (has links)
Future wireless communications (often referred to as 5G) are expected to operate at much higher frequencies compared to today’s wireless systems. During this thesis, we have investigated the option to use high frequency crystal oscillators, which along with a PLL, will generate the RF LO signal in the mmW range. Different topologies that consume low power and deliver low phase noise for better channel capacity have been studied and presented. In this report we provide a detailed analysis of crystal oscillator theory and designand we discuss techniques that we have used to simulate our models. During this project we have encountered various challenges such as parasitic oscillation, start-up behaviour and effects from package modeling. All these issues are discussed in detail while solutions, examples and results are demonstrated. Finally, along with the crystal oscillator we have also proceeded in the design of a buffer for a better input/output isolation. A squarer has been implemented for greater power savings.
14

Modelování lavinového ohrožení na území CHKO Jeseníky pomocí metod DPZ a GIS

Školoud, Libor January 2014 (has links)
This diploma thesis presents a comparison of the accuracy level of elevation data and 3D elevation countours and digital relief model 5. generation. These data are used in modeling of avalanche danger Velke Kotliny on the territory of CHKO Jeseniky. In ArcGIS 10.2 software model calculations are performed of break off zones using two equations, resulting in potential break off zones. The equation is based on the same basis, but it differs in approach of their authors inclusion of horizontal and vertical curvature of the terrain. Furthermore, the equations are different with their assigned values of individual variables, which may result in changing the source data and the associated change in details and accuracy. This facet follows modeling of avalanche paths in RAMMS software (Rapid Mass Movement System), wherein the input data are crucial for simulation of individual avalanches. Distinguishing of input date significantly affects the accuracy of the simulation of avalanche paths and calculating thier final values (pressure, speed, snow depth) in individual section of their paths.
15

Managing Radio and Energy Resources in LTE-Based Military Training Networks

Ramazanali, Hawar January 2017 (has links)
The number of wireless connected devices are growing exponentially and the importance of this research area is growing as well to meet the known and looming challenges and expectations. The 5:th Generation telecommunications standard is partly embodied by the Machine-to-Machine (M2M) and Internet of Things (IoT) technologies and standards to handle a big part of these devices and connections. An example within the IoT paradigm is military training systems where each system can consist of thousands of battery operated mobile devices and their shifting requirements shall be fullled in an energy-aware manner to increase battery operating times. Military training radio networks enables realistic combat training. The services and features provided in commercial telecommunications networks are desirable in these often proprietary and task specic networks, increasing capabilities and functionalities. To facilitate the current and future R&D of LTE based networks for adoption in military training networks and services this doctoral thesis intends to provide the starting ground for the energy-aware LTE based wireless communications. The thesis first presents general solutions on how to meet traffic deadlines in wireless networks for large number of nodes, and then continues with solutions for energy-aware LTE-based communications for the User Equipments (UEs). The work builds on the problem formulation how to provide energy-aware resource handling for LTE-based military training networks from where three research questions are derived. From the research questions we derive different hypotheses and then test these within the investigated area to answer the research questions. The contributions of this work are within areas of resource handling and power saving for mobile devices. In the first area an admission control using deterministic analysis is proposed fullling traffic requirements for military training mobile nodes. This admission control is enhanced for multiple-channel base stations, and evaluated using mobile nodes with different heterogeneous traffic requirements. In the second part energy-awareness is in focus for LTE/LTE-A based networks. The main power saving method for LTE/LTE-A UEs, Discontinuous Reception (DRX) mechanism, is evaluated and models for DRX in Idle and Connected state are proposed including metrics for wake-up delay and power saving. Additionally a mean queuing delay analysis is proposed for a variant of the Connected state DRX. Using these models and metrics, practical design guidelines for tuning of DRX parameters are proposed, including optimization of DRX parameters for either minimizing delay or maximizing power saving.
16

Beamforming techniques for millimeter wave relay networks

Abbas, Hatem January 2017 (has links)
The energy and data rate requirements for the next generation cellular networks urge the need for innovative solutions. Inspired by its massive bandwidth, millimeter wave (mmWave) band is thought-out to be one of the key elements to meet the aspirations. However, mmWave links are known to have short coverage distance due to the propagation losses introduced at high frequencies. The proposed solutions to overcome the transmission challenges include using large arrays with improved directivity, adopting smaller cells, and relying on cooperative networks to extend the mmWave link and avoid shadowing areas. This work aims to improve the connectivity of the mmWave link in the outdoor environments. One of the cost effective methods is to increase the array gain by using Analogue Beamforming (ABF). The performance of the ABF system in the presence of phase quantization error has been analytically investigated. The study also includes comparing three different channel sounding techniques, namely: exhaustive search, side-to-side search, and n-tier search. The time overhead related to each method and their energy consumption are calculated. The numerical results assist in determining the optimum search period to obtain a reasonable spectral efficiency using minimal power consumption. The results also help identify the minimum number of quantization bits required to produce about ninety percent of the optimistic results. In order to extend the coverage further, relay networks are considered an essential component in mmWave communications. The performance of a single hybrid beamforming full-duplex relay system and multi-relay networks were investigated. The design algorithms for the processors in the network are proposed based on the greedy pursuit approach. The performance of the proposed algorithms is analysed under various scenarios. The analysis highlights the influence of the array size, the number of RF chains, and the length of the channel sounding period. The performance of the proposed systems is compared from both the spectral efficiency and power consumption prospects. The results also establish that the number of antennas at the source and the relay receiver arrays have a superior impact on the system performance than the sizes of the array at the destination and the relay transmitter.
17

5G電信產業報告 / Industry report of 5G (telecom)

王子, Paranthaman, Raja Unknown Date (has links)
Currently the telecom world is moving towards next generation 5G (5th Generation) technology. Previous generations of mobile networks addressed human communications predominantly for voice & data but apart from human to human communications 5G brings machine to machine communication in a broader way. The possibilities of use cases are endless and 5G is a system of system. The vision for 5G is creating an ultra-connected society. 5G will be the general-purpose technology and 5G will act as a catalyst for the industry disruption. By interconnecting industries using the 5G technology will make them to be cost effective, efficient and more productive by optimally utilizing the infrastructure. It is expected that globally 5G value chain itself will contribute $3.5 trillion in output and provides 22million jobs in 2035. It is expected that 1 Trillion IoT devices by 2035 and will be worthy of $5 trillion. In Taiwan, 5G is expected to create 510,000 Taiwanese jobs and to unleash $134 billion economic value in gross output of goods and services. Apart from monetary benefits 5G is expected to bring social benefits to the human life too in enormous ways. To tap that potential many countries, governments encourage and push the mobile ecosystem to start to build the 5G networks and to launch it. 5G is coming earlier than expected and society needs to adopt to the upcoming disruption.
18

Wireless vehicle control : A study of the application of 5G

Holm, Rasmus January 2020 (has links)
In this day and age, with highly available and fast networks, many tasks are being performed remotely. However, certain tasks cannot be flawlessly executed remotely, for instance, the tasks performed by professional drivers. Their jobs demand a lot of visual cues, fast actions, and low response times, which is difficult in particular when task execution is performed wirelessly. With the release of 5G, which promises to deliver reliable and rapid response times with URLLC, high bitrates with eMBB, and supports a massive number of devices with mMTC, many companies and researchers are trying to investigate if 5G is an enabler for wireless control of commercial vehicles. This thesis first examines the latency requirements for remote control operations, and then see how 5G can meet those requirements. In this respect, the thesis discovers the latency thresholds without affecting the control performance in a scenario with users operating a small robot. Then, various tests were performed using a trial 5G system to evaluate its performance in terms of latency, video quality, bandwidth, and signal strength. In controlling robot experiments, the results showed that the highest acceptable cycle latency, both for accurate maneuvering and satisfying operator experience, is around 154ms. These results were then used as a benchmark in the tests conducted using a 4G public network and a single-cell 5G network. These tests revealed that 5G could deliver lower latencies, higher bitrates, and similar video quality when compared to 4G. However, it was difficult to retain good signal quality over 5G, especially when roaming in non-line-of-sight propagation areas. This behavior is as expected due to the terminal’s association with a single 5G base station, which can be easily mitigated with denser deployments.
19

Massive MIMO channel characterization and propagation-based antenna selection strategies : application to 5G and industry 4.0 / Caractérisation des canaux massive MIMO et stratégies de sélection d'antenne : application pour la 5G et l'industrie 4.0

Challita, Frédéric 26 September 2019 (has links)
Dans le domaine des télécommunications sans fil, les domaines applicatifs sont de plus en plus larges, s’étendant par exemple du grand public, à la voiture connectée, à l’internet des objets (IoT Internet of Things) et à l’industrie 4.0. Dans ce dernier cas, l’objectif est d’aboutir à une flexibilité et à une versatilité accrues des chaînes de production et à une maintenance prédictive des machines, pour ne citer que quelques exemples. Cependant, les réseaux sans fil actuels ne sont pas encore en mesure de répondre aux nombreuses lacunes de la quatrième génération des réseaux mobiles (4G) et aux exigences de la 5G quant à une connectivité massive, une ultra fiabilité et des temps de latence extrêmement faibles. L’optimisation des ressources spectrales est également un point très important. La 5G était initialement considérée comme une évolution, rendue possible grâce aux améliorations apportées à la LTE (Long Term Evolution), mais elle ne tardera pas à devenir une révolution et une avancée majeure par rapport aux générations précédentes.Dans ce cadre, la technologie des réseaux massifs ou Massive MIMO (Multiple-Input Multiple-Output) s’est imposée comme l’une des technologies de couche physique les plus prometteuses. L'idée principale est d'équiper les stations de base de grands réseaux d’antennes (100 ou plus) pour communiquer simultanément avec de nombreux terminaux ou équipements d’utilisateurs. Grâce à un prétraitement intelligent au niveau des signaux d’émission, les systèmes Massive MIMO promettent d’apporter une grande amélioration des performances, tout en assurant une excellente efficacité spectrale et énergétique. Cependant certains défis doivent encore être relevés avant le déploiement complet des communications basées sur le massive MIMO. Par exemple, l’élaboration de modèles de canaux représentatifs de l’environnement réel, l'impact de la diversité de polarisation, les stratégies de sélection optimale d’antennes et l'acquisition d'informations d'état du canal, sont des sujets importants à explorer. En outre, une bonne compréhension des canaux de propagation en milieu industriel est nécessaire pour optimiser les liens de communication de l'industrie intelligente du futur.Dans cette thèse, nous essayons de répondre à certaines de ces questions en nous concentrant sur trois axes principaux :1) La caractérisation polarimétrique des canaux massive MIMO en environnement industriel. Pour cela, on étudie des scénarios correspondant à des canaux ayant ou non une visibilité directe entre émetteur et récepteur (Line of Sight – LOS) ou Non LOS, et en présence de divers types d’obstacles. Les métriques associées sont soit celles utilisées en propagation telles que le facteur de Rice et la corrélation spatiale, soit orientées système comme la capacité totale du canal incluant des stratégies de précodage linéaire. De plus, les schémas de diversité de polarisation proposés montrent des résultats très prometteurs.2) En massive MIMO, un objectif important est de réduire le nombre de chaînes de fréquences radio et donc la complexité du système, en sélectionnant un ensemble d'antennes distribuées. Cette stratégie de sélection utilisant la corrélation spatiale du récepteur et une métrique de propagation comme facteur de mérite, permet d'obtenir une capacité totale quasi-optimale.3) Une technique efficace de réduction des ressources lors de l’acquisition d’informations du canal de propagation dans les systèmes FDD (frequency-division-duplex) est enfin proposée. Elle repose sur la corrélation spatiale au niveau de l'émetteur et consiste à résoudre un ensemble d'équations auto-régressives simples. Les résultats montrent que cette technique permet d’atteindre des performances qui ne sont pas trop éloignées de celles des systèmes TDD (time-division-duplex) initialement proposés pour le massive MIMO. / Continuous efforts have been made to boost wireless systems performance, however, current wireless networks are not yet able to fulfill the many gaps from 4G and requirements for 5G. Thus, significant technological breakthroughs are still required to strengthen wireless networks. For instance, in order to provide higher data rates and accommodate many types of equipment, more spectrum resources are needed and the currently used spectrum requires to be efficiently utilized. 5G, or the fifth generation of mobile networks, is initially being labeled as an evolution, made available through improvements in LTE, but it will not be long before it becomes a revolution and a major step-up from previous generations. Massive MIMO has emerged as one of the most promising physical-layer technologies for future 5G wireless systems. The main idea is to equip base stations with large arrays (100 antennas or more) to simultaneously communicate with many terminals or user equipments. Using smart pre-processing at the array, massive MIMO promises to deliver superior system improvement with improved spectral efficiency, achieved by spatial multiplexing and better energy efficiency, exploiting array gain and reducing the radiated power. Massive MIMO can fill the gap for many requirements in 5G use-cases notably industrial IOT (internet of things) in terms of data rates, spectral and energy efficiency, reliable communication, optimal beamforming, linear processing schemes and so on. However, the hardware and software complexity arising from the sheer number of radio frequency chains is a bottleneck and some challenges are still to be tackled before the full operational deployment of massive MIMO. For instance, reliable channel models, impact of polarization diversity, optimal antenna selection strategies, mutual coupling and channel state information acquisition amongst other aspects, are all important questions worth exploring. Also, a good understanding of industrial channels is needed to bring the smart industry of the future ever closer.In this thesis, we try to address some of these questions based on radio channel data from a measurement campaign in an industrial scenario using a massive MIMO setup. The thesis' main objectives are threefold: 1) Characterization of massive MIMO channels in Industry 4.0 (industrial IoT) with a focus on spatial correlation, classification and impact of cross-polarization at transmission side. The setup consists in multiple distributed user-equipments in many propagation conditions. This study is based on propagation-based metrics such as Ricean factor, correlation, etc. and system-oriented metrics such as sum-rate capacity with linear precoding and power allocation strategies. Moreover, polarization diversity schemes are proposed and were shown to achieve very promising results with simple allocation strategies. This work provides comprehensive insights on radio channels in Industry 4.0 capable of filling the gap in channel models and efficient strategies to optimize massive MIMO setups. 2) Proposition of antenna selection strategies using the receiver spatial correlation, a propagation metric, as a figure of merit. The goal is to reduce the number of radio frequency chain and thus the system complexity by selecting a set of distributed antennas. The proposed strategy achieves near-optimal sum-rate capacity with less radio frequency chains. This is critical for massive MIMO systems if complexity and cost are to be reduced. 3) Proposition of an efficient strategy for overhead reduction in channel state information acquisition of FDD (frequency-division-duplex) systems. The strategy relies on spatial correlation at the transmitter and consists in solving a set of simple autoregressive equations (Yule-Walker equations). The results show that the proposed strategy achieves a large fraction of the performance of TDD (time-division-duplex) systems initially proposed for massive MIMO.
20

Radio Frequency Exposure From5G Small Cells Utilizing MassiveMIMO

Dahlstedt, Mattias January 2018 (has links)
The radio frequency (RF) electromagnetic field (EMF) exposure of a 5G small cell radiobase station (RBS) using massive MIMO antenna is assessed. The compliance distance for auniform antenna excitation is determined for a 4x4- and an 8x8 planar array antenna at fourdifferent carrier frequencies, 10, 15, 28 and 60 GHz. Three different exposure standards areused to find the compliance distance, the ICNIRP-, the FCC- and a draft IEEE standard.Simulations using the method of moments (MoM) was used to analyze the antennas and calculatethe power density. The compliance distance converges to Fries far field formula in thefar field region, where said formula is valid. Each standard use different averaging areas andthe convergence is slower for a larger averaging area. This can be explained by the act ofaveraging working as a low pass filter. A lower frequency also leads to a slower convergence,as the far field is located further away.A statistical model is developed to assess the time-averaged realistic maximum power level,based on a 8x8 planar array antenna using a carrier frequency of 28 GHz. Parameters such asTDD, user position and utilization are considered and the model is valid in both the near fieldand the far field regions. The user positions are determined to obtain a realistic conservativeRF EMF exposure with a confidence level of 95%. The antenna can transmit the signal in adefined set of 47 different beam directions spanning -60 to 60 degrees in azimuth and -15 to15 degrees in elevation. The set of 47 beams are simulated using the method of moments tocalculate the electromagnetic fields in the vicinity of the RBS antenna. For the user distributionsinvestigated and at a distance of 20 cm, the power reduction factor is below 0.22. Asthe distance becomes larger the power reduction factor converges toward around 0.17 usinga weighted user distribution and toward 0.10 using a uniform user distribution. This impliesthat the compliance distance can be reduced significantly compared with the results using thetheoretical maximum power.A four panel model is created with the same input parameters as in the one panel case. Themodel is based on a small cell radio base station product produced by Ericsson. A statisticalmodel is created to assess the RF exposure which are made to converge towards the one panelcase far away from the antenna. The users are distributed uniformly and separately over the4 panels with priority given to the panels with highest exposure. The power reduction factoris one forth of the single panel case close to the antenna and converges toward the single panelresults. In general, a four panel product will also have a significant reduction in compliancedistance compared to the results obtained by using constant maximum power.

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