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Mobile Antenna Systems for 4G and 5G Applications with User Body InteractionZhao, Kun January 2017 (has links)
In the thesis, the user body effect on antennas in a mobile terminal is discussed. In order to overcome the degradation of Multiple-Input Multiple-Output (MIMO) performance due to the user body effect, a quad-elements MIMO antenna array which can mitigate the body effect through an adaptive antenna switching method is introduced for 4G mobile terminals. In addition, various bezel MIMO antennas that are robust to the impedance mismatching caused by the user effect have also been presented. The study of user body effect is later extended to frequency bands at 15 GHz and 28 GHz for future 5G communication systems. The results reveal that a human body will cause a significant shadowing loss, which will be a critical loss in 5G cellular networks. The electromagnetic field (EMF) exposure of a mobile terminal is also studied in this thesis. Below 6 GHz, the simultaneous transmission specific absorption rate (SAR) for MIMO antennas is the primary concern due to its complicated assessment procedures. Above 6 GHz, the free space power density is adopted as the basic parameter of exposure limits globally, and preliminary studies have been presented to address major challenges in EMF exposure assessment for 5G mobile terminals. / <p>QC 20171005</p>
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Modelování propagačního kanálu pro off-body komunikaci v oblasti milimetrových vln / Modelling of mmWave Propagation Channel for Off-body Communication ScenariosZeman, Kryštof January 2019 (has links)
Předkládaná disertační práce je zaměřena na \uv{Modelování propagačního kanálu pro off-body komunikaci v oblasti milimetrových vln}. Navzdory pokrokům v rámci bezdrátových sítí v přímé blízkosti člověka stále systémy 5. generace postrádají dostatečnou šířku pásma a dostatečně nízkou odezvu. To je způsobeno neefektivním využíváním rádiového spektra. Tento nedostatek je potřeba co nejdříve odstranit a právě z tohoto důvodu je hlavním cílem této práce navrhnout vylepšený model rádiového kanálů pro off-body komunikaci. Úkolem tohoto modelu je umožnit uživatelům efektivněji a přesněji simulovat propagaci signálu v rámci daného prostředí. Navržený model je dále optimalizován a ověřen vůči nejnovějším měřením, získaným z literatury. Nakonec je tento model implementován do simulačního nástroje NS-3, pomocí kterého je následně využit k simulaci množství scénářů. Hlavním výstupem této práce je ověřený model přenosového kanálu pro off-body komunikaci v rámci milimetrových vln, společně s jeho implementací do simulačního nástroje NS-3, díky čemuž je dostupný pro širokou veřejnost.
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CHANNEL TRAINING AND SIGNAL PROCESSING FOR MASSIVE MIMO WIRELESS COMMUNICATIONSTzu-Hsuan Chou (13947645) 13 October 2022 (has links)
<p>Future wireless applications will require networks to provide high rates, reduced power consumption, reliable communications, and low latencies in a wide range of deployment scenarios. To support the never-ending growth in wireless data traffic, a solution is to operate wireless networks on the wide bandwidth available at higher frequencies, e.g., millimeter wave (mmWave) and sub-terahertz (sub-THz) bands. However, new challenges arise as networks operating at higher frequencies experience harsher propagation characteristics. To compensate for such severe signal attenuation, the directional beamforming via massive multipleinput multiple-output (MIMO) is adopted to provide array gains, but it necessitates accurate MIMO channel state information incurring unacceptably large training overhead. Wireless system engineers will require to develop fast and efficient channel training algorithms for massive MIMO systems. Another new challenge arises in scenarios without a direct link between the source and destination due to serious pathloss, which requires cooperative relay beamforming to enhance the communication coverage. The beamforming weights of the distributed relays and the receive combiner can be jointly optimized to enhance Quality-of-Service in multi-user relay beamforming networks. Our contributions cover three specific topics as follows: First, we develop a learning-based beam alignment approach, which enables the position-aided beam recommendation to support users at new positions, to reduce the training overhead in MIMO systems. Second, we propose a compressed training framework to estimate the time-varying sub-THz MIMO-OFDM channels with dual-wideband effect. Lastly, we propose a joint relay beamforming and receive combiner design, considering an optimization problem formulation that maximizes the minimum of the receiving signal-to-interference-plus-noise ratios among multiple users. In each specific topic, we provide the algorithms and show the numerical results to demonstrate the improved performance over the state-of-the-art techniques.</p>
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Link blockage modelling for channel state prediction in high-frequencies using deep learning / Länkblockeringsmodellering för förutsägelse av kanaltillstånd i höga frekvenser med djupinlärningChari, Shreya Krishnama January 2020 (has links)
With the accessibility to generous spectrum and development of high gain antenna arrays, wireless communication in higher frequency bands providing multi-gigabit short range wireless access has become a reality. The directional antennas have proven to reduce losses due to interfering signals but are still exposed to blockage events. These events impede the overall user connectivity and throughput. A mobile blocker such as a moving vehicle amplifies the blockage effect. Modelling the blockage effects helps in understanding these events in depth and in maintaining the user connectivity. This thesis proposes the use of a four state channel model to describe blockage events in high-frequency communication. Two deep learning architectures are then designed and evaluated for two possible tasks, the prediction of the signal strength and the classification of the channel state. The evaluations based on simulated traces show high accuracy, and suggest that the proposed models have the potential to be extended for deployment in real systems. / Med tillgängligheten till generöst spektrum och utveckling av antennmatriser med hög förstärkning har trådlös kommunikation i högre frekvensband som ger multi-gigabit kortdistans trådlös åtkomst blivit verklighet. Riktningsantennerna har visat sig minska förluster på grund av störande signaler men är fortfarande utsatta för blockeringshändelser. Dessa händelser hindrar den övergripande användaranslutningen och genomströmningen. En mobil blockerare såsom ett fordon i rörelse förstärker blockeringseffekten. Modellering av blockeringseffekter hjälper till att förstå dessa händelser på djupet och bibehålla användaranslutningen. Denna avhandling föreslår användning av en fyrstatskanalmodell för att beskriva blockeringshändelser i högfrekvent kommunikation. Två djupinlärningsarkitekturer designas och utvärderas för två möjliga uppgifter, förutsägelsen av signalstyrkan och klassificeringen av kanalstatusen. Utvärderingarna baserade på simulerade spår visar hög noggrannhet och föreslår att de föreslagna modellerna har potential att utökas för distribution i verkliga system.
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Trychtýřová anténa s potlačenými bočními laloky / Horn antenna with suppressed side-lobe radiationKaděra, Petr January 2018 (has links)
This master´s thesis is focused on the ways of possible realisation of the directive horn antenna with suppressed side lobes in the frequency bands 71-76 GHz and 81-86 GHz. In this thesis a detailed research of the feasible options including parameters comparison and assessment of pros and cons of the particular solutions has been performed. Among the specified technical requirements, the emphasis has been placed on the manufacturing options and low cost availability of the materials applicable for the given antenna. The main part of the thesis deals with the conical horn antenna loaded with a hyperbolic dielectric lens, further the antenna with flat dielectric lens based on a transmitarray and also the integrated elliptical lens antenna. The following part of the thesis deals with the possibilities of characterizing the properties of the dielectric material of the lens.
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Vehicular Joint Radar-Communication in mmWave Bands using Adaptive OFDM TransmissionOzkaptan, Ceyhun Deniz January 2022 (has links)
No description available.
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Performance of In-Band Full-Duplex for 5G Wireless NetworksAl-Saadeh, Osama January 2016 (has links)
In-band full duplex is a new duplexing scheme that allows radio nodes to transmit and receive, utilizing the same frequency and time resources. The implementation of in-band full duplex was not feasible in practice, due to the effect of self-interference. But then, advances in signal processing made it possible to reduce this effect. However, the system level performance of in-band full duplex has not been investigated thoroughly.Through computer simulations, we investigate the performance of in-band full duplex, for indoor 5G small cell wireless networks. We examine the performance of in-band full duplex in comparison to dynamic and static time division duplexing. Additionally, we analyze the performance of the duplexing schemes with two interference mitigation techniques, namely beamforming and interference cancellation.Our results indicate that for highly utilized wireless networks, in-band full duplex should be combined with beamforming and interference cancellation, in order to achieve a performance gain over traditional duplexing schemes. Only then, in-band full duplex is considered advantageous, at any network utilization, and any downlink to uplink traffic demand proportion. Our results also suggest that in order to achieve a performance gain with in-band full duplex in both links, the transmit power of the access points should be comparable to the transmit power of the mobile stations. / Inomband hel duplex är en ny typ av duplexmetod som tillåter radionoder att sända och ta emot i samma frekvensoch tidsresurs. Att implementera inomband hel duplex har fram tills nu inte ansetts praktiskt genomförbart till följd av självstörningar. Framsteg inom signalbehandling har dock gjort det möjligt att begränsa denna självstörningseffekt. Emellertid har systemprestanda av inomband hel duplex inte undersökts tillräckligt noga i tidigare verk.Inomband hel duplex och dess prestanda för trådlösa 5G småcellsnätverk inomhus har studerats med hjälp av datasimuleringar och jämförts med dynamisk och statisk tidsdelning. Utöver detta har prestanda för de olika duplexmetoderna med avseende på två tekniker för störningsundertryckning, lobformning och störningseliminering, också undersökts.Våra resultat indikerar att för trådlösa nätverk med högt radioresursutnyttjande bör inomband hel duplex kombineras med lobformning och störningseliminering för att uppnå en prestandavinst jämfört med traditionella duplexmetoder. Bara då kan inomband hel duplex anses vara fördelaktig oberoende av radioresursutnyttjande och andelen upp- och nedlänkstrafik.Resultaten tyder också på att sändareffekten för radioaccesspunkterna bör vara jamförbar med den för mobilenheterna för att en prestandavinst med inomband hel duplex ska kunna uppnås. / Wireless networks, In-band full duplex, Static-time division duplexing, Dynamic-time division duplexing, Interference mitigation techniques, small cell, 5G, mmWave bands, Beamforming, Interference cancellation.
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