Search

Ever-increasing data rate demands in mobile networks and the spectrum scarcity at the microwave bands have resulted in the exploration of millimeter-wave (mmWave) frequencies for the next generation of wireless networks. While mmWave frequencies offer large bandwidth, communication at these frequencies is not straightforward due to the challenging propagation characteristics. One approach to overcome the propagation challenge is the use of directional communication with narrow beams at the base station and the user to prepare a link with sufficient received power. Hence, communications with narrow beams pose a new challenge in link establishment and channel estimation based on fine angular scanning. Current mmWave systems apply analog phase arrays that can scan one angle at a time, resulting in high latency and overhead during link establishment. Moreover, mmWave links are sensitive to blockages that lead to the high probability of beam misalignment and the frequent updating of beam scanning, especially in mobile scenarios. Hence, it is desirable to design a low overhead beam selection by exploiting the unique properties of the mmWave channel. Furthermore, to provide adequate coverage and capacity, the density of the base stations in mmWave networks is usually higher than the conventional sub-6 GHz network. This leads to frequent handovers and establishing and maintaining the mmWave links more challenging. Therefore, fast base station discovery (finding the target base station in the handover process), and efficient handover execution techniques, will be required to use the full promise of mmWave cellular networks. Motivated by the mentioned challenges, this thesis considers the beam alignment and handover problems. Specifically, in the first thread of the thesis, inspired by the unique properties of the spatial channel response of mmWave links, we propose a location-aided beam alignment method based on dividing the user trajectory into regions and storing a set of candidate beams for each region in mobile mmWave networks. Our analysis reveals that our proposed method can achieve a high signal-to-noise ratio, and low overhead while being more robust to the location information accuracy compared with some location-aided baselines in the literature. In the second thread of the thesis, we focus on the handover problem. To this end, we formulate the association problem that maximizes the aggregate data rate along the trajectory while guaranteeing a predefined data rate threshold. We also consider the effect of choosing beam tracking or handover when the serving link quality drops on the user throughput along the trajectory. We apply reinforcement learning to learn whether and when the handover and beam tracking should be performed and choose the target base stations. We evaluate the proposed methods through numerical simulations and show promising results in terms of the achieved rate and throughput compared with the comparable methods in the literature. In the third thread of the thesis, we focus on joint link configuration and resource allocation in a multi-user mobile scenario. We consider two kinds of link configuration: base station selection and beamwidth optimization in the case of handover. We apply reinforcement learning to approximate the solution of the association problem. In general, the main objective of our proposed method is to maximize the aggregate throughput of all the users along trajectories and ensure that their throughput in each location is higher than a threshold. Our numerical results demonstrate that the improved policy obtained from joint link configuration and resource allocation significantly outperforms other baseline policies in both throughput and achieved rate. Det ständigt ökande behovet av höga datatakter i system för mobil datakommunikation har medfört en frekvensbrist i mikrovågsområdet. För att tillgodose spektrumbehovet I nästa generations mobilsystem har därför intresset riktats mot millimetervågs-området. Den stora fördelen med detta frekvensområde är att här är tillgången på ledigt spektrum gott. Eftersom våglängden här är en storleksordning mindre än i mikrovågsområdet, är det möjligt att konstruera antenner med kraftig riktverkan, för både sändare och mottagare, på små chip. Å andra sidan medför dessa små antenner en stor utbredningsförlust, varför hög riktverkan är nödvändig. Kommunikationen sker med smala strålar och utmaningen är att kunna rikta dessa med god precision så att etableringen av förbindelser kan ske och att kommunikationskanalens egenskaper kan skattas på ett tillförlitligt sätt. Nuvarande millimetervågssystem använder sig av analoga fasstyrda antenner som kan rikta strålen i en riktning i taget, vilket gör att etableringen av förbindelser kan vara tidsödande. Ett annat problem är att de smala strålarna är känsliga för blockering av föremål som kommer i vägen för strålgången. Detta leder till antennernas strålningsmönster måste uppdateras ofta med hjälp av strålsökning. Speciellt i mobila system där både användare och blockerande föremål rör sig är detta ett problem. Ett annat problem som detta medför är att basstationstätheten i millimetervågsystem måste göra större än i konventionella mikrovågssystem för att kunna bibehålla en god täckning. Många basstationer leder emellertid till många basstationsbyten, s.k. ”Handover” vilket gör etableringen och underhållet av kommunikationslänkarna extra utmanande. Metoder för snabb identifiering av basstationer och effektiva handover-tekniker är nödvändiga för att kunna utnyttja millimetervågssystemens fulla potential. Mot bakgrunden av ovanstående utmaningar, intresserar vi oss i denna avhandling för effektiva strålsöknings- och handover metoder för millimetervågssystem. Mer specifikt så handlar avhandlingens första del om hur man kan utnyttja det faktum att millimetervågskanalens spatiella egenskaper är relativt likartade på närliggande platser. Vi utnyttjar här att strålgångar mätts upp i förväg i ett antal positioner längs mobilens väg. Med hjälp av positionsinformation kan vi nu snabba upp strålsökningen betydligt. Vår analys visar att vi kan uppnå ett högt signal-brus-förhållande och låg overhead samtidigt som metoden fungerar väl även när positionsinformationen är mindre noggrann. I avhandlingens andra del, fokuserar vi på handover-problemet. Vi formulerar basstationsvalet som ett optimeringsproblem där vi maximerar den aggregerade datatakten längs mobilens väg samtidigt som vi garanterar en minsta datatakt på alla platser. Vi tillämpar maskininlärning för valet mellan en mer noggrann strålsökning och handover när transmissionskvaliteten sjunker längs mobilens väg. Vi utvärderar metoderna genom simuleringar som visar lovande resultat vad avser uppnådd datatakt jämfört med tidigare föreslagna metoder. I avhandlingens sista del tar vi även resursallokeringen i beaktande i ett fleranvändar-scenario där många mobiler konkurrerar om ändliga kommunikationsresurser. Vi studerar kombinationer av basstationsval (handover) och strålgångsoptimering. Vi tillämpar maskininlärning för att hitta en approximativ lösning till problemet att maximera den aggregerade överförda datamängden längs mobilernas väg, samtidigt som vi garanterar en minsta datatakt. Våra simuleringsresultat bekräftar att vi kan erhålla en tillförlitlig förbindelse längs mobilernas väg med betydligt bättre prestanda än jämförbara lösningar. QC 20230504

The COVID-19 pandemic has accelerated our transition to an online and self-directed learning environment. In an effort to design better e-learning materials, we investigated the effectiveness of collecting psychophysiological eye-tracking data from participants in response to visual stimuli. In particular, we focused on collecting fixation data since this is closely related to human attention. Current wearable devices allow the measurement of visual data unobtrusively and in real-time, leading to new applications in wearable technology. Despite their accuracy, head-mounted eye trackers are too expensive for deployment on large-scale deployment. Therefore, we developed a low-cost, webcam-based eye tracking solution and compared its performance with a commercial head-mounted eye tracker. Four-minute lecture slides on the 3 rd year electronic engineering course were presented as stimuli to eight learners for data collection. Their eye movement was collected within the pre-defined area of interest (AOI). Our results demonstrate that a low-cost webcam-based eye-tracking solution, combined with machine learning algorithms, can achieve similar accuracy to the head-worn tracker. Based on these results, learners can use the eye tracker for attention guidance. Our work also demonstrates that these webcam-based eye trackers can be scaled up and used in large classrooms to provide real-time information to instructors regarding student attention and behaviour.

The outbreak of the COVID-19 pandemic has caused unprecedented disruption to education and progressed remote teaching as a predominant model for delivering educational content. However, the online teaching and learning model has its challenges, such as the lack of technological tools to quantity the student attention and engagement with the learning content. This paper focuses on developing an e-learning framework for capturing and analysing the students’ attention during remote teaching sessions and subsequently profiling their learning behaviour leveraging eye-tracking data. Our proposed eye-tracking solution deploys a webcam to capture and track raw gaze points that grant the user the freedom of natural head movement and scalability compared to conventional eye-tracking approaches. We derived various gaze metrics in conjunction with state-of the-art machine learning (ML) models like logistic regression, support vector machine and polynomial regression to classify the student attention with an accuracy above 91%. Furthermore, our findings can help in the early detection and diagnosis of attention deficit hyperactivity disorder (ADHD) among students, thus supporting their learning journeys by creating an adaptive learning environment tailored to their needs.

Extremely high data rate demands, and the spectrum scarcity at the microwave bands, make the millimeter wave (mmWave) band a promising solution to satisfy the high data rate demands in wireless networks. The main advantage of moving to the mmWave spectrum is the availability of large bandwidth. Moreover, due to an order of magnitude smaller wavelength of mmWave signals in compared to the conventional bands, many antenna elements can be incorporated in a small size chip to provide high directivity gain both at the transmitter and the receiver sides.Millimeter wave links experience severe vulnerability to the obstacles compared to the conventional sub-6 GHz networks for two main reasons. First, due to the tiny wavelength, mmWave signals can easily be blocked by obstacles in the environment and this causes severe loss. Second, due to the use of directional communications to compensate for the high path-loss (the distance-dependent component of the attenuation), mmWave links are sensitive to blockages that leads to the high probability of beam misalignment and the frequent updating of beamforming vectors. These issues are more challenging in mobile scenarios, in which mobility of the users and obstacles cause frequent re-execution of the beamforming process. Therefore, the tradeoff between the latency of the beamforming process (which latency increases with the number of the re-execution of the beamforming process) and instantaneous user rate is a significant design challenge in mmWave networks. Moreover, to provide adequate coverage and capacity, the density of the base stations in mmWave networks is usually higher than the conventional sub-6 GHz network. This leads to frequent handovers that make maintaining and establishing the mmWave links more challenging. Motivated by the mentioned challenges, this thesis considers the beamforming and handover problems and proposes lightweight joint beamforming and handover methods to guarantee a certain data rate along user trajectory. Specifically, in the first thread of the thesis, inspired by the fundamental properties of the spacial channel response of mmWave links, we propose a beamforming method in mobile mmWave networks. Our analysis reveals that our proposed method is efficient in terms of signaling and computation complexity, power consumption, and throughput in compared to the benchmark. In the second thread of the thesis, we focus on the handover problem. We formulate the association problem that maximizes the trajectory rate while guarantees a predefined data rate threshold. We then extend our problem to the multi-user dense scenario that the density of the users is higher than the base stations and consider the resource allocation in the association optimization problem. We apply reinforcement learning in order to approximate the solution of the association problem. In general, the main objective of our proposed method is to maximize the sum rates of all the users and minimize the number of the handovers and reduce the probability of the events in which the users' rate becomes less than a predefined threshold. Simulation results confirm that our proposed handover method provides a reliable connection along a trajectory in compared to the benchmarks. QC 20210407

Bakgrund: Under 1900-talet och fram till idag har en stor mängd människor invandrat till Sverige vilket har lett till ett mångkulturellt samhälle där personer med olika kulturer söker vård. För att kunna ge kulturkompetent och god vård behöver vårdpersonal en bra förståelse för hur patienter med invandrarbakgrund vill bli bemötta. Vårdpersonalen bör se patienten som en individ, ha ett respektfullt bemötande och ta hänsyn till patientens bakgrund vid mötet. Har vårdpersonalen en förståelse för hur patienterna önskas bemötas kan det minska risken för försämrade behandlingsresultat och sämre vård. Patienter med invandrarbakgrund är en utsatt grupp i det nya landet och en ökad förståelse för hur de upplever bemötandet av vårdpersonalen kan behövas för att potentiellt upplysa och förbättra vården i Sverige. Syfte: Att beskriva invandrares upplevelse av bemötande av vårdpersonal i Sverige. Metod: En kvalitativ litteraturstudie baserad på 12 kvalitativa, vetenskapliga studier från databaserna Pubmed och CINAHL. Resultat: Utifrån studierna framkom 3 huvudkategorier och 3 underkategorier. Huvudkategorierna omfattade “Individens uppfattning i mötet med vårdpersonalen”, “individens bakgrund och kulturella bakgrund” och även “kommunikationens påverkan på bemötandet”. De tre underkategorierna tillhörde huvudkategorin “Individens uppfattning i mötet med vårdpersonalen” vilka innefattade “en känsla av trygghet”, “ett ogynnsamt bemötande” samt “respekt och förståelse”. Dessa kategorier beskriver hur patienter med invandrarbakgrund upplever bemötande av vårdpersonal i Sverige. Patienterna hade en positiv uppfattning om bemötandet när vårdpersonalen lyssnade, tog deras beskrivning seriöst och såg dem som individer vilket skapade tillit till vården. Däremot fick patienter med invandrarbakgrund en negativ uppfattning när bemötandet upplevdes som diskriminerande och respektlöst mot patientens kulturella bakgrund. Slutsats: I resultatet framkom det att patienterna med invandrarbakgrund upplevde vårdpersonalens bemötande som både positivt och negativt. Vården bör anpassas efter individ, bakgrund och önskemål för att förbättra bemötandet till patienter med invandrarbakgrund. Nyckelord: Invandrare, bemötande, vård, upplevelse, vårdpersonal Background: During the 1900th century and to this day many people migrated to Sweden which have led to a multicultural society where people with different cultures are seeking medical care. The healthcare personnel need to have great understanding for how immigrated patients want to be treated to be able to give culturally competent and good care. The healthcare personnel needs to see the patient as an individual, treat with respect and take the patients background into account in the meeting. The risk of impaired treatment outcomes and impaired treatment can be reduced if the healthcare personnel have an understanding of how patients want to be treated. Immigrated patients are an exposed group in the new country and increased knowledge of how they experience the treatment of the healthcare personnel may be needed to potentially inform and improve the health care in Sweden. Aim: To describe immigrants' experience of the attitude of healthcare personnel in Sweden. Method: Literature review based on 12 qualitative scientific studies which was published on two databases Pubmed and CINAHL. Results: There were 3 main categories and 3 subcategories based on the studies .The main categories included “The experience in the meeting with healthcare personnel of the individual”, “Background and cultural background of the individual”, “The impact of communication on the treatment”. The 3 subcategories that belonged to “The experience in the meeting with healthcare personnel of the individual” included “ a feeling of safety”, “unfavorable treatment” and “Respect and understanding”. These categories describe how immigrant patients experience the treatment of healthcare personnel in Sweden. The patients had a positive perception about the treatment when the healthcare personnel listened, took them seriously and saw them as individuals which created a trust to the healthcare. However the patients experienced a negative perception when the treatment was experienced as discriminating and disrespectful to the patient's cultural background. Conclusion: The result presented that patients with an immigrant background experienced the attitude of the healthcare personnel as both positive and negative. Health care should be adapted to the individual, patient's background and request of care to improve the treatment to the immigrated patients. Keywords: Immigrant, treatment, healthcare, experience, healthcare personnel

Paleo-ice sheet reconstructions are complicated by large uncertainties, particularly since it is usually only possible to infer thickness from indirect means such as the response of glacial isostatic adjustment (GIA). Recently, there has been increased attention to refining the chronology of ice sheet margins of paleo-ice sheets, and changes in relative sea level in formerly glaciated regions. Using this information, it is possible to infer the configuration of the ice sheets through time. Using the program ICESHEET (Gowan et al 2016), we reconstruct past ice sheets using a simple, though glaciologically plausible ice sheet model. The ice sheet volume is reconstructed by adjusting the basal shear stress at discrete time intervals in the region of interest until the modelled sea level is consistent with the sea level indicators. We demonstrate this technique by applying it to the Innuitian Ice Sheet. We also show the utility of the models for use in paleo-geographic reconstructions, as well as usage in paleo-climate simulations.