Unmanned Aerial Vehicles (UAVs) connected to cellular networks present novel challenges and opportunities in mobility management and localization, distinct from those faced by terrestrial users. This thesis presents an integrated approach, combining two key aspects essential for the integration of UAVs with cellular networks. Firstly, it introduces the mobility management challenges for cellular-connected UAVs, which differ significantly from terrestrial users. While terrestrial mobility management primarily aims to prevent radio link failures near cell boundaries, aerial users experience fragmented and overlapping coverage with line-of-sight conditions involving multiple ground base stations (BSs). Thus, mobility management for UAVs extends beyond link failure avoidance, aiming to minimize unnecessary handovers while ensuring extended service availability, particularly in up-link communication. Line-of-sight conditions from a UAV to multiple BSs increase the likelihood of frequent handovers, resulting in control packet overheads and communication delays. This thesis proposes two approaches to address these challenges: 1) A model-based service availability-aware Mobility Robustness Optimization (MRO) adapting handover parameters to maintain high service availability with minimal handovers, and 2) A model-free approach using Deep Q-networks to decrease unnecessary handovers while preserving high service availability. Simulation results demonstrate that both the proposed algorithms converge promptly and increase the service availability by more than 40 %  while the number of handovers is reduced by more than 50%  as compared to traditional approaches. Secondly, to assess the ability of a network to support the range-based localization for cellular-connected UAVs, an analytical framework is introduced. The metric B-localizability is defined as the probability of successfully receiving localization signals above a specified Signal-to-Interference plus Noise Ratio (SINR) threshold from at least B ground BSs. The framework, accounting for UAV-related parameters in a three-dimensional environment, provides comprehensive insights into factors influencing localizability, such as distance distributions, path loss, interference, and received SINR. Simulation studies explore the correlation between localizability and the number of participating BSs, SINR requirements, air-to-ground channel characteristics, and network coordination. Additionally, an optimization problem is formulated to maximize localizability, investigating the impact of UAV altitude across different scenarios. Our study reveals that in an urban macro environment, the effectiveness of cellular network-based localization increases with altitude, with localizability reaching 100% above 60 meters. This finding indicates that utilizing cellular networks for UAV localization is a viable option. / Unmanned Aerial Vehicles (UAV) anslutna till cellulära nätverk presenterar nya utmaningar och möjligheter inom mobilitetshantering och lokalisering, skilda från dem som markanvändare står inför. Denna avhandling presenterar ett integrerat tillvägagångssätt, som kombinerar två nyckelaspekter som är väsentliga för integrationen av UAV:er med cellulära nätverk. För det första introducerar den mobilitetshanteringsutmaningarna för mobilanslutna UAV:er, som skiljer sig avsevärt från markbundna användare. Medan markbunden mobilitetshantering i första hand syftar till att förhindra radiolänkfel nära cellgränser, upplever antennanvändare fragmenterad och överlappande täckning med siktlinjeförhållanden som involverar flera markbasstationer (BS). Mobilitetshantering för UAV sträcker sig sålunda bortom att undvika länkfel, och syftar till att minimera onödiga överlämningar samtidigt som man säkerställer utökad servicetillgänglighet, särskilt i upplänkskommunikation. Synlinjeförhållanden från en UAV till flera BS:er ökar sannolikheten för frekventa överlämningar, vilket resulterar i kontrollpaketkostnader och kommunikationsförseningar. Denna avhandling föreslår två tillvägagångssätt för att möta dessa utmaningar: 1) En modellbaserad tjänsttillgänglighetsmedveten Mobility Robustness Optimization (MRO) som anpassar parametrar för överlämning för att bibehålla hög servicetillgänglighet med minimal överlämning, och 2) Ett modellfritt tillvägagångssätt med Deep Q- nätverk för att minska onödiga överlämningar samtidigt som hög servicetillgänglighet bibehålls. Simuleringsresultat visar att båda de föreslagna algoritmerna konvergerar snabbt och ökar tjänstens tillgänglighet med mer än 40% medan antalet överlämningar minskas med mer än 50% jämfört med traditionella metoder. För det andra, för att bedöma förmågan hos ett nätverk att stödja den räckviddsbaserade lokaliseringen för de cellulärt anslutna UAV:erna, introduceras ett analytiskt ramverk.Metriska B-lokaliseringsförmågan definieras som sannolikheten för att framgångsrikt ta emot lokaliseringssignaler över en specificerad signal-till-interferens plus brusförhållande (SINR) tröskel från minst B jord BSs.Ramverket, som tar hänsyn till UAV-relaterade parametrar i en tredimensionell miljö, ger omfattande insikter i faktorer som påverkar lokaliserbarhet, såsom avståndsfördelningar, vägförlust, störningar och mottagen SINR. Simuleringsstudier undersöker korrelationen mellan lokaliserbarhet och antalet deltagande BS:er, SINR-krav, luft-till-mark-kanalegenskaper och nätverkskoordination. Dessutom har ett optimeringsproblem formulerats för att maximera lokaliseringsförmågan, undersöka effekten av UAV-höjd över olika scenarier. Vår studie avslöjar att i en urban makromiljö ökar effektiviteten av mobilnätsbaserad lokalisering med höjden, med lokaliserbarhet som når 100% över $60$ meter. Detta fynd indikerar att användning av mobilnät för UAV-lokalisering är ett gångbart alternativ. / <p>QC 20240319</p>

Background: Society demands increased patient participation in healthcare. One strategy to achieve patient participation during hospital stay in a surgical ward is implementation of handover at the patient’s bedside. The literature discusses the meaning of the concept patient participation, it is therefore important to study if patient participation can be achieved through bedside handover on the clinical ward.Aim: To explore how the bedside handover in nursing was performed on a surgical ward from the patient’s perspective focusing and participation.Method: A qualitative descriptive design with focused observations and informal interviews. A total of 23 observations were done, the analysis was inspired by ethnographic method.Results: Five themes emerged from the analysis: A calm atmosphere, Conditions for participation, To create a sense of “us”, Conversation on equal ground and at last Integrity and secrecy. The patients were active participants during the bedside handovers, they contributed with information and asked questions. The medical vocabulary was simplified and adapted to the patient’s ability. During the interviews the patients stated that the bedside handover created a sense of security and control. The observations showed though, that the patients were not asked to participate nor were they prepared for the report beforehand.Conclusion: This study shows that bedside handover gives the patient a sense of participation in his or her own care and creates a feeling of security and control. The result also shows a need for improvement regarding information, preparation and the opportunity to decline bedside handover, which offers potential to improve the bedside handover’s ability to increase patient participation. / Bakgrund: Samhället efterfrågar ökad patientdelaktighet i vården och ett sätt att möta detta krav är införandet av bedsiderapport på vårdavdelning. Litteraturen förklarar betydelsen av begreppet patientdelaktighet i teorin, det är därför motiverat att genom observation undersöka om patientdelaktighet kan uppnås med hjälp av bedsiderapport i kliniken.Syfte: Att utforska hur bedsiderapportering genomförs på en kirurgisk vårdavdelning med fokus på patientens perspektiv och delaktighet.Metod: En kvalitativ deskriptiv design med fokuserade observationer och informella intervjuer. Totalt genomfördes 23 observationer vilka analyserades med etnografisk data-analysResultat: Studiens resultat mynnade ut i fem teman: En lugn stämning, Förutsättningar för delaktighet, Att skapa en ”vi- känsla”, Samtal på lika villkor samt Integritet och sekretess. Under observationerna sågs att patienterna deltog aktivt i rapporten, de bidrog med information och ställde frågor. Det medicinska språket förenklades och anpassades efter patientens förmåga. Under intervjun uppgav patienterna att bedsiderapporten skapade en känsla av trygghet och kontroll. Dock observerades att patienterna varken tillfrågades om medverkan eller förbereddes inför rapporten.Slutsats: Studien visar att införandet av bedsiderapport får patienten att känna delaktighet i den egna vården och skapar en känsla av trygghet och kontroll. Resultatet påvisar även behov av att genom förbättringsarbete utveckla arbetssättet vidare då brister observerades gällande information, förberedelser och möjlighet att avstå bedsiderapportering. Detta skulle ge potential till förbättring av bedsiderapportens förmåga att skapa patientdelaktighet.

Bakgrund: Sjuksköterskor har i sitt dagliga arbete till uppgift att ge och ta emot rapport om patienterna hen vårdar. En god kommunikation krävs för att säkerställa att relevant information förmedlas och inte patientsäkerheten hotas. Syfte: Att beskriva strategier för hur kommunikationen kan förbättras vid överrapportering mellan sjuksköterskor inom den somatiska slutenvården. Metod: Litteraturöversikten är baserad på 15 vetenskapliga artiklar med kvalitativ, kvantitativ och mixad ansats. Artiklarna identifierades via sökningar i databaserna Cinahl, PubMed och Web of Science. Resultat: Tre strategier framkom: personlig överrapportering, användandet av standardiserade formulär och överrapportering vid patientens säng. Strategierna gav en effektivare, säkrare och mer tidssparande överrapportering. Slutsats: En god kommunikation mellan sjuksköterskorna är oerhört viktigt för att bibehålla en trygg och säker vård för patienterna. För att få en förbättrad kommunikation mellan sjuksköterskor vid överrapportering kan olika strategier användas. Då sjuksköterskorna ofta har en hög arbetsbelastning så krävs det att överrapporteringarna är strukturerade för att inte tappa bort viktig information. / Background: Information handover about patients is a central task in registered nurses’ daily work. Communication is important to safeguard that relevant information is transferred and that patient safety is not violated. Aim: To describe strategies that can improve communication at handover between registered nurses in somatic hospital wards. Method: The literature review is based on 15 scientific articles including qualitative, quantitative and mixed approach, identified in the databases Cinahl, PubMed and Web of Science. Results: Three strategies were identified: individual handover, the use of standardized forms, and bedside nursing handover. These strategies provided a more efficient, safer and more time-saving handover. Conclusion: Different strategies can be used for enhanced handover communication between registered nurses. Registered nurses often have a heavy workload which requires that the handovers are well structured in order not to lose important information. A good communication between nurses are extremely important to maintain a safe and secure care for patients.

This Thesis is an embodiment of some research work carried out towards achieving faster and more reliable handover techniques in a Mobile WiMAX (Worldwide Interoperability for Microwave Access) network. Handover, also called handoff, is the critical mechanism that allows an ongoing session in a cellular mobile network like WiMAX to be seamlessly maintained without any call drop as the Mobile Station (MS) moves out of the coverage area of one base station (BS) to that of another. Mobile WiMAX supports three different types of handover mechanisms, namely, the hard handover, the Fast Base Station Switching (FBSS) and the Micro-Diversity Handover (MDHO). Out of these, the hard handover is the default handover mechanism whereas the other two are the optional schemes. Also, FBSS and MDHO provide better performance in comparison to hard handover, when it comes to dealing with the high-speed multimedia applications. However, they require a complex architecture and are very expensive to implement. So, hard handover is the commonly used technique accepted by the mobile broadband wireless user community including Mobile WiMAX users. The existing Mobile WiMAX hard handover mechanism suffers from multiple shortcomings when it comes to providing fast and reliable handovers. These shortcomings include lengthy handover decision process, lengthy and unreliable procedure of selecting the next BS, i.e., the target BS (TBS) for handover, occurrence of frequent and unwanted handovers, long connection disruption times (CDT), wastage of channel resources, etc. Out of these, reducing the handover latency and improving the handover reliability are the two issues that our present work has focused on. While the process of selecting the TBS for handover adds to the overall delay in completing the process of handover, choosing a wrong TBS for handover increases the chance of further unwanted handovers to occur or even a call drop to occur. The latter greatly hampers the reliability of a handover. In order to contribute to the solution of the above two problems of slow handover and unreliable handover, this Thesis proposes and investigates three handover techniques, which have been called Handover Techniques 1, 2 and 3, respectively. Out of these three techniques, the first two are fully MS-controlled while the third one is a dominantly serving BS-controlled. In Handover Techniques 1 and 2, which share between them some amount of commonness of ideas, the MS not only itself determines the need for a handover but also self-tracks its own independent movement with respect to the location of the (static) neighboring BSs (NBS). N both these handover techniques, the MS performs distance estimation of the NBSs from the signal strength received from the NBSs. But they (the two handover techniques) employ different kinds of “lookahead” techniques to independently choose, as the TBS, that NBS to which the MS is most likely to come nearest in the future. Being MS-controlled, both Handover Technique 1 and Handover Technique 2 put minimal handover-related workload on their respective SBSs who thus remain free to offer services to many more MSs. This interesting capability of the two handover techniques can increase the scalability of the WiMAX network considerably. In Handover Technique 3, which is a BS-controlled one with some assistance received from the MS, the SBS employs three different criteria or parameters to select the TBS. The first criterion, a novel one, is the orientation matching between the MS’s direction of motion and the geolocation of each NBS. The other two criteria are the current load of each NBS (the load provides an indication of a BS’s current QoS capabilities) and the signal strength received by the MS from each NBS. The BS assigns scores to each NBS against each of the three independent parameters and selects the TBS, which obtains the highest weighted average score among the NBSs. All three handover techniques are validated using simulation methods. While Handover Techniques 1 and 2 are simulated using Qualnet network simulator, for Handover Technique 3, we had to design, with barest minimum capability, our own simulation environment, using Python. Results of simulation showed that for Handover Techniques 1 and 2, it is possible to achieve around 45% improvement (approx) in the overall handover time by using the two proposed handover techniques. The emphasis in the simulation of the Handover Technique 3 was on studying its reliability in producing correct handovers rather than how fast handovers are. Five different arbitrary pre-defined movement paths of the MS were studied. Results showed that with orientation matching or orientation matching together with signal strength, reliability was extremely good, provided the pre-defined paths were reasonably linear. But reliability fell considerably when relatively large loads were also considered along with orientation matching and signal strength. Finally, the comparison between the proposed handover techniques in this Thesis and few other similar techniques in Mobile WiMAX proposed by other researchers showed that our techniques are better in terms providing fast, reliable and intelligent handovers in Mobile WiMAX networks, with scalability being an added feature.

Bakgrund: Studier visar att struktur och relevans i muntlig överrapportering är av stor vikt då detta ökar patientsäkerheten. I nuläget finns ingen allmänt accepterad mall för muntlig överrapportering av patienter i Sverige. En modell för muntlig överrapportering som nu börjat introduceras på svenska sjukhus är SBAR, vilken rekommenderas av Sveriges Kommuner och Landsting. Syfte: Att undersöka akutmottagningssjuksköterskors uppfattningar av muntlig överrapportering från ambulanspersonalen vid larm/prioritet 1, på ett av Stockholms sjukhus. Metod: En empirisk tvärsnittsstudie med enkät som underlag för datainsamlingen utfördes. Studien hade kvantitativ design med deskriptiv ansats. Enkätens frågor utformades utifrån SBAR för akuta situationer. Totalt insamlades 21 enkäter, besvarade av nio olika sjuksköterskor. Resultat: Alla deltagande sjuksköterskor utom en önskade en gemensam mall för överrapportering. Information om allergier, smittorisker, social bakgrund och ADL-förmåga, överrapporterades i mycket begränsad utsträckning. Sjuksköterskorna svarade, i majoriteten av fallen, att de inte saknade något i överrapporteringen. Slutsats: I denna studie finns en önskan om en gemensam mall för  överrapportering mellan ambulanspersonal och akutmottagningspersonal. Till skillnad från tidigare studier visar denna studie att viss information inte tycks vara nödvändig i den akuta situationen. / Background: Previous studies show that the structure and relevance in verbal handover of patients is of great importance with regard to patient safety. There is no generally accepted template for verbal handover of patients in Sweden. A model for verbal handover (SBAR) that is recommended by Swedish Association of Local Authorities and Regions is now being introduced in Swedish hospitals. Objective: To study the perception of verbal handover of patients from paramedics to emergency department nurses in an emergency hospital in Stockholm. Method: An empirical cross-sectional study with a questionnaire as a basis for data collection. This study had a quantitative design with a descriptive approach. The questionnaire was designed based on SBAR for emergency situations. In total 21 questionnaires from nine nurses were evaluated. Results: All nurses, except one, would appreciate a common template for verbal handover. Information on allergies, contagious risks, social background and ADL-capabilities was rarely reported during handover. The majority of nurses reported that they did not miss any information in the verbal handover. Conclusion: This study shows a need for a common template for verbal handover from ambulance staff to emergency department nurses. Contrary to previous studies there is also a view that some information is unnecessary in the emergency situation.

Regarding class transovers, there is a common problem when teachers of the first grade take over a new class. The problem is that the new teachers do not receive enough information about the pupils’ earlier knowledge from their development in school. It is also known that the writing education is one of the most important duties for teachers to teach pupils. The ability of writing thoughts into words is a source of communication between the writer and the reader. An undeveloped writing ability will cause a lack of communication for the pupils. The purpose of this study is to examine how individualizing is done at the transitions from pre-school to first grade. The study also explores how and with which methods teachers work with an individualized writing education in the subject Swedish in first grade. The study will also examine the possibilities and difficulties that can occur at an individualized writing education. I prepared three following questions to answer the aim of this study: How does the individualizing in class transfers look like from pre-school to first grade? How and with which methods teachers individualize the writing education in first grade? Which possibilities and difficulties can occur with an individualized writing education? The study is based on interviews with four pre-school teachers and four first grade teachers to get answers for this study’s aim. The study is also based on theories about transfers and individualized education. The results showed that pre-school teachers and first grade teachers do not have a clue about how the other teacher works with the pupils. The study shows that first grade teachers do not receive the information they need to individualize the education for the pupils. The results also show that all the teachers have a positive attitude to individualizing in the education, but are unable to plan individualized lessons and assignments for each student because of their lack of time and big classes.

Avec l’évolution rapide des technologies réseaux et télécoms radios mobiles, les chercheurs sont actuellement en train de préparer l’arrivée d’une nouvelle génération baptisée 4G. Le réseau de 4ème génération qui est encore l’objet de travaux de recherche vise à améliorer l’efficacité spectrale et à augmenter la capacité de gestion du nombre des mobiles dans une même cellule. Il tend à offrir des débits élevés en situation de mobilité à grande ou faible vitesse. Il vise aussi à permettre et à faciliter l’interconnexion et l’interopérabilité entre différentes technologies existantes en rendant transparent à l’utilisateur le passage entre les réseaux. Enfin, il vise à éviter l’interruption des services durant le transfert intercellulaire, et à basculer l’utilisation vers le tout IP. Dans ce contexte, nous nous sommes intéressés en premier lieu aux problématiques de la QoS en situation de mobilité au sein d’une technologie candidate à la 4G (WiMAX mobile) pour du trafic temps-réel. Pour cela, nous avons comparé la performance de plusieurs protocoles de mobilité dans le contexte du Handover de niveau 2 et de niveau 3 et plus. Nous avons pour cela fait varier les modèles de mobilité, les configurations et les scénarios. Enfin, nous avons modélisé un algorithme décisionnel qui gère le Handover dans le WiMAX mobile en fonction de plusieurs paramètres d’entrées. Au travers de ces études, nous avons dégagé des protocoles de mobilité qui offrent un niveau de QoS acceptable pour un trafic temps-réel dans le cadre des scénarios envisagés. En deuxième lieu, nous nous sommes concentrés sur les problèmes d’interconnexion et d’interopérabilité entre les réseaux en tenant compte de la mobilité et du Handover vertical entre deux technologies. Pour cela, nous avons proposé de comparer des protocoles de mobilité puis de les combiner afin de diminuer les délais des trafics temps-réel au cours du Handover. Au niveau de l’interconnexion, nous avons proposé des modèles entre WiMAX mobile et de nombreux autres standards (802.11e, UMTS, DVB-S/RCS, LTE). Outre les solutions d’interconnexion, nous avons également mis en évidence la ou les combinaisons de protocoles de gestion de la mobilité qui permettent de garantir de la QoS. / With the rapid evolution of mobile radio telecommunications and networks technologies, researchers are currently preparing the arrival of a new generation called 4G. The 4th generation network aims to improve spectral efficiency and increase capacity to manage a large number of mobiles in a cell. It tries to provide high flow rates under high or low mobility. It also aims to enable and facilitate the interconnection and the interoperability between different technologies allowing transparent transition between networks. Finally, it aims to avoid interruption of services during the handover, and to switch an all-IP system. In this context, we are concerned first with QoS and mobility issues in Mobile WiMAX for the real-time traffic. We compared the performance of several mobility protocols in the context of the level 2 and level 3+ handovers. Several mobility models, configurations and scenarios were considered. Finally, we modeled a decision algorithm that manages the handover in mobile WiMAX based on several input parameters.Through these studies, we have identified mobility protocols that provide an acceptable QoS level for real-time traffic under the proposed scenarios. Secondly, we focused on the problems of interconnection and interoperability between networks, taking into account the mobility and vertical handovers between two technologies. For this, we proposed to compare mobility protocols or combine them to reduce delays for real-time traffic during the handover. We also proposed interconnection models between mobile WiMAX and many other standards (802.11e, UMTS, DVB-S/RCS, LTE). Besides interconnection solutions, we also highlighted the combination or combinations of management mobility protocols that can guarantee QoS.

Bakgrund: Tidigare forskning har visat att patienter som överrapporteras från intensivvårdsavdelning till vårdavdelning är i en särskilt sårbar situation och att bristfälliga överrapporteringar är ett internationellt patientsäkerhetsproblem. Syfte: Syftet var att beskriva intensivvårdssjuksköterskors och avdelningssjuksköterskors upplevelser av överrapportering av patienter från intensivvårdsavdelning till vårdavdelning. Syftet var också att beskriva vad intensivvårdssjuksköterskor och avdelningssjuksköteskor ansåg vara viktigt vid överrapporteringen. Metod: Studien hade en kvalitativ ansats med beskrivande design. Åtta semistrukturerade intervjuer gjordes med intensivvårdssjuksköterskor (n=4) och legitimerade sjuksköterskor på vårdavdelning (n=4). Intervjuerna analyserades därefter med kvalitativ innehållsanalys. Huvudresultat: Vid analys av intervjuerna framträdde sex kategorier 1) Att se vikten av samverkan, 2) Att ta emot och ge relevant information för den fortsatta vården på vårdavdelningen, 3) Att ge och ta emot information från ett kunskapsområde till ett annat, 4) Miljöns betydelse vid överrapportering, 5) Att ha behov av strukturerad rapport och 6) Att känna ansvar. Intensivvårdssjuksköterskor och sjuksköterskor från vårdavdelning upplevde att brist på förberedelser inför överrapportering försvårade samarbetet. De upplevde att olika information var viktig vid överrapportering på grund av deras olika kunskapsområden. Båda yrkesgrupperna önskade att informationen skulle vara tydlig med relevant information för den fortsatta vården. De upplevde att miljön med frekventa störningar gjorde att information missades och att en strukturerad rapport gjorde överrapporteringen tydligare. De uttryckte också att de har ett ansvar vid informationsöverföringen. Slutsatser: Samverkan, strukturerad information för den fortsatta vården, kunskap, miljö och ansvar kan ha betydelse vid överrapportering och att utrymme för förbättring finns för att öka patientsäker överrapportering av patient mellan vårdinrättningar. / Background: Studies have shown that the patients that are handed over from the intensive care unit to ward are in a particular vulnerable situation, and that deficient handover is an international patient safety problem. Aim: The aim was to describe the intensive care nurse's and ward nurse's experiences of handover patients from the intensive care unit to the ward. The aim was also to describe what the intensive care nurses and ward nurses considered important during the handover. Method: The study had a qualitative approach with descriptive design. Eight semi structured interviews with intensive care unit nurses (n=4) and registered ward nurses (n=4) were conducted. The interviews were analyzed with qualitative content analysis. Main results: Thorough the analyze six categories emerged 1) To see the importance of collaboration, 2) To receive and provide relevant information for the continuum of care, 3) To give and receive information from one level at knowledge to another, 4) The importance of the environments during handover, 5) The need of a structured handover, and 6) To feel the responsibility. The intensive care nurses and the registered ward nurses experienced that lack of preparation before the handover complicated the cooperation during handover. They expressed that different information was important during handover and that they had different areas of knowledge. Both professional groups wanted the information to be clear and relevant for the continued care. They felt that the environment, with frequent interruptions, resulted in missing information and that a structured report made the handover more direct. They also felt that they had a responsibility in the transfer of information. Conclusions: Collaboration, structured information relevant for the continued care, knowledge, the environment, and responsibility can be important during handover and there is room for improvement to increase patient safe handover between healthcare facilities.

More and more so-called soft real-time traffic is being sent over IP-based networks. The bursty, data-limited traffic pattern as well as the latency requirements from this traffic present challenges to the traditional communication techniques, designed for bulk traffic without considering latency. To meet the requirements from soft real-time traffic, in particular from telephony signaling, the Stream Control Transmission Protocol (SCTP) was designed. Its support for connectivity to multiple networks, i.e., multihoming, provides robustness and opens up for concurrent multipath transfer (CMT) over multiple paths. Since SCTP is a general transport protocol, it also enables for handover of media sessions between heterogeneous networks. Migrating an ongoing session to a new network, as well as CMT with minimal latency, requires tuning of several protocol parameters and mechanisms. This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming from three perspectives. The first focus is on latency for signaling traffic in case of path failure, where a path switch, a failover, occurs. We regard quick failure detection as well as rapid startup on the failover target path. The results indicate that by careful parameter tuning, the failover time may be significantly reduced. The second focus in the thesis is on latency for signaling traffic using CMT. To this end, we address sender-side scheduling. We evaluate some existing schedulers, and design a dynamic stream-aware scheduler. The results indicate that the dynamic stream-aware scheduler may provide significantly improved latency in unbalanced networks. Finally, we target multihomed SCTP to provide for handover of a media session between heterogeneous wireless networks in a mobile scenario. We implement a handover scheme and our investigation shows that SCTP could provide for seamless handover of a media session at walking speed. / So-called soft real-time traffic may be sent over IP-based networks. The bursty, data-limited traffic pattern and the latency requirements from this traffic present a challenge to traditional communication techniques. The Stream Control Transmission Protocol (SCTP), with support for multihoming, was designed to better meet the requirements from soft-real time traffic. Multihoming provides for robustness and for concurrent multipath transfer (CMT) as well as for handover of sessions between heterogeneous networks. Still, to meet the timeliness requirements, tuning of protocol parameters and mechanisms is crucial. This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming. The first focus is on signaling traffic in case of path failure, where a path switch, a failover, occurs. We show that careful parameter tuning may reduce the failover time significantly. The second focus is on signaling traffic using CMT. We address sender-side scheduling and show that dynamic stream-aware scheduling may reduce latency when data is transmitted over asymmetric network  paths. The third focus is multihomed SCTP for handover between heterogeneous networks, where we show that SCTP could provide for seamless handover of a media session at walking speed. / <p>Paper 3 (Efficient Scheduling to Reduce Latency...) ingick i avhandlingen som manuskript med samma namn.</p>

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-08-04T11:41:55Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseHandoverUso.pdf: 2133192 bytes, checksum: ae58db52bf0b0c0d78cf1ef4fb5195c7 (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-09-04T14:45:47Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseHandoverUso.pdf: 2133192 bytes, checksum: ae58db52bf0b0c0d78cf1ef4fb5195c7 (MD5) / Made available in DSpace on 2014-09-04T14:45:47Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseHandoverUso.pdf: 2133192 bytes, checksum: ae58db52bf0b0c0d78cf1ef4fb5195c7 (MD5) Previous issue date: 2014 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O volume de tráfego de dados em redes celulares está crescendo exponencialmente. A explosão do uso de dispositivos e aplicações móveis nos últimos anos, tem levado a uma sobrecarga da infraestrutura da rede responsável pelo escoamento desse tráfego, afetando tanto o desempenho da rede quanto a experiência do usuário. Um dos elementos-chave nas redes LTE (Long Term Evolution) é a possibilidade de implantação de múltiplas femtocells para a melhoria de cobertura e taxa de dados. No entanto, as sobreposições arbitrárias na cobertura dessas células tornam a gestão do mecanismo de handover complexo e desafiador. Nesse sentido, esta dissertação propõe uma metodologia para o estudo do impacto do handover em redes LTE com femtocells. A partir de uma abordagem de simulação discreta, os efeitos da implantação de femtocells foram avaliados. Objetivou-se com isso, mensurar os impactos e a correlação do uso de femtocell nos parâmetros de QoS (Quality of Service) e indicadores de desempenho de handover. / The volume of data traffic in mobile networks is growing exponentially. The explosion of mobile devices and applications in recent years has led to an overload of the network infrastructure responsible for disposing of this traffic, thus affecting the performance of the network as the user experience. One of the key elements in the networks (LTE) Long Term Evolution is the possibility of deploying multiple femtocells for the improvement of coverage and data rate. However, arbitrary overlapping coverage of these cells makes the handover mechanism complex and challenging. Thus, this dissertation proposes a methodology to study the impact of handover in LTE networks with femtocells. From a discrete simulation approach, the effects of the deployment of femtocells were evaluated. This study aimed to measure the impact and correlation of the use of femtocell parameters of QoS (Quality of Service) and performance indicators handover.