Media independent handovers : network selection for mobile IP nodes in heterogeneous wireless networks

Includes abstract.Includes bibliographical references (p. 79-82).In Next Generation Networks (NGN), also known as 4G, Beyond 3G, Converged, Integrated and Interworked Network, user node mobility in wireless and wired environments will seamlessly cross disparate network boundaries. The effort to offer ubiquitous computing, providing access to services anywhere and anytime, strongly encourages the ability to roam across the different existing and future networks. Literature shows investigation of concepts such as Always Best Connected (ABC) when heterogeneous networks co-exist , which will work or compete with other schemes like Home Network Default (HND), Compatibility and Network Operator Agreements (CNOA) to guide network selection or access . With the variety of available networks, the mobile node may be faced with having to decide which network to connect to. We concentrate on the network selection aspects of these envisaged mobile, overlay and integrated environment in heterogeneous networks. The standard developments by the IEEE802.21 Working group and the IETF Networking group form the base of our approach that seeks to see mobility across heterogeneous networks a reality. We propose an IEEE802.21 Media Independent Handover Function (MIHF) based network discovery and network selection, leading to a handover. The selection may be further assisted by an MIHF capable Broker Node that is Third party to the Network Providers to provide a central yet distributed database of the available networks as encountered by the Mobile Node, to cater for Nodes with no prior knowledge of networks and software repository. A Mobile Node (MN) in our solution uses 802.21 communication messages to obtain information about foreign networks encountered before selecting the networks to connect to. Our evaluation through simulations, shows that network selection in heterogeneous wireless networks environment for the appropriately equipped devices is greatly enhanced by the use of the Media Independent Handover Protocol. In scenarios where the mobile node has no prior knowledge of the encountered different network architectures, the use of a Broker node can, for an optimal number of available networks also greatly enhance the mobile node’s network selection by reducing the delay associated and the packet losses incurred

Network-Assisted Handover for Heterogeneous Wireless Networks using IEEE 802.21

The IEEE 802.21 is a standard for enabling handover in heterogeneous wireless networks. Published in January 2009, it defines protocols and messages for mobile-to-node and node-to-node communication in a technology-neutral and flexible manner. The need arises because of the widespread diffusion of different technologies for wireless communications (e.g., WiFi, WiMAX, LTE) coexisting in the same geographical area. Even though the number of multi-radio multi-technology mobile devices is increasing significantly, there are no open solutions in the market to enable efficient inter-technology handover. As is often the case with communication standards, the structure of the required components, the procedures, and the algorithms are left unspecified by the IEEE 802.21 standard so as to promote competion by differentiation of equipment capabilities and services. The contribution of this thesis is two-fold: i) a design and an implemenation of the Media Independent Information Service (MIIS) server; and, ii) a solution to enable network-assisted handover using the IEEE 802.21 standard, aimed at reducing the handover latency and the energy consumption of mobile devices due to scanning. The MIIS server has been fully implemented in C++ under Linux. In order to perform testbed evaluations, all the required components have been implemented, as well, within an open source framework for IEEE 802.21 called ODTONE. Modifications to the latter have been performed for optimization and fine tuning, and for extending those functional modules needed but not fully implemented. For a realistic evaluation, Linux-based embedded COTS devices have been used, equipped with multiple IEEE 802.11a and IEEE 802.11g wireless network interface cards. This has required additional development for kernel/user space binding and hardware control. Testbed results are reported to show the effectiveness of the proposed solution, also proving the MIIS server scalability

Investigating seamless handover in VANET systems

Wireless communications have been extensively studied for several decades, which has led to various new advancements, including new technologies in the field of Intelligent Transport Systems. Vehicular Ad hoc Networks or VANETs are considered to be a long-term solution, contributing significantly towards Intelligent Transport Systems in providing access to critical life-safety applications and infotainment services. These services will require ubiquitous connectivity and hence there is a need to explore seamless handover mechanisms. Although VANETs are attracting greater commercial interest, current research has not adequately captured the realworld constraints in Vehicular Ad hoc Network handover techniques. Due to the high velocity of the vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one Road Side Unit (RSU) to another and this comes at the cost of overlapping signals of adjacent RSUs. Therefore, a framework is needed to be able to calculate the regions of overlap in adjacent RSU coverage ranges to guarantee ubiquitous connectivity. This thesis is about providing such a framework by analysing in detail the communication mechanisms in a VANET network, firstly by means of simulations using the VEINs framework via OMNeT++ and then using analytical analysis of the probability of successful packet reception. Some of the concepts of the Y-Comm architecture such as Network Dwell Time, Time Before Handover and Exit Times have been used to provide a framework to investigate handover issues and these parameters are also used in this thesis to explore handover in highly mobile environments such as VANETs. Initial investigation showed that seamless communication was dependant on the beacon frequency, length of the beacon and the velocity of the vehicle. The effects of each of these parameters are explored in detail and results are presented which show the need for a more probabilistic approach to handover based on cumulative probability of successful packet reception. In addition, this work shows how the length of the beacon affects the rate of change of the Signal-to-Noise ratio or SNR as the vehicle approaches the Road-Side Unit. However, the velocity of the vehicle affects both the cumulative probability as well as the Signal-to-Noise ratio as the vehicle approaches the Road-Side Unit. The results of this work will enable systems that can provide ubiquitous connectivity via seamless handover using proactive techniques because traditional models of handover are unable to cope with the high velocity of the vehicles and relatively small area of coverage in these environments. Finally, a testbed has been set-up at the Middlesex University, Hendon campus for the purpose of achieving a better understanding of VANET systems operating in an urban environment. Using the testbed, it was observed that environmental effects have to be taken into considerations in real-time deployment studies to see how these parameters can affect the performance of VANET systems under different scenarios. This work also highlights the fact that in order to build a practical system better propagation models are required in the urban context for highly mobile environments such as VANETs

Development of a model to address the content, process and communication aspects of emergency centre handover

Introduction: The emergency centre forms the first formal interaction between the prehospital and inhospital phases of the patient care continuum. There are several variables that have the potential to affect handover efficacy. Poor handover has been associated with an increase in sentient events and a risk to patient safety. This thesis aimed to investigate the perceptions of the practice of patient handover between prehospital emergency care providers and the emergency centre. This information was used to generate a model that addresses identified aspects of the emergency centre handover, namely content, process, and communication. Methods: The methodology followed a sequential, explanatory, mixed-methods design. Data were collected from prehospital emergency care personnel (PECP) and emergency centre personnel (ECP) in the Johannesburg area of South Africa. Study One and Study Two formed the quantitative and qualitative data collection phases respectively. Study One formed the quantitative component of the study using a survey that utilised a crosssectional, convenience design. Questionnaires were compiled de novo using data sourced from a search of major databases and were pilot tested prior to distribution. Questionnaires contained a mix of Likert-type, forced binary and open-ended questions. Questionnaires were distributed using a purposive, convenience strategy where potential participants were approached at their place of work. Data were analysed descriptively and reported on. The responses to the open-ended questions were used to compile the interview schedule used in Study Two. Study Two formed the qualitative approach of the thesis and used a qualitative descriptive design. Questions for Study Two were compiled using the results of the coding, analysis and interpretation of the responses to the open-ended questions from the paper-based questionnaire. Data were collected from 15 PECP and 15 ECP using face-to-face, semi structured interviews. Participants were approached using a purposive strategy and, where consent was obtained, were interviewed in a location that was conveniently available and afforded an adequate amount of privacy. Interviews were transcribed and then analysed using Computer-Assisted Qualitative Data Analysis Software Atlas.ti. Data were read and reread, coded and analysed to identify categories and themes that were then reported. A code-recode strategy ensured trustworthiness. Results: Handover content variables were ranked according to the perceived level of importance by prehospital emergency care and ECP. Physiological variables dominated the ten most important variables for both PECP and ECP. Handover quality was perceived by both PECP and ECP as requiring improvement. Less than half of both PECP and ECP had been exposed to formal handover training. Mnemonic knowledge was generally poor, and the most familiar mnemonic used by PECP was unfamiliar to the ECP. The same was true for the mnemonic most familiar to the ECP. Process factors that had the potential to affect the efficacy of emergency centre handover included repetition of information and having to hand over multiple times. The busyness of the emergency centre and the noisy environment associated with it were linked to compromised patient privacy and a distractive environment in which to hand over. Understaffing and overworked staff were identified as barriers to an effective handover process and contributors to some of the identified issues related to poor emergency centre handover. There were several communication factors identified by both PECP and ECP that negatively affected handover efficacy. Verbal, non-verbal and paraverbal cues were identified as having he potential to act as facilitators of or barriers to effective emergency centre handover. Listening skills were identified as a barrier to effective handover by both PECP and ECP. Interprofessional communication and relationships were identified as important for effective emergency centre handover. Using the data, a novel model was developed using an iterative process. The model proposes solutions to some of the content, process and communication problems that were identified in this thesis. The model sees handover as comprising of five phases of information flow and unlike many previous models, recognises the bidirectional nature of communication within the handover process. Conclusion: Emergency centre handover between PECP and ECP needs improvement. The novel model proposed in this thesis divides handover into phases, each of which has identified factors that have the potential to act as facilitators of or barriers to effective handover. The model has potential to be implemented in emergency centre handover environments and may also have relevance in other patient handover environments

Security-centric analysis and performance investigation of IEEE 802.16 WiMAX

fi=vertaisarvioitu|en=peerReviewed

Support of resource-aware vertical handovers in WLAN hotspots

Endgeräte wie Smartphones oder Tablets bieten häufig eine Vielfalt drahtloser Zugänge zum Internet an. Üblicherweise schließt dies die 802.11 WLANs und auch Technologien drahtloser Weitverkehrsnetze (WWANs) aus dem Bereich LTE oder WiMAX ein. Aufgrund dieser Optionen haben sich die Endanwender daran gewöhnt, überall und zu jeder Zeit auf ihre Internetdienste zuzugreifen. Damit hat auch der Datenverkehr pro Anwender zugenommen, was eine Herausforderung insbesondere für die Betreiber von WWANs ist. Soweit verfügbar, favorisieren Endanwender heutzutage eher einen drahtlosen Zugang zum Internet über WLANs als über WWANs. Des Weiteren haben die 3GPP-Standardisierungsgremien Ansätze erarbeitet, die zusätzlich Verkehr aus WWANs in Netze mit geringerer Abdeckung wie WLAN- oder Femto-Zellen abgeben. Solche Ansätze werden auch als "Traffic Offloading" bezeichnet und haben das Ziel, die WWANs zu entlasten. Dabei werden jedoch eher einfache Strategien verfolgt, die auf der Nutzung zusätzlicher Kapazitäten heterogener Netze beruhen und dann angewendet werden, wenn ein alternatives Zugangsnetz für ein Endgerät verfügbar ist. Im Rahmen dieser Arbeit zeigen wir Gewinne auf, die entstehen, wenn man die Auswahl der Endgeräte für ein WLAN-Netz stattdessen auf Basis der von ihnen belegten Ressourcen durchführt. In diesem Kontext schlagen wir vor, Geräte mit stark negativem Einfluss auf die WLAN-Kapazität wieder zurück in das WWAN zu reichen, was wir als "Onloading" bezeichnen. Ein solches "Onloading" zieht Herausforderungen in unterschiedlichen Richtungen mit sich. Die fortschreitende Miniaturisierung hat in den letzten Jahren zu dem Trend geführt, die Anzahl der Netzwerkkarten (NICs) in Endgeräten zu reduzieren. Wir bezeichnen eine NIC als multimodal, wenn sie mehrere Funktechnologien unterstützt, aber zu einem bestimmten Zeitpunkt immer nur eine davon genutzt werden kann. Deswegen stellt für eine multimodale NIC das "Onloading" während einer laufenden Verbindung eine Herausforderung dar. Wir schlagen einen Ansatz vor, der vorbereitende Mechanismen für ein "Onloading" als auch eine laufende Verbindung im WLAN über eine solche NIC ermöglicht. Des Weiteren ist es wichtig, in einem WLAN Hotspot zu entscheiden, welche Geräte einen negativen Einfluss auf die Kapazität des Netzes haben. Dafür haben wir eine Metrik entwickelt, die eine Entscheidungsgrundlage für das Onloading bildet. Diese Metrik basiert rein auf einer Beobachtung des Netzes und seiner Geräte, ermöglicht jedoch keine Entscheidung für sich neu assoziierende Geräte im WLAN. Erschwerend kommt hinzu, dass viele Eigenschaften der NICs durch herstellerabhängige Implementierungen geprägt werden. Solche Algorithmen bieten eine zusätzliche Herausforderung, da ihre internen Abläufe üblicherweise unbekannt sind. Ein bekanntes Beispiel für solche Algorithmen stellt die Anpassung der WLAN-Link-Datenraten dar. Diese Algorithmen wählen die jeweiligen Modulations- und Kodierungsschemata (MCSs) für die drahtlosen Übertragungen aus. Robuste MCSs resultieren dabei in geringere Link-Datenraten und haben somit einen starken Einfluss auf die Kapazität einer WLAN-Zelle. Aus diesem Grund fokussieren wir uns auf eine Abschätzung der Datenratenwahl eines Endgerätes. Damit lassen sich im Vorfeld Aussagen treffen, ob ein Gerät starken Einfluss auf die WLAN-Kapazität haben wird, so dass es für ein "Onloading" in Frage kommt.End-user devices such as smart phones and tablets have become very popular as they offer a variety of wireless Internet accesses ranging from the WLAN standards to WWAN technologies such as LTE or even WiMAX. Due to these different wireless access options and new emerging applications—e.g., from the areas of video streaming, social networks, as well as Internet clouds—people are increasingly connecting to the Internet with their de- vices while being on the move. In line with this, the number of devices as well as the traffic demand of end users have been reported to increase rapidly over the last years which imposes a strong challenge especially for the operators of WWANs. Thereby, end users frequently tend to use settings that favor a connectivity to the Internet whenever possible rather over WLAN than over WWAN access. Further, the cellular standardization bodies of the 3GPP envision solutions to hand over on-going wireless sessions from cellular to other small cell accesses such as WLANs or femto cells. This is also known as traffic offloading essentially freeing capacity in terms of users with a certain service in the cellular accesses. Nevertheless this offloading follows a rather simple strategy to utilize additional capacity of heterogeneous accesses such as WLANs whenever being available for a given device. This thesis shows that stronger gains can be expected if the selection of devices to be served in WLANs is conducted in a resource-aware fashion including an evaluation of the WLAN traffic in terms of the channel occupation time and MAC overhead as result of contention, interference, and fluctuating channels. In this context, this thesis envisions to onload unfavorable devices negatively affecting the WLAN capacity back to WWAN accesses. A support of such an onloading imposes challenges in different dimensions. From the hardware design of devices, there is a strong trend to limit the number of separate network interface cards (NICs) due to space and cost issues. We refer to a multi-mode NIC if it covers multiple technologies, while at a given time only access to one technology is possible. Thus, smoothly onloading a device with such a NIC is by far not trivial. We present an approach that conducts handover preparation mechanisms, while also allowing a continuous WLAN communication over a multi-mode NIC. Further, it is by far not trivial to judge which subset of associated devices is negatively affecting the capacity of a WLAN hotspot. Thus, a careful evaluation of devices regarding a selection for an onloading back to WWAN accesses imposes a challenge yet. In this direction, we present a performance metric that identifies devices degrading the WLAN capacity. While our performance metric tackles a reactive selection, it falls short to support a predictive evaluation, e.g., of devices which just joined the WLAN cell. Even worse, proprietary algorithms inside a WLAN stack impose a severe challenge as their internal routines are usually not conveyed via typical management interfaces. A well-known example for this category of algorithms are the link data rate adaptation schemes, with which WLAN devices adjust the modulation and coding scheme (MCS) for their transmissions. As MCSs resulting in low link data rates may specifically degrade the capacity of a WLAN cell, we focus on an estimation regarding the data rate selection of a device as a third contribution of this thesis. This estimation enables to select devices that will likely degrade the capacity of the WLAN hotspot for an onloading in advance

A framework for secure mobility in wireless overlay networks

Various wireless networks are widely deployed world wide. Current technologies employed in these networks vary widely in terms of bandwidths, latencies, frequencies, and media access methods. Most existing wireless network technologies can be divided into two categories: those that provide a low-bandwidth service over a wide geographic area, for example UMTS, and those that provide a high bandwidth service over a narrow geographic area, for example 802.11. Although it would be desirable to provide a high- bandwidth service over a wide coverage region to mobile users all the time, no single wireless network technology simultaneously satisfies these require- ments. Wireless Overlay Networks, a hierarchical structure of wireless personal area, local area, and wide area data networks, is considered as an efficient and scalable way to solve this problem. Due to the wide deployment of UMTS and 802.11 WLAN, this study attempts to combine them to implement the concept of Wireless Overlay Net- works. Furthermore, the information transmitted over this Wireless Overlay Networks is protected in terms of authentication, integrity and confidentiality. To achieve this goal, this study aims to combine GPRS, Mobile IP and IPSec to propose a framework for secure mobility in Wireless Overlay Networks. The framework is developed in three steps: Firstly, this study addresses the problem of combining GPRS and Mo- bile IP, so that GPRS users are provided with Mobile IP service. This results in presenting a uniform Mobile IP interface to peers regardless of whether mobile users use UMTS or 802.11 WLAN. Secondly, this study discovers the existing problem when combining Mobile IP and IPSec, and proposes a Dual Home Agent Architecture to achieve secure mobility. Finally, based on the output of the previous two steps, a complete framework is proposed, which achieves secure mobility in Wireless Overlay Networks, specifically, in UMTS and 802.11 WLAN. The framework also implements seamless handover when mobile users switch between UMTS and 802.11. This results in UMTS and 802.11 WLAN looking like a single network when participating in this framework, and presents seamless and secure mobility

A video analysis of clinical handovers between ambulance services and emergency departments

This thesis examines how clinical handovers between ambulance and emergency services were conducted. Clinical handovers are an exchange of patient information and responsibility from one healthcare team to another. They have been a key area of concern due to potential patient safety issues arising through non-technical human factor skills of communication and teamworking. However, there remains a lack of research that has examined clinical in the context of multidisciplinary settings. To redress this gap in knowledge this thesis adopted a video analysis methodology of pre-existing handover videos. Data was derived from television programs and provided naturally occurring instances of handovers being conducted. The video analysis approach was underpinned by conversation analysis, which allowed an examination of interactional features used by team members to structure handover activity. The three analytical chapters that make up this thesis how the handover activity was carried out: 1) the clinical handover structure, 2) epistemic knowledge claims, and 3) embodied actions. Overall the findings illustrated the different conversational tools used by interdisciplinary team members which shaped how information was communicated. It showed how speakers would use resources to develop engagement during discussions that aided the handover process. This showed that the handover went beyond a structured institutionally derived activity, but one shaped by the interactants. This thesis has added to the knowledge of how the interactional order of clinical handovers predominate irrespective of the continuous attempts to standardize the activity. These findings showed how handovers are carried out through an analytical lens of “work as done” rather than “work as imagined” providing understandings that can inform practice and shape future research directions

Acesso banda larga sem fios em ambientes heterogéneos de próxima geração

Doutoramento em Engenharia InformáticaO acesso ubíquo à Internet é um dos principais desafios para os operadores de telecomunicações na próxima década. O número de utilizadores da Internet está a crescer exponencialmente e o paradigma de acesso "always connected, anytime, anywhere" é um requisito fundamental para as redes móveis de próxima geração. A tecnologia WiMAX, juntamente com o LTE, foi recentemente reconhecida pelo ITU como uma das tecnologias de acesso compatíveis com os requisitos do 4G. Ainda assim, esta tecnologia de acesso não está completamente preparada para ambientes de próxima geração, principalmente devido à falta de mecanismos de cross-layer para integração de QoS e mobilidade. Adicionalmente, para além das tecnologias WiMAX e LTE, as tecnologias de acesso rádio UMTS/HSPA e Wi-Fi continuarão a ter um impacto significativo nas comunicações móveis durante os próximos anos. Deste modo, é fundamental garantir a coexistência das várias tecnologias de acesso rádio em termos de QoS e mobilidade, permitindo assim a entrega de serviços multimédia de tempo real em redes móveis. Para garantir a entrega de serviços multimédia a utilizadores WiMAX, esta Tese propõe um gestor cross-layer WiMAX integrado com uma arquitectura de QoS fim-a-fim. A arquitectura apresentada permite o controlo de QoS e a comunicação bidireccional entre o sistema WiMAX e as entidades das camadas superiores. Para além disso, o gestor de cross-layer proposto é estendido com eventos e comandos genéricos e independentes da tecnologia para optimizar os procedimentos de mobilidade em ambientes WiMAX. Foram realizados testes para avaliar o desempenho dos procedimentos de QoS e mobilidade da arquitectura WiMAX definida, demonstrando que esta é perfeitamente capaz de entregar serviços de tempo real sem introduzir custos excessivos na rede. No seguimento das extensões de QoS e mobilidade apresentadas para a tecnologia WiMAX, o âmbito desta Tese foi alargado para ambientes de acesso sem-fios heterogéneos. Neste sentido, é proposta uma arquitectura de mobilidade transparente com suporte de QoS para redes de acesso multitecnologia. A arquitectura apresentada integra uma versão estendida do IEEE 802.21 com suporte de QoS, bem como um gestor de mobilidade avançado integrado com os protocolos de gestão de mobilidade do nível IP. Finalmente, para completar o trabalho desenvolvido no âmbito desta Tese, é proposta uma extensão aos procedimentos de decisão de mobilidade em ambientes heterogéneos para incorporar a informação de contexto da rede e do terminal. Para validar e avaliar as optimizações propostas, foram desenvolvidos testes de desempenho num demonstrador inter-tecnologia, composta pelas redes de acesso WiMAX, Wi-Fi e UMTS/HSPA.Ubiquitous Internet access is one of the main challenges for the telecommunications industry in the next decade. The number of users accessing the Internet is growing exponentially and the network access paradigm of “always connected, anytime, anywhere” is a central requirement for the so-called Next Generation Mobile Networks (NGMN). WiMAX, together with LTE, was recently recognized by ITU as one of the compliant access technologies for 4G. Nevertheless, WiMAX is not yet fully prepared for next generation environments, mainly due to the lack of QoS and mobility crosslayer procedures to support real-time multimedia services delivery. Furthermore, besides the 4G compliant WiMAX and LTE radio access technologies, UMTS/HSPA and Wi-Fi will also have a significant impact in the mobile communications during the next years. Therefore, it is fundamental to ensure the coexistence of multiple radio access technologies in what QoS and mobility procedures are concerned, thereby allowing the delivery of real-time services in mobile networks. In order to provide the WiMAX mobile users with the demanded multimedia services, it is proposed in this Thesis a WiMAX cross-layer manager integrated in an end-to-end all-IP QoS enabled architecture. The presented framework enables the QoS control and bidirectional communication between WiMAX and the upper layer network entities. Furthermore, the proposed cross-layer framework is extended with media independent events and commands to optimize the mobility procedures in WiMAX environments. Tests were made to evaluate the QoS and mobility performance of the defined architecture, demonstrating that it is perfectly capable of handling and supporting real time services without introducing an excessive cost in the network. Following the QoS and mobility extensions provided for WiMAX, the scope of this Thesis is broaden and a seamless mobility architecture with QoS support in heterogeneous wireless access environments is proposed. The presented architecture integrates an extended version of the IEEE 802.21 framework with QoS support, as well as an advanced mobility manager integrated with the IP level mobility management protocols. Finally, to complete the work within the framework of this Thesis, it is proposed an extension to the handover decisionmaking processes in heterogeneous access environments through the integration of context information from both the network entities and the enduser. Performance tests were developed in a real testbed to validate the proposed optimizations in an inter-technology handover scenario involving WiMAX, Wi-Fi and UMTS/HSPA