Design of interface selection protocols for multi-homed wireless networks

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University on 10 December 2010.The IEEE 802.11/802.16 standards conformant wireless communication stations have multi-homing transmission capability. To achieve greater communication efficiency, multi-homing capable stations use handover mechanism to select appropriate transmission channel according to variations in the channel quality. This thesis presents three internal-linked handover schemes, (1) Interface Selection Protocol (ISP), belonging to Wireless Local Area Network (WLAN)- Worldwide Interoperability for Microwave Access (WiMAX) environment (2) Fast Channel Scanning (FCS) and (3) Traffic Manager (TM), (2) and (3) belonging to WiMAX Environment. The proposed schemes in this thesis use a novel mechanism of providing a reliable communication route. This solution is based on a cross-layer communication framework, where the interface selection module uses various network related parameters from Medium Access Control (MAC) sub-layer/Physical Layer (PHY) across the protocol suite for decision making at the Network layer. The proposed solutions are highly responsive when compared with existing multi-homed schemes; responsiveness is one of the key factors in the design of such protocols. Selected route under these schemes is based on the most up to date link-layer information. Therefore, such a route is not only reliable in terms of route optimization but it also fulfils the application demands in terms of throughput and delay. Design of ISP protocol use probing frames during the route discovery process. The 802.11 mandates the use of different rates for data transmission frames. The ISP-metric can be incorporated into various routing aspects and its applicability is determined by the possibility of provision of MAC dependent parameters that are used to determine the best path metric values. In many cases, higher device density, interference and mobility cause variable medium access delays. It causes creation of ‘unreachable zones’, where destination is marked as unreachable. However, by use of the best path metric, the destination has been made reachable, anytime and anywhere, because of the intelligent use of the probing frames and interface selection algorithm implemented. The IEEE 802.16e introduces several MAC level queues for different access categories, maintaining service requirement within these queues; which imply that frames from a higher priority queue, i.e. video frames, are serviced more frequently than those belonging to lower priority queues. Such an enhancement at the MAC sub-layer introduces uneven queuing delays. Conventional routing protocols are unaware of such MAC specific constraints and as a result, these factors are not considered which result in channel performance degradation. To meet such challenges, the thesis presents FCS and TM schemes for WiMAX. For FCS, Its solution is to improve the mobile WiMAX handover and address the scanning latency. Since minimum scanning time is the most important issue in the handover process. This handover scheme aims to utilize the channel efficiently and apply such a procedure to reduce the time it takes to scan the neighboring access stations. TM uses MAC and physical layer (PHY) specific information in the interface metric and maintains a separate path to destination by applying an alternative interface operation. Simulation tests and comparisons with existing multi-homed protocols and handover schemes demonstrate the effectiveness of incorporating the medium dependent parameters. Moreover, show that suggested schemes, have shown better performance in terms of end-to-end delay and throughput, with efficiency up to 40% in specific test scenarios

Secure and safe virtualization-based framework for embedded systems development

Tese de Doutoramento - Programa Doutoral em Engenharia Electrónica e de Computadores (PDEEC)The Internet of Things (IoT) is here. Billions of smart, connected devices are proliferating at rapid pace in our key infrastructures, generating, processing and exchanging vast amounts of security-critical and privacy-sensitive data. This strong connectivity of IoT environments demands for a holistic, end-to-end security approach, addressing security and privacy risks across different abstraction levels: device, communications, cloud, and lifecycle managment. Security at the device level is being misconstrued as the addition of features in a late stage of the system development. Several software-based approaches such as microkernels, and virtualization have been used, but it is proven, per se, they fail in providing the desired security level. As a step towards the correct operation of these devices, it is imperative to extend them with new security-oriented technologies which guarantee security from the outset. This thesis aims to conceive and design a novel security and safety architecture for virtualized systems by 1) evaluating which technologies are key enablers for scalable and secure virtualization, 2) designing and implementing a fully-featured virtualization environment providing hardware isolation 3) investigating which "hard entities" can extend virtualization to guarantee the security requirements dictated by confidentiality, integrity, and availability, and 4) simplifying system configurability and integration through a design ecosystem supported by a domain-specific language. The developed artefacts demonstrate: 1) why ARM TrustZone is nowadays a reference technology for security, 2) how TrustZone can be adequately exploited for virtualization in different use-cases, 3) why the secure boot process, trusted execution environment and other hardware trust anchors are essential to establish and guarantee a complete root and chain of trust, and 4) how a domain-specific language enables easy design, integration and customization of a secure virtualized system assisted by the above mentioned building blocks.Vivemos na era da Internet das Coisas (IoT). Biliões de dispositivos inteligentes começam a proliferar nas nossas infraestruturas chave, levando ao processamento de avolumadas quantidades de dados privados e sensíveis. Esta forte conectividade inerente ao conceito IoT necessita de uma abordagem holística, em que os riscos de privacidade e segurança são abordados nas diferentes camadas de abstração: dispositivo, comunicações, nuvem e ciclo de vida. A segurança ao nível dos dispositivos tem sido erradamente assegurada pela inclusão de funcionalidades numa fase tardia do desenvolvimento. Têm sido utilizadas diversas abordagens de software, incluindo a virtualização, mas está provado que estas não conseguem garantir o nível de segurança desejado. De forma a garantir a correta operação dos dispositivos, é fundamental complementar os mesmos com novas tecnologias que promovem a segurança desde os primeiros estágios de desenvolvimento. Esta tese propõe, assim, o desenvolvimento de uma solução arquitetural inovadora para sistemas virtualizados seguros, contemplando 1) a avaliação de tecnologias chave que promovam tal realização, 2) a implementação de uma solução de virtualização garantindo isolamento por hardware, 3) a identificação de componentes que integrados permitirão complementar a virtualização para garantir os requisitos de segurança, e 4) a simplificação do processo de configuração e integração da solução através de um ecossistema suportado por uma linguagem de domínio específico. Os artefactos desenvolvidos demonstram: 1) o porquê da tecnologia ARM TrustZone ser uma tecnologia de referência para a segurança, 2) a efetividade desta tecnologia quando utilizada em diferentes domínios, 3) o porquê do processo seguro de inicialização, juntamente com um ambiente de execução seguro e outros componentes de hardware, serem essenciais para estabelecer uma cadeia de confiança, e 4) a viabilidade em utilizar uma linguagem de um domínio específico para configurar e integrar um ambiente virtualizado suportado pelos artefactos supramencionados

Design of interface selection protocols for multi-homed wireless networks

The IEEE 802.11/802.16 standards conformant wireless communication stations have multi-homing transmission capability. To achieve greater communication efficiency, multi-homing capable stations use handover mechanism to select appropriate transmission channel according to variations in the channel quality. This thesis presents three internal-linked handover schemes, (1) Interface Selection Protocol (ISP), belonging to Wireless Local Area Network (WLAN)- Worldwide Interoperability for Microwave Access (WiMAX) environment (2) Fast Channel Scanning (FCS) and (3) Traffic Manager (TM), (2) and (3) belonging to WiMAX Environment. The proposed schemes in this thesis use a novel mechanism of providing a reliable communication route. This solution is based on a cross-layer communication framework, where the interface selection module uses various network related parameters from Medium Access Control (MAC) sub-layer/Physical Layer (PHY) across the protocol suite for decision making at the Network layer. The proposed solutions are highly responsive when compared with existing multi-homed schemes; responsiveness is one of the key factors in the design of such protocols. Selected route under these schemes is based on the most up to date link-layer information. Therefore, such a route is not only reliable in terms of route optimization but it also fulfils the application demands in terms of throughput and delay. Design of ISP protocol use probing frames during the route discovery process. The 802.11 mandates the use of different rates for data transmission frames. The ISP-metric can be incorporated into various routing aspects and its applicability is determined by the possibility of provision of MAC dependent parameters that are used to determine the best path metric values. In many cases, higher device density, interference and mobility cause variable medium access delays. It causes creation of ‘unreachable zones’, where destination is marked as unreachable. However, by use of the best path metric, the destination has been made reachable, anytime and anywhere, because of the intelligent use of the probing frames and interface selection algorithm implemented. The IEEE 802.16e introduces several MAC level queues for different access categories, maintaining service requirement within these queues; which imply that frames from a higher priority queue, i.e. video frames, are serviced more frequently than those belonging to lower priority queues. Such an enhancement at the MAC sub-layer introduces uneven queuing delays. Conventional routing protocols are unaware of such MAC specific constraints and as a result, these factors are not considered which result in channel performance degradation. To meet such challenges, the thesis presents FCS and TM schemes for WiMAX. For FCS, Its solution is to improve the mobile WiMAX handover and address the scanning latency. Since minimum scanning time is the most important issue in the handover process. This handover scheme aims to utilize the channel efficiently and apply such a procedure to reduce the time it takes to scan the neighboring access stations. TM uses MAC and physical layer (PHY) specific information in the interface metric and maintains a separate path to destination by applying an alternative interface operation. Simulation tests and comparisons with existing multi-homed protocols and handover schemes demonstrate the effectiveness of incorporating the medium dependent parameters. Moreover, show that suggested schemes, have shown better performance in terms of end-to-end delay and throughput, with efficiency up to 40% in specific test scenarios.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Arm TrustZone: evaluating the diversity of the memory subsystem

Dissertação de mestrado em Engenharia Eletrónica Industrial e ComputadoresThe diversification of the embedded market has led the once single-purpose built embedded device to become a broader concept that can accommodate more general-purpose solutions, by widening its hardware and software resources. A huge diversity in system resources and requirements has boosted the investigation around virtualization technology, which is becoming prevalent in the embedded systems domain, allowing timing and spatial sharing of hardware and software resources between specialized subsystems. As strict timing demands imposed in realtime virtualized systems must be met, coupled with a small margin for the penalties incurred by conventional software-based virtualization, resort to hardware-assisted solutions has become indispensable. Although not a virtualization but security-oriented technology, Arm TrustZone is seen by many as a reliable hardware-based virtualization alternative, with the low cost and high spread of TrustZone-enabled processors standing as strong arguments for its acceptance. But, since Trust- Zone only dictates the hardware infrastructure foundations, providing SoC designers with a range of components that can fulfil specific functions, several key-components and subsystems of this technology are implementation defined. This approach may hinder a system designer’s work, as it may impair and make the portability of system software a lot more complicated. As such, this thesis proposes to examine how different manufacturers choose to work with the TrustZone architecture, and how the changes introduced by this technology may affect the security and performance of TrustZone-assisted virtualization solutions, in order to scale back those major constraints. It identifies the main properties that impact the creation and execution of system software and points into what may be the most beneficial approaches for developing and using TrustZone-assisted hardware and software.A recente metamorfose na área dos sistemas embebidos transformou estes dispositivos, outrora concebidos com um único e simples propósito, num aglomerado de subsistemas prontos para integrar soluções mais flexíveis. Este aumento de recursos e de requisitos dos sistemas potenciou a investigação em soluções de virtualização dos mesmos, permitindo uma partilha simultânea de recursos de hardware e software entre os vários subsistemas. A proliferação destas soluções neste domínio, onde os tempos de execução têm de ser respeitados e a segurança é um ponto-chave, tem levado à adoção de técnicas de virtualização assistidas por hardware. Uma tecnologia que tem vindo a ser utilizada para este fim é a Arm TrustZone, apesar de inicialmente ter sido desenvolvida como uma tecnologia de proteção, dado a sua maior presença em placas de médio e baixo custo quando comparada a outras tecnologias. Infelizmente, dado que a TrustZone apenas fornece diretrizes base sobre as quais os fabricantes podem contruir os seus sistemas, as especificações da tecnologia divergem de fabricante para fabricante, ou até entre produtos com a mesma origem. Aliada à geral escassez de informação sobre esta tecnologia, esta característica pode trazer problemas para a criação e portabilidade de software de sistema dependente desta tecnologia. Como tal, a presente tese propõe examinar, de uma forma sistematizada, de que forma diferentes fabricantes escolhem implementar sistemas baseados na arquitetura TrustZone e em que medida as mudanças introduzidas por esta tecnologia podem afetar a segurança e desempenho de soluções de virtualização baseadas na mesma. São identificadas as principais características que podem influenciar a criação e execução de software de sistema e potenciais medidas para diminuir o seu impacto, assim como boas práticas a seguir no desenvolvimento na utilização de software e hardware baseados na TrustZone

The Role of Social Workers in Addressing Patients' Unmet Social Needs in the Primary Care Setting

Indiana University-Purdue University Indianapolis (IUPUI)Unmet social needs pose significant risk to both patients and healthcare organizations by increasing morbidity, mortality, utilization, and costs. Health care delivery organizations are increasingly employing social workers to address social needs, given the growing number of policies mandating them to identify and address their patients’ social needs. However, social workers largely document their activities using unstructured or semi-structured textual descriptions, which may not provide information that is useful for modeling, decision-making, and evaluation. Therefore, without the ability to convert these social work documentations into usable information, the utility of these textual descriptions may be limited. While manual reviews are costly, time-consuming, and require technical skills, text mining algorithms such as natural language processing (NLP) and machine learning (ML) offer cheap and scalable solutions to extracting meaningful information from large text data. Moreover, the ability to extract information on social needs and social work interventions from free-text data within electronic health records (EHR) offers the opportunity to comprehensively evaluate the outcomes specific social work interventions. However, the use of text mining tools to convert these text data into usable information has not been well explored. Furthermore, only few studies sought to comprehensively investigate the outcomes of specific social work interventions in a safety-net population. To investigate the role of social workers in addressing patients’ social needs, this dissertation: 1) utilizes NLP, to extract and categorize the social needs that lead to referral to social workers, and market basket analysis (MBA), to investigate the co-occurrence of these social needs; 2) applies NLP, ML, and deep learning techniques to extract and categorize the interventions instituted by social workers to address patients’ social needs; and 3) measures the effects of receiving a specific social work intervention type on healthcare utilization outcomes

Ambient Air Quality in the Czech Republic

Ambient air quality in the present-day Czech Republic (CR), one of the two succession countries of Czechoslovakia post-1993, was perceived as a major problem with severe human health and environmental consequences, particularly between the 1970s and 1990s. Since that time, the ambient air quality in the CR has improved substantially, due to newly introduced stringent legislation and technical countermeasures. Nevertheless, there are still activities which represent significant emission sources, such as local heating and increased vehicle travel through communities. After a substantial decrease in emissions in both the CR and its neighbouring countries, the levels of some ambient air pollutants from the 2000s are still not satisfactory. In this respect, aerosol, ground-level ozone, and benzo[a]pyrene remain major problems, as they do elsewhere in Europe. The book provides a valuable update both on time trends and spatial changes in ambient air quality, and highlights the recent activities in both monitoring and modelling of principle ambient air pollutants in the CR

Improved Iptv Channel Change times Through Multicast Caching of Pre-selected Channels

Name: RAY, THOMAS Date of Degree: DECEMBER, 2014 Title of Study: IMPROVED IPTV CHANNEL CHANGE TIMES THROUGH MULTICAST CACHING OF PRE-SELECTED CHANNELSMajor Field: ELECTRICAL ENGINEERINGAbstract: IPTV has grown in recent years to an estimated 100 million users worldwide. IPTV uses IGMP processes to stream an individual channel to a user until the next channel change when the current channel is stopped and the new selection begins streaming. One of the critical factors determining customer satisfaction is the requirement to have reasonably rapid channel change times of 2 seconds or less, but current channel change times are frequently above that threshold. Numerous research efforts have been ongoing to reduce these times including edge servers, I-frame management, buffering improvements, dynamic video coding, and pre-selecting channels. Channel pre-selection involves sending additional channels in hopes that the user's next selection will already be present at the user's set top box to reduce the channel change time. While this pre-selection technique has previously been proposed, the proposals have been limited in scope, typically based on set top box replacement, and lack specific details regarding the expected channel change reductions attained. This research addressed all of these shortcomings beginning with laboratory testing to verify that the channel change time reduction for successful pre-selection is two times the network delay plus the IGMP processing time which equates to an average of 320 millisecond reduction per channel change. Several pre-selection models were developed and evaluated using theoretical calculations, functional testing, and performance simulations. Sample data was generated to reflect a wide range of user IPTV viewing behavior for use in the performance simulations. The top two models resulted in an average of well over 70% success rates in accurately pre-streaming the user's next selection in the multicast cache output. This approach also has the benefit of being implemented on IPTV provider equipment and would typically only require firmware upgrades without the need for expensive new equipment or changes to existing standards. Operational considerations were also discussed to reduce problems and delays during the implementation phase of the system. Additional applications and future improvements were also presented.Electrical Engineerin