Wireless Real-Time Communication in Tunnel-like Environments using Wireless Mesh Networks: The WICKPro Protocol

En los últimos años, las redes inalámbricas se están utilizando cada vez más en entornos industriales debido a sus ventajas respecto a redes cableadas: menor coste de instalación, soporte de movilidad, instalación en lugares donde los cables pueden ser problemáticos y mayor facilidad de reconfiguración. Estas redes inalámbricas normalmente deben proporcionar comunicación en tiempo real para satisfacer los requerimientos de las aplicaciones. Podemos encontrar ejemplos de comunicación en tiempo real con redes inalámbricas para entornos industriales en el campo de la automatización industrial y en el control de procesos, donde redes inalámbricas de radiofrecuencia han sido utilizadas para posibilitar comunicación en tiempo real con un despliegue sencillo. Asimismo, la industria también está interesada en comunicaciones en tiempo real en entornos subterráneos, puesto que existen diversas actividades que se llevan a cabo en escenarios tales como túneles y minas, incluyendo operaciones de minería, vigilancia, intervención y rescate. Las redes inalámbricas malladas (Wireless Mesh Networks, WMNs) representan una solución prometedora para conseguir comunicaci ón en tiempo real en entornos inalámbricos, dado que proporcionan una red troncal inalámbrica formada por encaminadores (routers) que es utilizada por terminales móviles. Sin embargo, las WMNs también presentan algunos retos: la naturaleza multisalto de estas redes causa interferencias entre flujos e interferencias de un flujo consigo mismo, además de que la propagación inalámbrica sufre shadowing y propagación multicamino. El estándar IEEE 802.11 ha sido ampliamente utilizado en redes WMNs debido a su bajo coste y la operación en bandas frecuenciales sin licencia. El problema es que su protocolo de acceso al medio (Medium Access Control, MAC) no es determinista y que sus comunicaciones sufren los problemas del terminal oculto y expuesto. Esta tesis doctoral se centra en el soporte de comunicaciones en tiempo real en entornos tipo túnel utilizando redes WMNs. Con este objetivo, desarrollamos un protocolo MAC y de nivel de red denominado WIreless Chain networK Protocol (WICKPro) que funciona sobre IEEE 802.11. Más concretamente, en este trabajo diseñamos dos versiones de este protocolo para proporcionar soporte de tráfico de tiempo real firme (Firm Real-Time, FRT) y de tiempo real no estricto (Soft Real-Time, SRT): FRT-WICKPro y SRT-WICKPro. Asimismo, proponemos un algoritmo de hand-off conocido como Double-Threshold Hand-off (DoTHa) para el manejo de la movilidad en SRT-WICKPro WICKPro utiliza un esquema de paso de testigo para solventar las interferencias entre flujos y de un flujo consigo mismo, así como los problemas del terminal oculto y expuesto, dado que este esquema no permite que dos nodos transmitan al mismo tiempo. Esta solución es razonable para redes pequeñas donde el re uso espacial es imposible o limitado. Para tratar la naturaleza no determinista de IEEE 802.11, combinamos el esquema de paso de testigo con una planificación cíclica global. Como es habitual en planificación cíclica, el hiperperiodo es dividido en un conjunto de ciclos secundarios. FRT-WICKPro inicia el paso de testigo de forma síncrona para satisfacer estrictamente dichos ciclos secundarios, mientras que SRT-WICKPro implementa un paso de testigo asíncrono y permite sobrepasar los ciclos secundarios, por lo que desacopla los ciclos secundarios reales de los te_oricos. Finalmente, DoTHa lidia con el shadowing y la propagación multicamino. Para abordar el shadowing, DoTHa permite llevar a cabo el proceso de hand-off en la región conectada y en la región de transición de un enlace, mientras que la propagación multicamino es ignorada para el proceso de hand-off porque la potencia recibida es promediada. Nuestras propuestas fueron validadas en experimentos de laboratorio y de campo, así como en simulación. Como un estudio de caso, llevamos a cabo la teleoperación de un robot móvil en dos entornos confinados: los pasillos de un edificio y el túnel del Somport. El túnel del Somport es un antiguo túnel ferroviario fuera de servicio que conecta España y Francia por los Pirineos Centrales. Aunque los robots autónomos son cada vez más importantes, la tecnología no está suficientemente madura para manejar entornos con alto dinamismo como sistemas de fabricación reconfigurables, o para realizar decisiones de vida o muerte, por ejemplo después de un desastre con contaminación radiactiva. Las aplicaciones que pueden beneficiarse de la teleoperación de robots móviles incluyen la monitorización en tiempo real y el uso de maquinaria robotizada, por ejemplo camiones dumper y máquinas tuneladoras, que podrían ser operadas remotamente para evitar poner en peligro vidas humanas.Industrial applications have been shifting towards wireless networks in recent years because they present several advantages compared with their wired counterparts: lower deployment cost, mobility support, installation in places where cables may be problematic, and easier reconfiguration. These industrial wireless networks usually must provide real-time communication to meet application requirements. Examples of wireless real-time communication for industrial applications can be found in factory automation and process control, where Radio Frequency wireless communication technologies have been employed to support flexible real-time communication with simple deployment. Likewise, industry is also interested in real-time communication in underground environments, since there are several activities that are carried out in scenarios such as tunnels and mines, including mining, surveillance, intervention, and rescue operations. Wireless Mesh Networks (WMNs) are promising enablers to achieve wireless real-time communication because they provide a wireless backbone comprised by dedicated routers that is utilized by mobile terminals. However, WMNs also present several challenges: wireless multi-hopping causes inter-flow and intra-flow interferences, and wireless propagation suffers shadowing and multi-path fading. The IEEE 802.11 standard has been widely used in WMNs due to its low cost and the operation in unlicensed frequency bands. The downside is that its Medium Access Control (MAC) protocol is non-deterministic, and that its communications suffer from the hidden and exposed terminal problems. This PhD thesis focuses on real-time communication in tunnel-like environments by using WMNs. Particularly, we develop a MAC and network protocol on top of the IEEE 802.11 standard to provide real-time capabilities, so-called WIreless Chain networK Protocol (WICKPro). Two WICKPro versions are designed to provide Firm Real-Time (FRT) or Soft Real-Time (SRT) traffic support: FRT-WICKPro and SRT-WICKPro. We also propose a hand-off algorithm dubbed Double-Threshold Hand-off (DoTHa) to manage mobility in SRT-WICKPro. WICKPro employs a token-passing scheme to solve the inter-flow and intra-flow interferences as well as the hidden and exposed terminal problems, since this scheme does not allow two nodes to transmit at the same time. This is a reasonable solution for small-scale networks where spatial reuse is impossible or limited. The non-deterministic nature of IEEE 802.11 is faced by combining the token-passing mechanism with a polling approach based on a global cyclic packet schedule. As usual in cyclic scheduling, the hyper-period is divided into minor cycles. FRT-WICKPro triggers the token synchronously and fulfills strictly minor cycles, whereas SRT-WICKPro carries out asynchronous token-passing and lets minor cycles be overrun, thereby decoupling the theoretic and the actual minor cycles. Finally, DoTHa deals with shadowing and multi-path fading. Shadowing is addressed by providing the opportunity of triggering hand-off in the connected and transitional regions of a link, while multi-path fading is neglected for hand-off purposes by smoothing the received signal power. We tested our proposals in laboratory and field experiments, as well as in simulation. As a case study, we carried out the tele-operation of a mobile robot within two confined environments: the corridors of a building and the Somport tunnel. The Somport tunnel is an old out-of-service railway tunnel that connects Spain and France through the Central Pyrenees. Although autonomous robots are becoming more and more important, technology is not mature enough to manage highly dynamic environments such as reconfigurable manufacturing systems, or to make life-and-death decisions, e.g., after a disaster with radioactivity contamination. Applications that can benefit from mobile robot tele-operation include real-time monitoring and the use of robotized machinery, for example, dumper trucks and tunneling machines, which could be remotely operated to avoid endangering human lives

Project Final Report: HPC-Colony II

This report recounts the HPC Colony II Project which was a computer science effort funded by DOE's Advanced Scientific Computing Research office. The project included researchers from ORNL, IBM, and the University of Illinois at Urbana-Champaign. The topic of the effort was adaptive system software for extreme scale parallel machines. A description of findings is included

Containerization in Cloud Computing: performance analysis of virtualization architectures

La crescente adozione del cloud è fortemente influenzata dall’emergere di tecnologie che mirano a migliorare i processi di sviluppo e deployment di applicazioni di livello enterprise. L’obiettivo di questa tesi è analizzare una di queste soluzioni, chiamata “containerization” e di valutare nel dettaglio come questa tecnologia possa essere adottata in infrastrutture cloud in alternativa a soluzioni complementari come le macchine virtuali. Fino ad oggi, il modello tradizionale “virtual machine” è stata la soluzione predominante nel mercato. L’importante differenza architetturale che i container offrono ha portato questa tecnologia ad una rapida adozione poichè migliora di molto la gestione delle risorse, la loro condivisione e garantisce significativi miglioramenti in termini di provisioning delle singole istanze. Nella tesi, verrà esaminata la “containerization” sia dal punto di vista infrastrutturale che applicativo. Per quanto riguarda il primo aspetto, verranno analizzate le performances confrontando LXD, Docker e KVM, come hypervisor dell’infrastruttura cloud OpenStack, mentre il secondo punto concerne lo sviluppo di applicazioni di livello enterprise che devono essere installate su un insieme di server distribuiti. In tal caso, abbiamo bisogno di servizi di alto livello, come l’orchestrazione. Pertanto, verranno confrontate le performances delle seguenti soluzioni: Kubernetes, Docker Swarm, Apache Mesos e Cattle

Workload Schedulers - Genesis, Algorithms and Comparisons

In this article we provide brief descriptions of three classes of schedulers: Operating Systems Process Schedulers, Cluster Systems, Jobs Schedulers and Big Data Schedulers. We describe their evolution from early adoptions to modern implementations, considering both the use and features of algorithms. In summary, we discuss differences between all presented classes of schedulers and discuss their chronological development. In conclusion, we highlight similarities in the focus of scheduling strategies design, applicable to both local and distributed systems

Introducing the new paradigm of Social Dispersed Computing: Applications, Technologies and Challenges

[EN] If last decade viewed computational services as a utility then surely this decade has transformed computation into a commodity. Computation is now progressively integrated into the physical networks in a seamless way that enables cyber-physical systems (CPS) and the Internet of Things (IoT) meet their latency requirements. Similar to the concept of ¿platform as a service¿ or ¿software as a service¿, both cloudlets and fog computing have found their own use cases. Edge devices (that we call end or user devices for disambiguation) play the role of personal computers, dedicated to a user and to a set of correlated applications. In this new scenario, the boundaries between the network node, the sensor, and the actuator are blurring, driven primarily by the computation power of IoT nodes like single board computers and the smartphones. The bigger data generated in this type of networks needs clever, scalable, and possibly decentralized computing solutions that can scale independently as required. Any node can be seen as part of a graph, with the capacity to serve as a computing or network router node, or both. Complex applications can possibly be distributed over this graph or network of nodes to improve the overall performance like the amount of data processed over time. In this paper, we identify this new computing paradigm that we call Social Dispersed Computing, analyzing key themes in it that includes a new outlook on its relation to agent based applications. We architect this new paradigm by providing supportive application examples that include next generation electrical energy distribution networks, next generation mobility services for transportation, and applications for distributed analysis and identification of non-recurring traffic congestion in cities. The paper analyzes the existing computing paradigms (e.g., cloud, fog, edge, mobile edge, social, etc.), solving the ambiguity of their definitions; and analyzes and discusses the relevant foundational software technologies, the remaining challenges, and research opportunities.Garcia Valls, MS.; Dubey, A.; Botti, V. (2018). Introducing the new paradigm of Social Dispersed Computing: Applications, Technologies and Challenges. Journal of Systems Architecture. 91:83-102. https://doi.org/10.1016/j.sysarc.2018.05.007S831029

Supporting Quality of Service in Scientific Workflows

While workflow management systems have been utilized in enterprises to support businesses for almost two decades, the use of workflows in scientific environments was fairly uncommon until recently. Nowadays, scientists use workflow systems to conduct scientific experiments, simulations, and distributed computations. However, most scientific workflow management systems have not been built using existing workflow technology; rather they have been designed and developed from scratch. Due to the lack of generality of early scientific workflow systems, many domain-specific workflow systems have been developed. Generally speaking, those domain-specific approaches lack common acceptance and tool support and offer lower robustness compared to business workflow systems. In this thesis, the use of the industry standard BPEL, a workflow language for modeling business processes, is proposed for the modeling and the execution of scientific workflows. Due to the widespread use of BPEL in enterprises, a number of stable and mature software products exist. The language is expressive (Turingcomplete) and not restricted to specific applications. BPEL is well suited for the modeling of scientific workflows, but existing implementations of the standard lack important features that are necessary for the execution of scientific workflows. This work presents components that extend an existing implementation of the BPEL standard and eliminate the identified weaknesses. The components thus provide the technical basis for use of BPEL in academia. The particular focus is on so-called non-functional (Quality of Service) requirements. These requirements include scalability, reliability (fault tolerance), data security, and cost (of executing a workflow). From a technical perspective, the workflow system must be able to interface with the middleware systems that are commonly used by the scientific workflow community to allow access to heterogeneous, distributed resources (especially Grid and Cloud resources). The major components cover exactly these requirements: Cloud Resource Provisioner Scalability of the workflow system is achieved by automatically adding additional (Cloud) resources to the workflow system’s resource pool when the workflow system is heavily loaded. Fault Tolerance Module High reliability is achieved via continuous monitoring of workflow execution and corrective interventions, such as re-execution of a failed workflow step or replacement of the faulty resource. Cost Aware Data Flow Aware Scheduler The majority of scientific workflow systems only take the performance and utilization of resources for the execution of workflow steps into account when making scheduling decisions. The presented workflow system goes beyond that. By defining preference values for the weighting of costs and the anticipated workflow execution time, workflow users may influence the resource selection process. The developed multiobjective scheduling algorithm respects the defined weighting and makes both efficient and advantageous decisions using a heuristic approach. Security Extensions Because it supports various encryption, signature and authentication mechanisms (e.g., Grid Security Infrastructure), the workflow system guarantees data security in the transfer of workflow data. Furthermore, this work identifies the need to equip workflow developers with workflow modeling tools that can be used intuitively. This dissertation presents two modeling tools that support users with different needs. The first tool, DAVO (domain-adaptable, Visual BPEL Orchestrator), operates at a low level of abstraction and allows users with knowledge of BPEL to use the full extent of the language. DAVO is a software that offers extensibility and customizability for different application domains. These features are used in the implementation of the second tool, SimpleBPEL Composer. SimpleBPEL is aimed at users with little or no background in computer science and allows for quick and intuitive development of BPEL workflows based on predefined components