Analytical Performance Comparison of BNP Scheduling Algorithms

Parallel computing is related to the application of many computers running in parallel to solve computationally intensive problems. One of the biggest issues in parallel computing is efficient task scheduling. In this paper, we survey the algorithms that allocate a parallel program represented by an edge-directed acyclic graph (DAG) to a set of homogenous processors with the objective of minimizing the completion time. We examine several such classes of algorithms and then compare the performance of a class of scheduling algorithms known as the bounded number of processors (BNP) scheduling algorithms. Comparison is based on various scheduling parameters such as makespan, speed up, processor utilization and scheduled length ratio. The main focus is given on measuring the impact of increasing the number of tasks and processors on the performance of these four BNP scheduling algorithms

CASCH: a tool for computer-aided scheduling

A software tool called Computer-Aided Scheduling (CASCH) for parallel processing on distributed-memory multiprocessors in a complete parallel programming environment is presented. A compiler automatically converts sequential applications into parallel codes to perform program parallelization. The parallel code that executes on a target machine is optimized by CASCH through proper scheduling and mapping.published_or_final_versio

A List Scheduling Heuristic with New Node Priorities and Critical Child Technique for Task Scheduling with Communication Contention

Task scheduling is becoming an important aspect for parallel programming of modern embedded systems. In this chapter, the application to be scheduled is modeled as a Directed Acyclic Graph (DAG), and the architecture targets parallel embedded systems composed of multiple processors interconnected by buses and/or switches. This chapter presents new list scheduling heuristics with communication contention. Furthermore, we define new node priorities (top level and bottom level) to sort nodes, and propose an advanced technique named critical child to select a processor to execute a node. Experimental results show that the proposed method is effective to reduce the schedule length, and the runtime performance is greatly improved in the cases of medium and high communication. Since the communication cost is increasing from medium to high in modern applications like digital communication and video compression, the proposed method is well-adapted for scheduling these applications over parallel embedded systems

Advanced list scheduling heuristic for task scheduling with communication contention for parallel embedded systems

WOSInternational audienceModern embedded systems tend to use multiple cores or processors for processing parallel applications. This paper indeed aims at task scheduling with communication contention for parallel embedded systems and proposes three advanced techniques to improve the list scheduling heuristic. Five groups of node levels (two existing groups and three new groups) are firstly used as node priorities to generate node lists. Then the critical child technique improves the selection of a processor in the scheduling process. Finally, the communication delay technique enlarges the idle time intervals on communication links. We also propose an advanced dynamic list scheduling heuristic by combining the three techniques. Experimental results show that the combined advanced dynamic heuristic is efficient to shorten the schedule length for most of the randomly generated DAGs in the cases of medium and high communication. Our method accelerates an application up to 80% in the case of high communication and can also reduce the use of hardware resources

Analysis of the impact of wireless mobile devices in critical industrial applications

The main objective of the thesis is to study the impact of mobile nodes in industrial applications with strict reliability and time constraints in both centralized and decentralized topologies. Considering the harsh wireless channel conditions of industrial environments, that goal implies a considerable challenge. In order not to compromise the performance of the system, a deterministic Real-Time (RT) communication protocol is needed, along with a mechanism to deal with changes in the topology due to the movements of the wireless devices. The existing wireless standard technologies do not satisfy the requirements demanded by the most critical industrial applications such as Distributed Control Systems (DCS) and, thus, wired communication cannot be directly replaced by wireless solutions. Nevertheless, the adoption of wireless communications can be seen as an extension to the existing wired networks to create hybrid networks with mobility requirements. The design of a proper communication solution depends mainly on the choice of the Medium Access Control (MAC) protocol, which is responsible for controlling access to the medium and thereby plays a vital role in decreasing latency and packet errors. Furthermore, the changes in the topology due to the movement of the wireless devices must be managed correctly in order not to affect the performance of the entire network. In this doctoral thesis, a hybrid centralized architecture designed for industrial applications with strict requirements in terms of robustness, determinism and RT is proposed and evaluated. For that, a wireless RT MAC scheme based on the IEEE 802.11 physical layer is proposed along with a Real-Time Ethernet (RTE) MAC scheme. This hybrid system ensures seamless communication between both media. With the aim of including mobile devices in the proposed architecture, a soft-handover algorithm is designed and evaluated. This algorithm guarantees an uninterrupted communication during the handover process without the need for a second radio interface and with a reduced growth in network overhead. Finally, the impact of mobile nodes in a decentralized wireless topology is analysed. For that, the Self-Organizing Time Division Multiple Access (STDMA) protocol is evaluated to analyse its viability as an alternative to carrying out a handover in industrial applications without centralized systems.El objetivo principal de la tesis es estudiar el impacto de los nodos móviles en las aplicaciones inalámbricas industriales con requisitos estrictos de tiempo y robustez tanto para topologías centralizadas como descentralizadas. Este objetivo supone un gran desafío dadas las adversas condiciones del canal inalámbrico en los entornos industriales. Para no comprometer el rendimiento del sistema, es necesario un protocolo de comunicación determinista y con garantías de tiempo real, junto con un mecanismo para hacer frente a los cambios en la topología debido al movimiento de los dispositivos inalámbricos. Las tecnologías estándar inalámbricas existentes no satisfacen los requisitos exigidos por las aplicaciones industriales más críticas, como los Sistemas de Control Distribuido (DCS - Distributed Control Systems) y, por lo tanto, las comunicaciones cableadas no pueden ser reemplazadas directamente por soluciones inalámbricas. Sin embargo, la adopción de las comunicaciones inalámbricas puede verse como una extensión de las redes cableadas existentes con el objetivo de crear redes híbridas con requisitos de movilidad. El diseño de una solución de comunicación adecuada depende principalmente de la elección del protocolo de control de acceso al medio (MAC - Medium Access Control), el cual, desempeña un papel vital en la disminución de la latencia y del número de paquetes erróneos. Además, los cambios en la topología debidos al movimiento de los dispositivos inalámbricos deben gestionarse correctamente para que el rendimiento de toda la red no se vea afectado. En esta tesis doctoral se propone y se evalúa una arquitectura híbrida centralizada diseñada para aplicaciones industriales con requisitos estrictos de robustez, determinismo y tiempo real. Para ello, se propone un esquema MAC inalámbrico con garantías de tiempo real basado en la capa física IEEE 802.11 junto con un esquema MAC basado en Ethernet en tiempo real (RTE - Real-Time Ethernet). Este esquema híbrido garantiza una comunicación continua entre ambos medios de comunicación. Con el objetivo de incluir dispositivos móviles en la arquitectura propuesta, se propone y evalúa un algoritmo de soft-handover. Este algoritmo garantiza una comunicación ininterrumpida durante el proceso de handover sin la necesidad de una segunda interfaz de radio y con un aumento reducido de la sobrecarga de la red. Finalmente, se analiza el impacto de los nodos móviles en una topología inalámbrica descentralizada. Para ello, se evalúa el protocolo del estado del arte Self-Organizing Time Division Multiple Access (STDMA) con el objetivo de analizar su viabilidad como alternativa para realizar un handover en las aplicaciones industriales sin sistemas centralizados.Tesi honen helburu nagusia, nodo mugikorrek fidagarritasun eta denboraren aldetik baldintza ugari eskatzen duten aplikazio industrial zentralizatu eta deszentralizatuetan duten eragina aztertzea da. Eremu industrialetako haririk gabeko kanaletan ematen diren komunikazioetarako baldintza bereziki aurkakoak direla medio, helburu honek erronka handia sortzen du. Sarearen errendimendua arriskuan ez jartzeko, determinista eta denbora errealeko komunikazio protokolo bat beharrezkoa da, haririk gabeko nodoen mugimenduaren ondorioz topologiaren aldaketei aurre egiteko mekanismo batekin batera. Haririk gabeko teknologia estandarrek ez dute aplikazio industrial kritikoenek dituzten baldintzak betetzen eta, beraz, kable bidezko komunikazioak ezin dira haririk gabeko sistemekin ordezkatu. Hala ere, haririk gabeko komunikazioen erabilpena jadanik existitzen diren kable bidezko komunikazioen hedadura bezala kontsidera daiteke, mobilitate baldintzak dituzten sare hibridoak sortuz. Komunikazio sistemaren diseinu egokia Medium Access Control (MAC) protokoloaren hautaketa zuzenean oinarritzen da gehien bat, sarbidea kontrolatzeaz arduratzen baita, honela ezinbesteko papera izanik latentzian eta pakete erroreen murrizketan. Horretaz aparte, bai sare zentralizatu eta deszentralizatuen kasuan, haririk gabeko nodoen mugimenduek sortutako tipologia aldaketak azkar eta zuzen kudeatu behar dira sare osoko errendimenduak kalterik ez jasateko. Doktore tesi honetan, fidagarritasun zorrotz, determinismo eta denbora-errealeko baldintzak dituzten industria aplikazioetarako arkitektura hibrido zentralizatu bat proposatu eta ebaluatu da. Horretarako, IEEE 802.11 maila fisikoan oinarritutako haririk gabeko MAC eskema bat proposatu da, Real-Time Ethernet-en (RTE) oinarritutako MAC eskema batekin batera. Eskema hibrido honek bi komunikabideen artean etengabeko komunikazioa bermatzen du. Proposatutako arkitekturan nodo mugikorrak kontuan hartu ahal izateko, soft-handover algoritmo bat proposatu eta ebaluatu da. Algoritmo honek etenik gabeko komunikazioa bermatzen du handover prozesuan zehar bigarren irrati interfaze baten beharrik gabe eta sareko gainkarga oso gutxi handituz. Azkenik, nodo mugikorrek duten eragina haririk gabeko topologia deszentralizatuetan aztertu da. Horretako, bibliografiako Self-Organizing Time Division Multiple Access (STDMA) protokoloa ebaluatu da industrial aplikazioetako sistema zentralizatuen handover mekanismoaren alternatiba gisa

Towards Dynamic Vehicular Clouds

Motivated by the success of the conventional cloud computing, Vehicular Clouds were introduced as a group of vehicles whose corporate computing, sensing, communication, and physical resources can be coordinated and dynamically allocated to authorized users. One of the attributes that set Vehicular Clouds apart from conventional clouds is resource volatility. As vehicles enter and leave the cloud, new computing resources become available while others depart, creating a volatile environment where the task of reasoning about fundamental performance metrics becomes very challenging. The goal of this thesis is to design an architecture and model for a dynamic Vehicular Cloud built on top of moving vehicles on highways. We present our envisioned architecture for dynamic Vehicular Cloud, consisting of vehicles moving on the highways and multiple communication stations installed along the highway, and investigate the feasibility of such systems. The dynamic Vehicular Cloud is based on two-way communications between vehicles and the stations. We provide a communication protocol for vehicle-to-infrastructure communications enabling a dynamic Vehicular Cloud. We explain the structure of the proposed protocol in detail and then provide analytical predictions and simulation results to investigate the accuracy of our design and predictions. Just as in conventional clouds, job completion time ranks high among the fundamental quantitative performance figures of merit. In general, predicting job completion time requires full knowledge of the probability distributions of the intervening random variables. More often than not, however, the data center manager does not know these distribution functions. Instead, using accumulated empirical data, she may be able to estimate the first moments of these random variables. Yet, getting a handle on the expected job completion time is a very important problem that must be addressed. With this in mind, another contribution of this thesis is to offer easy-to-compute approximations of job completion time in a dynamic Vehicular Cloud involving vehicles on a highway. We assume estimates of the first moment of the time it takes the job to execute without any overhead attributable to the working of the Vehicular Cloud. A comprehensive set of simulations have shown that our approximations are very accurate. As mentioned, a major difference between the conventional cloud and the Vehicular Cloud is the availability of the computational nodes. The vehicles, which are the Vehicular Cloud\u27s computational resources, arrive and depart at random times, and as a result, this characteristic may cause failure in executing jobs and interruptions in the ongoing services. To handle these interruptions, once a vehicle is ready to leave the Vehicular Cloud, if the vehicle is running a job, the job and all intermediate data stored by the departing vehicle must be migrated to an available vehicle in the Vehicular Cloud

QoS Abstraction Layer in 4G Access Networks

Tese de Mestrado. Redes e Serviços de Comunicação. Faculdade de Engenharia. Universidade do Porto. 200

Integration and characterisation of the performance of fifth-generation mobile technology (5g) connectivity over the University of Oulu 5g test network (5gtn) for cognitive edge node based on fractal edge platform

Abstract. In recent years, there has been a growing interest in cognitive edge nodes, which are intelligent devices that can collect and process data at the edge of the network. These nodes are becoming increasingly important for various applications such as smart cities, industrial automation, and healthcare. However, implementing cognitive edge nodes requires a reliable and efficient communication network. Therefore, this thesis assesses the performance of direct cellular (5G) and IEEE 802.11-based Wireless Local Area Network (WLAN) technology for three network architectures, which has the potential to offer low-latency, high-throughput and energy-efficient communication, for cognitive edge nodes. The study focused on evaluating the network performance metrics of throughput, latency, and power consumption for three different FRACTAL-based network architectures. These architectures include IEEE 802.11-based last mile, direct cellular (5G) backbone, and IEEE 802.11-based last mile over cellular (5G) backbone topologies. This research aims to provide insights into the performance of 5G technology for cognitive edge nodes. The findings suggest that the power consumption of IEEE 802.11-enabled nodes was only slightly higher than the reference case, indicating that it is more energy-efficient than 5G-enabled nodes. Additionally, in terms of latency, IEEE 802.11 technology may be more favourable. The throughput tests revealed that the cellular (5G) connection exhibited high throughput for communication between a test node and an upper-tier node situated either on the internet or at the network edge. In addition, it was found that the FRACTAL edge platform is flexible and scalable, and it supports different wireless technologies, making it a suitable platform for implementing cognitive edge nodes. Overall, this study provides insights into the potential of 5G technology and the FRACTAL edge platform for implementing cognitive edge nodes. The results of this research can be valuable for researchers and practitioners working in the field of wireless communication and edge computing, as it sheds light on the feasibility and performance of these technologies for implementing cognitive edge nodes in various applications