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- A framework for offloading real-time applications in a distributed environmentPublication . Maia, Cláudio; Silva, Guilherme; Ferreira, Luís; Pinho, Luís Miguel; Nogueira, Luís; Gonçalves, JoelThis work focuses on highly dynamic distributed systems with Quality of Service (QoS) constraints (most importantly real-time constraints). To that purpose, real-time applications may benefit from code offloading techniques, so that parts of the application can be offloaded and executed, as services, by neighbour nodes, which are willing to cooperate in such computations. These applications explicitly state their QoS requirements, which are translated into resource requirements, in order to evaluate the feasibility of accepting other applications in the system.
- Reliable real-time communication in CAN networksPublication . Pinho, Luís Miguel; Vasques, FranciscoController area network (CAN) is a fieldbus network suitable for small-scale distributed computer controlled systems (DCCS), being appropriate for sending and receiving short real-time messages at speeds up to 1 Mbit/sec. Several studies are available on how to guarantee the real-time requirements of CAN messages, providing preruntime schedulability conditions to guarantee the real-time communication requirements of DCCS traffic. Usually, it is considered that CAN guarantees atomic multicast properties by means of its extensive error detection/signaling mechanisms. However, there are some error situations where messages can be delivered in duplicate or delivered only by a subset of the receivers, leading to inconsistencies in the supported applications. In order to prevent such inconsistencies, a middleware for reliable communication in CAN is proposed, taking advantage of CAN synchronous properties to minimize the runtime overhead. Such middleware comprises a set of atomic multicast and consolidation protocols, upon which the reliable communication properties are guaranteed. The related timing analysis demonstrates that, in spite of the extra stack of protocols, the real-time properties of CAN are preserved since the predictability of message transfer is guaranteed.
- Abstract Timers and their Implementation onto the ARM Cor tex-M family of MCUsPublication . Lindgren, Per; Fresk, Emil; Lindner, Marcus; Lindner, Andreas; Pereira, David; Pinho, Luís MiguelReal-Time For the Masses (RTFM) is a set of languages andto ols b eing develop ed to facilitate emb edded software development and provide highly efficient implementations gearedto static verification. The RTFM-kernel is an architecturedesigned to provide highly efficient and predicable Stack Resource Policy based scheduling, targeting bare metal (singlecore) platforms.We contribute b eyond prior work by intro ducing a platform independent timer abstraction that relies on existingRTFM-kernel primitives. We develop two alternative implementations for the ARM Cortex-M family of MCUs: ageneric implementation, using the ARM defined SysTick-/DWT hardware; and a target sp ecific implementation, using the match compare/free running timers. While sacrificing generality, the latter is more flexible and may reduceoverall overhead. Invariants for correctness are presented,and metho ds to static and run-time verification are discussed. Overhead is b ound and characterized. In b oth casesthe critical section from release time to dispatch is less than2us on a 100MHz MCU. Queue and timer mechanisms aredirectly implemented in the RTFM-core language and canb e included in system-wide scheduling analysis.
- Dynamic QoS-Aware coalition formationPublication . Nogueira, Luís; Pinho, Luís MiguelUsers of wireless devices increasingly demand access to multimedia content with speci c quality of service requirements. Users might tolerate di erent levels of service, or could be satis ed with di erent quality combinations choices. However, multimedia processing introduces heavy resource requirements on the client side. Our work tries to address the growing demand on resources and performance requirements, by allowing wireless nodes to cooperate with each other to meet resource allocation requests and handle stringent constraints, opportunistically taking advantage of the local ad-hoc network that is created spontaneously, as nodes move in range of each other, forming a temporary coalition for service execution. Coalition formation is necessary when a single node cannot execute a speci c service, but it may also be bene cial when groups perform more e ciently when compared to a single s node performance.
- ENCOURAGEing Results on ICT for Energy Efficient BuildingsPublication . Le Guilly, Thibaut; Skou, Arne; Olsen, Petur; Printz Madsen, Per; Albano, Michele; Ferreira, Luís Lino; Pinho, Luís Miguel; Casals, Miquel; Macarulla, Marcel; Gangolells, MartaThis paper presents how the ICT infrastructure developed in the European ENCOURAGE project, centered around a message oriented middleware, enabled energy savings in buildings and households. The components of the middleware, as well as the supervisory control strategy, are overviewed, to support the presentation of the results and how they could be achieved. The main results are presented on three of the pilots of the project, a first one consisting of a single household, a second one of a residential neighborhood, and a third one in a university campus.
- Evaluating Android OS for embedded real-time systemsPublication . Maia, Cláudio; Nogueira, Luís; Pinho, Luís MiguelSince its official public release, Android has captured the interest from companies, developers and the general audience. From that time up to now, this software platform has been constantly improved either in terms of features or supported hardware and, at the same time, extended to new types of devices different from the originally intended mobile ones. However, there is a feature that has not been explored yet - its real-time capabilities. This paper intends to explore this gap and provide a basis for discussion on the suitability of Android in order to be used in Open Real-Time environments. By analysing the software platform, with the main focus on the virtual machine and its underlying operating system environments, we are able to point out its current limitations and, therefore, provide a hint on different perspectives of directions in order to make Android suitable for these environments. It is our position that Android may provide a suitable architecture for real-time embedded systems, but the real-time community should address its limitations in a joint effort at all of the platform layers.
- sMapReduce: a programming pattern for wireless sensor networksPublication . Gupta, Vikram; Tovar, Eduardo; Pinho, Luís Miguel; Kim, Junsung; Lakshmanan, Karthik; Rajkumar, Ragunathan (Raj)Wireless Sensor Networks (WSNs) are increasingly used in various application domains like home-automation, agriculture, industries and infrastructure monitoring. As applications tend to leverage larger geographical deployments of sensor networks, the availability of an intuitive and user friendly programming abstraction becomes a crucial factor in enabling faster and more efficient development, and reprogramming of applications. We propose a programming pattern named sMapReduce, inspired by the Google MapReduce framework, for mapping application behaviors on to a sensor network and enabling complex data aggregation. The proposed pattern requires a user to create a network-level application in two functions: sMap and Reduce, in order to abstract away from the low-level details without sacrificing the control to develop complex logic. Such a two-fold division of programming logic is a natural-fit to typical sensor networking operation which makes sensing and topological modalities accessible to the user.
- Dynamic QoS adaptation of inter- dependent task sets in cooperative embedded systemsPublication . Nogueira, Luís; Pinho, Luís MiguelDue to the growing complexity and dynamism of many embedded application domains (including consumer electronics, robotics, automotive and telecommunications), it is increasingly difficult to react to load variations and adapt the system's performance in a controlled fashion within an useful and bounded time. This is particularly noticeable when intending to benefit from the full potential of an open distributed cooperating environment, where service characteristics are not known beforehand and tasks may exhibit unrestricted QoS inter-dependencies. This paper proposes a novel anytime adaptive QoS control policy in which the online search for the best set of QoS levels is combined with each user's personal preferences on their services' adaptation behaviour. Extensive simulations demonstrate that the proposed anytime algorithms are able to quickly find a good initial solution and effectively optimise the rate at which the quality of the current solution improves as the algorithms are given more time to run, with a minimum overhead when compared against their traditional versions.
- Time-bounded distributed QoS-aware service configuration in heterogeneous cooperative environmentsPublication . Nogueira, Luís; Pinho, Luís MiguelThe scarcity and diversity of resources among the devices of heterogeneous computing environments may affect their ability to perform services with specific Quality of Service constraints, particularly in dynamic distributed environments where the characteristics of the computational load cannot always be predicted in advance. Our work addresses this problem by allowing resource constrained devices to cooperate with more powerful neighbour nodes, opportunistically taking advantage of global distributed resources and processing power. Rather than assuming that the dynamic configuration of this cooperative service executes until it computes its optimal output, the paper proposes an anytime approach that has the ability to tradeoff deliberation time for the quality of the solution. Extensive simulations demonstrate that the proposed anytime algorithms are able to quickly find a good initial solution and effectively optimise the rate at which the quality of the current solution improves at each iteration, with an overhead that can be considered negligible.
- A Closer Look into the AER ModelPublication . Maia, Cláudio; Nogueira, Luís Miguel; Pinho, Luís Miguel; Gracia Pérez, DanielCommercial-of-the-shelf based multi-core systems present timing anomalies that cannot be ignored by the real-time systems community due to their unpredictable behaviour. These timing anomalies, often caused by applications’ uncontrolled accesses to shared resources such as the components in the memory hierarchy or in the I/O subsystem, introduce interference that may lead to deadline misses if the problem is neglected. The Acquisition Execution Restitution (AER) execution model was previously proposed to circumvent this problem and, therefore, mitigate inter-task interference. In this model, applications decouple communication (acquisition and restitution phases) from the actual execution in a way that at most one acquisition or restitution phase is in execution at any instant of time while the execution phase of different tasks can progress in parallel on multiple cores. Thus, keeping each task’s derived worst-case execution time closer to the one measured in isolation. In this paper, we study the AER execution model and compare it against a global Earliest Deadline First (EDF) approach where interferences are considered. Our results show that a priority assignment heuristic which assigns the priorities based on the tasks’ periods dominates all the other proposed heuristics and that due to interference it can also schedule task sets which are not schedulable by using the global EDF approach.