Björn Andersson

Björn Andersson
Carnegie Mellon University | CMU · Software Engineering Institute

About

91
Publications
9,330
Reads
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2,217
Citations
Introduction
Education
February 1999 - September 2003
Chalmers University of Technology
Field of study
  • Computer Engineering
September 1993 - February 1999
Chalmers University of Technology
Field of study
  • Electrical engineering

Publications

Publications (91)
Article
Full-text available
Consider fixed-priority preemptive partitioned scheduling of constrained-deadline sporadic tasks on a multiprocessor. A task generates a sequence of jobs and each job has a deadline that must be met. Assume tasks have Corunner-dependent execution times; i.e., the execution time of a job J depends on the set of jobs that happen to execute (on other...
Article
Many solutions for composability and compositionality rely on specifying the interface for a component using bandwidth. Some previous works specify period (P) and budget (Q) as an interface for a component. Q/P provides us with a bandwidth (the share of a processor that this component may request); P specifies the time granularity of the allocation...
Conference Paper
The problem of composing multiple, possibly conflicting, runtime enforcers for a cyber-physical system (CPS) is considered. A formal definition of utility-agnostic and utility-maximizing CPS enforcers is presented, followed by an algorithm to combine multiple enforcers, and resolve their conflicts based on a design-time prioritization. To implement...
Conference Paper
Consider the problem of scheduling a taskset on a multiprocessor to meet all deadlines. Assume constrained-deadline sporadic tasks and stage-parallelism (i.e., a task comprises one or more stages with a stage comprising one or more segments so that segments in the same stage are allowed to execute in parallel and a segment is allowed to execute onl...
Conference Paper
Full-text available
In commercial-off-the-shelf (COTS) multi-core systems , a task running on one core can be delayed by other tasks running simultaneously on other cores due to interference in the shared DRAM main memory. Such memory interference delay can be large and highly variable, thereby posing a significant challenge for the design of predictable real-time sys...
Article
Consider scheduling of real-time tasks on a multiprocessor where migration is forbidden. Specifically, consider the problem of determining a task-to-processor assignment for a given collection of implicit-deadline sporadic tasks upon a multiprocessor platform in which there are two distinct types of processors. For this problem, we propose a new al...
Article
Consider the problem of scheduling a task set tau of implicit-deadline sporadic tasks to meet all deadlines on a t-type heterogeneous multiprocessor platform where tasks may access multiple shared resources. The multiprocessor platform has m (k) processors of type-k, where ka{1,2,aEuro broken vertical bar,t}. The execution time of a task depends on...
Conference Paper
Full-text available
Consider the problem of scheduling a set of implicit-deadline sporadic tasks to meet all deadlines on a uniform multiprocessor platform where each task may access at most one of ρ shared resources and at most once by each job of that task. The resources have to be accessed in a mutually exclusive manner. We propose an algorithm, GIS-vpr, which offe...
Conference Paper
Graphics processors were originally developed for rendering graphics but have recently evolved towards being an architecture for general-purpose computations. They are also expected to become important parts of embedded systems hardware -- not just for graphics. However, this necessitates the development of appropriate timing analysis techniques wh...
Conference Paper
Full-text available
Consider the problem of assigning real-time tasks on a heterogeneous multiprocessor platform comprising two different types of processors — such a platform is referred to as two-type platform. We present two linearithmic time-complexity algorithms, SA and SA-P, each providing the following guarantee. For a given two-type platform and a given task s...
Conference Paper
Consider non-preemptive fixed-priority scheduling of arbitrary-deadline sporadic tasks on a single processor assuming that the execution time of a job J depends on the actual schedule (sequence) of jobs executed before J. We present exact schedulability analysis for such a system.
Conference Paper
Full-text available
Consider the problem of scheduling a set of implicit-deadline sporadic tasks to meet all deadlines on a two-type heterogeneous multiprocessor platform where a task may request at most one of \(\left|R\right|\) shared resources. There are m 1 processors of type-1 and m 2 processors of type-2. Tasks may migrate only when requesting or releasing resou...
Conference Paper
Full-text available
The current industry trend is towards using Commercially available Off-The-Shelf (COTS) based multicores for developing real-time embedded systems, as opposed to the usage of custom-made hardware. In typical implementation of such COTS-based multicores,multiple cores access the main memory via a shared bus. This often leads to contention on this sh...
Chapter
Full-text available
This paper addresses sensor network applications which need to obtain an accurate image of physical phenomena and do so with a high sampling rate in both time and space. We present a fast and scalable approach for obtaining an approximate representation of all sensor readings at high sampling rate for quickly reacting to critical events in a physic...
Conference Paper
Full-text available
Consider the problem of scheduling a set of sporadic tasks on a multiprocessor system to meet deadlines using a task splitting scheduling algorithm. Task-splitting (also called semi partitioning) scheduling algorithms assign most tasks to just one processor but a few tasks are assigned to two or more processors, and they are dispatched in a way tha...
Conference Paper
Full-text available
The usage of COTS-based multicores is becoming widespread in the field of embedded systems. Providing real-time guarantees at design-time is a pre-requisite to deploy real-time systems on these multicores. This necessitates the consideration of the impact of the contention due to shared low-level hardware resources on the Worst-Case Execution Time...
Article
Full-text available
Consider the problem of scheduling a set of implicit-deadline sporadic tasks to meet all deadlines on a heterogeneous multiprocessor platform. We consider a restricted case where the maximum utilization of any task on any processor in the system is no greater than one. We use an algorithm proposed in [1] (we refer to it as LP-EE) from state-of-the-...
Conference Paper
Embedded real-time systems often have to support the embedding system in very different and changing application scenarios. An aircraft taxiing, taking off and in cruise flight is one example. The different application scenarios are reflected in the software structure with a changing task set and thus different operational modes. At the same time t...
Article
Full-text available
Known algorithms capable of scheduling implicit-deadline sporadic tasks over identical processors at up to 100% utilisation invariably involve numerous preemptions and migrations. To the challenge of devising a scheduling scheme with as few preemptions and migrations as possible, for a given guaranteed utilisation bound, we respond with the algorit...
Conference Paper
Full-text available
Consider the problem of scheduling a set of sporadic tasks on a multiprocessor system to meet deadlines using a task-splitting scheduling algorithm. Task-splitting (also called semi-partitioning) scheduling algorithms assign most tasks to just one processor but a few tasks are assigned to two or more processors, and they are dispatched in a way tha...
Conference Paper
Full-text available
Consider the problem of designing an algorithm for acquiring sensor readings. Consider specifically the problem of obtaining an approximate representation of sensor readings where (i) sensor readings originate from different sensor nodes, (ii) the number of sensor nodes is very large, (iii) all sensor nodes are deployed in a small area (dense netwo...
Article
Consider a single processor and a software system. The software system comprises components and interfaces where each component has an associated interface and each component comprises a set of constrained-deadline sporadic tasks. A scheduling algorithm (called global scheduler) determines at each instant which component is active. The active compo...
Article
Full-text available
Multi-mode real-time systems are those which support applications with different modes of operation, where each mode is characterized by a specific set of tasks. At run-time, such systems can, at any time, be requested to switch from its current operating mode to another mode (called "new mode") by replacing the current set of tasks with that of th...
Article
This paper studies static-priority preemptive scheduling on a multiprocessor using partitioned scheduling. We propose a new scheduling algorithm and prove that if the proposed algorithm is used and if less than 50% of the capacity is requested then all deadlines are met. It is known that for every static-priority multiprocessor scheduling algorithm...
Conference Paper
Full-text available
Consider the problem of partitioned scheduling of an implicit-deadline sporadic task set on heterogeneous multiprocessors to meet all deadlines. Each processor is either of type-1 or type-2. We present a new algorithm, FF-3C, for this problem. FF-3C offers low time-complexity and provably good performance. Specifically, FF-3C offers (i) a time-comp...
Article
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We present a 12(1+3R/(4m)) competitive algorithm for scheduling implicit-deadline sporadic tasks on a platform comprising m processors, where a task may request one of R shared resources.
Conference Paper
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Multiprocessors, particularly in the form of multicores, are becoming standard building blocks for executing reliable software. But their use for applications with hard real-time requirements is non-trivial. Well-known real-time scheduling algorithms in the uniprocessor context (Rate-Monotonic (1) or Earliest-Deadline-First (1)) do not perform well...
Article
Full-text available
Consider the problem of scheduling a set of spo-radic tasks on a multiprocessor to meet deadlines even at high processor utilizations. We assume that task preemption and migration is allowed but because of their associated overhead, their frequency of use should be kept small. Task-splitting (also called semi-partitioning) is a family of algorithms...
Article
Full-text available
Cooperating objects (COs) is a recently coined termused to signify the convergence of classical embedded computersystems, wireless sensor networks and robotics and control. Wepresent essential elements of a reference architecture for scalabledata processing for the CO paradigm.
Article
Full-text available
Contention on the memory bus in COTS based multicore systems is becoming a major determining factor of the execution time of a task. Analyzing this extra execution time is non-trivial because (i) bus arbitration protocols in such systems are often undocumented and (ii) the times when the memory bus is requested to be used are not explicitly control...
Article
Full-text available
WiDom is a wireless prioritized medium access control (MAC) protocol which offers a very large number of priority levels. Hence, it brings the potential for employing non-preemptive static-priority scheduling and schedulability analysis for a wireless channel assuming that the overhead of WiDom is modeled properly. One schedulability analysis for W...
Conference Paper
Full-text available
Known algorithms capable of scheduling implicit-deadline sporadic tasks over identical processors at up to 100% utilisation invariably involve numerous preemptions and migrations. To the challenge of devising a scheduling scheme with as few preemptions and migrations as possible, for a given guaranteed utilisation bound, we respond with a new algor...
Conference Paper
Full-text available
In this paper we consider global fixed-priority preemptive multiprocessor scheduling of constrained-deadline sporadic tasks that share resources in a non-nested manner. We develop a novel resource-sharing protocol and a corresponding schedulability test for this system. We also develop the first schedulability analysis of priority inheritance proto...
Conference Paper
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Consider the problem of scheduling sporadic tasks on a multiprocessor platform under mutual exclusion constraints. We present an approach which appears promising for allowing large amounts of parallel task executions and still ensures low amounts of blocking.
Conference Paper
Full-text available
WiDom is a previously proposed prioritized medium access control protocol for wireless channels. We present a modification to this protocol in order to improve its reliability. This modification has similarities with cooperative relaying schemes, but, in our protocol, all nodes can relay a carrier wave. The preliminary evaluation shows that, under...
Conference Paper
Full-text available
Consider a distributed computer system comprising many computer nodes, each interconnected with a controller area network (CAN) bus. We prove that if priorities to message streams are assigned using rate-monotonic (RM) and if the requested capacity of the CAN bus does not exceed 25% then all deadlines are met.
Conference Paper
Full-text available
We consider the global and preemptive scheduling problem of multi-mode real-time systems upon identical multiprocessor platforms. Since it is a multi-mode system, the system can change from one mode to another such that the current task set is replaced with a new task set. Ensuring that deadlines are met requires not only that a schedulability test...
Conference Paper
Full-text available
Consider the problem of designing an algorithm with ahigh utilisation bound for scheduling sporadic tasks withimplicit deadlines on identical processors. A task is characterisedby its minimum interarrival time and its executiontime. Task preemption and migration is permitted. Still, lowpreemption and migration counts are desirable.We formulate an a...
Conference Paper
Full-text available
We focus on large-scale and dense deeply embedded systems where, due to the large amount of information generated by all nodes, even simple aggregate computations such as the minimum value (MIN) of the sensor readings become notoriously expensive to obtain. Recent research has exploited a dominance-based medium access control(MAC) protocol, the CAN...
Chapter
Full-text available
Consider a wireless sensor network (WSN) where a broadcast from a sensor node does not reach all sensor nodes in the network; such networks are often called multihop networks. Sensor nodes take individual sensor readings, however, in many cases, it is relevant to compute aggregated quantities of these readings. In fact, the minimum and maximum of a...
Article
Full-text available
When the Internet was born, the purpose was to interconnect computers to share digital data at large-scale. On the other hand, when embedded systems were born, the objective was to control system components under real-time constraints through sensing devices, typically at small to medium scales. With the great evolution of the Information and Commu...
Conference Paper
Consider the problem of scheduling sporadically-arriving tasks with implicit deadlines using Earliest-Deadline-First (EDF) on a single processor. The system may undergo changes in its operational modes and therefore the characteristics of the task set may change at run-time. We consider a well-established previously published mode-change protocol a...
Conference Paper
Full-text available
Consider the problem of scheduling real-time tasks on a multiprocessor with the goal of meeting deadlines. Tasks arrive sporadically and have implicit deadlines, that is, the deadline of a task is equal to its minimum inter-arrival time. Consider this problem to be solved with global static-priority scheduling. We present a priority-assignment sche...
Article
Full-text available
Distributed real-time systems, such as factory automation systems, require that computer nodes communicate with a known and low bound on the communication delay. This can be achieved with traditional time division multiple access (TDMA). But improved flexibility and simpler upgrades are possible through the use of TDMA with slot-skipping (TDMA/SS),...
Conference Paper
Full-text available
A new algorithm is proposed for scheduling preemptible arbitrary-deadline sporadic task systems upon multiprocessor platforms, with interprocessor migration permitted. This algorithm is based on a task-splitting approach - while most tasks are entirely assigned to specific processors, a few tasks (fewer than the number of processors) may be split a...
Conference Paper
Full-text available
We present a distributed algorithm for cyber-physical systems to obtain a snapshot of sensor data. The snapshot is an approximate representation of sensor data; it is an interpolation as a function of space coordinates. The new algorithm exploits a prioritized medium access control (MAC) protocol to efficiently transmit information of the sensor da...
Conference Paper
Consider the problem of scheduling n sporadic tasks so as to meet deadlines on m identical processors. A task is characterised by its minimum interarrival time and its worst-case execution time. Tasks are preemptible and may migrate between processors. We propose an algorithm with limited migration, configurable for a utilisation bound of 88% with...
Conference Paper
Full-text available
Consider a multihop network comprising Ethernet switches. The traffic is described with flows and each flow is characterized by its source node, its destination node, its route and parameters in the generalized multiframe model. Output queues on Ethernet switches are scheduled by static-priority scheduling and tasks executing on the processor in an...
Article
Full-text available
The availability of small inexpensive sensor elements enables the employment of large wired or wireless sensor networks for feeding control systems. Unfortunately, the need to transmit a large number of sensor measurements over a network negatively affects the timing parameters of the control loop. This paper presents a solution to this problem by...
Conference Paper
Full-text available
Consider the problem of scheduling a set of sporadically arriving implicit-deadline tasks to meet deadlines on a uniprocessor. Static-priority scheduling is considered using the slack-monotonic priority-assignment scheme. We prove that its utilization bound is 50%.
Article
Full-text available
In this paper, we focus on large-scale and dense Cyber-Physical Systems, and discuss methods that tightly integrate communication and computing with the underlying physical environment. We present Physical Dynamic Priority Dom-inance ((PD) 2) protocol that exemplifies a key mechanism to devise low time-complexity communication protocols for large-s...
Conference Paper
Full-text available
Consider a network where all nodes share a single broadcast domain such as a wired broadcast network. Nodes take sensor readings but individual sensor readings are not the most important pieces of data in the system. Instead, we are interested in aggregated quantities of the sensor readings such as minimum and maximum values, the number of nodes an...
Conference Paper
Consider the problem of deciding whether a set of n sporadic message streams meet deadlines on a Controller Area Network (CAN) bus for a specified priority assignment. It is assumed that message streams have implicit deadlines and no release jitter. An algorithm to solve this problem is well known but unfortunately it time complexity is non-polynom...
Conference Paper
Full-text available
Consider the problem of scheduling a set of sporadically arriving tasks on a uniform multiprocessor with the goal of meeting deadlines. A processor p has the speed S<sub>p</sub>. Tasks can be preempted but they cannot migrate between processors. On each processor, tasks are scheduled according to rate-monotonic. We propose an algorithm that can sch...
Conference Paper
Full-text available
Consider a communication medium shared among a set of computer nodes; these computer nodes issue messages that are requested to be transmitted and they must finish their transmission before their respective deadlines. TDMA/SS is a protocol that solves this problem; it is a specific type of time division multiple access (TDMA) where a computer node...
Conference Paper
Full-text available
Consider a wireless sensor network (WSN) where a broadcast from a sensor node does not reach all sensor nodes in the network; such networks are often called multihop networks. Sensor nodes take sensor readings but individual sensor readings are not very important. It is important however to compute aggregated quantities of these sensor readings. Th...
Article
Full-text available
Wireless networks play an increasingly important role in application areas such as factory-floor automation, process control, and automotive electronics. In this paper, we address the problem of sharing a wireless channel among a set of sporadic message streams where a message stream issues transmission requests with real-time deadlines. For this p...
Conference Paper
Full-text available
Consider the problem of scheduling a set of sporadically arriving tasks on a uniform multiprocessor with the goal of meeting deadlines. A processor p has the speed S<sub>p</sub>. Tasks can be preempted but they cannot migrate between processors. We propose an algorithm which can schedule all task sets that any other possible algorithm can schedule...
Article
Admission-controllers are used to prevent overload in systems with dynamically arriving tasks. Typically, these admission-controllers are based on sufficient (but not necessary) capacity bounds in order to maintain a low computational complexity. In this paper we present how exact admission-control for aperiodic tasks can be efficiently obtained. O...
Article
Full-text available
We discuss the development of a simple globally prioritized multi-channel medium access control (MAC) protocol for wireless networks. This protocol provides "hard" pre-run-time real-time guarantees to sporadic message streams, exploits a very large fraction of the capacity of all channels for "hard" real-time traffic and also makes it possible to f...
Article
Full-text available
Consider a wireless network where links may be unidirectional, that is, a computer node A can broadcast a message and computer node B will receive this message but if B broadcasts then A will not receive it. Assume that messages have deadlines. We propose a medium access control (MAC) protocol which replicates a message in time with carefully selec...
Conference Paper
Full-text available
We propose a schedulability analysis for a particular class of time division multiple access (TDMA) networks, which we label as TDMA/SS. SS stands for slot skipping, reflecting the fact that a slot is skipped whenever it is not used. Hence, the next slot can start earlier in benefit of hard real-time traffic. In the proposed schedulability analysis...
Conference Paper
Full-text available
Consider the problem of scheduling sporadic message transmission requests with deadlines. For wired channels, this has been achieved successfully using the CAN bus. For wireless channels, researchers have recently proposed a similar solution; a collision-free medium access control (MAC) protocol that implements static-priority scheduling. Unfortuna...
Conference Paper
Full-text available
Consider the problem of scheduling a set of periodically arriving tasks on a multiprocessor with the goal of meeting deadlines. Processors are identical and have the same speed. Tasks can be preempted and they can migrate between processors. We propose an algorithm with a utilization bound of 66% and with few preemptions. It can trade a higher util...
Article
Full-text available
Consider a distributed computer system such that every computer node can perform a wireless broadcast and when it does so, all other nodes receive this message. The computer nodes take sensor readings but individual sensor readings are not very important. It is important however to compute the aggregated quantities of these sensor readings. We show...
Conference Paper
Full-text available
Consider the problem of scheduling sporadic messages with deadlines on a wireless channel. We propose a collision-free medium access control (MAC) protocol which implements static-priority scheduling and present a schedulability analysis technique for the protocol. The MAC protocol allows multiple masters and is fully distributed; it is an adaptati...
Conference Paper
Full-text available
Admission controllers are used to prevent overload in systems with dynamically arriving tasks. Typically, these admission controllers are based on sufficient (but not necessary) capacity bounds in order to maintain a low computational complexity. In this paper we present how exact admission-control for aperiodic tasks can be efficiently obtained. O...
Article
Full-text available
Consider the problem of disseminating data from an arbitrary source node to all other nodes in a distributed computer system, like Wireless Sensor Networks (WSNs). We assume that wireless broadcast is used and nodes do not know the topology. We propose new protocols which disseminate data faster and use fewer broadcasts than the simple broadcast pr...
Conference Paper
This paper studies preemptive static-priority scheduling on multiprocessors. We consider two approaches: global pfair static-priority scheduling and partitioned traditional static priority scheduling. We prove that if presented algorithms are used and if less than 50% of the capacity is used then all deadlines are met. It is known that no static-pr...
Conference Paper
Full-text available
This paper studies multiprocessor scheduling for aperiodic tasks where future arrivals are unknown. A previously proposed priority-driven scheduling algorithm for periodic tasks with migration capability is extended to aperiodic scheduling and is shown to have a capacity bound of 0.5. This bound is close to the best achievable for a priority-driven...
Conference Paper
Full-text available
This paper studies multiprocessor scheduling for aperiodic tasks where future arrivals are unknown. We propose an algorithm for tasks without migration capabilities and prove that it has a capacity bound of 0.31. No algorithm for tasks without migration capabilities can have a capacity bound greater than 0.50.
Article
Full-text available
Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utilization bound for schedulability of periodic tasks. In 2001 this bound was generalized by Abdelzaher and Lu to the aperiodic task case. In t...
Conference Paper
Full-text available
Preemptive scheduling of periodically arriving tasks on a multiprocessor is considered. We show that many common multiprocessor real-time scheduling algorithms suffer from scheduling anomalies, that is, deadlines are originally met, but a decrease in execution times or an increase in periods of tasks can cause deadlines to be missed. We propose a p...
Article
Full-text available
The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical multiprocessors is considered. A scheduling algorithm is proposed for static-priority scheduling of such systems; this algorithm is a simple extension of the uniprocessor ratemonotonic scheduling algorithm. It is proven that this algorithm successful...
Conference Paper
Full-text available
The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical processors is considered. A scheduling algorithm is proposed for static-priority scheduling of such systems; this algorithm is a simple extension of the uniprocessor rate-monotonic scheduling algorithm. It is proven that this algorithm successfully s...
Conference Paper
Full-text available
Traditional multiprocessor real-time scheduling partitions a task set and applies uniprocessor scheduling on each processor. By allowing a task to resume on another processor than the task was preempted on, some task sets can be scheduled where the partitioned method fails. We address fixed-priority preemptive scheduling of periodically arriving ta...
Conference Paper
Traditional multiprocessor real-time scheduling partitions a task set and applies uniprocessor scheduling on each processor. By allowing a task to resume on another processor than the task was preempted on, some task sets can be scheduled where the partitioned method fails. We address fixed-priority preemptive scheduling of periodically arriving ta...