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Modeling Replication and Placement in the PEACE Parallel Operating System - A Case for Dual Objects
(1992)
Implicit Sleep Mode Determination in Power Management of Event-driven Deeply Embedded Systems
(2009)
Implicit Sleep Mode Determination in Power Management of Event-driven Deeply Embedded Systems
(2008)
CLIX - A Hybrid Programming Environment for Distributed Objects and Distributed Shared Memory
(2000)
MLMAC-UL and ECTS-MAC - Two MAC Protocols for Wireless Sensor Networks with Unidirectional Links
(2009)
The battery dictates the lifetime of many embedded systems, especially wireless sensor networks.This makes it necessary to deal with battery management.In this paper we present an approach for a battery management which enables a sensor node to reach a defined lifetime.The presented approach gives feedback to an energy manager if the current power consumption must be lowered or can be increased to reach the runtime goal.In contrast to other systems the battery is handled as black box to keep the system independent from the battery type and brand.First experiments yield promising results of this concept to reach a certain lifetime goal while maintaining a high application quality.
Mission Statement: ToleranceZone : A Self-Stabilizing Middleware for Wireless Sensor Netzworks
(2012)
Today's applications and services become more dependent on fast wireless communication, for the upcoming years data-rate demands of 100Gbit/s can be easily expected. However, fulfilling that demand is a task which cannot simply be solved by upscaling existing technologies. While most of the research tackles the challenges regarding the transmission technology from the physical layer up to base-band processing, we focus on the challenges concerning the handling of that vast amount of data. The overall goal is to bring together the transmission technology with the operating system to create a suitable end-to-end communication solution.
In this paper we argue that communication can be understood as a soft-realtime problem and how that helps introducing parallelism into protocol-processing.
Design and performance measurements of an FPGA accelerator for a 100Gbps wireless data link layer
(2015)
Currently, new storage technologies which unite the latency and byte-addressability of DRAM with the persistence of disks are being developed. This non-volatile memory (NVRAM) may start a software revolution. Traditionally, software was developed for two levels of storage and NVRAM reduces the hierarchy to a single-level store. Current research projects are already exploring the potential of NVRAM, but they face a challenge when they want to evaluate the performance: The new hardware is not yet available.
In this paper, we discuss why benchmark results which are gained on existing DRAM are insufficient for a prediction of the performance on NVRAM. Either existing instructions have to be changed or new ones have to be introduced. We further show that the bochs emulator can be used to build systems which resemble NVRAM, to predict the NVRAM's consequences, and it even allows a comparison of algorithms for NVRAM.
Experiments have shown that the number of asymmetric and unidirectional links often exceeds the number of bidirectional ones, especially in the transitional area of the communication range of wireless sensor nodes. Still, most of today’s routing protocols ignore their existence or try to remove their implications. Also, links are not stable over time, and routes become unusable often, resulting in a need for new routing protocols that can handle highly dynamic links and use unidirectional links to their advantage. At Sensorcomm 2014, we presented BuckshotDV, a routing protocol which is resilient against link fluctuations and uses the longer reach of unidirectional links to increase its performance. Furthermore, its distance vector nature makes it scalable for large sensor networks. This paper is an extended version which adds some implementation details and the evaluation of BuckshotDV in two more application scenarios.
Experiments with wireless sensor networks have shown that links are often asymmetric or unidirectional. This represents a serious problem for many routing protocols, which often depend on bidirectional links. Routing protocols that can use unidirectional links often induce a high overhead. To overcome this problem we introduced Unidirectional Link Triangle Routing, a routing protocol, which uses neighborhood information, gathered actively or passively, to route around unidirectional links. In this paper, we describe Unidirectional Link Triangle Routing in further detail and present additional evaluation results from different application scenarios.
Experiments with wireless sensor networks have shown that asymmetric and unidirectional links do not only exist, but are indeed quite common. Still, many people argue that the gain in connectivity is not worth the effort of making them usable for routing protocols. In this paper, we follow the opposite approach and introduce Unidirectional Link Triangle Routing, which reduces the overhead and, therefore, makes unidirectional links usable on the routing layer.
Energy is the crucial factor for the lifetime of wireless sensor networks. Nonlinear battery effects and nonuniform workload distribution can lead to early node failures. This makes it necessary to manage energy consumption. But to manage energy it is essential to know how much energy is spent by the system. Additionally, for a more fine-grained management it is necessary, to know where the energy is spent. This can be a complicated task, since nodes are not identical due to device variations and the consumption can change over time.
In this paper we present an online energy accounting approach which focuses on simplicity instead on fine granularity and timing accuracy. We argue that the efficacy of an energy accounting model depends more on the input consumption data than on exact timing, especially when the real consumption varies between nodes and in time. Results show that this approach is capable of correctly accounting the energy that nodes spend in scenarios with deviating environment conditions.
Energy and run time are mayor concerns in wireless sensor networks. Reliable information about the energy consumption is needed to be able to build a network and tune its application. In this paper we take a look on the energy consumption of the Texas Instruments eZ430-Chronos, an MSP430 based wireless sensor node, and compare it to the manufacturers datasheet. The measurements show how reliable these specifications are and which consequences should be taken.
Nodes within sensor networks often have tight bound goals for the lifetime while running from a non-renewable energy source. Variations within the hardware or induced by the software complicate the prediction of the energy consumption. Additionally, batteries are vulnerable to temperature and non-linear effects. To reach certain lifetime goals under these influences without sacrificing energy due to pessimistic estimations, online energy management is necessary. At Sensorcomm 2015 we presented policies to control the behavior of applications and devices using energy budgets. This paper is an extended version which adds further details and the evaluation of the proposed dynamic energy management in a real-world scenario.
The erratic behavior of wireless channels is still a major hurdle in the implementation of robust applications in wireless networks. In the past it has been argued that self-stabilization is a remedy to provide the needed robustness. This assumption has not been verified to the extent necessary to convince engineers implementing such applications. A major reason is that the time in which a self-stabilizing system returns to a valid state is unpredictable and potentially unbound. Failure rates typically depend on physical phenomena and in self-stabilizing systems each node tries to react to failures in an inherently adaptive fashion by the cyclic observation of its neighbors' states. When the frequency of state changes is too high, the system may never reach a state sufficiently stable for a specific task. In this paper we substantiate the conditions under which self-stabilization leads to fault tolerance in wireless networks and look at the myths about the power of self-stabilization as a particular instance of self-organization. We investigate the influences of the error rate and the neighbor state exchange rate on the stability and the convergence time on topology information acquired in real network experiments.
Protocol Processing for 100 Gbit/s and Beyond - A Soft Real-Time Approach in Hardware and Software
(2017)
The strive for performance, low power consumption, and less chip area have been diminishing the reliability and the time to fault occurrences due to wear out of electronic devices. Recent research has shown that functional units within processors usually execute a different amount of operations when running programs. Therefore, these units present different individual wear out during their lifetime. Most existent schemes for reconfiguration of processors due to fault detection and other processor parameters are done at the level of cores which is a costly way to achieve redundancy. This paper presents a low latency (approximately 1 clock cycle) software controlled mechanism to reconfigure units within processor cores according to predefined parameters. Such reconfiguration capability delivers features like wear out balance of processor functional units, configuration of units according to the criticality of tasks running on an operating system and configurations to gain in performance (e.g. parallel execution) when possible. The focus of this paper is to show the implemented low latency reconfiguration mechanism and highlight its possible main features.
Scaling minimum features of ICs down to the 10nm- area and below has allowed high integration rates in electronics. Scaling at supply voltages of 1V and below also implies a rising level of stress which drives aging effects that reduce switching speed and the expected life time. Additionally, vulnerability from particle radiation is increased. Hence, fault detection and on- line correction become a must for many applications. However, not only fault tolerance but self-awareness becomes also an advantage. Provided that by being aware of its own healthy state allow optimized configurations regarding system operation modes and configurable hardware mechanism. This paper shows a preliminary work in a configurable circuit and explores its configuration possibilities when integrated into a complete system.
RESCUE: Interdependent Challenges of Reliability, Security and Quality in Nanoelectronic Systems
(2019)
An Unnoticed Property in QC-LDPC Codes to Find the Message from the Codeword in Non-Systematic Codes
(2019)
The tiny logic elements in modern integrated circuits increase the rate of transient failures significantly. Therefore, redundancy on various levels is necessary to retain reliability. However, for mixed-criticality scenarios, the typical processor designs offer either too little fault-tolerance or too much redundancy for one part of the applications. Amongst others, we specifically address redundant processor internal functional units (FU) to cope with transient errors and support wear leveling. A real-time operating system (RTOS) was extended to control our prototypical hardware platform and, since it can be configured deterministically within few clock cycles, we are able to reconfigure the FUs dynamically, at process switching time, according to the specified critically of the running processes. Our mechanisms were integrated into the Plasma processor and the Plasma-RTOS. With few changes to the original software code, it was, for example, possible to quickly change from fault-detecting to fault-correcting modes of the processor on demand.
High-speed protocol processing that provides data-rates of 100 Gbit/s and beyond to the application stresses the whole communication system up to its outer limits. Such a system can only be utilized by employing highly specialized, application specific protocols, that are tailored for certain communication parameters, such as the packet loss rate. However, the requirements for most applications are not static, and a protocol designer cannot anticipate all possible communication conditions upfront. The contradiction between specialized protocols and unknown communication parameters can be solved by adapting the protocol implementation on demand to the current communication conditions. However, such an approach needs a protocol description language that allows the automatic specialization of protocols. In this paper, we present the Protocol Engine Template Language (PETL), that allows the automatic implementation of protocols by a constructive approach for a variety of communication conditions from protocol implementation templates.
Pinpoint the Joules: Unifying Runtime-Support for Energy Measurements on Heterogeneous Systems
(2020)
For the design and operation of today's computer systems, power and energy requirements are highest priorities. Unlike performance analyses, however, power and energy measurements of heterogeneous systems are difficult to conduct. Especially at the system-software level, performing power and energy measurements remains challenging. Yet, such measurements are essential to improve software components for low power and high energy-efficiency.In this paper, we analyze and discuss the power and energy characteristics of several heterogeneous systems with up to 20 cores (160 hardware threads) and 1 TB of main memory. For the analyzed systems, we outline challenges regarding power and energy measurements and show ways to overcome limitations (i.e., sampling constraints). To improve the current state of the art in power and energy measurements at the system-software level, we present the design and implementation of PINPOINT, an energy-profiling tool which unifies different power and energy measurement interfaces.
Embedded systems, e.g. nodes within sensor networks, often have tight bound goals for lifetime while running from a not renewable energy source. Mostly batteries are used, which are vulnerable to temperature and non-linear effects. Additionally, variations within the hardware or induced by the software make the prediction of the available and consumed energy a complicated task. To reach certain lifetime goals under these influences, online energy management is necessary. For a fine-grained management on the level of individual sub-tasks, it is necessary to know where in the system the energy is consumed.
In this work, we extend our online energy accounting approach to enable online energy management. We present ways to control application and device behavior, and, thus, energy using energy budgets. First experiments yield promising results, reaching their lifetime goals while maintaining a high application quality.
MPC++
(1996)