Implementation of middleware fault tolerance support for real-time embedded applications

Critical real-time embedded systems need to apply fault tolerance strategies to deal with operation time errors, either in hardware or software. In this paper we present the ongoing work to provide application fault tolerance by means of implementing middleware transparent support over the BOSS embedded operating system. The middleware uses a publishersubscriber protocol and enables the execution of several fault tolerance strategies with minimum burden to the application level softwareFundação para a Ciência e a Tecnologia (FCT

Middleware Fault Tolerance Support for the BOSS Embedded Operating System

Critical embedded systems need a dependable operating system and application. Despite all efforts to prevent and remove faults in system development, residual software faults usually persist. Therefore, critical systems need some sort of fault tolerance to deal with these faults and also with hardware faults at operation time. This work proposes fault-tolerant support mechanisms for the BOSS embedded operating system, based on the application of proven fault tolerance strategies by middleware control software which transparently delivers the added functionality to the application software. Special attention is taken to complexity control and resource constraints, targeting the needs of the embedded market.Fundação para a Ciência e a Tecnologia (FCT

Application-level fault tolerance in real-time embedded systems

Critical real-time embedded systems need to make use of fault tolerance techniques to cope with operation time errors, either in hardware or software. Fault tolerance is usually applied by means of redundancy and diversity. Redundant hardware implies the establishment of a distributed system executing a set of fault tolerance strategies by software, and may also employ some form of diversity, by using different variants or versions for the same processing. This work proposes and evaluates a fault tolerance framework for supporting the development of dependable applications. This framework is build upon basic operating system services and middleware communications and brings flexible and transparent support for application threads. A case study involving radar filtering is described and the framework advantages and drawbacks are discussed.Fundação para a Ciência e a Tecnologia (FCT

Applying aspects to a real-time embedded operating system

The application of aspect-oriented programming (AOP) to the embedded operating system domain is still a very controversial topic, as this area demands high performance and small memory footprint. However, recent studies quantifying aspects overheads in AspectC++ show that the resource cost is very low. Therefore, operating system development may benefit with the modularization of crosscutting concerns and system specialization offered by AOP. This paper addresses our experience in applying aspects to synchronization (mutual exclusion) and logging in a real-time embedded operating system (BOSS). Furthermore, we present our ideas for future investigation in aspect-oriented implementations for fault tolerance, middleware customization and platform variability.(undefined

Prediction techniques on FPGA for latency reduction on tactile internet

Tactile Internet (TI) is a new internet paradigm that enables sending touch interaction information and other stimuli, which will lead to new human-to-machine applications. However, TI applications require very low latency between devices, as the system’s latency can result from the communication channel, processing power of local devices, and the complexity of the data processing techniques, among others. Therefore, this work proposes using dedicated hardware-based reconfigurable computing to reduce the latency of prediction techniques applied to TI. Finally, we demonstrate that prediction techniques developed on field-programmable gate array (FPGA) can minimize the impacts caused by delays and loss of information. To validate our proposal, we present a comparison between software and hardware implementations and analyze synthesis results regarding hardware area occupation, throughput, and power consumption. Furthermore, comparisons with state-of-the-art works are presented, showing a significant reduction in power consumption of ≈1300× and reaching speedup rates of up to ≈52×

An efficient adaptive data-link-layer architecture for LoRa networks

LoRa is one of the most popular low-power wireless network technologies for implementation of the Internet of Things, with the advantage of providing long-range communication, but lower data rates, when compared with technologies such as Zigbee or Bluetooth. LoRa is a single-channel physical layer technology on top of which LoRaWAN implements a more complex multi-channel network with enhanced functionalities, such as adaptive data rate. However, LoRaWAN relies on expensive hardware to support these functionalities. This paper proposes a LoRa data-link-layer architecture based on a multi-layer star network topology that adapts relevant LoRa parameters for each end node dynamically taking into account its link distance and quality in order to balance communication range and energy consumption. The developed solution is comprised of multiple components, including a LoRa parameter calculator to help the user to configure the network parameters, a contention-free MAC protocol to avoid collisions, and an adaptive spreading factor and transmission power mechanism. These components work together to ensure a more efficient use of the chosen ISM band and end node resources, but with low-cost implementation and operation requirements.This research was funded by FEDER through COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI) grant number POCI-01-0145-FEDER-028247 and by FCT—Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/202

Aspect-oriented fault tolerance for real-time embedded systems

Real-time embedded systems for safety-critical applications have to introduce fault tolerance mechanisms in order to cope with hardware and software errors. Fault tolerance is usually applied by means of redundancy and diversity. Redundant hardware implies the establishment of a distributed system executing a set of fault tolerance strategies by software, and may also employ some form of diversity, by using different variants or versions for the same processing. This paper describes our approach to introduce fault tolerance in distributed embedded systems applications, using aspect-oriented programming (AOP). A real-time operating system sup-porting middleware thread communication was integrated to a fault tolerant framework. The introduction of fault tolerance in the system is performed by AOP at the application thread level. The advantages of this approach include higher modularization, less efforts for legacy systems evolution and better configurability for testing and product line development. This work has been tested and evaluated successfully in several fault tolerant configurations and presented no significant performance or memory footprint costs.Fundação para a Ciência e a Tecnologia (FCT

Bioaugmentation strategies to enhance long chain fatty acids (LCFA) conversion to methane

Bioaugmentation of bioreactors with LCFA-degrading bacteria is a possibility for improving methane production from lipid-rich wastes/wastewaters. Cavaleiro et al. [1] has shown that methane production from oleate (unsaturated LCFA) is faster and more efficient in batch tests bioaugmented with Syntrophomonas zehnderi, a bacterium that is able to degrade a wide range of both saturated and unsaturated LCFA [2]. In this work, anaerobic sludge bioaugmentation with S. zehnderi was studied in order to evaluate: (I) the recovery of bioreactors after an episode of LCFA overload; (II) the potential for decreasing reactor start-up periods. The potential of using S. zehnderi for recovering LCFA-overloaded sludge was tested using anaerobic sludge collected from a oleate-fed bioreactor at three different operation times. Bioaugmentation batches were prepared with LCFA loaded biomasses in the presence of S. zehnderi. Controls were set using inactivated S. zehnderi. Methane yields of 72, 53 and 40% were obtained from the first, second and third collected sludge samples respectively. However, addition of S. zehnderi did not significantly improve LCFA conversion loaded-sludges as similar yields were achieved in non-bioaugmented controls. Fed-batch bioreactor start-up, using a non-acclimated sludge, was attempted in the presence of S. zehnderi. Assays were conducted in the presence and absence of both a solid microcarier (sepiolite) and a substoichiometric amount of ferric hydroxide. Blank (no oleate) and control assays (inactivated S. zehnderi) were also prepared. Bioaugmentation assays with sepiolite and ferric hydroxide showed the highest methane yield, with an observed methane yield 16% higher than in non-bioaugmented controls. The potential of bioaugmenting S. zehnderi as means to recover methanogenic activity of LCFA-loaded biomass was not demonstrated. However faster reactor start-up could be accomplished since higher methane yield was achieved in bioaugmented fed-batch assays in the presence of sepiolite with ferric hydroxide. [1] Cavaleiro, A.J., Sousa, D.Z. and Alves, M.M. 2010. Water Res 44:4940-7. [2] Sousa, D.Z., Smidt, H., Alves, M.M. and Stams, A.J.M. 2007. Int J Syst Evol Microbiol 57:609-15. Acknowledgments: This study has been funded by FEDER, through the COMPETE program, and by Portuguese funds, through Portuguese Foundation for Science and Technology (FCT), in the frame of the project FCOMP-01-0124-FEDER-014784. References