A Real-time Calculus Approach for Integrating Sporadic Events in Time-triggered Systems

In time-triggered systems, where the schedule table is predefined and statically configured at design time, sporadic event-triggered (ET) tasks can only be handled within specially dedicated slots or when time-triggered (TT) tasks finish their execution early. We introduce a new paradigm for synthesizing TT schedules that guarantee the correct temporal behavior of TT tasks and the schedulability of sporadic ET tasks with arbitrary deadlines. The approach first expresses a constraint for the TT task schedule in the form of a maximal affine envelope that guarantees that as long as the schedule generation respects this envelope, all sporadic ET tasks meet their deadline. The second step consists of modeling this envelope as a burst limiting constraint and building the TT schedule via simulating a modified Least-Laxity-First (LLF) scheduler. Using this novel technique, we show that we achieve equal or better schedulability and a faster schedule generation for most use-cases compared to other approaches inspired by, e.g., hierarchical scheduling. Moreover, we present an extension to our method that finds the most favourable schedule for TT tasks with respect to ET schedulability, thus increasing the probability of the computed TT schedule remaining feasible when ET tasks are later added or changed

Improving RFC5865 Core Network Scheduling with a Burst Limiting Shaper

We define a novel core network router scheduling architecture to carry and isolate time constrained and elastic traffic flows from best-effort traffic. To date, one possible solution has been to implement a core DiffServ network with standard fair queuing and scheduling mechanisms as proposed in the well-known “A Differentiated Services Code Point (DSCP) for Capacity-Admitted Traffic” from RFC5865. This architecture is one of the most selected solutions by internet service provider for access networks (e.g. Customer-Premises Equipment or satellite PEP). In this study, we argue that the proposed standard implementation does not allow to efficiently quantify the reserved capacity for the AF class. By using a novel credit based shaper mechanism called Burst Limiting Shaper, we show that we can provide the same isolation for the time constrained EF class while better quantifying the part allocated to the AF class

Scheduling Rate Constrained traffic in End Systems of Time-Aware Networks

Nowadays, most of cyber-physical systems in avionics, automotive or recent Industry 4.0 domains require networked communication for mixed-critical applications. Ethernet-based networks such as AFDX, TTEthernet or TSN are capable to support transmission of both safety-critical and non-critical flows. This paper focuses on the TTEthernet network compliant with the avionics ARINC 664-P7 standard supporting time-triggered communication (TT) together with rate-constrained (RC) and best-effort (BE) traffic. Due to a global synchronization, TTcommunication with low latency and minimal jitter is ensured with static schedules computed offline. For event-triggered RC flows, bounded jitter at the source and end-to-end latency are guaranteed with worst-case analysis methods. With the increasing demands of applications, flows with Quality of Service (QoS) requirements such as video or audio may be transmitted as BE flows. However, on current configurations, no guarantees are offered to BE flows. In this paper, we aim at increasing the maximum RC utilization and improving the QoS of BE flows to allow the transmission of video or audio traffic with low jitter and end-to-end delay requirements. For this, we focus on the scheduling mechanisms and propose a scheduling approach based on a static slotted table that is applied at end systems. This table integrates the TT schedules usually obtained with Satisfiability Modulo Theories (SMT) approaches and establishes offsets of RC flows that reduce the end-to-end delay of BE flows. Several strategies for offset computations are proposed based on the distribution of flows locally at end system or globally at switch. We show that local strategies perform better than the global ones to reduce end-to-end delay of BE flows

Mixed-Criticality on the AFDX Network: Challenges and Potential Solutions

In this paper, we first assess the most relevant existing solutions enabling mixed-criticality on the AFDX and select the most adequate one. Afterwards, the specification of an extended AFDX, based on the Burst-Limiting Shaper (BLS), is detailed to fulfill the main avionics requirements and challenges. Finally, the preliminary evaluation of such a proposal is conducted through simulations. Results show its ability to guarantee the highest criticality traffic constraints, while limiting its impact on the current AFDX traffic

Contrôle de drones et robots par reconnaissance de mouvements complexes.

Dans cette étude, deux méthodes ont été appliquées à la reconnaissance de mouvements complexes dans le contexte du pilotage de drones et de robots par des mouvements de l'opérateur détectés par des accéléromètres sur trois axes : la première basée sur un filtre de Kalman supprime le bruit et donne une visualisation 3D du mouvement reconnaissable par un être humain, la seconde basée sur des Chaînes de Markov Cachées permet d'identifier le mouvement de manière automatique. Nous présentons ici les résultats obtenus avec une implémentation sur la plateforme Android

Worst-Case Timing Analysis of AFDX Networks With Multiple TSN/BLS Shapers

This paper addresses the problem of worst-case timing analysis of extended Avionics Full Duplex Switched Ethernet (AFDX) networks, incorporating Time-Sensitive Networking (TSN) shapers called Burst Limiting Shapers (BLS), to enable the interconnection of different avionics domains with mixed-criticality levels, e.g., current AFDX traffic, Flight Control and In-Flight Entertainment. Conducting such an analysis is a challenging issue when considering multiple BLS-shaped traffic classes, due to the sophisticated inter-dependencies between the different shapers sharing the same output capacity. We tackle this problem through extending the applicability domain of our previous work for computing maximum delay bounds using Network Calculus and considering only one BLS class, called Continuous Credit-based Approach (CCbA), to handle multiple TSN/BLS classes. We provide further insights into the sensitivity and tightness issues of worst-case delay bounds yielded with the Generalized CCbA (GCCbA). Our assessments show that the tightness ratio is up to 85%, with reference to Achievable Worst-Case delays. We also show the improvements against recent state-of-the-art approaches in terms of tightness and complexity, where the computation time is up to 105 faster. Finally, we evaluate the efficiency of GCCbA for realistic avionics case studies, e.g., adding A350 flight control traffic to the AFDX. Results show the good applicability of GCCbA and confirm the efficiency of the extended AFDX, which decreases the delay bounds of the existing AFDX traffic by up to 49.9%, in comparison with the current AFDX standard

Performance Enhancement of Extended AFDX via Bandwidth Reservation for TSN/BLS Shapers

To support mixed-criticality applications, the AFDX may integrate multiple traffic classes: Safety-Critical Traffic (SCT) with hard real-time constraints, Rate-Constrained (RC) traffic requiring bounded latencies and Best Effort (BE) traffic with no delivery constraints. These traffic classes are managed based on a Non-Preemptive Strict Priority (NP-SP) Scheduler, where the highest priority traffic (SCT) is shaped with a Burst Limiting Shaper (BLS). The latter has been defined by the Time Sensitive Networking (TSN) task group to limit the impact of high priority flows on lower priority ones. This paper proposes two bandwidth reservation methods for BLS shapers in AFDX networks. The proposed methods are evaluated on a realistic AFDX configuration. Results show their efficiency to noticeably enhance the RC delay bounds and the SCT schedulability, in comparison to an intuitive method

Incorporating TSN/BLS in AFDX for Mixed-Criticality Applications: Model and Timing Analysis

In this paper, we model and analyse the timing performance of an extended AFDX standard, incorporating the Burst Limiting Shaper (BLS) proposed by the Time Sensitive Networking group. The extended AFDX will enable the interconnection of different avionics domains with mixed-criticality levels, e.g., current AFDX traffic, Flight Control and In-Flight Entertainment. First, we present the model and the worst-case timing analysis, using the Network Calculus framework, of such an extended AFDX to infer real-time guarantees. Secondly, we conduct its performance evaluation on a representative AFDX configuration. Results show the tightness of the proposed model, with reference to simulation results. Moreover, they confirm the efficiency of incorporating the BLS in the AFDX standard to noticeably enhance the medium priority level delay bounds, while respecting the higher priority level constraints, in comparison with the current AFDX standard

Network Calculus-based Timing Analysis of AFDX networks with Strict Priority and TSN/BLS Shapers

A homogeneous avionic communication architecture based on the AFDX supporting mixed-criticality applications will bring significant advantages, i.e., easier maintenance and reduced costs. To cope with this emerging issue, the AFDX may integrate multiple traffic classes: Safety-Critical Traffic (SCT) with hard real-time constraints, Rate-Constrained (RC) traffic requiring bounded latencies and Best Effort (BE) traffic with no delivery constraints. These traffic classes are managed based on a Non-Preemptive Strict Priority (NP-SP) Scheduler, where the highest priority traffic (SCT) is shaped with a Burst Limiting Shaper (BLS). The latter has been defined by the Time Sensitive Networking (TSN) task group to limit the impact of high priority flows on lower priority ones. This paper proposes a Network Calculus-based approach to compute the end-to-end delay bounds of SCT and RC classes. We consider the impact of the BLS and the multi-hop network architecture. We also provide proofs of service curves guaranteed to SCT and RC classes, needed to derive delay bounds with Network Calculus. The proposed approach is evaluated on a realistic AFDX configuration. Results show the efficiency of incorporating the TSN/BLS on top of a NPSP scheduler in the AFDX to noticeably enhance the RC delay bounds while guaranteeing the SCT deadline, in comparison to an AFDX implementing only a NP-SP scheduler