Vers la convergence de réseaux dans l'avionique

AFDX est le standard Ethernet commuté utilisé pour la transmission des flux avioniques. Pour des raisons de certification, le réseau AFDX déployé à présent dans les avions civils est très peu chargé. Cette thèse vise à étudier la possibilité envisagée par les avionneurs d’utiliser la bande passante AFDX restante pour transporter des flux non-avioniques additionnels (vidéo, audio, service). Ces flux ne doivent pas affecter les délais de transmission des flux avioniques. Pour multiplexer des flux avioniques et non-avioniques des politiques d’ordonnancement sont nécessaires au niveau des systèmes d’extrémité (end systems) et des commutateurs. Dans cette thèse, nous considérons l’exemple de la transmission sur AFDX de flux vidéo provenant des caméras de surveillance de l’avion. Le multiplexage des flux avioniques et vidéo est réalisé par l’introduction d’une table d’ordonnancement au niveau des end systems émetteurs et d’une politique de type SPQ dans les ports de sortie du commutateur. Cette solution préserve les contraintes temps-réel des flux avioniques, mais peut introduire des variations sur les délais de bout-en-bout des flux vidéo. Une allocation appropriée des flux avioniques dans la table d’ordonnancement peut réduire le retard d’émission des flux vidéo et ainsi, limiter les variations de délai. Nous proposons deux stratégies d’allocation des flux avioniques dans la table d’ordonnancement : une heuristique simple et une allocation optimale. L’allocation optimale est dérivée en résolvant un problème d’optimisation par contraintes qui minimise le retard d’émission des flux vidéo. Dans le cas des end systems moins chargés, l’allocation par heuristique est proche de l’optimale

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

Rethinking LEO Constellations Routing with the Unsplittable Multi-Commodity Flows Problem

This study investigates the performance of an innovative routing protocol inspired by the Unsplittable Multi-Commodity Flow (UMCF) problem. LEO routing schemes are often based on Shortest Path (SP) algorithms, the Floyd-Warshall algorithm is usually chosen to compute these network paths within the constellation and their end-to-end latency. Instead of considering latency as a criterion, we seek to optimize the overall amount of IP traffic crossing the constellation. This criterion can be optimized by considering the Unsplittable Multi Commodity Flow problem associated with the system. To solve this problem, we use a heuristic algorithm based on randomized rounding that was shown to return solutions of good quality of the Unsplittable Multi Commodity Flow problem in the optimization literature. Using network simulation over Telesat constellation, we show this proposal significantly reduces the overall congestion level compared to the standard SP routing schemes

Utilisation des noeuds DecaWiNo pour la localisation indoor précise d'objets communicants en UWB

Une des applications privilégiées de l'Ultra Wide Band (UWB) est la localisation indoor de noeuds communicants. Le mécanisme d'évaluation de la distance entre les noeuds (ranging) permet d'alimenter des algorithmes et des calculs géométriques afin de déterminer la position de noeuds communicants avec une précision d'une dizaine de centimètres. Les travaux de recherche présentés dans cet article s'inscrivent dans cette thématique et visent à utiliser les liens radio de type UWB, proposés par l'amendement [1] de l'année 2007 de la norme IEEE 802.15.4. Nous présentons les noeuds DecaWino, basés sur un tranceiver DecaWave [2] DW1000, et un processeur Cortex-M4 Freescale MK20DX256VLH7, présent sur le module Teensy 3.2 de l'écosystème Arduino. Associés aux noeuds DecaWino que nous avons conçus, notre plateforme logicielle Decaduino [3], offre un environnement logiciel [4] adapté et permet le prototypage rapide de solutions de localisation de noeuds UWB

Towards networks convergence in avionics

AFDX est le standard Ethernet commuté utilisé pour la transmission des flux avioniques. Pour des raisons de certification, le réseau AFDX déployé à présent dans les avions civils est très peu chargé. Cette thèse vise à étudier la possibilité envisagée par les avionneurs d’utiliser la bande passante AFDX restante pour transporter des flux non-avioniques additionnels (vidéo, audio, service). Ces flux ne doivent pas affecter les délais de transmission des flux avioniques. Pour multiplexer des flux avioniques et non-avioniques des politiques d’ordonnancement sont nécessaires au niveau des systèmes d’extrémité (end systems) et des commutateurs. Dans cette thèse, nous considérons l’exemple de la transmission sur AFDX de flux vidéo provenant des caméras de surveillance de l’avion. Le multiplexage des flux avioniques et vidéo est réalisé par l’introduction d’une table d’ordonnancement au niveau des end systems émetteurs et d’une politique de type SPQ dans les ports de sortie du commutateur. Cette solution préserve les contraintes temps-réel des flux avioniques, mais peut introduire des variations sur les délais de bout-en-bout des flux vidéo. Une allocation appropriée des flux avioniques dans la table d’ordonnancement peut réduire le retard d’émission des flux vidéo et ainsi, limiter les variations de délai. Nous proposons deux stratégies d’allocation des flux avioniques dans la table d’ordonnancement : une heuristique simple et une allocation optimale. L’allocation optimale est dérivée en résolvant un problème d’optimisation par contraintes qui minimise le retard d’émission des flux vidéo. Dans le cas des end systems moins chargés, l’allocation par heuristique est proche de l’optimale.AFDX is the standard switched Ethernet solution for transmitting avionic flows. Today’s AFDX deployments in commercial aircrafts are lightly loaded to ensure the determinism of control and command operations. This thesis aims at investigating a practical alternative envisioned by manufacturers that takes advantage of the remaining AFDX bandwidth to transfer additional nonavionic flows (video, audio, service). These flows must not compromise the in-time arrival of avionic ones. Thus, appropriate scheduling policies formultiplexing avionic flows with non-avionic flows are required at the emitting end systems and switch egress ports. We mainly focus on the transmission of additional flows carrying video streams from cameras located on the airplane to cockpit display. Multiplexing avionic flows with video flows is tackled by introducing table scheduling at the emitting end systems and a 2-priority levels SPQ service policy at switch egress ports. This solution preserves the real-time constraints of avionic flows but may introduce variations of the end-to-end delay of video ones. An appropriate allocation of slots to avionic flows in table scheduling can reduce the emission lag of video flows and thus, limit their delay variations. We propose two strategies to allocate avionic flows in the table scheduling: a simple one based on heuristics and an optimal one. Optimal schedules are derived by solving a constraint programming model minimizing the emission lag of video flows. For light traffic end systems, heuristic allocation is close to optimal

Qualitative and Quantitative Analysis of Avionics Full DupleX Network Models

The Avionics Full DupleX (AFDX) is a redundant and reliable Ethernet network that ensures deterministic communication. Unlike papers that exclusively address AFDX with performance evaluation in mind, this pa- per use both quantitative and qualitative analysis to characterize the transmission of flows in the network. Qualitative analysis enables checking the SysML model of the network against temporal constraints. Quantita- tive analysis uses a simulation approach to evaluate the timing performances of the network

Towards Quality of Service Provision with Avionics Full Duplex Switching

International audienceAvionics Full-Duplex Switched Ethernet (AFDX) has been designed to carry exclusively time-critical flows dictated by the severe real-time constraints of avionics. Certification methods ensure end-to-end communication delays are upper bounded at the cost of an over-provision of network bandwidth. This paper investigates the issues related to the efficient use of such wasted communication capacity. The basic idea is to push additional Ethernet flows of lower priority into the network with the goal of offering different quality of service levels to them. This addition should of course be transparent to real-time flows. Different scheduling policies, enforced at the end system and at the switches, can provide such features. This paper questions i) their impact on the real-time flow end-to-end delay and ii) the quality of service non real-time flows can expect in terms of end-to-end delay distribution. The ultimate goal of this study is to decide if such a network configuration offers the opportunity to deploy multimedia applications such as VoIP traffic, live video streaming over an AFDX industrial configuration. A first study investigates the use of static priority queuing and traffic scheduling tables on an industrial A350 AFDX configuration. Traffic scheduling tables are shown to be promising as they can spread non-critical traffic more evenly over time, reducing congestion peaks at switches. I. APPLICATION DOMAIN & CHALLENGE A. Application domain Avionics Full DupleX switching (AFDX) networks have become the de-facto technology for commercial avionics embedded networks in the last decade. AFDX follows ARINC664 Part 7 norm [1] and is currently deployed by the biggest aircraft manufacturers. A complex industrial ecosystem has been created around this technology to efficiently design, prototype and certify such networks. Even though alternative solutions are being investigated, this protocol will remain in use for couple of decades in the industry. AFDX is a switched Ethernet network where network interface cards (the so-called end systems) can only emit frames following a pre-defined virtual link (VL) setting. A VL is defined by minimum and maximum frame sizes, together with a BAG duration (Bandwidth Allocation Gap) that expresses the minimum duration that separates two consecutive frames of the VL. A given bandwidth is as such associated to a VL. BAG durations are selected within the discrete power set of {1, 2, 4, 8, 16, 32, 64, 128} milliseconds. AFDX switches are configured statically with VL routes that can be set as multicast. For each egress port, two queues with different priority levels exist. Fig. 1: Example of an A350-like AFDX network topology. Switches are given by red vertices, other nodes representing end systems. Figure 1 represents an example network similar to the ones deployed on an A350 aircraft. It is composed of 126 end systems interconnected by two redundant AFDX networks composed of 7 switches each. End systems generate 1106 VLs

Multiplexing Avionics and additional flows on a QoS-aware AFDX network

International audienceAFDX is the standard switched Ethernet solution for the transmission of avionics flows. Today's AFDX deployments in commercial aircrafts are lightly loaded to ensure the determinism of control and command operations. Manufacturers envision to take advantage of the remaining AFDX bandwidth to transmit additional non avionics flows (video, audio, service). These flows must not compromise the in-time transmission of avionics ones: constraints on jitter at source end system and end-to-end latency have to be insured for each avionics flow. In this paper, we investigate the scheduling of avionics and additional flows, mainly at the end system level. We show that an event-triggered strategy is better than a time-triggered one for additional flows at source level, but it might compromise the jitter constraint of avionics flows and increase the end-to-end latency of additional ones. We consider two time-triggered scheduling strategies, i.e. an optimal one and a simpler one based on a heuristic. We show that the later one performs nearly as well as the former one and that, for both of them, the difference with an event-triggered strategy at source level is limited and can be statically bounded

Impact of source scheduling on end-to-end latencies in a QoS-aware avionics network

International audienceThis paper investigates the impact of a novel source scheduling framework tailored to introduce Quality of Service (QoS) in legacy embedded avionics networks. The protocol of interest is the Avionics Full Duplex Switched Ethernet (AFDX) deployed in modern civilian aircrafts to handle the transmission of time-critical avionics flows. Our aim is to introduce soft real-time flows on such networks in order to carry video flows. Multiplexing avionics real-time flows with video flows is tackled by introducing table scheduling at the end systems (i.e. transmitters). We propose herein a solution that preserves the worst-case end-to-end delay of avionics flows, and show how their scheduling in the table impacts the jitter of the video flows. Thorough simulations on a A350-like network architecture underline that table schedules mostly impact the jitter of video flows at the source and have limited impact on the jitter introduced by the network transfer

Mutation of Formally Verified SysML Models

Model checking of SysML models contributes to detect design errors and to check design decisions against user requirements. Yet, each time a model is modified, formal verification must be performed again, which makes model evolution costly and hampers the use of agile development methods. Based on former contri- butions on dependency graphs, the paper proposes to facilitate updates (also called mutations) on models: whenever a mutation is performed on a model, the algorithms introduced in this paper can determine which proofs remain valid and which ones must be performed again. In this latter case, our algorithm reuses as much as possible previous proofs results in order to lower the proof complexity. The paper focuses on reachability proofs, and relies on a real-time communication architecture based on TSN (Time Sensitive Network) to exemplify the approach and give performance results