Stefan Schneele

A performance study of Audio Video Bridging in aeronautic Ethernet networks

Audio-Video-Bridging (AVB) is a promising new commercially available Ethernet-based standard providing mechanism for audio and video transmission over Ethernet supporting demanding audio and video transmission delay requirements. This paper addresses the applicability of using AVB in a fully-switched Ethernet network that covers safety-related functions in the aeronautics. Avionic systems leveraging such digital networks have stringent requirements in terms of audio quality, latency, and jitter; e.g., latency can be at most a few milliseconds. The result of this work is a performance study of audio transmission approaches in aeronautics where we address AVB without synchronization and AVB synchronization with 802.1AS. We pay special attention to the failure mode of losing synchronization during operation. Two real-world scenarios are addressed in the experimental results - a demonstration of a switched Ethernet aircraft cabin and a demonstration for a highly safety-related audio system. For these two scenarios hard performance bounds are required in terms of synchronous playback that cannot easily be fulfilled, especially when time synchronization is lost.

Power-over-Ethernet for avionic networks

Avionic networks are to an increasing extent based on Ethernet physical layer implementations due to economical and technical motivations. While conventional Ethernet-based systems are built up in star topologies, the physical layer can also be used to establish linear networks. Power-over-Ethernet (PoE) uses Ethernet data cabling for the transmission of power. Existing technology however is not able to transmit sufficient power for many avionic applications, particularly for such implemented in a linear topology. With a customized PoE approach, the power capabilities of PoE links can significantly be increased to more than 100 W. With an adequate fail-safe concept, the reliability of a linear Ethernet implementation can be increased, reducing the immanent safety drawback of a linear topology. The presented methods offer the potential to significantly reduce cost, complexity and weight of Ethernet-based system installations, aiming at greener avionics for future aircraft.

Recent IEEE 802 developments and their relevance for the avionics industry

The need for high data-rates enabled the adoption of Ethernet in avionics systems and, indeed, today Ethernet according to the ARINC 664 part 7 standard is used in prominent airplanes such as the Airbus A380 or the Boeing 787 as well as several other aerospace programs. Meanwhile, Ethernet continues to evolve also in its native standardization body, the IEEE. In particular, Ethernet grows in two directions, speed and services, and we consider two specific developments to be of particular interest to the avionics industry. First, the 1000BASE-T1 PHY Task Force (IEEE P802.3bp) and the IEEE 100BASE-T1 Task Force (IEEE 802.3bw) are standardizing Ethernet PHYs considering usage in harsh environments like industrial or automotive at Gbit/sec and 100 Mbit/sec transmission speeds. Secondly, the time-sensitive networking task group (IEEE 802.1 TSN) is currently standardizing basic forms of time-triggered communication to minimize the transmission latency and jitter of Ethernet. In this paper we give an overview of the current developments in IEEE 802.3bp, IEEE 802.3bw and IEEE 802.1 TSN and formulate a perspective on the future use of Ethernet in avionics systems.

Towards stochastic flow-level network modeling: Performance evaluation of short TCP flows

We present in this paper a stochastic flow-level network model for the performance evaluation of IP networks with multiple bottlenecks supporting short-lived and long-lived TCP flows. Flow-level network models are efficient at estimating the mean bandwidth of TCP flows in various topologies, but they are generally limited to the study of infinite flows. This paper extends such models in order to evaluate short-lived flows alternating between idle and active periods where data of random size is transferred. We study the interaction between multiple flows and derive mean bandwidths, durations of file transfer or average number of active flows. We first study a single bottleneck, and then extend our analysis to networks with multiple bottlenecks as well as the effect of slow-start. We apply our results to various networks and assess the accuracy of our approach by comparing our analytical results with results of the discrete event simulator ns-2.

Evaluation of Audio/Video Bridging forwarding method in an avionics switched ethernet context

Possible evolution of Avionics Full-Duplex Switched Ethernet (AFDX) are currently investigated. Such network should support existing time-constrained avionics flows, as well as new best effort traffic, requiring scheduling algorithms to meet guarantees on avionics flows. Following the current trend of the automotive industry to move toward Audio/Video Bridging (AVB), this paper evaluates an application of the scheduling scheme described in the emerging IEEE 802.1 AVB standard in an avionics switched Ethernet scenario. Results are compared to other common scheduling strategies such as strict priority queuing, and different fair scheduling variants.

Quality of service IP cabin infrastructure

Modern avionics industry spends much effort in cabin wiring due to the topics of reliability, complexity and configuration. This paper addresses an approach that replaces cabin communication infrastructure by standard Ethernet components without loss in reliability and a strong benefit in terms of simplicity and level of reuse. This paper shows analytically that necessary requirements will be satisfied. Furthermore, discrete event simulation techniques are used to model worst case scenarios.

Flexible communication architecture for dependable time-triggered systems

The trend for more flexible communication architectures, in particular for safety critical aeronautic applications, reflects the growing need for an optimized design approach. Customer requirements for additional functionality and changes caused by unpredictable obsolescence policies may necessitate requests for renewal of technologies during the product life cycle in a maintainable approach. The challenge is to develop an architecture approach, allowing reusability of existing application code, scalability and providing independence of the underlying system communication. Over recent years, shared networks have become a rapidly emerging technology in aeronautics and space, since they offer -- in contrast to point-to-point connections--more flexibility in terms of architecture and reduced wiring. Thus, they present the prospect of potential savings in cost and weight. In particular, due to their reliability and strongly deterministic behavior, time-triggered shared networks have evolved as eligible communication protocols for safety-critical applications in aerospace. We propose an approach in terms of dependable and flexible communication architecture that permits more flexibility in the use of time-triggered technologies and delivers a more effective, reliable and dependable system design.

Multi-objective optimization of aircraft networks for weight, performance and survivability

With a current utilization of around 25% of its total weight, optimization of cabling and harness plays an important role in the design of an aircraft. This is a multi-objective optimization problem as the physical properties of the harness (e.g., length and weight) as well as the logical properties of the underlying network (survivability and performance) have to be taken into account. We propose in this paper to investigate this multi-objective optimization problem and provide different algorithms to solve it. We first focus on expressing it as a mixed integer binary linear program. Due to the complexity of solving this class of linear programs, we propose various heuristics for providing a good solution to this problem.

Performance Evaluation of an Ethernet-Based Cabin Network Architecture Supporting a Low-Latency Service

Aircraft cabin data network is a key element in today’s aircraft, where several functionalities of the cabin are grouped in four different security domains. In todays architectures, each domain is normally separated from the others and uses different standards, ranging from ARINC based standards to customized Ethernet. We present here a future of cabin data network, where the main key principle is the use of a common Gigabit full-duplex Ethernet backbone, shared by all domains. As this new network has to be compliant with existing applications and their requirements, a specific Quality-of-Service (QoS) architecture is investigated in this paper. The contributions of this paper are the description of a new network architecture for cabin networks, and the introduction of a scheduling algorithm called Time-Aware Deficit Round Robin (TADRR) enabling an ultra low-latency time-triggered service. We show the benefits of this new architecture via a performance evaluation carried out with the simulator OMNeT++.