An Evaluation of Ethernet as Data Transport System in Avionics

Abstract: ÅF Digital Solutions AB are looking to replace their current legacy system for audio transmissions within aircrafts with a new system based on Ethernet. They also want the system to be as closely matching the current Audio Integration System as possible as well as preferably using commercial off the shelf components. The issue evaluated in this thesis is whether it is feasible to port the legacy protocol over to an Ethernet based solution with as few modifications as possible, what performance requirements are present on the Ethernet solution as well as what remaining capacity is available in the network. Furthermore is ÅF Digital Solutions AB interested in what avionics related Ethernet based protocols and standards are already present on the market.The work is conducted in two tracks - one track of experimental measurements and statistical analysis of the latency present in the proposed solutions and one track with a survey regarding the integration of the present Audio Integration System protocol into the propesed Ethernet based solutions. The study finds two standards present on the market: Avionics Full-Duplex Ethernet (AFDX) and Time-Triggered Ethernet (TTEthernet). Two prototype implementations are built, one implementing AFDX and one custom built upon Ethernet and UDP. The latency of these are measured and found to be largely similar at ideal conditions. Ethernet is found to be more flexible, whilst AFDX allow for interoperation with other manufacturers and TTEthernet facilitates strict timing requirements at the cost of specialised hardware. The bandwidth utilisation of AFDX at ideal conditions is found to be 0.980% per stream and for the Ethernet solution 0.979% per stream.It is proposed that ÅF Digital Solutions AB pursue a custom Ethernet based solution unless they require interoperability on the same network with other manufacturers as a custom solution with full control over the network allows the largest flexibility in regards to timings and load. If interoperability is required is AFDX proposed instead as it is a standardised protocol and without the, for ÅF Digital Solutions AB, unnecessary overhead of TTEthernet.