Leveraging MIL-STD-1553's physical layer for use in aircraft data networks

Modern commercial aircraft developers strive to deliver systems with more advanced capabilities while providing increased safety and reliability. A common trend in system design is a shift from a centralized/federated architecture to a more distributed architecture. The use of a distributed architecture provides more flexibility in terms of redundancy and fault tolerance. One of the challenges of utilizing a distributed processing architecture in real-time, critical systems is that the implementation requires the use of a reliable digital data network. There are numerous commercially available data network solutions but very few, if any, will meet the unique combination of performance and environmental requirements of an aircraft system. In particular lightning and EMI requirements create significant challenges for a data network's physical layer. Protection circuitry can be added but it usually results in degradation in performance. MIL-STD-1553 was developed specifically for use in high reliability aircraft systems, and as such was designed to meet the unique environmental requirements of an aircraft. 1553 has a well established record of reliability based on 30 years of in service history in military aircraft. Airbus's recent selection of MIL-STD-1553 for the primary flight control system on the A350XWB is an indication of the suitability of 1553 to modern aircraft applications. This paper includes an overview of the unique benefits of MIL-STD-1553's 1 Mbps physical layer and presents new solutions based on derivatives of MIL-STD-1553. Derivatives of MIL-STD-1553 include both higher data rates and the use of 1553's physical layer with other protocols. An exploration of an increase in MIL-STD-1553's data rate is presented and supported by analytical and experimental data. Spice simulations are used to predict the performance limitations of data rates beyond 1 Mbps. Testing on demonstration hardware is used to confirm the results of the simulations. Test results for a TTP (Time Triggered Protocol) controller with a 1553 physical layer running at 4 Mbps are presented along with a discussion of the use of MIL-STD-1553's physical layer with other protocols.