Network protocol for distribution and handling of data from JAS 39 Gripen

Abstract: On board the aircraft JAS 39 Gripen a measuring system, Data Acquisition System (DAS), is sending sensor data to a server on the ground. In this master thesis, a unified API for distribution and handling of the sensor data is designed and implemented. The work has been carried out at Saab Aeronautics, Linköping during, 2014. During flights with the aircraft the engineers at Saab need to monitor different sensors in the aircraft, including the exact commands of the pilots. All that data is serialized and sent via radio link to a server at Saab. The current data distribution solution includes several clients that need to connect to the server. Each client has its own connection protocol, making the system complex and difficult to maintain. An API is needed in order to make the clients connect in a unified manner. This would also enable future clients to implement the API and start receiving sensor data from the server. The research conducted in the thesis project was centered on the different choices that exist for designing such an API. The question that needed answering was; how can an existing complex system can be replaced by a publish-subscribe system and what the benefits would be in terms of latency and flexibility of the system? The design would have to be flexible enough to support multiple clients. The investigated research question was answered with a design utilizing ZMQ, pthreads and a design pattern. The result is a flexible system that was sufficiently fast for the requirements set at Saab and open to future extensions. The thesis work also included designing a unified API with requirements on latency and functionality. The resulting API was designed using the publish-subscribe design pattern, the network library Zero Message Queue (ZMQ) and the threading library pthreads. The resulting system supports multiple coexisting servers and clients that request sensor data. A new feature is that the clients can start sending calculations performed on samples to other clients. To demonstrate that the solution provides a unified framework, two existing clients and the server were developed with the proposed API. To test the latency requirements, tests were performed in the control room at Saab.