Dependable real-time communications for systems with integrated wired and wireless connectivity

Ensuring sufficiently reliable and timely data communication between embedded computer systems using the wireless transmission medium has been considered problematic for decades. The open medium in which wireless networks operate makes them prone to errors, as interference from other users must be tolerated and transmission errors occur due to shadowing, fading and path loss. For this reason, key application areas such as industrial automation, automotive, avionics or robotics still rely almost exclusively on wired solutions to meet their reliability and real-time requirements. At the same time, communication technologies for consumer electronics have evolved dramatically, with a focus on higher throughput and affordable commercial off-the-shelf (COTS) hardware. This evolution is based on the success of two technologies: Ethernet and Wi-Fi. The success of Ethernet is displacing the wide range of reliable and real-time capable proprietary solutions in favor of standardized options such as time sensitive networking (TSN). With TSN, Ethernet can now meet reliability and real-time requirements, a step that its wireless counterpart, Wi-Fi, has not yet taken. This thesis addresses these limitations and opportunities and provides a comprehensive overview of how wireless communication can be introduced both as a replacement for and as a supplement to wired solutions. The thesis addresses demanding and critical scenarios where reliability and real-time guarantees are required, but where a variety of other, often conflicting, requirements may also apply. The solutions provided can be realized using COTS hardware based on Wi-Fi. They are outlined at the medium access control (MAC) level of the communication architecture, as this is important for managing access to communication resources. Several mechanisms are introduced to improve reliability and other dependability requirements by applying fault prevention and fault tolerance techniques, utilizing the diversity of communication channels, and focusing on scheduling the communication resources. The solutions are supported and evaluated by a mixture of reliability analysis, computer simulations and hardware implementation to advance the state of the art regarding dependable real-time communications for systems with integrated wired and wireless connectivity.