  Wirelessly interconnected sensors, actuators, and controllers promise greater
flexibility, lower installation and maintenance costs, and higher robustness in
harsh conditions than wired solutions. However, to facilitate the adoption of
wireless communication in cyber-physical systems (CPS), the functional and
non-functional properties must be similar to those known from wired
architectures. We thus present Time-Triggered Wireless (TTW), a wireless
architecture for multi-mode CPS that offers reliable communication with
guarantees on end-to-end delays among distributed applications executing on
low-cost, low-power embedded devices. We achieve this by exploiting the high
reliability and deterministic behavior of a synchronous transmission based
communication stack we design, and by coupling the timings of distributed task
executions and message exchanges across the wireless network by solving a novel
co-scheduling problem. While some of the concepts in TTW have existed for some
time and TTW has already been successfully applied for feedback control and
coordination of multiple mechanical systems with closed-loop stability
guarantees, this paper presents the key algorithmic, scheduling, and networking
mechanisms behind TTW, along with their experimental evaluation, which have not
been known so far. TTW is open source and ready to use: ttw.ethz.ch
