  The adoption of wireless communications and, in particular, Wi-Fi, at the
lowest level of the factory automation hierarchy has not increased as fast as
expected so far, mainly because of serious issues concerning determinism.
Actually, besides the random access scheme, disturbance and interference
prevent reliable communication over the air and, as a matter of fact, make
wireless networks unable to support distributed real-time control applications
properly. Several papers recently appeared in the literature suggest that
diversity could be leveraged to overcome this limitation effectively. In this
paper a reference architecture is introduced, which describes how seamless
link-level redundancy can be applied to Wi-Fi. The framework is general enough
to serve as a basis for future protocol enhancements, and also includes two
optimizations aimed at improving the quality of wireless communication by
avoiding unnecessary replicated transmissions. Some relevant solutions have
been analyzed by means of a thorough simulation campaign, in order to highlight
their benefits when compared to conventional Wi-Fi. Results show that both
packet losses and network latencies improve noticeably.
