  Flooding protocols based on concurrent transmissions are regarded as the most
reliable way to collect or disseminate data across a multi-hop low-power
wireless mesh network. Recent works have shown that such protocols are
effective for narrowband communication not only over IEEE 802.15.4, but also
over the BLE 5 physical layers (PHYs). However, to date, existing literature
has only built synchronous flooding solutions on top of a single PHY, and there
has been no attempt to leverage different PHYs at runtime to increase
performance. This paper fills this gap and presents OSF, an open-source
framework that enables the design of multi-PHY synchronous flooding solutions
thanks to a novel radio driver and middle-ware architecture capable of
dynamically switching the underlying physical layer. This allows exploitation
of the specific benefits of each PHY (e.g., higher data-rate, increased
robustness) on-demand during each flood, increasing performance. We tailor OSF
to the off-the-shelf nRF52840 platform, and showcase its benefits by comparing
single-PHY and multi-PHY synchronous flooding solutions on a real-world
testbed.
