  The popularity of concurrent transmissions (CT) has soared after recent
studies have shown their feasibility on the four physical layers specified by
BLE 5, hence providing an alternative to the use of IEEE 802.15.4 for the
design of reliable and efficient low-power wireless protocols. However, to
date, the extent to which physical layer properties affect the performance of
CT has not yet been investigated in detail. This paper fills this gap and
provides the first extensive study on the impact of the physical layer on
CT-based solutions using IEEE 802.15.4 and BLE 5. We first highlight through
simulation how the impact of errors induced by de-synchronization and beating
on the performance of CT highly depends on the choice of the underlying
physical layer. We then confirm these observations experimentally on real
hardware through an analysis of the bit error distribution across received
packets, unveiling possible techniques to effectively handle these errors. We
further study the performance of CT-based flooding protocols in the presence of
radio interference on a large-scale, and derive important insights on how the
used physical layer affects their dependability.
