  With more than 4 billion devices produced in 2020, Bluetooth and Bluetooth
Low Energy (BLE) have become the backbone of the Internet of Things. Bluetooth
and BLE mitigate interference in the crowded 2.4 GHz band via Adaptive
Frequency Hopping (AFH), spreading communication over the entire spectrum, and
further allows the exclusion of interfered channels. However, exclusion is
challenging in dynamic environments or with user mobility: as a user moves
around, interference affects new channels, forcing AFH to deprive itself of new
frequencies, while some other excluded channels are now free of losses but
remain excluded. Channel re-inclusion is a primordial, yet often left out,
aspect of AFH, as it is non-trivial to assess the new situation of excluded
frequencies. We present eAFH, a mechanism for channel exclusion and inclusion.
eAFH introduces informed exploration to AFH: using only past measurements, eAFH
assesses which frequencies we are most likely to benefit from re-including in
the hopping sequence. As a result, eAFH adapts in dynamic scenarios where
interference varies over time. We show that eAFH achieves 98-99.5% link-layer
reliability in the presence of dynamic Wifi interference with 1% control
overhead and 40% higher channel diversity than state-of-the-art approaches.
