A wireless MAC protocol that uses a topology-dependent slot schedule is vulnerable to link failures. This becomes severer in industrial fields due to node mobility and various obstructions unfriendly to wireless communication. The proposed protocol allocates a big sharable slot to each tree level, producing a topology-independent schedule that makes the protocol highly responsive to the changes of topology. Then, the nodes at the same level use CSMA/CA for data transmission and channel hopping to cope with the varying condition of a channel. The use of CSMA/CA and channel hoping makes data transmission reliable against internal and external interferences. Another feature is that every node gets its sharable slot using a slot generation function independently of other nodes. Simulations and experiments verify that the proposed protocol achieves good performance in terms of packet delivery ratio and energy efficiency against the variation of multipath fading, various external sources of interference, and node mobility.