In wifi, this is handled by the base station if I'm correct. It assigns slots for the associated receivers. Assigning slots in a mesh network without coordination is effectively a graph coloring problem and difficult to solve.
My professor for my master thesis was the author of LMAC, which attempted to assign slots to each node. It worked great in theory, but not so much in practice.
To take up the tangent, it seems to me that the graph coloring problem can either be (1) solved universally (any local mesh will have distinct boundaries which make absolute coordination feasible) by adding some sort of explicitly negotiated or progressively developed shared state to act as a coordination layer (2) solved temporarily, for example by implementing a best-effort failover/fallback (CSMA/CD feeds back to "color") (3) Ignored.
Solution class 1 is obviously challenging to apply to for mobile and ad-hoc mesh networks. Solution class 2 seems more realistic for this category of use case. Solution class 3 works well if you have full control of the application layer (eg. wireless sensor network is push-only with short packets with high temporal tolerance for retransmissions).
Feels a bit like "Energy optimization / throughput / ad-hoc topology / traffic generality. Choose any three."
Also, relatively speaking, modern wireless transfer rates are very fast and therefore transmissions will only be sporadic, and 200mA is not a lot of power. Ignoring other factors, napkin says you would have to hold 200mA consumption solidly for 15 hours to deplete a modern smartphone's 3000mAh battery. Most mobile mesh networking use cases will have long since concluded by that point.
According to a 2017 PhD dissertation[0] on a sample device cellular eats way more than wifi in the normal idle mode (p56). Therefore, if we ditch cellular there may actually be power budget savings when idle. However, all radio communications are totally dwarfed by display power (p58, p67, p72), especially at high brightness levels (p59).
[0] https://trustworthy.systems/publications/papers/Carroll%3Aph...