100+ simultaneous data connections: which communication protocol?

So...., bit of a newbie question here.

Suppose I would want to have 100+ objects communicate with an internet-connected hub, every 3 seconds. Communication is simple information like availability yes/no + a user ID that gets assigned to the object.

To my understanding, BT is not usable, because it cannot handle that many connections simultaneously. What would be the best low-cost, low-energy solution here? We are in a concrete basement, so no cellular. 

Any tip into the right direction is appreciated!