Hidden node problem
Collision
Because of Signal attenuation over 3d space and 2d surface energy conservation
Hidden node problem
In wireless networking, the hidden node problem or hidden terminal problem occurs when a node can communicate with a wireless access point (AP), but cannot directly communicate with other nodes that are communicating with that AP. This leads to difficulties in medium access control sublayer since multiple nodes can send data packets to the AP simultaneously, which creates interference at the AP resulting in no packet getting through.
https://en.wikipedia.org/wiki/Hidden_node_problem

Seonglae Cho