In a traditional mobile network, all messages between two user equipments (UEs) pass through a base station, even if the two UEs communicating with each other are in close physical proximity.
Device-to-device (D2D) communication has more recently been introduced to allow for UEs in close proximity to directly communicate with each other without using the base station.
As the number of UEs in a mobile network increases, there may be more potential opportunities for D2D communication.