The D2D underlying cellular networks performance is thoroughly examined in this study. When D2D communications are used in combination with cellular system, the collective interference measured on licensed users is strongly guaranteed. To analyze this issues three different power allocation schemes that are Path loss-based are designed, Equal and Random with the performance analysis of outage probability (OP), average rate and amount of fading (AoF) of the D2D networks. Background noise, interference from cellular networks and intra-D2D pair interference effects are taken into account under examination, which involves numerous random variables and creates a challenging mathematical structure. Additionally, the behavior of the OP in relation to the transmit power is described.