1. A method for controlling power in Device to Device (D2D) transmission, the method comprising:
determining, by an base station (BS), an interference power upper limit for a UE, which is the highest interference level,
allowed by the BS, caused by D2D transmission to cellular transmission; and
sending, by the BS, the interference power upper limit to the UE so that the UE determines a D2D transmission power upper
limit from the interference power upper limit;
wherein the D2D transmission power upper limit is determined by the UE in the equation of:
wherein PLM,D2D(i) represents a D2D transmission power upper limit in the i-th sub-frame; PO_Interf_UL represents the interference power upper limit; ? represents a compensation factor, and 0???1; PL represents the path loss
from the UE to the BS; and A=0 or A=10 log10(MD2D(i)), where MD2D(i) represents a bandwidth of D2D transmission in the i-th sub-frame.