A user equipment (UE) in a frame based equipment (FBE) mode may determine that a communication channel in an unlicensed spectrum is available for use, and transmit, in the communication channel, a transmission to a gNB in a fixed frame period (FFP) associated with the UE to initiate a channel occupancy time (COT) by the UE in the FFP. The transmission starts at the beginning of the FFP and ends before an idle period within the FFP. The gNB receives the transmission and, based thereon, determines that the UE has initiated the COT. The gNB may acknowledge or reject initiation of the COT by the UE.