A method of UE includes receiving a radio resource control (RRC) message for configuring bandwidth parts (BWPs) of a serving cell, receiving a physical downlink control channel (PDCCH) indicating activation of a first BWP, performing a BWP switching to the first BWP indicated by the PDCCH, and starting a first downlink BWP timer associated with the first BWP. A UE includes a transceiver, and at least one controller coupled with the transceiver, the at least one controller configured to receive an RRC message for configuring BWPs of a serving cell, receive a PDCCH indicating activation of a first BWP, perform a BWP switching to the first BWP indicated by the PDCCH, and start a first downlink BWP timer associated with the first BWP.