Method and apparatus for transmitting or receiving downlink signal in unlicensed band of wireless communication system

A transmission node configured to performing channel sensing in an unlicensed band and transmit downlink signals associated with in a wireless communication system, the transmission node comprising:

• a transmitter;
• a receiver;
• and
• a processor configured to control the transmitter and the receiver,
• wherein the processor senses a channel scheduled to transmit downlink signals on a secondary cell (S-Cell) in the unlicensed band, wherein the downlink signals are intended for a user equipment (UE) to decode, and when the channel scheduled to transmit the downlink signals is determined to be in an unoccupied state according to the channel sensing, transmits the downlink signals through a secondary cell (S-Cell) transmission structure having a boundary of a transmission unit shifted by a specific time index from a boundary of a transmission unit of a primary cell (P-Cell) transmission structure,
• wherein the specific time index is selected from among a plurality of candidate time indexes,
• wherein at least one of the downlink signals transmitted on the S-Cell are transmitted at transmission times same as transmission times of the P-Cell transmission structure, and the remaining downlink signals other than the at least one of the downlink signals are transmitted on the S-Cell at transmission times defined for the S-Cell transmission structure,
• wherein the remaining downlink signals include a first downlink signal and a second downlink signal, the first downlink signal having a plurality of candidate transmission times which are defined in reference to a single transmission time of the second downlink signal, and
• wherein, when occupation of the channel scheduled to transmit the downlink signals on the S-Cell in the unlicensed band is succeeded by the transmission node, first transmission times in the transmission times defined for the S-Cell transmission structure carry control signals and first data signals among the downlink signals and correspond to continuous time indices, and second transmission times in the transmission times defined for the S-Cell transmission structure carry second data signals among the downlink signals and correspond to discontinuous time indices, wherein values of the continuous time indices are less than values of the discontinuous time indices.