A method for a first device to perform wireless communication and an apparatus supporting the same are provided. The method comprises, triggering resource selection in a first slot; determining a time interval of a selection window from the first slot based on a remaining packet delay budget (PDB), wherein the selection window includes Y candidate slots; performing sensing for L slots after the first slot; selecting at least one resource for sidelink (SL) transmission within the selection window based on the sensing for the L slots; transmitting, to a second device through a physical sidelink control channel (PSCCH), a first sidelink control information (SCI) for scheduling of a physical sidelink shared channel (PSSCH) and a second SCI; and transmitting, to the second device through the PSSCH, the second SCI and data.