In one embodiment, a method for performing an operation for a first terminal in a wireless communication system comprises the steps of: determining that a physical layer problem has occurred during communication with a base station; switching from resource allocation mode 1 to resource allocation mode 2 on the basis of the physical layer problem; and transmitting, in resource allocation mode 2, sidelink data to a second terminal by using a sidelink resource, wherein the sidelink resource is determined as a sensing-based resource and/or a random selection-based resource in consideration of the latency budget and sensing validity period of the sidelink data.