A user equipment, UE (120, 305, 605) for wireless communication, comprising: a memory; and one or more processors, coupled to the memory, configured to: select, for a sidelink transmission over an unlicensed band and associated with a medium access control, MAC protocol data unit, PDU, one or more candidate resources of a set of candidate resources that are within an adaptive effective contention window, ECW; adjust at least one parameter of the adaptive ECW to determine an adjusted at least one parameter based at least in part on a channel access output associated with the one or more candidate resources, wherein the channel access output comprises an indication of channel access success or channel access failure and wherein the user equipment is configured to adjust the at least one parameter by increasing the adaptive ECW for a channel access failure and decreasing the adaptive ECW when channel access is successful; and transmit the MAC PDU using the one or more candidate resources or an additional one or more candidate resources, wherein the additional one or more candidate resources are selected based at least in part on the adjusted at least one parameter. a memory; and one or more processors, coupled to the memory, configured to: select, for a sidelink transmission over an unlicensed band and associated with a medium access control, MAC protocol data unit, PDU, one or more candidate resources of a set of candidate resources that are within an adaptive effective contention window, ECW; adjust at least one parameter of the adaptive ECW to determine an adjusted at least one parameter based at least in part on a channel access output associated with the one or more candidate resources, wherein the channel access output comprises an indication of channel access success or channel access failure and wherein the user equipment is configured to adjust the at least one parameter by increasing the adaptive ECW for a channel access failure and decreasing the adaptive ECW when channel access is successful; and transmit the MAC PDU using the one or more candidate resources or an additional one or more candidate resources, wherein the additional one or more candidate resources are selected based at least in part on the adjusted at least one parameter. select, for a sidelink transmission over an unlicensed band and associated with a medium access control, MAC protocol data unit, PDU, one or more candidate resources of a set of candidate resources that are within an adaptive effective contention window, ECW; adjust at least one parameter of the adaptive ECW to determine an adjusted at least one parameter based at least in part on a channel access output associated with the one or more candidate resources, wherein the channel access output comprises an indication of channel access success or channel access failure and wherein the user equipment is configured to adjust the at least one parameter by increasing the adaptive ECW for a channel access failure and decreasing the adaptive ECW when channel access is successful; and transmit the MAC PDU using the one or more candidate resources or an additional one or more candidate resources, wherein the additional one or more candidate resources are selected based at least in part on the adjusted at least one parameter.