Methods, systems, and devices for wireless communications are described. A user equipment (UE) may obtain access to a shared radio frequency spectrum band for a transmission opportunity. The UE may perform an autonomous uplink transmission over the shared radio frequency spectrum band during a first portion of the transmission opportunity. The UE may transmit a physical layer scheduling request comprising a transmission size parameter for a second portion of the transmission opportunity. The UE may receive an uplink grant for the second portion of the transmission opportunity based at least in part on the scheduling request. The UE may perform a scheduled uplink transmission over the shared radio frequency spectrum band during the second portion of the transmission opportunity according to the uplink grant.