A method and apparatus for uplink transmission by a user equipment (UE) includes receiving an uplink grant for data transmission in a subframe on an uplink channel, wherein the uplink grant includes an assignment to a resource block. The UE determines a resource block for sending a channel usage beacon signal (CUBS) over a contention-based spectrum based on the assignment included in the uplink grant. The CUBS reserves the uplink channel for the data transmission by indicating that the UE is sending the data transmission in a later subframe according to the assignment. The UE transmits the CUBS in a preceding subframe on the resource block in response to performing a successful clear channel assessment on the uplink channel, the preceding subframe directly preceding the subframe for the uplink data transmission.