A wireless transmit receive unit (WTRU) may send a grant free transmission comprising a first and a second part, each of which may be associated with a priority. The first part's priority may be higher than the second part's priority. The WTRU may select a first back of value from a first range of back off values. The WTRU may determine whether the grant free transmission was successful. If the grant free transmission was not successful, the WTRU may send a retransmission of the grant free transmission, which may include the first part and may not include the second part. The retransmission may select a second back off value from a second range of back off values, which may be a larger than the first range of back off values. The second back off value may indicate the number of grant free resource to skip prior to sending the retransmission.