1. A method implemented by a user equipment (UE), the method comprising:determining to pursue grant free transmission on first data of a first buffer of a plurality of buffers and determining not to pursue grant free transmission on second data of a second buffer of the plurality of buffers;
determining a size of a grant free transport block (GFTB) based on a configuration of radio resources available for grant free transmission;
determining that a size of the first data of the first buffer is larger than the size of the GFTB;
determining to transmit using grant free transmission a first portion of the first data from the first buffer according to a priority of the first portion of the first data of the first buffer;
populating the GFTB with at least the first portion of the first data from the first buffer to produce a populated GFTB;
transferring the populated GFTB from a media access control (MAC) layer to a physical layer (PHY); and
performing grant based transmission on a second portion of the first data of the first buffer and on the second data of the second buffer.