A method of transmitting data includes storing high-priority data blocks in a high-priority queue, storing low-priority data blocks in a low-priority queue, and generating a first data unit that includes one or more of the high-priority data blocks and one or more of the low-priority data blocks. Generating the first data unit includes arranging the one or more high-priority data blocks and the one or more low-priority data blocks in a sequence in which the one or more high-priority data blocks precede the one or more low-priority data blocks. Generating the first data unit further includes indexing the one or more high-priority data blocks and the one or more low-priority data blocks in accordance with the sequence. The first data unit is transmitted.