Section: 6.1.6 MAC PDU (SL-SCH)
Content: A MAC PDU consists of a MAC header, one or more MAC Service Data Units (MAC SDU), and optionally padding; as described in Figure 6.1.6-4. Both the MAC header and the MAC SDUs are of variable sizes. A MAC PDU header consists of one SL-SCH subheader, one or more MAC PDU subheaders; each subheader except SL-SCH subheader corresponds to either a MAC SDU or padding. The SL-SCH subheader consists of the seven header fields V/R/R/R/R/SRC/DST. A MAC PDU subheader consists of the six header fields R/R/E/LCID/F/L but for the last subheader in the MAC PDU. The last subheader in the MAC PDU consists solely of the four header fields R/R/E/LCID. A MAC PDU subheader corresponding to padding consists of the four header fields R/R/E/LCID. Figure 6.1.6-1: R/R/E/LCID/F/L MAC subheader Figure 6.1.6-2: R/R/E/LCID MAC subheader Figure 6.1.6-3: SL-SCH MAC subheader for V ="0001" and "0010" Figure 6.1.6-3a: SL-SCH MAC subheader for V="0011" MAC PDU subheaders have the same order as the corresponding MAC SDUs and padding. Padding occurs at the end of the MAC PDU, except when single-byte or two-byte padding is required. Padding may have any value and the MAC entity shall ignore it. When padding is performed at the end of the MAC PDU, zero or more padding bytes are allowed. When single-byte or two-byte padding is required, one or two MAC PDU subheaders corresponding to padding are placed after the SL-SCH subheader and before any other MAC PDU subheader. A maximum of one MAC PDU can be transmitted per TB. Figure 6.1.6-4: Example of MAC PDU consisting of MAC header, MAC SDUs and padding