ntifies the group of logical channels whose buffer status are being reported, and one or several LCG; for the long BSR format, which indicate the presence of the buffer size field for the ith LCG. For the long truncated BSR format, this field indicates whether the ith LCG has data available. The buffer size field identifies the total amount of data available according to the data volume calculation procedure in references [10,11] across all logical channels of an LCG after the MAC PDU has been created, that is, after the logical channel prioritization procedure, which may result in setting the value of the buffer size field to zero. The amount of data is indicated in number of bytes. The size of the RLC and MAC headers are not considered in the buffer size calculation. The length of this field for the short BSR format and the short truncated BSR format is 5 bits and for the long BSR format and the long truncated BSR for- mat is 8 bits. For the long BSR format and the long truncated BSR format, the buffer size fields are included in ascending order based on the LCGi. For the long truncated BSR format the number of buffer size fields included is maximized, as long as it does not exceed the number of padding bits. The structure and content of some MAC CEs are shown in Fig. 2.8. As we mentioned earlier, a [transparent] MAC PDU may only consist of a MAC SDU whose size is aligned to a permissible transport block. This MAC PDU is used for transmis- sions on PCH, BCH, and DL-SCH including BCCH. Furthermore, a random-access response MAC PDU format is defined which consists of one or more MAC sub-PDUs and may contain some padding bits. Each MAC sub-PDU consists of a MAC sub-header with backoff indicator; a MAC sub-header with random access preamble identifier (RAPID), which is an acknowledgment for SI request; or a MAC sub-header with RAPID and MAC New Radio Access Layer 2/3 Aspects and System Operation 209 LCG ID Buffer size Octet 1 C-RNTI Octet 1 Short BSR and short truncated BSR MAC CE C-RNTI Octet 2 C-RNTI MAC CE Octet