DCI Format 1A

It is used in Idle mode only.

DCI format 1A is used for the compact scheduling of one PDSCH codeword in one cell and random access procedure initiated by a PDCCH order. The DCI corresponding to a PDCCH order can be carried by PDCCH or EPDCCH.

- Carrier indicator – 0 or 3 bits.
- Flag for format0/format1A differentiation or flag for format0A/format1A differentiation – 1 bit, where value 0 indicates format 0 or format 0A and value 1 indicates format 1A

Format 1A is used for random access procedure initiated by a PDCCH order only if format 1A CRC is scrambled with C-RNTI and all the remaining fields are set as follows:

- Localized/Distributed VRB assignment flag – 1 bit is set to '0'
- Resource block assignment –   log )2/)1(( DL RB DL 2 RB NN + bits, where all bits shall be set to 1
- Preamble Index – 6 bits
- PRACH Mask Index – 4 bits,
- All the remaining bits in format 1A for compact scheduling assignment of one PDSCH codeword are set to zero

Otherwise,
- Localized/Distributed VRB assignment flag – 1 bit
- Resource block assignment –   log )2/)1(( DL RB DL 2 RB NN + bits
- For localized VRB:   log )2/)1(( DL RB DL 2 RB NN + bits provide the resource allocation
- For distributed VRB: - If 50 DL NRB < or if the format 1A CRC is scrambled by RA-RNTI, P-RNTI, SI-RNTI, SC-RNTI or GRNTI:
 -   log )2/)1(( DL RB DL 2 RB NN + bits provide the resource allocation

- Else
- 1 bit, the MSB indicates the gap value, where value 0 indicates gap = NN gap,1 and value 1 indicates gap = NN gap,2
- (  log )1)2/)1(( DL RB DL 2 RB NN −+ bits provide the resource allocation,