Content for TS 38.323 Word version: 18.3.0
6.2.3 Control PDU
6.2.3.1 Control PDU for PDCP status report
6.2.3.2 Control PDU for interspersed ROHC feedback
6.2.3.3 Control PDU for EHC feedback
6.2.3.4 Control PDU for UDC feedback
6.2.3.5 Control PDU for PDCP SN gap report
6.3 Parameters
6.3.1 General
6.3.2 PDCP SN
6.3.3 Data
6.3.4 MAC-I
6.3.5 COUNT
6.3.6 R
6.3.7 D/C
6.3.8 PDU type
6.3.9 FMC
6.3.10 Bitmap
6.3.11 Interspersed ROHC feedback
6.3.12 SDU Type
6.3.13 KNRP-sess ID
6.3.14 FE
6.3.15 FDC
6.3.16 Discard Bitmap
...
...
6.2.3 Control PDU p. 41
6.2.3.1 Control PDU for PDCP status report p. 41
Figure 6.2.3.1-1 shows the format of the PDCP Control PDU carrying one PDCP status report. This format is applicable for UM DRBs, AM DRBs (including sidelink DRBs for unicast) and AM MRBs.
6.2.3.2 Control PDU for interspersed ROHC feedback p. 42
Figure 6.2.3.2-1 shows the format of the PDCP Control PDU carrying one interspersed ROHC feedback. This format is applicable for UM DRBs, AM DRBs (including sidelink DRBs for unicast), UM MRBs and AM MRBs.
6.2.3.3 Control PDU for EHC feedback |R16| p. 42
Figure 6.2.3.3-1 shows the format of the PDCP Control PDU carrying one EHC feedback. This format is applicable for UM DRBs, AM DRBs, UM MRBs and AM MRBs.
6.2.3.4 Control PDU for UDC feedback |R17| p. 42
Figure 6.2.3.4-1 shows the format of the PDCP Control PDU carrying one UDC feedback. This format is applicable for AM DRBs.
6.2.3.5 Control PDU for PDCP SN gap report |R18| p. 42
Figure 6.2.3.5-1 shows the format of the PDCP control PDU carrying the PDCP SN gap report. This format is applicable for UM DRBs and AM DRBs.
6.3 Parameters p. 43
6.3.1 General p. 43
If not otherwise mentioned in the definition of each field then the bits in the parameters shall be interpreted as follows: the left most bit string is the first and most significant and the right most bit is the last and least significant bit.
Unless otherwise mentioned, integers are encoded in standard binary encoding for unsigned integers. In all cases the bits appear ordered from MSB to LSB when read in the PDU.
6.3.2 PDCP SN p. 43
Length:
12 or 18 bits as indicated in Table 6.3.2-1. The length of the PDCP SN is configured by upper layers (pdcp-SN-SizeUL, pdcp-SN-SizeDL, or sl-PDCP-SN-Size in TS 38.331).
| Length | Description |
|---|---|
| 12 | SRBs, UM DRBs, AM DRBs (including sidelink SRBs and sidelink DRBs), UM MRBs and AM MRBs |
| 18 | UM DRBs, AM DRBs (including sidelink DRBs for unicast), UM MRBs and AM MRBs |
6.3.3 Data p. 43
Length:
Variable
This field includes one of the followings:
- Uncompressed PDCP SDU (user plane data, or control plane data);
- Compressed PDCP SDU (user plane data only).
6.3.4 MAC-I p. 44
Length:
32 bits
This field carries a message authentication code calculated as specified in clause 5.9.
For SRBs for Uu interface, the MAC-I field is always present. If integrity protection is not configured, the MAC-I field is still present but should be padded with padding bits set to 0.
For sidelink SRB1, SRB2 and SRB3, the MAC-I field is present only when the sidelink SRB1, SRB2 and SRB3 are configured with integrity protection.
For DRBs (including sidelink DRBs for unicast), the MAC-I field is present only when the DRB is configured with integrity protection.
6.3.5 COUNT p. 44
Length:
32 bits
The COUNT value is composed of a HFN and the PDCP SN. The size of the HFN part in bits is equal to 32 minus the length of the PDCP SN.
6.3.6 R p. 44
Length:
1 bit
Reserved. In this version of the specification reserved bits shall be set to 0. Reserved bits shall be ignored by the receiver.
6.3.7 D/C p. 44
Length:
1 bit
This field indicates whether the corresponding PDCP PDU is a PDCP Data PDU or a PDCP Control PDU.
| Bit | Description |
|---|---|
| 0 | Control PDU |
| 1 | Data PDU |
6.3.8 PDU type p. 44
Length:
3 bits
This field indicates the type of control information included in the corresponding PDCP Control PDU.
| Bit | Description |
|---|---|
| 000 | PDCP status report |
| 001 | Interspersed ROHC feedback |
| 010 | EHC feedback |
| 011 | UDC feedback |
| 100 | PDCP SN gap report |
| 101-111 | Reserved |
6.3.9 FMC p. 45
Length:
32 bits
First Missing COUNT. This field indicates the COUNT value of the first missing PDCP SDU within the reordering window, i.e. RX_DELIV.
6.3.10 Bitmap p. 45
Length:
Variable. The length of the bitmap field can be 0.
This field indicates which SDUs are missing and which SDUs are correctly received in the receiving PDCP entity. The bit position of Nth bit in the Bitmap is N, i.e., the bit position of the first bit in the Bitmap is 1.
| Bit | Description |
|---|---|
| 0 | PDCP SDU with COUNT = (FMC + bit position) modulo 232 is missing. |
| 1 | PDCP SDU with COUNT = (FMC + bit position) modulo 232 is correctly received. |
6.3.11 Interspersed ROHC feedback p. 45
Length:
Variable
This field contains one ROHC packet with only feedback, i.e. a ROHC packet that is not associated with a PDCP SDU as defined in clause 5.7.4.
6.3.12 SDU Type |R16| p. 45
Length:
3 bits
PDCP SDU type, i.e. Layer-3 Protocol Data Unit type as specified in [13] and [18]. PDCP entity may handle the SDU differently per SDU Type, e.g. ROHC is applicable to IP SDU but not Non-IP SDU, Ethernet SDU, Unstructured SDU and ARP SDU.
| Bit | Description |
|---|---|
| 000 | IP |
| 001 | Non-IP |
| 010 | Ethernet |
| 011 | Unstructured |
| 100 | ARP |
| 101-111 | Reserved |
6.3.13 KNRP-sess ID |R16| p. 45
Length:
16 bits
KNRP-sess Identity as specified in TS 33.536.
For the SLRB that does not need integrity and ciphering protection, the UE shall set KNRP-sess ID to "0" in the PDCP PDU header.
6.3.14 FE |R17| p. 46
Length:
1 bit
Indication of whether checksum error is detected or not. Value '1' means checksum error is detected and the UE shall reset the compression buffer.
| Bit | Description |
|---|---|
| 0 | No Error |
| 1 | Checksum Error Notification |
6.3.15 FDC |R18| p. 46
Length:
32 bits
First discarded COUNT. This field indicates the smallest COUNT value among the COUNT value(s) associated with the discarded PDCP SDU(s).
6.3.16 Discard Bitmap |R18| p. 46
Length:
Variable. The length of the discard bitmap field can be 0.
This field indicates which SDUs are discarded and which SDUs are not discarded in the transmitting PDCP entity. The bit position of the Nth bit in the Discard Bitmap is N, i.e., the bit position of the first bit in the Discard Bitmap is 1.
| Bit | Description |
|---|---|
| 0 | PDCP SDU with COUNT = (FDC + bit position) modulo 232 is not discarded. |
| 1 | PDCP SDU with COUNT = (FDC + bit position) modulo 232 is discarded. |
