12 RLC/MAC block structure

3GPP44.160General Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocol Iu modeRelease 16TS

12.1 RLC/MAC block structure

See 3GPP TS 44.060 sub-clause 10.0a.

12.2 RLC/MAC block format conventions

See 3GPP TS 44.060 sub-clause 10.0b.

12.3 Spare bits

See 3GPP TS 44.060 sub-clause 10.1.

12.4 GPRS RLC data blocks (PDTCH)

12.4.1 Downlink RLC data block

The Downlink RLC data block together with its MAC header is formatted as shown in figure 12.4.1.1.

Bit

8

7

6

5

4

3

2

1

Payload Type

RRBP

S/P

USF

MAC header

PR

TFI

FBI

Octet 1

BSN

E

Octet 2

SRBid

spare

Ebis

M="0"

E="0"

Octet 3 (optional) See note

Length indicator

M

E

Octet 4 (optional)

.
.
.

.

.

.

Length indicator

M

E

Octet M (optional)

Octet M+1

RLC data

.

.

.

Octet N2-1

Octet N2

spare

spare

(if present)

NOTE: This octet is present only in case the RLC data block is sent on SFACCH.

Figure 12.4.1.1: Downlink RLC data block with MAC header

12.4.2 Uplink RLC data block

The Uplink RLC data block together with its MAC header is formatted as shown in figure 12.4.2.1.

Bit

8

7

6

5

4

3

2

1

Payload Type

Countdown Value

SI

R

MAC header

spare

PI

TFI

GI

Octet 1

BSN

E

Octet 2

SRBid

spare

Ebis

M="0"

E="0"

Octet 3 (optional) See note

Length indicator

M

E

Octet 4 (optional)

.
.
.

.

.

.

Length indicator

M

E

Octet M (optional)

Octet M+1 \

TLLI/G-RNTI

Octet M+2 \

Octet M+3 \

Octet M+4 } (optional)

G-RNTI extension

RB id

E

Octet M+5 /

RB id

HFN LSB

spare

E

Octet M+6 /

Octet M+7

RLC data

.

.

.

Octet N-1

Octet N

spare

spare

(if present)

NOTE: This octet is present only in case the RLC data block is sent on SFACCH.

Figure 12.4.2.1: Uplink RLC data block with MAC header

12.5 RLC/MAC control blocks (PACCH)

See 3GPP TS 44.060 sub-clause 10.3.

12.6 EGPRS RLC data blocks and RLC/MAC headers (PDTCH)

12.6.1 General

See 3GPP TS 44.060 sub-clause 10.3a.0.

12.6.2 EGPRS downlink RLC data block

See 3GPP TS 44.060 sub-clause 10.3a.1.

12.6.3 EGPRS uplink RLC data block

The EGPRS uplink RLC data block is formatted according to figure 12.6.3.1.

Bit

2

1

GI

E

Bit

8

7

6

5

4

3

2

1

Length indicator

E

Octet 1 (optional)

.
.
.

.

.

.

Length indicator

E

Octet M (optional)

Octet M+1 \

TLLI/G-RNTI

Octet M+2 } (optional)

Octet M+3 /

Octet M+4 /

G-RNTI extension

RBid

E

Octet M+5 /

RBid

HFN_LSB

spare

E

Octet M+6 /

Octet M+7

RLC data

.

.

.

Octet N2-1

Octet N2

NOTE: The field mapping convention for EGPRS (see 3GPP TS 44.060 sub-clause 10.0b.3.2) applies. According to that, in particular regarding the TLLI/G-RNTI field, the least significant octet of the TLLI/G-RNTI value shall be mapped on octet M+1 and the most significant octet of the TLLI/G-RNTI value shall be mapped on octet M+4 of the uplink EGPRS RLC data block.

Figure 12.6.3.1: Uplink EGPRS RLC data block

12.6.4 EGPRS downlink RLC/MAC header

See 3GPP TS 44.060 sub-clause 10.3a.3.

12.6.5 EGPRS uplink RLC/MAC header

See 3GPP TS 44.060 sub-clause 10.3a.4.

12.7 RLC/MAC block formats on FACCH, SACCH, SDCCH and CDCH

12.7.1 RLC/MAC block

The size of an RLC/MAC block on FACCH, SDCCH and CDCH is 23 octets. On SACCH, it is 21 octets, due to a 2 octets physical layer header (see 3GPP TS 44.003). RLC/MAC blocks for FACCH and SDCCH, as well as SACCH blocks (RLC/MAC block together with the 2 octet physical layer header) shall always be encoded using the coding scheme CS-1 (see 3GPP TS 45.003 and 3GPP TS 44.004). RLC/MAC blocks for CDCH shall always use the signalling TFC as specified in 3GPP TS 44.118.

An RLC/MAC block may be for either data or control message transfer.

Bit

8

7

6

5

4

3

2

1

Octet

RLC/MAC block
(184 bits – 23 octets)

1

…

23

Figure 12.7.1.1: FACCH/SDCCH/CDCH block

Bit

8

7

6

5

4

3

2

1

Octet

Physical Layer header (see 3GPP TS 44.003)

1

2

RLC/MAC block
(168 bits – 21 octets)

3

…

23

Figure 12.7.1.2: SACCH block

12.7.2 Downlink RLC/MAC block for data transfer

Bit

8

7

6

5

4

3

2

1

Octet

PT

P

RRBid

BSN

1

BSN

AI

spare

E

…

Length Indicator

M

E

Length Indicator

M

E

Extension

Ack/Nack Description

Optional

(2 octets)

RLC Data (byte aligned)

…

21(see note)/23

NOTE: 21 octets apply only in case of SACCH.

Figure 12.7.2.1: Downlink RLC/MAC block for data transfer on FACCH,
SACCH, SDCCH and CDCH (PT=00)

12.7.3 Uplink RLC/MAC block for data transfer

Bit

8

7

6

5

4

3

2

1

Octet

PT

P

RRBid

BSN

1

BSN

AI

SI

GI

spare

E

…

Length Indicator

M

E

Length Indicator

M

E

Extension

Ack/Nack Description

Optional

(2 octets)

G-RNTI

Optional
(4 octets)

RLC Data (byte aligned)

…

21(see note)/23

NOTE: 21 octets apply only in case of SACCH.

Figure 12.7.3.1: Uplink RLC/MAC block for data transfer on FACCH, SACCH, SDCCH and CDCH (PT=00)

12.7.4 RLC/MAC block for control message transfer

The RLC/MAC block formats for control message transfer are applicable in both uplink and downlink directions.

Figure 12.7.4.1 represents the RLC/MAC block for control message transfer related to an on-going temporary block flow on FACCH, SACCH or SDCCH.

Bit

8

7

6

5

4

3

2

1

Octet

PT

P

RRBid

spare

1

Control Message Content

…

21 (see note)/23

NOTE: 21 octets apply only in case of SACCH.

Figure 12.7.4.1: RLC/MAC block for control message transfer on FACCH,
SACCH and SDCCH (PT=01)

Figure 12.7.4.2 represents the RLC/MAC block for control message transfer on FACCH related to an on-going temporary block flow on TCH. This message may be used for e.g. acknowledgement of the data transfer on TCH.

Bit

8

7

6

5

4

3

2

1

Octet

PT

P

S

RBSN

RTI

spare

1

Control Message Content

…

23

Figure 12.7.4.2: RLC/MAC block for control message transfer on FACCH (PT=10)

12.8 RLC/MAC block format on TCH (NT-RLC)

12.8.1 RLC/MAC block

12.8.1.1 General

Each TCH block shall contain an RLC/MAC block followed by a 24-bit frame check sequence (FCS), as illustrated in figures 12.8.1.1.1, 12.8.1.1.2 and 12.8.1.1.3.

RLC/MAC block

FCS

556 bits

24 bits

Figure 12.8.1.1.1: E-TCH/F28.8 block structure

RLC/MAC block

FCS

616 bits

24 bits

Figure 12.8.1.1.2: E-TCH/F32.0 block structure

RLC/MAC block

FCS

846 bits

24 bits

Figure 12.8.1.1.3: E-TCH/F43.2 block structure

12.8.1.2 RLC/MAC block for E-TCH/F28.8 coding scheme

Figure 12.8.1.2.1 represents the RLC/MAC block for E-TCH/F28.8 coding scheme.

Bit

8

7

6

5

4

3

2

1

Octet

RLC/MAC block
(556 bits)

1

…

69

N=70

Figure 12.8.1.2.1: RLC/MAC block for E-TCH/F28.8

12.8.1.3 RLC/MAC block for E-TCH/F32.0 coding scheme

Figure 12.8.1.3.1 represents the RLC/MAC block for E-TCH/F32.0 coding scheme.

Bit

8

7

6

5

4

3

2

1

Octet

RLC/MAC block
(616 bits)

1

…

N=77

Figure 12.8.1.3.1: RLC/MAC block for E-TCH/F32.0

12.8.1.4 RLC/MAC block for E-TCH/F43.2 coding scheme

Figure 12.8.1.4.1 represents the RLC/MAC block for E-TCH/F43.2 coding scheme.

Bit

8

7

6

5

4

3

2

1

Octet

RLC/MAC block
(846 bits)

1

…

105

N=106

Figure 12.8.1.4.1: RLC/MAC block for E-TCH/F43.2

12.8.2 Downlink RLC/MAC block for data transfer

Figure 12.8.2.1 represents the RLC/MAC block for data transfer for E-TCH/F28.8, E-TCH/F32.0 and E-TCH/F43.2 coding schemes, achieving bit rates of 27,8 kbits/s, 30,8 kbits/s and 42,3 kbits/s respectively.

8

7

6

5

4

3

2

1

Octet

BSN

1

spare

P

E

2

Length indicator

E

3 (optional)

…

optional

Length indicator

E

M (optional)

RLC data

M+1

N

Figure 12.8.2.1: Downlink RLC/MAC block for data transfer on TCH

12.8.3 Uplink RLC/MAC block for data transfer

Figure 12.8.3.1 represents the RLC/MAC block for data transfer for E-TCH/F28.8, E-TCH/F32.0 and E-TCH/F43.2 coding schemes, achieving bit rates of 27,8 kbits/s, 30,8 kbits/s and 42,3 kbits/s respectively.

Bit

8

7

6

5

4

3

2

1

Octet

BSN

1

SI

spare

P

E

2

Length indicator

E

3 (optional)

…

optional

Length indicator

E

M (optional)

RLC data

M+1

N

Figure 12.8.3.1: Uplink RLC/MAC block for data transfer on TCH

12.8.4 RLC/MAC block for control message transfer

RLC/MAC blocks for control message transfer shall be sent on FACCH with Payload Type = "10" as described in sub-clause 12.7.4.

12.8a RLC/MAC block for control message transfer on ADCH

12.8a.1 Downlink RLC/MAC control block format

Bit

8

7

6

5

4

3

2

1

PT

P

S

RBSN

RTI

Octet 1

Control message content

Octet 2

.

.

.

Octet N=23

Figure 12.8a.1.1: Downlink RLC/MAC control block together with its MAC header (PT=10)

12.8a.2 Uplink RLC/MAC control block format

Bit

8

7

6

5

4

3

2

1

PT

P

Octet 1

Control message content

Octet 2

.

.

.

Octet N=23

Figure 12.8a.2.1: Uplink RLC/MAC control block together with its MAC header (PT=10)

12.8b RLC/MAC blocks for URB data transfer on UDCH

12.8b.1 Downlink RLC/MAC block for data transfer

12.8b.1.1 RLC unacknowledged mode

Bit

8

7

6

5

4

3

2

1

PT

TFI (=RB Id)

P

Octet 1

BSN

E

Length Indicator

Octet 2

Length Indicator

E

…

Octet 3

…

E

LI

Length Indicator

E

Octet M

RLC data

Octet M + 1

.

.

.

Octet N (see note)

NOTE: the RLC data may contain a non-integer number of octets.

Figure 12.8b.1.1.1: Downlink RLC/MAC block for data transfer in RLC unacknowledged mode (PT=01)

12.8b.1.2 RLC acknowledged mode

Bit

8

7

6

5

4

3

2

1

PT

TFI (=RB Id)

P

Octet 1

BSN

Octet 2

BSN

SPB

E

Length Indicator

Octet 3

Length Indicator

E

…

…

E

LI

Length Indicator

E

Octet M

RLC data

Octet M+1

.

.

.

Octet N (see note)

NOTE: the RLC data may contain a non-integer number of octets.

Figure 12.8b.1.2.1: Downlink RLC/MAC block for data transfer in RLC acknowledged mode (PT=01)

12.8b.1.3 RLC transparent mode

Bit

8

7

6

5

4

3

2

1

RLC data

Octet 1

.

.

.

Octet N (see note)

NOTE: the RLC data may contain a non-integer number of octets. N1.

Figure 12.8b.1.3.1: Downlink RLC/MAC block for data transfer in RLC transparent mode

NOTE: No payload type allows for making the distinction between an RLC/MAC block for data transfer in T-RLC and other RLC/MAC blocks. The identification of such an RLC/MAC block shall be done through the TFCI, i.e. some transport formats shall be reserved exclusively for using in T-RLC mode.

12.8b.2 Uplink RLC/MAC block for data transfer

12.8b.2.1 RLC unacknowledged mode

The uplink RLC/MAC block format for data transfer in RLC unacknowledged mode is the same as for downlink, as specified in sub-clause 12.8b.1.1.

12.8b.2.2 RLC acknowledged mode

Bit

8

7

6

5

4

3

2

1

PT

TFI (=RB Id)

P

Octet 1

BSN

Octet 2

BSN

SPB

SI

E

Length Indicator

Octet 3

Length Indicator

E

…

…

E

Length Indicator

E

Octet M

RLC data

Octet M+1

.

.

.

Octet N (see note)

NOTE: the RLC data may contain a non-integer number of octets

Figure 12.8b.2.2.1: Uplink RLC/MAC block for data transfer in RLC acknowledged mode (PT=01)

12.8b.2.3 RLC transparent mode

Bit

8

7

6

5

4

3

2

1

RLC data

Octet 1

.

.

.

Octet N (see note)

NOTE: the RLC data may contain a non-integer number of octets. N1

Figure 12.8b.2.3.1: Uplink RLC/MAC block for data transfer in RLC transparent mode

NOTE: No payload type allows for making the distinction between an RLC/MAC block for data transfer in T-RLC and other RLC/MAC blocks. The identification of such an RLC/MAC block shall be done through the TFCI, i.e. some transport formats shall be reserved exclusively for using in T-RLC mode.

12.9 Header fields

12.9.1 General

The header fields described in this sub-clause are applicable only for the blocks described in the present TS.

12.9.2 Payload Type (PT) field

The Payload Type field shall indicate the type of data contained in remainder of the RLC/MAC block. The encoding of the Payload Type field is shown in table 12.9.2.1 and in table 12.9.2.2.

Table 12.9.2.1: Payload Type (PT) field (PDTCH, PACCH, FACCH, SACCH, SDCCH)

Bit

2 1

PT: Payload Type

0 0

RLC Data block

0 1

RLC Control block related to an on-going RLC Data flow on the same logical channel (The corresponding RB is referred to with Reduced RBid field)

1 0

RLC Control block on FACCH related to an on-going RLC Data flow on TCH

1 1

Reserved

Table 12.9.2.2: Payload Type (PT) field for FLO (CDCH, UDCH, ADCH)

Bit

2 1

PT: Payload Type

0 0

RLC Data block – SRB

0 1

RLC Data block – URB

1 0

RLC/MAC block for control message transfer

1 1

Reserved

12.9.3 Polling (P) bit

The polling bit indicates whether or not the transmitter is polling for acknowledgement. With FLO, when included in an RLC/MAC block for data transfer, it also allows the reporting of link quality measurements along with the requested acknowledgement. It is encoded as shown in table 12.9.3.1.

Table 12.9.3.1: Polling (P) bit

Bit

P: Polling Bit

0

No polling

1

Polling: acknowledgement required

12.9.4 Reduced Radio Bearer identity (RRBid) field

The reduced radio bearer identity field provides a one-to-one mapping with the RBid of the RB to which either the RLC data block belongs, or the RLC/MAC control block relates. This field is used in the same way as is the TFI in (E)GPRS RLC/MAC blocks. It is encoded as shown in table 12.9.4.1.

Table 12.9.4.1: Reduced Radio Bearer identity (RRBid) field

Bit

3 2 1

RRBid: Reduced Radio Bearer identity

0 0 0

Signalling Radio Bearer 1

0 0 1

Signalling Radio Bearer 2

0 1 0

Signalling Radio Bearer 3

0 1 1

Signalling Radio Bearer 4

1 x x

User-plane Radio Bearer

The correspondence between Reduced RBid and the RBid in this case is provided at RB setup.

12.9.5 More (M) bit and Extension (E) bit

These bits are used in the same way as is described in 3GPP TS 44.060 sub-clauses 10.4.11 and 10.4.13 for GPRS TBF mode.

12.9.6 Extension bis (Ebis) bit

The Extension bis (Ebis) bit is used to indicate the presence of an optional octet in the RLC data block header.

Table 12.9.6.1: Extension bis (Ebis) bit

bit 1

Ebis bit

0

Extension octet follows immediately

1

No extension octet follows

12.9.7 Stall Indicator (SI) bit

The Stall Indicator bit is used as is described in 3GPP TS 44.060 sub-clause 10.4.3.

12.9.8 Ack Indicator (AI) field

The Ack Indicator field indicates whether or not an acknowledgement bitmap is piggy-backed in the RLC/MAC block. It is encoded as shown in table 12.9.8.1.

Table 12.9.8.1: Ack Indicator (AI) field

Bit

2 1

AI: Ack Indicator

0 0

Ack/Nack description field not included – Reserved

0 1

Ack/Nack description not included. No retransmission requested (all RLC blocks received, similar to FINAL_ACK_INDICATION==1)

1 0

Ack/Nack description field included

1 1

Reserved

12.9.9 Ack/Nack Description field

Table 12.9.9.1: Ack/Nack Description field

Ack/Nack Description

< Ack/Nack Description IE> ::=

<Reduced RBid : bit(3)>

<STARTING_SEQUENCE_NUMBER : bit(4)>

<RECEIVED_BLOCK_BITMAP : bit(8)>

Reduced Rbid

The reduced radio bearer identity field provides a one-to-one mapping with the RBid of the RB in the opposite direction to which the acknowledgement bitmap is targetted. It is encoded as shown in table 12.3, sub-clause 12.9.4.

STARTING_SEQUENCE_NUMBER (SSN):

The SSN contains the value of V(R) when this field was transmitted. This field is encoded as the binary representation of V(R).

Range 0 to 15

RECEIVED_BLOCK_BITMAP (RBB):

The RBB is a bitmap representing Block Sequence Numbers. The bitmap is indexed relative to SSN as follows:

BSN=(SSN – bit_number) modulo 16 for bit_number=1 to 8.

The BSN values represented range from (SSN-1) mod 16 to (SSN-8) mod 16.

The value of each bit is encoded as:

0: Negative acknowledgement of the RLC data block with BSN=(SSN-bit_number) mod 16

1: Positive acknowledgement of the RLCdata block with BSN=(SSN-bit_number) mod 16.

Mapping of the bitmap is defined in sub-clause 11.

12.9.10 G-RNTI indicator (GI) bit

The G-RNTI indicator bit indicates the presence of an optional G-RNTI field within the RLC data block, when on SDCCH. It is encoded as shown in table 12.9.10.1.

Table 12.9.10.1: G-RNTI indicator (GI) bit

Bit

GI: G-RNTI indicator bit

0

G-RNTI field is not present

1

G-RNTI field is present

12.9.11 Segmentation (S) bit

The Segmentation bit indicates whether or not the RLC/MAC control block is a segment of an RLC/MAC control message. It is encoded as shown in table 12.9.11.1.

Table 12.9.11.1: Segmentation (S) bit

Bit

S: Segmentation bit

0

The RLC/MAC control block contains an entire RLC/MAC control message

1

The RLC/MAC control block is a segment of an RLC/MAC control message

12.9.12 Reduced Block Sequence Number (RBSN) bit

The Reduced Block Sequence Number (RBSN) bit carries the sequence number of the RLC/MAC control blocks. The RBSN bit is encoded as a binary number with range 0 to 1. The RBSN bit is present if and only if the S bit is set (see sub-clause 12.9.11).

12.9.13 (void)

12.9.14 Radio Transaction Identifier (RTI) field

The Radio Transaction Identifier (RTI) field is used to group the RLC/MAC control blocks that make up an RLC/MAC control message and identifies the segmented control message sequence with which the RLC/MAC control block is associated. The RTI field is 2 bits in length with range 0 to 3. The RTI field is present if and only if the S bit is set (see sub-clause 12.9.11). The RTI is unique on a given logical channel in a given direction.

NOTE: An RTI value may be repeated in both directions on a given logical channel (e.g. FACCH uplink and FACCH downlink), and across logical channels (e.g.. FACCH and SACCH).

12.9.15 Block Sequence Number (BSN) field

The Block Sequence Number (BSN) field carries the sequence absolute Block Sequence Number (BSN’) modulo Sequence Number Space (SNS) (16 in DCCH TBF mode, 256 in TCH TBF mode (NT-RLC)) of each RLC data block within the TBF.

In DCCH TBF mode and CDCH TBF mode, the BSN is 4 bits in length and is encoded as a binary number with range 0 to 15.

In TCH TBF mode (NT-RLC), the BSN is 8 bits in length and is encoded as a binary number with range 0 to 255.

In UDCH TBF mode, in RLC unacknowledged mode, the BSN is 4 bits in length and is encoded as a binary number with range 0 to 15.

In UDCH TBF mode, in RLC acknowledged mode, the BSN is 10 bits in length and is encoded as a binary number with range 0 to 1023.

12.9.16 Radio Bearer Identity (RB Id) field

The Rb Id uniquely identifies a Radio Bearer. This field is encoded as a binary number with range 0-31.

12.9.17 Signalling Radio Bearer Identity (SRB Id) field

The Signalling Radio Bearer Identity (SRB Id) field is used to identify the SRB to which the RLC data block belongs. It is encoded as shown in table 12.9.17.1.

Table 12.9.17.1: Signalling Radio Bearer Identity (SRB Id) field

Bit

2 1

SRB Id: Signalling Radio Bearer Identity

0 0

SRB1

0 1

SRB2

1 0

SRB3

1 1

SRB4

12.9.18 GERAN Radio Network Temporary Identity Extension (G-RNTI Extension) field

This field contains the extra 4 bits of the G-RNTI not included in the TLLI / G-RNTI field.

12.9.19 Length Indicator (LI) field

In GPRS TBF mode, EGPRS TBF mode, TCH TBF mode, DCCH TBF mode and CDCH TBF mode, the Length Indicator bit is used as is described in 3GPP TS 44.060 sub-clauses 10.4.14 and 10.4.14a.

In UDCH TBF mode, the Length Indicator is used as described in 3GPP TS 44.060 sub-clauses 10.4.14 and 10.4.14a, with the following exceptions:

– The Length Indicator field is 8 bits in length and shall be encoded as a binary number.

– The valid values are the values ranging from 0 to 171, and the value 255. All other values are reserved.

– An 8-bit Length Indicator of value 255 shall be treated as described in 3GPP TS 44.060 for a 7-bit Length Indicator of value 127

– An 8-bit Length Indicator of value 127 shall be treated as a length indication of 127 octets, and not as a 7-bit Length Indicator of value 127

The interpretation of the value contained in the length indicator with corresponding E bit in UDCH TBF mode is summarized in table 12.9.19.1.

Table 12.9.19.1: Interpretation of values of LI field and E bit in UDCH TBF mode

Value of LI in a RLC data block

Value of the following E bit

Interpretation

k-th LI:

0< value <172

(k>0 integer)

The value of the k-th LI is the number of octets of the k-th Upper Layer PDU, or the last segment of it, in the current RLC data block.

0

There is at least one Upper Layer PDU following the k-th Upper Layer PDU in the current RLC data block.

1

There is no more than one Upper Layer PDU following the k-th Upper Layer PDU in the current RLC data block.

1st LI: value =0

0

The last Upper Layer PDU of the previous in sequence RLC data block ends at the boundary of that RLC data block and it has no LI in the header of that RLC data block.

k-th LI:

0< value <172

(k>1 integer)

The k-th LI contains the number of octets of the (k-1)-th Upper Layer PDU in the current RLC data block.

0

There is at least one Upper Layer PDU following the (k-1)-th Upper Layer PDU in the current RLC data block.

1

There is no more than one Upper Layer PDU following the (k-1)-th Upper Layer PDU in the current RLC data block.

k-th LI: value=255

1

The octets between the end of the Upper Layer PDU indicated by the (k-1)-th LI and the end of the current RLC data block are filling octets, or the octets contain part of an Upper Layer PDU that cannot be transmitted completely in the current RLC data block and will not be continued in the next in-sequence RLC data block.

1st LI: value=0

1

The previous RLC data block contains a Upper Layer PDU, or a part of it, that fills precisely the previous data block and for which there is no length indicator in that RLC data block. The current RLC data block contains a Upper Layer PDU that either fills the current RLC data block precisely or continues in the next RLC data blcok.

1st LI: value=255

1

All octets of the RLC Data block contain filling information.

No LI field present

n.a.

The Upper Layer PDU that starts with the current RLC data block either fills the current RLC data block precisely or continues in the following in-sequence RLC data block

12.9.20 PFI Indicator (PI) field

The PFI Indicator is not used in Iu mode.

12.9.21 HFN Least Significant Bit (HFN_LSB) field

The HFN Least Significant Bit (HFN_LSB) field contains the least significant bit of the HFN of the radio bearer to which the RLC/MAC block belongs, in the direction where this RLC/MAC block is sent.