6.2.2 Parameters

36.3223GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Radio Link Control (RLC) protocol specificationRelease 15TS

6.2.2.1 General

In the definition of each field in sub clauses 6.2.2.2 to 6.2.2.19, the bits in the parameters are represented in which the first and most significant bit is the left most bit and the last and least significant bit is the rightmost bit. Unless mentioned otherwise, integers are encoded in standard binary encoding for unsigned integers.

6.2.2.2 Data field

Data field elements are mapped to the Data field in the order which they arrive to the RLC entity at the transmitter.

For TMD PDU, UMD PDU and AMD PDU:

– The granularity of the Data field size is one byte;

– The maximum Data field size is the maximum TB size minus the sum of minimum MAC PDU header size and minimum RLC PDU header size.

For TMD PDU:

– Only one RLC SDU can be mapped to the Data field of one TMD PDU.

For UMD PDU, AMD PDU and AMD PDU segment:

– Either of the following can be mapped to the Data field of one UMD PDU, AMD PDU or AMD PDU segment:

– Zero RLC SDU segments and one or more RLC SDUs;

– One or two RLC SDU segments and zero or more RLC SDUs;

– RLC SDU segments are either mapped to the beginning or the end of the Data field;

– A RLC SDU or RLC SDU segment larger than 2047 octets for 11 bits LI can only be mapped to the end of the Data field;

– When there are two RLC SDU segments, they belong to different RLC SDUs.

6.2.2.3 Sequence Number (SN) field

Length: 10 bits or 16 bits (configurable) for AMD PDU and AMD PDU segments. 5 bits or 10 bits (configurable) for UMD PDU.

The SN field indicates the sequence number of the corresponding UMD or AMD PDU. For an AMD PDU segment, the SN field indicates the sequence number of the original AMD PDU from which the AMD PDU segment was constructed from. The sequence number is incremented by one for every UMD or AMD PDU.

6.2.2.4 Extension bit (E) field

Length: 1 bit.

The E field indicates whether Data field follows or a set of E field and LI field follows. The interpretation of the E field is provided in Table 6.2.2.4-1 and Table 6.2.2.4-2.

Table 6.2.2.4-1: E field interpretation (for E field in the fixed part of the header)

Value

Description

0

Data field follows from the octet following the fixed part of the header

1

A set of E field and LI field follows from the octet following the fixed part of the header

Table 6.2.2.4-2: E field interpretation (for E field in the extension part of the header)

Value

Description

0

Data field follows from the octet following the LI field following this E field

1

A set of E field and LI field follows from the bit following the LI field following this E field

6.2.2.5 Length Indicator (LI) field

Length: 11 bits for RLC UM, 11 bits or 15 bits for RLC AM. The length of the LI field for RLC AM is configured by upper layers.

The LI field indicates the length in bytes of the corresponding Data field element present in the RLC data PDU delivered/received by an UM or an AM RLC entity. The first LI present in the RLC data PDU header corresponds to the first Data field element present in the Data field of the RLC data PDU, the second LI present in the RLC data PDU header corresponds to the second Data field element present in the Data field of the RLC data PDU, and so on. The value 0 is reserved.

6.2.2.6 Framing Info (FI) field

Length: 2 bits.

The FI field indicates whether a RLC SDU is segmented at the beginning and/or at the end of the Data field. Specifically, the FI field indicates whether the first byte of the Data field corresponds to the first byte of a RLC SDU, and whether the last byte of the Data field corresponds to the last byte of a RLC SDU. The interpretation of the FI field is provided in Table 6.2.2.6-1.

Table 6.2.2.6-1: FI field interpretation

Value

Description

00

First byte of the Data field corresponds to the first byte of a RLC SDU.

Last byte of the Data field corresponds to the last byte of a RLC SDU.

01

First byte of the Data field corresponds to the first byte of a RLC SDU.

Last byte of the Data field does not correspond to the last byte of a RLC SDU.

10

First byte of the Data field does not correspond to the first byte of a RLC SDU.

Last byte of the Data field corresponds to the last byte of a RLC SDU.

11

First byte of the Data field does not correspond to the first byte of a RLC SDU.

Last byte of the Data field does not correspond to the last byte of a RLC SDU.

6.2.2.7 Segment Offset (SO) field

Length: 15 bits or 16 bits (configurable).

The SO field indicates the position of the AMD PDU segment in bytes within the original AMD PDU. Specifically, the SO field indicates the position within the Data field of the original AMD PDU to which the first byte of the Data field of the AMD PDU segment corresponds to. The first byte in the Data field of the original AMD PDU is referred by the SO field value "000000000000000" or "0000000000000000", i.e., numbering starts at zero.

6.2.2.8 Last Segment Flag (LSF) field

Length: 1 bit.

The LSF field indicates whether or not the last byte of the AMD PDU segment corresponds to the last byte of an AMD PDU. The interpretation of the LSF field is provided in Table 6.2.2.8-1.

Table 6.2.2.8-1: LSF field interpretation

Value

Description

0

Last byte of the AMD PDU segment does not correspond to the last byte of an AMD PDU.

1

Last byte of the AMD PDU segment corresponds to the last byte of an AMD PDU.

6.2.2.9 Data/Control (D/C) field

Length: 1 bit.

The D/C field indicates whether the RLC PDU is a RLC data PDU or RLC control PDU. The interpretation of the D/C field is provided in Table 6.2.2.9-1.

Table 6.2.2.9-1: D/C field interpretation

Value

Description

0

Control PDU

1

Data PDU

6.2.2.10 Re-segmentation Flag (RF) field

Length: 1 bit.

The RF field indicates whether the RLC PDU is an AMD PDU or AMD PDU segment. The interpretation of the RF field is provided in Table 6.2.2.10-1.

Table 6.2.2.10-1: RF field interpretation

Value

Description

0

AMD PDU

1

AMD PDU segment

6.2.2.11 Polling bit (P) field

Length: 1 bit.

The P field indicates whether or not the transmitting side of an AM RLC entity requests a STATUS report from its peer AM RLC entity. The interpretation of the P field is provided in Table 6.2.2.11-1.

Table 6.2.2.11-1: P field interpretation

Value

Description

0

Status report not requested

1

Status report is requested

6.2.2.12 Reserved 1 (R1) field

Length: 1 bit.

The R1 field is a reserved field for this release of the protocol. The transmitting entity shall set the R1 field to "0". The receiving entity shall ignore this field.

6.2.2.13 Control PDU Type (CPT) field

Length: 3 bits.

The CPT field indicates the type of the RLC control PDU. The interpretation of the CPT field is provided in Table 6.2.2.13-1.

Table 6.2.2.13-1: CPT field interpretation

Value

Description

000

STATUS PDU

001-111

Reserved

(PDUs with this coding will be discarded by the receiving entity for this release of the protocol)

6.2.2.14 Acknowledgement SN (ACK_SN) field

Length: 10 bits or 16 bits (configurable).

The ACK_SN field indicates the SN of the next not received RLC Data PDU which is not reported as missing in the STATUS PDU. When the transmitting side of an AM RLC entity receives a STATUS PDU, it interprets that all AMD PDUs up to but not including the AMD PDU with SN = ACK_SN have been received by its peer AM RLC entity, excluding those AMD PDUs indicated in the STATUS PDU with NACK_SN and portions of AMD PDUs indicated in the STATUS PDU with NACK_SN, SOstart and SOend.

6.2.2.15 Extension bit 1 (E1) field

Length: 1 bit.

The E1 field indicates whether or not a set of NACK_SN, E1 and E2 follows. The interpretation of the E1 field is provided in Table 6.2.2.15-1.

Table 6.2.2.15-1: E1 field interpretation

Value

Description

0

A set of NACK_SN, E1 and E2 does not follow.

1

A set of NACK_SN, E1 and E2 follows.

6.2.2.16 Negative Acknowledgement SN (NACK_SN) field

Length: 10 bits or 16 bits (configurable).

The NACK_SN field indicates the SN of the AMD PDU (or portions of it) that has been detected as lost at the receiving side of the AM RLC entity.

6.2.2.17 Extension bit 2 (E2) field

Length: 1 bit.

The E2 field indicates whether or not a set of SOstart and SOend follows. The interpretation of the E2 field is provided in Table 6.2.2.17-1.

Table 6.2.2.17-1: E2 field interpretation

Value

Description

0

A set of SOstart and SOend does not follow for this NACK_SN.

1

A set of SOstart and SOend follows for this NACK_SN.

6.2.2.18 SO start (SOstart) field

Length: 15 bits or 16 bits (configurable).

The SOstart field (together with the SOend field) indicates the portion of the AMD PDU with SN = NACK_SN (the NACK_SN for which the SOstart is related to) that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOstart field indicates the position of the first byte of the portion of the AMD PDU in bytes within the Data field of the AMD PDU. The first byte in the Data field of the original AMD PDU is referred by the SOstart field value "000000000000000" or "0000000000000000", i.e., numbering starts at zero.

6.2.2.19 SO end (SOend) field

Length: 15 bits or 16 bits (configurable).

The SOend field (together with the SOstart field) indicates the portion of the AMD PDU with SN = NACK_SN (the NACK_SN for which the SOend is related to) that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOend field indicates the position of the last byte of the portion of the AMD PDU in bytes within the Data field of the AMD PDU. The first byte in the Data field of the original AMD PDU is referred by the SOend field value "000000000000000" or "0000000000000000", i.e., numbering starts at zero. The special SOend value "111111111111111" or "1111111111111111" is used to indicate that the missing portion of the AMD PDU includes all bytes to the last byte of the AMD PDU.