UMTS RLC Status PDU: SUFI LIST

The List Super-Field consists of a type identifier field (LIST), a list length field (LENGTH) and a list of LENGTH number of pairs.

LENGTH

• Length: 4 bits
• The number of (SNi, Li) pairs in the super-field of type LIST.
• The value 0000 is INVALID and STATUS PDU is discarded.

SNi

• Lenght: 12 bits
• ”Sequence number” of AMD PDU, which was not correctly received.

Li

• Length: 4 bits
• Number of consecutive AMD PDUs not correctly received following AMD PDU with”Sequence number” SNi.

Type = LIST

LENGTH

SN-1

L-1

SN-2

L-2

—–

SN-Length

L-Length

Example

In this example:

• RLC AMD PDUs with Sequence Number 0, 1, 2, 3, 6, 7 are received correctly
• PDUs with sequence number 4 and 5 are missing.

Encoding of Status PDU

0	0	0	0	0	0	1	1
0	0	0	1	0	0	0	0
0	0	0	0	0	1	0	0
0	0	0	1

Explanation

Octet #1:

0: D/C: Data or control PDU. As it is a control PDU this bit is set to 0.
000: Control PDU Type: 000 indicates it is a Status PDU.
0011: SUFI Type. This is SUFI LIST

Octet #2 and #3

0001: LENGTH field. This indicates the number of (SNi, Ni) pairs. Here there is only one pair
0000 0000 0100: (SNi): The start sequence number. This is the Sequence number of the missing PDU. Here the missing PDUs start from Sequence Number 4 (100).
0001: (Li): The number of consecutive missing PDUs following sequence number 4 (SNi). Here there is only 1 (Sequence number 5)

Rest of the Status PDU may be encoded for SUFI ACK and Padding.

Reference

• Radio Link Control (RLC) protocol specification: 3GPP TS 25.322
• WCDMA Design Handbook
• UMTS Signaling: UMTS Interfaces, Protocols, Message Flows and Procedures Analyzed and Explained