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

    clip image0012 UMTS RLC Status PDU: SUFI LIST

    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

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