Loading...UMTS RLC Status PDU: SUFI LIST
Catch Up
LIST Super field
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
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- 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.
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Type = LIST
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LENGTH
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SN1
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L1
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SN2
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L2
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…
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SNLENGTH
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LLENGTH
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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
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7
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6
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5
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4
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3
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2
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1
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0
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0 |
0 |
0 |
0 |
0 |
0 |
1 |
1 |
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0 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
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0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
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0 |
0 |
0 |
1 |
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SUFI ACK + PADDING |
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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
Related posts:
- UMTS RLC Status PDU: SUFI NO_MORE & SUFI ACK
- UMTS RLC Status PDU: SUFI RLIST
- UMTS: Radio Link Protocol (RLC) Overview 25.322
- UMTS: RLC Length Indicator (RLC LI)
- UMTS Radio Link Protocol Decoder
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