| Protocol | rrc | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 38.331 | Spec Section | 5.2.2.4.18, 6.3.1 |
| Direction | gNB -> UE | Message Type | Broadcast System Information |
| Full message name | 5G NR - System Information Block 17 (SIB17) |
|---|---|
| Protocol | RRC |
| Technology | 5G |
| Direction | gNB -> UE |
| Interface | Uu |
| Signaling bearer / channel | Broadcast transport / BCCH-DL-SCH |
| Typical trigger | Broadcast when the cell provides TRS resources for idle or inactive UEs. |
| Main purpose | Provides idle or inactive TRS resource configuration so the UE can use the correct reference signal occasions for availability and mobility-related behavior. |
| Main specification | 3GPP TS 38.331, 5.2.2.4.18, 6.3.1 |
| Release added | Release 17 |
| Procedures where used | System Information Acquisition, Idle / Inactive TRS Configuration |
| Related timers | SIB17 does not use a dedicated UE-specific transaction timer |
| Related cause values | SIB17 does not carry reject causes |
System Information Block 17 (SIB17) is an NR broadcast system information block used to provide TRS resource configuration for idle and inactive UEs.
Provides idle or inactive TRS resource configuration so the UE can use the correct reference signal occasions for availability and mobility-related behavior.
SIB17 carries TRS configuration for idle and inactive UEs, and it may arrive in multiple segments.
Call flow position: Read as additional SI after MIB and SIB1.
Typical state: UE is camped and expanding broadcast context for idle or inactive measurements and availability.
Preconditions:
Next likely message: UE applies the TRS configuration locally
Previous message(s): MIB, System Information Block 1 (SIB1)
Next message(s): Idle or inactive TRS-based behavior
Security context: Broadcast information. It is cell-common and not protected by dedicated AS security.
SystemInformation-IEs ::= SEQUENCE {
sib-TypeAndInfo SEQUENCE (SIZE (1..maxSIB)) OF CHOICE {
sib17-v1700 SIB17-r17,
...
},
...
}
SIB17-r17 ::= SEQUENCE {
segmentNumber-r17 INTEGER (0..63),
segmentType-r17 ENUMERATED {notLastSegment, lastSegment},
segmentContainer-r17 OCTET STRING
}
The important practical detail is segmentation. Engineers need all segments before concluding that the TRS configuration is complete.
BCCH-DL-SCH-Message
message: c1
systemInformation
criticalExtensions
systemInformation
sib-TypeAndInfo
sib17
segmentNumber-r17: 0
segmentType-r17: notLastSegment
segmentContainer-r17: present
| IE | Required | Description |
|---|---|---|
segmentNumber-r17 | Yes | Indicates which segment of SIB17 is being carried. |
segmentType-r17 | Yes | Shows whether this segment is the last segment or whether more SIB17 segments follow. |
segmentContainer-r17 | Yes | Contains the encoded SIB17-IEs segment, including TRS configuration. |
segmentNumber-r17Indicates which segment of SIB17 is being carried.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
segmentType-r17Shows whether this segment is the last segment or whether more SIB17 segments follow.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
segmentContainer-r17Contains the encoded SIB17-IEs segment, including TRS configuration.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
Likely cause: The UE may not have acquired all SIB17 segments.
What to inspect: Check segmentNumber-r17, segmentType-r17, and whether the final segment was received.
Next step: Reconstruct the full SIB17 payload before analyzing TRS behavior.
SIB11 covers measurement configuration, while SIB17 focuses on TRS resources for idle or inactive UEs.
SIB17 is System Information Block 17, used to broadcast TRS resources for idle and inactive UEs.
Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.