| Protocol | rrc | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 38.331 | Spec Section | 5.2.2.4.26, 6.3.1 |
| Direction | gNB -> UE | Message Type | Broadcast System Information |
| Full message name | 5G NR - System Information Block 25 (SIB25) |
|---|---|
| Protocol | RRC |
| Technology | 5G |
| Direction | gNB -> UE |
| Interface | Uu |
| Signaling bearer / channel | Broadcast transport / BCCH-DL-SCH |
| Typical trigger | Broadcast in NTN-related deployments where the UE needs TN coverage information. |
| Main purpose | Provides terrestrial network coverage information so the UE can apply the correct behavior in NTN scenarios that depend on TN coverage awareness. |
| Main specification | 3GPP TS 38.331, 5.2.2.4.26, 6.3.1 |
| Release added | Release 18 |
| Procedures where used | System Information Acquisition, NTN Access and Mobility with TN Awareness |
| Related timers | SIB25 does not use a dedicated UE-specific transaction timer |
| Related cause values | SIB25 does not carry reject causes |
System Information Block 25 (SIB25) is an NR broadcast system information block used to provide TN coverage information for NTN-related operation.
Provides terrestrial network coverage information so the UE can apply the correct behavior in NTN scenarios that depend on TN coverage awareness.
SIB25 gives the UE TN coverage information that is relevant for NTN-related behavior.
Call flow position: Read as additional SI after the basic broadcast context is available.
Typical state: UE is camped and extending broadcast context for NTN behavior with TN coverage awareness.
Preconditions:
Next likely message: UE applies the TN coverage information locally
Call flow position: Used when the UE needs TN coverage information as part of NTN-related operation.
Typical state: UE is using NTN-related broadcast context rather than only terrestrial assumptions.
Preconditions:
Next likely message: Access or mobility decision using TN coverage context
Previous message(s): MIB, System Information Block 1 (SIB1), System Information Block 19 (SIB19)
Next message(s): NTN-aware access or mobility behavior using TN coverage information
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 {
sib25-v1800 SIB25-r18,
...
},
...
}
SIB25-r18 ::= SEQUENCE {
... -- TN coverage information
}
The practical focus is whether TN coverage information is present and whether it matches the NTN scenario being debugged.
BCCH-DL-SCH-Message
message: c1
systemInformation
criticalExtensions
systemInformation
sib-TypeAndInfo
sib25
tn-CoverageInfo-r18: present
| IE | Required | Description |
|---|---|---|
TN coverage information | Yes | Main SIB25 payload that exposes TN coverage information relevant to NTN-aware behavior. |
TN coverage informationMain SIB25 payload that exposes TN coverage information relevant to NTN-aware behavior.
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: SIB25 may be missing or its TN coverage information may not match the deployment.
What to inspect: Check the SIB25 TN coverage block and compare it with SIB19 NTN context.
Next step: Validate the broadcast coverage assumptions before treating the issue as only RF or core signaling.
SIB19 provides NTN-specific parameters, while SIB25 provides TN coverage information used in NTN-related behavior.
SIB25 is System Information Block 25, used to broadcast TN coverage information for NTN-related operation.
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.