| Protocol | rrc | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 38.331 | Spec Section | 5.2.2.4.23, 6.3.1 |
| Direction | gNB -> UE | Message Type | Broadcast System Information |
| Full message name | 5G NR - System Information Block 22 (SIB22) |
|---|---|
| Protocol | RRC |
| Technology | 5G |
| Direction | gNB -> UE |
| Interface | Uu |
| Signaling bearer / channel | Broadcast transport / BCCH-DL-SCH |
| Typical trigger | Broadcast when the cell supports ATG operation and needs to expose ATG-specific parameters. |
| Main purpose | Provides ATG-specific broadcast parameters so the UE can apply the correct access and mobility behavior in air-to-ground deployments. |
| Main specification | 3GPP TS 38.331, 5.2.2.4.23, 6.3.1 |
| Release added | Release 18 |
| Procedures where used | System Information Acquisition, ATG Access and Mobility |
| Related timers | SIB22 does not use a dedicated UE-specific transaction timer |
| Related cause values | SIB22 does not carry reject causes |
System Information Block 22 (SIB22) is an NR broadcast system information block used to provide ATG-specific parameters for the serving cell and optionally neighboring cells.
Provides ATG-specific broadcast parameters so the UE can apply the correct access and mobility behavior in air-to-ground deployments.
SIB22 is the NR broadcast block that carries ATG-specific parameters.
Call flow position: Read as additional SI after the essential broadcast context is available.
Typical state: UE is camped and expanding broadcast context for ATG operation.
Preconditions:
Next likely message: UE applies ATG-specific parameters locally
Previous message(s): MIB, System Information Block 1 (SIB1)
Next message(s): ATG-aware access preparation
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 {
sib22-v1800 SIB22-r18,
...
},
...
}
SIB22-r18 ::= SEQUENCE {
... -- ATG-specific serving and optional neighbor parameters
}
SIB22 is release-18 broadcast information for ATG deployments. In practice, engineers inspect whether the ATG-specific parameter block is present and matches the deployment they are debugging.
BCCH-DL-SCH-Message
message: c1
systemInformation
criticalExtensions
systemInformation
sib-TypeAndInfo
sib22
atg-Parameters-r18: present
| IE | Required | Description |
|---|---|---|
atg-specific parameters | Yes | Main ATG parameter block for the serving cell and, where present, neighboring ATG cells. |
atg-specific parametersMain ATG parameter block for the serving cell and, where present, neighboring ATG cells.
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: SIB22 may be missing or its ATG-specific parameters may not match the deployment.
What to inspect: Check the ATG parameter block and any neighbor-cell information.
Next step: Correlate the decoded SIB22 content with observed access and mobility behavior.
SIB19 is NTN-focused, while SIB22 is ATG-focused.
SIB22 is System Information Block 22, used for ATG-specific serving-cell and optional neighbor-cell parameters.
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.