| Protocol | rrc | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 38.331 | Spec Section | 6.2.2 |
| Direction | UE -> gNB | Message Type | System Information Control |
| Full message name | 5G NR - RRC SystemInfo Request |
|---|---|
| Protocol | RRC |
| Technology | 5G |
| Direction | UE -> gNB |
| Interface | Uu |
| Signaling bearer / channel | SRB0 / SRB1 / UL-CCCH / UL-DCCH |
| Typical trigger | Used when the UE needs specific system information from the network. |
| Main purpose | Lets the UE ask the network for needed system information when the relevant information is not already available through normal broadcast acquisition. |
| Main specification | 3GPP TS 38.331, 6.2.2 |
| Release added | Release 15 |
| Procedures where used | System Information Acquisition, On-Demand SI Handling |
| Related timers | None highlighted |
RRC SystemInfo Request is the NR RRC message the UE uses to request system information directly from the network.
Lets the UE ask the network for needed system information when the relevant information is not already available through normal broadcast acquisition.
RRC SystemInfo Request lets the UE ask the network for specific system information.
Call flow position: Used when the UE explicitly requests system information instead of only passively waiting for broadcast delivery.
Typical state: UE needs additional system information to continue correctly.
Preconditions:
Next likely message: System Information or dedicated SI delivery
Previous message(s): MIB, System Information Block 1 (SIB1)
Next message(s): System Information, Dedicated SIB delivery
Security context: Depends on whether the request is sent before or after full connected context is active.
RRCSystemInfoRequest ::= SEQUENCE {
requestInfo OCTET STRING
}
Engineers mainly correlate the request with the following System Information or dedicated SI response.
UL-CCCH-Message
message: rrcSystemInfoRequest
requestInfo: present
| IE | Required | Description |
|---|---|---|
requestedSIB / requestInfo | Yes | Identifies the information the UE is requesting. |
requestedSIB / requestInfoIdentifies the information the UE is requesting.
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 request may be absent, wrong, or unanswered.
What to inspect: Check the request content and the later downlink SI response.
Next step: Compare the request path with normal broadcast scheduling.
It asks the network for system information the UE needs.
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.