| Protocol | lte-rrc | Network | lte |
|---|---|---|---|
| Spec | 3GPP TS 36.331 | Spec Section | 5.4.4, 6.2.2 |
| Direction | eNodeB -> UE | Message Type | Inter-RAT Handover Preparation |
| Full message name | LTE RRC Handover From EUTRA Preparation Request |
|---|---|
| Protocol | LTE-RRC |
| Technology | LTE |
| Direction | eNodeB -> UE |
| Interface | Uu |
| Signaling bearer / channel | SRB1 / DL-DCCH |
| Typical trigger | The source eNodeB has decided to prepare an inter-RAT handover toward cdma2000 and needs UE-side preparation information to be delivered. |
| Main purpose | Provides the UE with the cdma2000 preparation information needed before the later inter-RAT handover execution path continues. |
| Main specification | 3GPP TS 36.331, 5.4.4, 6.2.2 |
| Release added | Release 8 |
| Procedures where used | Inter-RAT Handover to cdma2000, Handover Preparation |
| Related timers | T304 |
Downlink LTE RRC message used when the source E-UTRA side starts handover preparation toward cdma2000.
Provides the UE with the cdma2000 preparation information needed before the later inter-RAT handover execution path continues.
Handover From EUTRA Preparation Request is the LTE source-side message that starts the UE preparation branch for cdma2000 handover.
Call flow position: Source-side preparation message delivered before the final move away from LTE.
Typical state: UE is in RRC_CONNECTED and the inter-RAT handover decision is already made.
Preconditions:
Next likely message: ULHandoverPreparationTransfer
Call flow position: Preparation branch used when a fallback-related cdma2000 preparation exchange is needed before mobility execution.
Typical state: UE is still in connected LTE signaling.
Preconditions:
Next likely message: MobilityFromEUTRACommand
Previous message(s): MeasurementReport, Inter-RAT mobility decision
Next message(s): ULHandoverPreparationTransfer, MobilityFromEUTRACommand
Security context: Normally sent as protected connected-mode signaling after LTE AS security is active.
HandoverFromEUTRAPreparationRequest ::= SEQUENCE {
criticalExtensions CHOICE {
c1 CHOICE {
handoverFromEUTRAPreparationRequest-r8 HandoverFromEUTRAPreparationRequest-r8-IEs,
spare3 NULL,
spare2 NULL,
spare1 NULL
},
criticalExtensionsFuture SEQUENCE {}
}
}
HandoverFromEUTRAPreparationRequest-r8-IEs ::= SEQUENCE {
cdma2000-Type CDMA2000-Type,
rand BIT STRING (SIZE (32)),
mobilityParameters OCTET STRING,
nonCriticalExtension SEQUENCE {} OPTIONAL
}
The useful checks are the cdma2000 target type and whether the preparation payload matches the later target branch.
DL-DCCH-Message
message c1 : handoverFromEUTRAPreparationRequest : {
criticalExtensions c1 : handoverFromEUTRAPreparationRequest-r8 : {
cdma2000-Type cdma2000-1XRTT,
rand '0A1B2C3D'H,
mobilityParameters 'A1034F22'H
}
}
| IE | Required | Description |
|---|---|---|
cdma2000-Type | Yes | Shows whether the preparation applies to cdma2000 1XRTT or HRPD. |
rand | Yes | Random value used as part of the cdma2000 preparation exchange. |
mobilityParameters | Yes | Opaque cdma2000 preparation container passed to the UE. |
nonCriticalExtension | Optional | Release-extension branch for later additions. |
cdma2000-TypeShows whether the preparation applies to cdma2000 1XRTT or HRPD.
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.
randRandom value used as part of the cdma2000 preparation exchange.
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.
mobilityParametersOpaque cdma2000 preparation container passed to the UE.
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.
nonCriticalExtensionRelease-extension branch for later additions.
Presence: Optional
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: Preparation may have started but the wider inter-RAT branch did not complete.
What to inspect: Check this message, ULHandoverPreparationTransfer, and whether a later MobilityFromEUTRACommand appears.
Next step: Treat the failure as a preparation-stage mobility issue rather than a target-access issue.
Likely cause: The handover decision may differ from the assumed target system.
What to inspect: Check cdma2000-Type and the later mobility execution command.
Next step: Align the expected target RAT with what the preparation message actually carries.
HandoverFromEUTRAPreparationRequest prepares the UE for the later cdma2000 branch. MobilityFromEUTRACommand is the final move-away command.
It is the LTE downlink RRC message used to start the UE-side preparation branch for cdma2000 handover.
No. It is a preparation message. The later move-away command appears in MobilityFromEUTRACommand.
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.