LTE: UE Capability Enquiry

Direction: E-UTRAN => UE
Signalling Radio Bearer: SRB1
RLC Mode: AM
Logical Channel: DCCH
Transport Channel: DL-SCH

The UE CAPABILITY ENQUIRY message is used to request the transfer of UE radio access capabilities for E-UTRA as well as for other RATs (UTRA, GERAN-CS, GERAN-PS, and CDMA2000)

As the UE’s AS capability may contain several RATs capabilities, the information can be rather very large. To reduce the overhead in the air interface during transition from RRC_IDLE mode to RRC_CONNECTED mode, MME stores UE's AS capability and provides it to eNodeB during initial UE context setup over S1 interface. In case if the MME doesn’t have the valid UE's AS capability, the MME does not provide UE's AS capability to the eNodeB. The eNobeB has to acquire UE's AS capability from UE using UE CAPABILITY ENQUIRY.
NOTE: Change of the UE's GERAN UE radio capabilities in RRC_IDLE is supported by use of TRACKING AREA UPDATE

This message contains only one IE as shown below;
ue-CapabilityRequest: List of the RATs for which the UE is requested to transfer the UE radio access capabilities i.e. E-UTRA, UTRA, GERAN-CS, GERAN-PS, CDMA2000

Example: UE CAPABILITY ENQUIRY for E-UTRA















Reference: 3GPP TS 36.331

23 comments:

  1. What does it mean "AS" abbreviation?

    Piotr

    ReplyDelete
  2. Is there any timer limiting the time for the UE to respond to the capability enquiry?

    ReplyDelete
    Replies
    1. There is no timer defined for UE capability transfer procedure. But eNodeB might have some timers within which if the UECapabilityInformation message is not received, it may abort connection establishment procedure.

      Delete
  3. Hi Kumar,
    Is UE CapabilityInformation is same for all operators for same mobile model. Or is it different

    ReplyDelete
  4. Hi Kumar,
    Is UE CapabilityInformation is same for all operators for same mobile model. Or is it different

    ReplyDelete
    Replies
    1. The UE report same UE capability per RAT irrespective of the operator.

      Delete
  5. How the eNodeB takes UE Capability. Example, If UE reports DL CAT-16 , MIMO Layers = 4. But lets say eNodeB is only capable of CAT-12 and two MIMO layers. How EnodeB configures the UE for DL Category ?

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    ReplyDelete
  7. Hi
    i got system fail error with this message "Receive UE Radio Capability and UeRadioCap's length is over!", the LTE subscriber is normal and attached in the network , does this error effect voice service ??

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  8. Hi Kumara,

    Thanks for your nice explanation....I have a doubt:
    2 times Enodeb asks for ue capability enquiry to the UE (1st time its for the enodeb itself and 2nd time it will pass it to MME). so my question is how UE knows that enodeb is asking for which ue capability(please let me know the IE for the 2 different capability enquiry).

    BR
    Partha

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  9. A "UE Capability Enquiry" refers to a message or command in the context of mobile telecommunications. Stream Unwatchable Lag "UE" stands for User Equipment, which refers to a mobile device.

    ReplyDelete