Saturday, October 15, 2011

RRC Connection Reconfiguration

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


RRC CONNECTION RECONFIGURATION message is the command to modify an RRC connection. The purpose of this procedure is,
·            To establish/modify/release Radio Bearers
·            To perform Handover
·            To setup/modify/release Measurements
·            To add/modify/release SCells
·            Dedicated NAS Information might also be transferred from eNodeB to UE

Differences with 3G system's radio resource configuration procedure:
·         In LTE, RRC CONNECTION RECONFIGURATION is the only message used to perform all logical, transport, and physical channel configurations where as in case UMTS, there exists Transport Channel, Physical Channel and Radio Bearer Reconfiguration messages
·         In LTE, RRC CONNECTION RECONFIGURATION can also be used to send NASdedicated signalling to the UE to reduce the latency whereas this option is not available in 3G
·         LTE has only one RRC connected mode state (RRC_CONNECTED), so it has only one Temporary Radio Network Temporary Identity (RNTI) i.e. C-RNTI
·         In 3G, MEASUREMENT CONTROL is used to setup/modify/release measurements where as in LTE, RRC CONNECTION RECONFIGURATION message is the only message for this purpose

E-UTRAN includes the mobilityControlInfo (Handover) only when AS-security has been activated, and SRB2 with at least one DRB are setup but not suspended. The establishment of RBs (other than SRB1, which is established during RRC connection establishment) is included only when AS-security has been activated

          If the UE is unable to comply with (part of) the configuration included in the RRC CONNECTION RECONFIGURATION message, the UE shall continue using the configuration used prior to the reception of RRC CONNECTION RECONFIGURATION message. If the security has not been activated, UE should leave RRC_CONNECTED state, else, UE initiates the connection re-establishment procedure which is used to resume SRB1 operation and to reactivate security


Example1: RRC CONNECTION RECONFIGURATION to setup SRB2 and DRB


Example2: RRC CONNECTION RECONFIGURATION - Measurement Configuration






















Example3: RRC CONNECTION RECONFIGURATION - Mobility Config Information


Example4: RRC CONNECTION RECONFIGURATION - DedicatedInfoNAS (Other IEs are not shown)


8 comments:

  1. Hi..Very useful info in one place. Can you please check this sentence ...it seems there is a typing error. "onnection re-establishment procedure which is used to resume SRB1 operation and to reactivate s640rity" - what is s640rity?

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  2. I am not sure if you would be covering the IRAT aspects in another blog? I just wanted to know when and how does these IRAT related measurement procedure takes place? how are the measurement gaps handled in LTE?

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  3. Hi RV,

    The E-UTRAN configures the UE with measurement gaps for IRAT using RRC Connection reconfiguration (for measurement configuration). The IE MeasGapConfig specifies the measurement gap configuration and controls setup/release of measurement gaps

    I have uploaded (to below location) an example of how measurement gaps are configured for CDMA2000

    https://docs.google.com/leaf?id=0B_BgrMWsGcp_YzI0YmZhMzktM2U0ZS00YTA5LWJiZTMtODJiMTA4Mjg4ZWVi&hl=en_US

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  4. Hi Kumar Swamy,

    very useful information!!! Thanks alot for such great effort.

    ReplyDelete
  5. hi

    can you please explain the importance of each IE's in RRC CONNECTION RECONFIGURATION - Measurement Configuration

    thanks in advance

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  6. Hi,

    If UE is unable to comply with any of the configuration which is received in RRC Connection Reconfiguration Message then UE will discard all this configuration received in RRC Connection Reconfiguration Message.
    If AS security is enable then UE will trigger RRC Connection Re-establishment Request with cause :: reconfiguration failure.
    Note:: Reconfiguration message contains NAS pdu "attach_accept" at the time initial attach. If reconfiguration is failed then UE will not get "attach_accept" message and in between re-establishment procedure , it will send attach_request message to eNodeB for "attach_accept" message.

    If this scenario is happens then how eNodeB handled it.

    Can anyone please tell me in brief ?

    ReplyDelete