LTE X2 handover UE interactions PDF - EventHelix.com
LTE X2 handover UE interactions PDF - EventHelix.com
LTE X2 handover UE interactions PDF - EventHelix.com
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<strong>UE</strong> Interfaces (Successful Handover)<strong>LTE</strong> MobileeNodeB Network<strong>UE</strong> Target eNodeB Source eNodeBBefore the <strong>handover</strong>RRC-ConnectedDownlink data flow before <strong>handover</strong>Downlink DataEventStudio System Designer 620-Apr-13 20:27 (Page 1)The <strong>UE</strong> and Source eNodeB are in RRCConnected state.Uplink data flow before <strong>handover</strong>Uplink DataHandover preparationrrcRRC Measurement ControlrrcThe network sets the measurement thresholds forsending measurement reports.rrcRRC Measurement ReportrrcNeighboring cell signal quality is now better thanthe serving cell.Signal strength of serving cell,Signal strength of neighborsHandover executionrrcRRC Connection Reconfiguration RequestRACH Preamble Assignment,Target C-RNTI,Target DRB ID (UL/DL),Target eNB AS Security AlgorithmrrcThe Source eNodeB sends a <strong>handover</strong> <strong>com</strong>mandto the <strong>UE</strong>. The message contains a new C-RNTIand new DRB IDs. A RACH preamble is alsoincluded for contention free RACH access.Uplink data flow during <strong>handover</strong> preparationUplink DatabeginSwitching to Target eNodeBMeanwhile, the <strong>UE</strong> has received the <strong>handover</strong><strong>com</strong>mand and it is switching to the new target cell.Detach from Source eNodeBGenerates KeNB (KeNB = KeNB*) andAS keysSynchronizing with target cellrrcRACH Preamblerrc<strong>UE</strong> uses the preamble assigned in the <strong>handover</strong><strong>com</strong>mand to send a RACH to the target eNodeB.Random Access ResponserrcTiming Advance,Target C-RNTI,Uplink grantrrcThe target eNodeB accepts the request andresponds back with a timing adjustment and anuplink resource grant.
<strong>UE</strong> Interfaces (Successful Handover)<strong>LTE</strong> MobileeNodeB Network<strong>UE</strong> Target eNodeB Source eNodeBRRC Connection Reconfiguration CompleterrcrrcTarget C-RNTIEventStudio System Designer 620-Apr-13 20:27 (Page 2)The <strong>UE</strong> uses the assigned resources to transmitthe Handover Confirm message (RRC ConnectionReconfiguration Complete).endSwitching to Target eNodeBAS layer security procedureTransmit transmission of queued downlink dataDownlink DataDownlink DataDownlink DataDownlink data flow during <strong>handover</strong> executionDownlink DataUplink data flow during <strong>handover</strong> executionUplink DataHandover <strong>com</strong>pletionSwitching pathDownlink data flow after <strong>handover</strong>Downlink Data
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