Please clarify below doubts when UE goes in IDLE mode..

Question

As Far As I know, When UE is in IDLE mode,
1) EnodeB will remove the context of UE but MME will not.. right?
2) When UE is in idle state will MME have the TEID(s1ap,s1u)? If yes then during Pagging ans Service Request will MME use the same TEID?
3) If MME removes the TEID then during Pagging how will MME selects EnodeB?
4)If EnodeB has removed all context then how EnodeB will send pagging message to UE?
5)If EnodeB has removed the context then how UE Measurment (RSRP,RSSI,RSRQ) done?
6)If UE is idle for few days then MME will remove the context of UE? if not then what about the Purge UE Request (PUR) message between MME-HSS. (As far as i know MME will send PUR when UE is idle state for few days)

Answer 1

When UE is idle mode then
1. Both UE and MME removes the UE context.
2. As in step 1 .. MME does not have context of UE so will not have TEID but make ECM state Idle.. (not much sure)
3. MME selects eNodeB on the basis to TA list. MME will send paging to all the eNodeB belongs to that TA list to broadcast paging.
4. Paging message is broadcast in the cell with PRNTI(0XFFFF). All UE can read the paging . It is not UE specific.
5. When UE is in idle mode then UE does not need to send measurement to eNodeB.
6. MME have TAU update timer. If UE is not again updating the TA after expiring the TAU timer after that MME purse that UE.

Comments

I do not agree with the 1st point. MME maintains the NAS context. It deletes the S1-AP context

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PRNTI value is 0XFFFE