Please explain these LTE terms in simple understanding way - RRC CONNECTED, RRC IDLE, ECM CONNECTED and ECM IDLE?

Question

Please explain these LTE terms in simple understanding way -
RRC CONNECTED
RRC IDLE
ECM CONNECTED
ECM IDLE

Answer 1

Hi chakri,

RRC connected - > Have Signalling connection between ENB and UE (SRB 0 or 1 bearers available)
RRC IDLE -> No SRB 0 or 1 bearers available

ECM connected - > Have s1 signalling bearers or DRB available.

ECM Idle -> No Connection between UE and MME . i.e No S1 signalling ( No SRB1/2 bearers).

Comments

Thanks,

Is it possible that ECM IDLE and RRC CONNECTED (and) ECM CONNECTED and RRC IDLE stages ?

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ECM IDLE and RRC Connected is possible, But RRC IDLE and ECM connected is not possible.

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Hi Jaganathan, Can you please give share a scenario in which UE will be in ECM IDLE and RRC CONNECTED ?

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As i understood ECM Connected and RRC IDLE can be possible. In this case MME knows UE location in Tracking Area wise and initiate pagging from MME to get back into RRC CONNECTED state.

But ECM IDLE and RRC CONNECTED state not all possible.  Please comment my understanding is right or not ?

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Hi,

Actually during initial attach procedure UE will initiate RRC connection request , that time UE will have only RRC signalling connection but ECM will be IDLE state,  but after attach IF UE is in ECM Idle then RRC also will be idle state. Only During attach procedure this is possible. But im not sure during attach procedure they will maintain states, above statement is my guess