Thursday 3 September 2009

LTE NAS and AS states and their relation

Continuing from where we left yesterday.

As you can see that there are three different states in an LTE system we are talking about.

The first is the RRC state that goes from RRC_IDLE to RRC_CONNECTED everytime the UE needs to be connected to the eNodeB.

Once the UE is RRC_CONNECTED, it can register with the Mobility Management Entity (MME), and the EPS Mobility Management (EMM) state moves from EMM-DEREGISTERED to EMM-REGISTERED

The EPS Connection Management (ECM) state (ECM-IDLE or ECM-CONNECTED) reflects the connectivity of the UE with the Evolved Packet Core (EPC). See the Interface diagram for details.

The NAS states, and their relationship to the AS RRC states can be seen in the diagram above

I have picked up some information from: LTE: The UMTS Long Term Evolution: From Theory to Practice

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