How Non Access Stratum procedures works in LTE
The procedures for the Non Access Stratum, especially power management procedures are substantially similar to UMTS. Main change is that the UMTS EPS allows concatenation certain procedures to allow faster creation of connection and media.
Create MME UE context, when the UE is on and attaches to the network. Assign a unique ID called SAE short temporary Mobile Subscriber Identity Temporary (S-TMSI) which identifies the context of the UE MME. This context the UE has user subscription information downloaded from HSS.
Local storage of data in the MME subscription allows faster execution of the procedures, such as setting the carrier because it eliminates the need to consult HSS every time. In addition, the UE context has also dynamic information such as the list of carriers that are set and terminal capabilities. To reduce overhead in E-UTRAN and processing in the UE, all UE-related information in the access network, including wireless carriers, may be released during long periods of inactivity data.
This is the state-ECM IDLE.MME kept in the UE context and information about carriers established in those periods of inactivity. To enable the network to contact an ECM IDLE UE, network updates as UE the new location whenever it comes out of the current track (TA) This is called an update tracking area.MME domain is responsible for tracking the location user, while the UE is in ECM-IDLE.
When there is a need to provide data downlink at UE ECM-IDLE, MME sends a paging message to all current eNodeBs its TA and UE eNodeBs page radio interface. Upon receiving a paging message, the UE makes a call for service, leading to the displacement UE ECM connected state. Such UE-related information is created in E-UTRAN and radio bearers are restabilite.MME is responsible for restoring and updating radio bearers UE context eNodeB.
This transition between the UE is called a transition-inactive to active. To speed-inactive to active transition and establishing carrier EPS support concatenation of NAS and Access Stratum (AS) bearer activation procedures.
Some relations between the NAS and AS protocol is used intentionally to allow the procedure to run simultaneously rather than sequentially, as in the UMTS. For example, the procedure for determining the carrier can be carried by the network without waiting for the conclusion of safety.
Security features are the responsibility of the MME for both signaling and user data. When a UE attaches to the network, mutual authentication is done between the EU network and MME / HSS. This authentication feature sets also security keys are used to encrypt carriers.