Chapter 10
Functionality of LTE/SAE
10.1 Introduction
This chapter presents the state of the LTE UE and network. This is explained using examples of typical procedures prior to and during an LTE call. This chapter also presents the signaling flows for different cases, together with the protocol messages. End-to-end functionality is explained with examples. Operations-related topics are presented for fault, configuration, backupandrestore, and inventory management. Principles for online and offline charging are presented. Finally, signal protection is presented.
10.2 States
There are two states in EPS and LTE UE: EMM (EPS Mobility Management) and ECM (EPS Connection Management). Figure 10.1 clarifies the transitions between the states, and how they overlap with each other. In the EMM-Deregistered state, the UE is not reachable for the LTE/SAE network. The transition from the EMM Deregistered state to the EMM-Registered state happens via the Attach procedure or via the Tracking Area Update from GERAN or UTRAN. At the same time, the UE moves to ECM-Connected state. After the release of the signaling, the UE moves to ECM-Idle state. It still keeps the EMM-Registered state. The UE can move back to the ECM-Connected/EMM-Registered stage when the signaling connection has been established. The UE can also move directly to the EMM-Deregistered state if the Detach procedure is carried out. This Detach procedure can also move UE to the EMM-Deregistered ...
