Section: 4.6.3.1 ECM-IDLE
Content: A UE is in ECM-IDLE state when no NAS signalling connection between UE and network exists. In ECM-IDLE state, a UE performs cell selection/reselection according to TS 36.304[ Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) procedures in idle mode ]  [34] and PLMN selection according to TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [10]. Except for UEs that have had their RRC connection suspended, as described in clause 5.3.4A, there exists no UE context in E-UTRAN for the UE in the ECM-IDLE state. There is no S1_MME and no S1_U connection for the UE in the ECM-IDLE state. In the EMM-REGISTERED and ECM-IDLE state, the UE shall: - perform a tracking area update if the current TA is not in the list of TAs that the UE has received from the network in order to maintain the registration and enable the MME to page the UE; - perform the periodic tracking area updating procedure to notify the EPC that the UE is available; - perform a tracking area update if the RRC connection was released with release cause "load balancing TAU required"; - perform a tracking area update when the UE reselects an E-UTRAN cell and the UE's TIN indicates "P-TMSI"; - perform a tracking area update for a change of the UE's Core Network Capability information or the UE specific DRX parameter; - perform a tracking area update when a change in conditions in the UE require a change in the extended idle mode DRX parameters previously provided by the MME. - perform a tracking area update when the UE manually selects a CSG cell, and the CSG ID and associated PLMN of that cell is absent from both the UE's Allowed CSG list and the UE's Operator CSG list; - answer to paging from the MME by performing a service request procedure or, if the UE has had its RRC connection suspended, the UE initiates the Connection Resume procedure (clause 5.3.5A); - perform the service request procedure in order to establish the radio bearers when uplink user data is to be sent, or uplink NAS signalling is to be sent for UE requested bearer modification procedure (clause 5.4.5), UE requested PDN connectivity (clause 5.10.2), UE requested PDN disconnection (clause 5.10.3), or if the UE has had its RRC connection suspended the UE initiates the Connection Resume procedure (clause 5.3.5A). The UE and the MME shall enter the ECM-CONNECTED state when the signalling connection is established between the UE and the MME. Initial NAS messages that initiate a transition from ECM-IDLE to ECM-CONNECTED state are Attach Request, Tracking Area Update Request, Service Request or Detach Request. A successful completion of the Connection Resume procedure, described in clause 5.3.5.A, initiates at UE and MME a state transition from ECM-IDLE to ECM-CONNECTED. When the UE is in ECM-IDLE state, the UE and the network may be unsynchronized, i.e. the UE and the network may have different sets of established EPS bearers. When the UE and the MME enter the ECM-CONNECTED state, the set of EPS Bearers is synchronized between the UE and network.