Section: 5.1 Overview 5.1.1 General
Content: This clause describes the procedures used for mobility management for EPS services (EMM) at the radio interface (reference point "LTE-Uu"). The main function of the mobility management sublayer is to support the mobility of a user equipment, such as informing the network of its present location and providing user identity confidentiality. A further function of the mobility management sublayer is to provide connection management services to the session management (SM) sublayer and the short message services (SMS) entity of the connection management (CM) sublayer. All the EMM procedures described in this clause can only be performed if a NAS signalling connection has been established between the UE and the network. Else, the EMM sublayer has to initiate the establishment of a NAS signalling connection (see 3GPP TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [22]). NOTE: In a satellite E-UTRAN access, a GNSS fix time in lower layers can delay transmission of an initial UL NAS message by up to 100 seconds (GNSS cold state).