There are some supporters behind the proposal to include the NSSAI in the RRC Connection Establishment msg 5 and even if this is not agreed in Rel-15, it may be introduced in later releases. A concern is that including the NSSAI information in the RRC signaling would make possible the avoidance of situations associated with core network (CN) overload.

One additional aspect to be considered is the RRC inactive state. According to 3GPP TS 38.331, a UE is either in RRC_CONNECTED state or in RRC_INACTIVE state when an RRC connection has been established. If this is not the case, i.e. no RRC connection is established, the UE is in RRC_IDLE state. The RRC states can further be identified as follows:

• • RRC_IDLE 206:
    • A UE specific discontinuous reception (DRX) may be configured by upper layers;
    • UE controlled mobility based on network configuration;
    • The UE:
      • Monitors a paging channel for CN paging using fifth generation serving temporary mobile subscriber identity (5G-S-TMSI);
      • Performs neighbouring cell measurements and cell (re-)selection;
      • Acquires system information and can send system information (SI) request (if configured).
  • RRC_INACTIVE 204: