This approach to the provision of isolated operation (e.g. when there is no S1 connectivity to the macro EPC) assumes that the IOPS-capable eNodeB is co-sited with, or can reach, a Local EPC instance which is used in IOPS mode. The Local EPC instance includes at least MME, SGW/PDN-GW and HSS functionality. A PLMN identity is dedicated to IOPS mode of operation and is broadcast in System Information by the eNodeB when IOPS mode is in operation. Only authorized IOPS-enabled UEs can access a PLMN indicated as an IOPS PLMN. Support of application services over the IOPS network will be based upon the LTE-Uu radio interface and EPS bearer services supported by the Local EPC. An IOPS network will provide local connectivity services, i.e. for an IP PDN type, IP address assignment and local routing in the IOPS network. For an IP PDN type, During the attachment procedure to the local EPC a local IP address is assigned to the UE as per the standard procedure when attaching to a Macro EPC. The Local EPC acts as a router among the UEs locally attached to the same IOPS network. When operating in IOPS mode IOPS-enabled UEs only use the appropriate USIM credentials defined in the UICC, i.e. those defined exclusively for use in an IOPS PLMN.

An IOPS-enabled UE has the dedicated IOPS PLMN identity configured in a separate dedicated USIM application as an HPLMN along with the Access Class status of 11 or 15, subject to regional/national regulatory requirements and operator policy. An IOPS-enabled UE can display information on available PLMNs, including the IOPS PLMN, assisting the user to activate an appropriate USIM application. Subject to user preferences, e.g. to maintain a group communication, the user can perform a manual USIM application switch at any time. When an authorized IOPS-enabled UE, with the dedicated IOPS USIM application activated, selects an IOPS-mode cell, it selects the dedicated IOPS PLMN identity, attaches to the IOPS PLMN (supported by the Local EPC) and is authenticated using security procedures as specified in TS 33.401 and the security credentials from the active IOPS USIM application.

An IOPS network can comprise either:

• a Local EPC and a single isolated IOPS-capable eNodeB, which may be co-located or have connectivity to the Local EPC; or
• a Local EPC and two or more IOPS-capable eNodeBs, which have connectivity to a single Local EPC.

Existing procedures described in TS 36.300 can be used to achieve dynamic configuration of the S1-MME interface. An IOPS-capable eNodeB can be pre-provisioned with IP endpoint information, relating to the MMEs of one or more candidate Local EPC instances. For each local MME in turn the eNodeB can try to initialize a SCTP association. Once SCTP connectivity has been established, the eNodeB and local MME exchange application level configuration data over the S1-MME application protocol with the S1 Setup Procedure (see TS 36.413). In line with local operator policies the eNodeB can be provisioned with the IP endpoint of a preferred Local EPC MME instance and the IP endpoints of one or more alternative Local EPC MME instances. The alternative Local EPC instances will be used if an S1-MME path cannot be established with the local MME of the preferred Local EPC instance. All Local EPCs deployed by a public safety authority / operator assume the same PLMN-Id. In order to achieve the broadcast of different TAIs on separate IOPS networks the TACs broadcast by the cells of eNodeBs connected to different Local EPCs are distinct to ensure the required UE mobility behaviour (see clause K.2.5). Therefore, the TAC broadcast by the cells of an eNodeB operating in IOPS mode will be dependent upon the Local EPC to which the eNodeB has established an S1-MME connection. If the scope of service of a Local EPC is a single eNodeB, then all cells served by the eNodeB share the same TAC (assigned for use in IOPS mode) and neighbouring eNodeBs that are also operating in IOPS mode with the same dedicated PLMN-Id are assigned different TACs (resulting in different TAIs) so a TAU attempt is triggered upon mobility. If multiple eNodeBs are configured to be served by a single Local EPC, configuration of TAIs for IOPS can be done according to local operator policies in such a way that a reselection to a cell operating a PLMN in normal mode always triggers an attach request. If sharing the same PLMN-Id, it is assumed the TAC assigned to cells in a Nomadic EPS would be different from the TACs assigned to infrastructure eNodeBs operating in IOPS mode, so as to trigger a TAU between these systems. The support by IOPS network entities of S1-flex and/or eMBMS is up to local operator policy and configuration.

The decision by an IOPS-capable eNodeB to enter IOPS mode of operation is made in accordance with the local policies of the RAN operator. Such policies can be affected by any RAN sharing agreements that are in place. In situations when the backhaul to the Macro EPC is lost and an eNodeB can start IOPS mode of operation based on local policies, or an eNodeB is deployed as part of a Nomadic EPS, the following eNodeB behaviour is expected:

• If the eNodeB can reach a Local EPC for IOPS mode of operation, the eNodeB uses the Local EPC.
• If the eNodeB cannot reach a Local EPC, then the eNodeB enters a state where UEs do not attempt to select the cells under its control.

In this release of the specification IOPS networks will be established by the independent actions of each eNodeB entering IOPS mode of operation. An IOPS network comprising two or more eNodeBs will be established as a result of multiple eNodeBs entering IOPS mode of operation and establishing S1-MME paths to the local MME of the same Local EPC instance. An eNodeB in IOPS mode of operation, indicates/broadcasts the IOPS PLMN cell(s) as "Not Barred" & "Reserved for Operator Use", for the IOPS PLMN identity, as defined in TS 36.304. This "Cell Reserved for Operator Use" feature will allow the IOPS-enabled UEs to get access to the IOPS network while barring other non-IOPS-enabled UEs in the same area. The dedicated IOPS USIM application configuration (clause K.2.2) is restricted to use only by users authorised to access a network in IOPS mode of operation. When a backhaul to the Macro EPC is re-established, the S1 connections to the Local EPC are released according to the local IOPS network policies, to move the UEs to Idle mode, and IOPS mode of operation ceases. The PLMN identity of the Macro EPC is announced by the eNodeB so that UEs reselect the normal PLMN and attach afresh to the Macro EPC. Figure K.2.4-1 provides an example of the basic steps involved in IOPS network establishment, access and termination.

A number of distinct UE mobility scenarios can be identified given the following assumptions:

• multiple eNodeBs can be configured to be served by a single Local EPC;
• a single dedicated PLMN-Id will be advertised by all eNodeBs operating in IOPS mode (of a given public safety authority/operator);
• the TACs broadcast by cells (eNodeBs) served by different Local EPCs will be different.

The mobility scenarios that can be distinguished are: The expected mobility behaviour in each of these scenarios is summarised in Table K.2.5-1.