Page 500 - 5G Basics - Core Network Aspects

1 Core network aspects

1.11 The TLM-FE configures the NAC-FE as in step 1.11 of the previous clause, except that network-
based mobility is indicated. In addition, the address of the MLM-FE(P) and keying material
associated with the MLM-FE(P) are unnecessary and are not passed.
Phase 2: IP configuration

The procedure is as described in clause II.1, numeral 2) of [ITU-T Y.2014], with the following modifications:
2.1-2.2 No change from [ITU-T Y.2014].
2.3 The UE is configured with its persistent IP address as its new local address. It is also configured with
keying material for the security associations with the HDC-FE and, if required, the NID-FE. If it
indicated support for host-based mobility, it may also be given an indication that network-based
mobility is to be used.
2.4 Depending on local arrangements, the NAC-FE may pass the persistent address or the address of the
lower tunnel end point back to the TLM-FE with the profile information.

Phase 3: Mobility location management
3.1 After the (Pre)authentication and (pre)authorization procedure, the TLM-FE pushes an indication to
the MLM-FE(P) that network-based mobility is to be provided.
3.2-3.3 The TLM-FE pushes keying material for communication with the UE during network discovery and
selection to the HDC-FE and NID-FE.
3.4 The MLM-FE(P) notifies the HDC-FE to begin handover. The HDC-FE oversees creation of a new
tunnel as described in clause 7.3.3 and returns the address of the tunnel end point at the lower end.

3.5 The MLM-FE(P) initiates the mobility location management procedure at the MLM-FE(C).
3.6 The MLM-FE(C) records the binding information, notifies the old MLM-FE(P) to delete its mobile
location bindings and responds to the new MLM-FE(P).

Phase 4: Transport location management
As described in clause II.1, numeral 4) of [ITU-T Y.2014].

7.3 Handover
7.3.1 Network discovery and decision

Before the UE can achieve handover to a new access point or network, the network discovery and decision
procedure must be performed. The information needed to make the handover decision includes:

• radio signal strength, from the UE;
• link events, from the L2HE-FE (in the case where the HDC-FE makes the decision);
• static neighbouring network information (e.g., local policies, cost), from the NID-FE;
• resource availability in candidate networks, from RACF;
• applicable UE-specific policy, from the user mobility service profile.

Network discovery is performed by the UE, when it detects alternative access points to which it may move.
The handover decision is the process of choosing an access point to which to move. Network discovery and
the handover decision must consider three cases:
• the network makes the handover decision with input from the UE;

• the UE makes the handover decision with the assistance of information from the network;
• the UE makes the handover decision without assistance from the network.
In the latter two cases the UE can request user input or can be constrained by user intervention.

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