Page 480 - 5G Basics - Core Network Aspects

1 Core network aspects

6.3.2 Resource and admission control functions (RACF)

RACF is responsible for resource and admission control in NGN. When a UE attaches to an access network or
moves to another access network, an admission decision is required for the access network. If the decision
is to admit, appropriate network resources must be reserved. Network resources should be dynamically
configured according to the new access network that a mobile UE attaches to. The handover decision and
control functional entity (HDC-FE) requests RACF to re-provision the resource and QoS for the flows of the
moved UE. For that purpose, the HDC-FE is required to submit binding information for the flows of the moved
UE to the PD-FE in RACF. If the original session information is not visible at the resource and QoS enforcement
points of RACF, RACF is required to have the capability to provision resources and QoS for the aggregated
flows.
NOTE – Some access technologies manage QoS locally rather than through RACF for movements within a limited scope.

The mobility architecture in this Recommendation supports:
• proactive QoS resource reservation;
• adaptive QoS resource management.

6.3.3 Mobility management and control functions (MMCF)
The MMCF are responsible for mobility management and control in NGN. As defined in [ITU-T Q.1707], MMCF
is composed of two sub-functions, LMF and HCF for location management function and handover control
function, respectively. The LMF and HCF as defined in [ITU-T Q.1707] are composed of several functional
entities which are described in clause 6.4.

6.3.4 Mobility transport functions
In order to support mobility in the NGN network, mobility-specific transport functions are needed in the
forwarding plane of the transport stratum. These functions are defined in order to provide handover
enforcement in the transport nodes.
In this Recommendation, we define one functional entity to provide handover execution at layer 2, and a
function embedded within the EN-FE, ABG-FE and IBG-FE to provide handover execution at layer 3. The
definition of those mobility node functions makes it easier to explain forwarding plane procedures in mobility
functional scenarios.

6.4 Functional entities

The functional entities required for support of mobility in the control plane of the transport stratum are:
• mobile location management functional entity (MLM-FE);
• handover decision and control functional entity (HDC-FE);
• network information distribution functional entity (NID-FE);
• network information repository functional entity (NIR-FE).

The following functional entity has been defined within the forwarding plane of the transport stratum for
support of mobility:

• Layer 2 handover execution functional entity (L2HE-FE).
In addition to the functions contained within the above-listed functional entities, the following function has
been identified for support of mobility:
• Layer 3 handover execution function (L3HEF), which is embedded within the EN-FE, ABG-FE, and
IBG-FE in the forwarding plane and communicates with the HDC-FE.
These functional entities and functions are described in the following clauses.

6.4.1 Mobile location management functional entity (MLM-FE)
The mobile location management functional entity (MLM-FE) has the following responsibilities:
• in the case of network-based mobility, initiating location registration on behalf of the UE;

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