Page 1369 - 5G Basics - Core Network Aspects

Signalling aspects 3

I.2 Signalling protocol procedures

In this clause, attention is given to the signalling flow to support seamless handover in heterogeneous radio
access technologies. In order to illustrate the signalling flow, we introduce the high-level requirements
required to support seamless handover.

Handover refers to the ability of transferring an ongoing call or data session from one NE to another NE,
without any interruption, to the ongoing services. The handover procedure for radio resource allocation
comprises four stages, as shown in Figure I.1.
In the first stage, handover initiation starts from the link corruption detection until the request for initiating
a new link.

In the second stage, handover preparation consists of all steps of link measurements, collection of
information about neighbouring networks, and exchange of information about QoS offered by these
networks.
In the third stage, the handover decision is the procedure to decide whether the connection is to be switched
to a new network based on parameters collected in the handover initiation phase. Radio resource allocation
is decided by the NE or SDN CE, based on the radio link status or the radio resource allocation of neighbouring
RANs.

In the last stage, radio resources (e.g., frequency, time, interface mode and power) are configured by the NE
or SDN CE. MN prepares to connect to the RAN with the newly allocated radio resources as an action of
handover execution. After that, the NE reports its allocated radio resources to the SDN CE and neighbouring
NE.

Figure I.1 – Seamless handover in SDMNs procedures

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