Inter-RAT Handover Signaling via Direct RAN Interface
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Solution Overview
Problem
Current handover procedures between the Next Generation (NG) System and LTE systems do not adequately transfer handover signaling messages on a direct inter-base-station interface, leading to incomplete information for handover execution.
Innovation Solution
The proposed solution involves a method where a target RAN node in the NG System receives a handover request message from a source RAN node in the LTE System on a direct interface, and subsequently receives slice information and flow information from the core network to control the communication of the radio terminal based on this information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If handover procedures are implemented between NG System and LTE systems, then radio terminal mobility is enabled, but signaling message transfer completeness deteriorates
Solution Approach 1:
The handover signaling process is segmented into multiple distinct message exchanges: Handover Request, Handover Request Acknowledge, and Handover Command. Each message carries specific information elements (slice information, flow information, radio resource configuration) that are transferred separately through the direct interface, ensuring complete information transfer while enabling Inter-RAT handover capability.
Solution Approach 2:
A direct interface is introduced as an intermediary communication channel between the source RAN node and target RAN node. This intermediary enables reliable transfer of handover signaling messages and associated information elements (slice information, flow information) without relying on existing core network routing paths, thereby preventing information loss during handover.
2Loss of information
If direct interface signaling transfer is implemented, then handover information completeness is improved, but network interface complexity increases
Solution Approach 1:
The direct interface is designed with multi-functionality, serving both as a control plane channel for handover signaling transfer and as a mechanism for transferring user plane data. By consolidating multiple functions into a single interface, the need for separate dedicated signaling interfaces is eliminated, thereby reducing overall network interface complexity while ensuring complete handover information transfer.
3Reliability
If slice information and flow information are transferred during handover, then QoS continuity is improved, but signaling message size increases
Solution Approach 1:
Slice information and flow information are transferred in advance during the handover preparation phase (Handover Request and Handover Request Acknowledge messages) before the actual handover execution. This preliminary transfer ensures QoS parameters are pre-configured at the target RAN node, enabling seamless QoS continuity during handover without requiring additional signaling messages after connection establishment.
Data Source
AI summary
In response to receiving from a source RAN node (2), on a direct interface (101), a message requesting a handover of a radio terminal (1) from a first network to a second network, a target RAN node (3) receives at least one of slice information and flow information from a core network (5), and controls communication of the radio terminal (1) based on at least one of the slice information and the flow information. The slice information relates to a network slice in the second network. The flow information relates to at least one session to be established in the second network, serving as a bearer-less network, in order to transfer at least one packet flow of the radio terminal (1). It is thus possible, for example, to provide an Inter-RAT handover procedure involving transfer of handover signaling messages on a direct inter-base-station interface.