Conditional Handover with Network Slice Availability
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Solution Overview
Problem
Existing conditional handover technologies in 5G networks do not effectively consider network slice area of service (NS-AoS) availability, leading to potential service interruptions when a user equipment (UE) handovers to a cell without available network slices.
Innovation Solution
The proposed solution involves an apparatus and method for a user equipment (UE) to receive a conditional handover configuration from a radio access network node, which includes network slice area of service availability information. The UE then selects a preferred target cell based on this information and the radio condition, allowing it to autonomously perform a handover to a cell with available network slices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs handover based solely on radio conditions without considering network slice availability, then the handover process is simple and fast, but service interruptions occur when handover targets cells without available network slices
Solution Approach 1:
The network provides S-NSSAI location availability information to the UE in advance (in RRCRelease or system information) before handover is needed. This preliminary action enables the UE to know which network slices are available in which cells, so when handover is required, the UE can immediately select a target cell that satisfies both radio conditions and network slice availability, avoiding service interruptions without complex real-time evaluation
2Productivity
If the UE autonomously selects target cells using CHO configuration, then handover efficiency is improved, but the UE may select cells without available network slices causing service disruption
Solution Approach 1:
The network provides feedback information (S-NSSAI location availability) to the UE that guides the autonomous CHO selection process. The UE uses this feedback to evaluate potential target cells not only on radio conditions but also on network slice availability, ensuring that autonomous handover decisions lead to cells that can actually provide the required services
3Reliability
If the network provides detailed S-NSSAI location availability information to all UEs, then service continuity is ensured, but network signaling overhead and processing load increase
Solution Approach 1:
The network provides S-NSSAI location availability information selectively - only to UEs that support this feature and only for the specific S-NSSAIs that the UE is configured with. The information is provided in a compact format (e.g., as a bitmap or list of cell IDs) rather than exhaustive details for all cells and all slices, reducing signaling overhead while maintaining service continuity for supporting UEs
Data Source
AI summary
There is herein disclosed a method for receiving, from a radio access network node, a conditional handover configuration for a plurality of target cells and a radio condition for conditional handover of the UE for a plurality of target cells. The method further comprises receiving, from the radio access network node, an indication that the UE is allowed to select and connect to a preferred target cell from the plurality of target cells. The method further comprises selecting the preferred target cell from the plurality of target cells based on network slice area of service availability information for each target cell configured at the UE and the radio condition and transmitting, a request to connect to the preferred target cell.