Conditional Handover for NR Cell Addition in 5G NSA
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Solution Overview
Problem
In 5G wireless communication systems, the addition of a New Radio (NR) cell in non-standalone mode is often delayed due to failures in transmitting NR measurement reports or the anchor cell failing to add secondary cells, leading to extended wait times for users equipped with multi-SIM cards operating in different frequency ranges.
Innovation Solution
The implementation of a conditional handover (CHO) feature allows user equipment (UE) to receive a CHO command from an anchor cell, deconfigure NR measurement objects, and perform a handover to a second anchor cell with improved link quality, facilitating the addition of secondary NR cells for simultaneous communication across different frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits for NR measurement report transmission or anchor cell to add secondary cells, then NR cell addition can be completed, but the process experiences extended wait times and delays
Solution Approach 1:
The network pre-configures conditional handover (CHO) commands and measurement objects to the UE before NR cell addition is actually needed. This preliminary configuration enables the UE to immediately execute handover when conditions are met, eliminating the need to wait for measurement report transmission and secondary cell addition procedures, thus resolving the time delay while ensuring reliable NR cell addition.
2Stability of the object's composition
If the UE remains connected to the first anchor cell, then the existing connection is maintained, but NR cell addition fails due to measurement report transmission failures or anchor cell issues
Solution Approach 1:
The network pre-configures multiple CHO commands with different target anchor cells and corresponding measurement objects before NR cell addition is attempted. When the first anchor cell fails to add secondary cells or transmission fails, the UE can immediately switch to a pre-configured second anchor cell using the pre-configured measurement objects, ensuring NR cell addition success without compromising connection stability.
Solution Approach 2:
The system prepares backup CHO configurations and measurement objects in advance to cushion against potential failures in the primary anchor cell. This beforehand cushioning ensures that if the first anchor cell fails to add secondary cells or transmission fails, the UE has alternative configurations ready to execute, thereby ensuring NR cell addition success while maintaining connection stability.
3Reliability
If the UE performs frequent handovers to maintain optimal connection, then link quality is improved, but ping pong handovers occur causing instability
Solution Approach 1:
The network pre-configures multiple CHO commands with different target anchor cells and associates each with specific measurement objects and triggering conditions. The UE evaluates these pre-configured options against current measurement results and only executes handover when conditions are met, avoiding unnecessary frequent handovers. This approach improves link quality by selecting appropriate anchor cells while preventing ping pong handovers through condition-based execution, thereby maintaining handover stability.
Data Source
AI summary
Aspects relate to techniques for expediting New Radio (NR) cell addition in non-standalone (NSA) mode. The UE may receive a conditional handover (CHO) command from a first anchor cell operating a first frequency range (e.g., a Long Term Evolution (LTE) frequency range) that enables the UE to subsequently select a different anchor cell to which to perform a handover. The UE may then receive a deconfiguration from the first anchor cell of a measurement object for secondary cell addition in a second frequency range (e.g., a NR frequency range). Based on the CHO command and the deconfiguration of the measurement object, the UE may then perform a handover to a second anchor cell in the first frequency range to facilitate addition of at least one secondary cell in the second frequency range.