Lower-Layer Mobility Triggering for Low-Latency 5G Handover
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Solution Overview
Problem
Existing wireless communication networks face significant latency and signaling overhead issues during handover procedures due to the use of layer 3 (RRC) messages, which hinder efficient mobility management, especially in 5G and emerging 6G systems.
Innovation Solution
Implementing lower layer triggered mobility (LTM) using layer 1/Layer 2 signaling to facilitate seamless handovers by configuring user equipment (UE) with candidate cells, managing LTM configurations, and performing RLC reestablishment and PDCP recovery without RRC reconfiguration, thereby reducing latency and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If layer 3 (RRC) messages are used for handover procedures, then handover reliability is maintained, but latency and signaling overhead increase
Solution Approach 1:
The patent segments the handover control into multiple layers: layer 1/Layer 2 for fast triggering and execution, and layer 3 for configuration and supervision. This segmentation allows L1/L2 to handle time-critical actions (reducing latency) while L3 maintains reliability through configuration management and failure recovery.
Solution Approach 2:
The patent introduces layer 2 (MAC layer) as an intermediary between layer 3 (RRC) and layer 1 (physical layer). The MAC layer receives handover commands from RRC and executes fast handover triggering based on L1 measurements, acting as a mediator that enables rapid response while maintaining RRC-level reliability through configured fallback mechanisms.
2Reliability
If layer 3 (RRC) messages are used for handover procedures, then handover completeness is ensured, but signaling overhead increases
Solution Approach 1:
The patent extracts the handover triggering function from layer 3 (RRC) and places it at layer 1/Layer 2. This extraction eliminates the need for frequent RRC message exchanges during normal handover execution, reducing signaling overhead while maintaining completeness through pre-configured handover parameters and L3-supervised failure recovery.
Solution Approach 2:
The patent implements preliminary action by having the network pre-configure multiple candidate cells and handover parameters at layer 3 before handover is needed. When handover is triggered at L1/L2, the UE can immediately execute using pre-configured parameters without waiting for additional RRC signaling, reducing overhead while ensuring completeness through pre-validated configurations.
3Speed
If LTM configurations are implemented, then handover speed increases, but device complexity increases
Solution Approach 1:
The patent applies partial action by implementing LTM configurations selectively for specific candidate cells rather than all cells. The network configures LTM parameters only for cells that are likely handover targets based on measurement patterns, reducing UE complexity while maintaining fast handover speed for the most critical scenarios.
Data Source
AI summary
The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments herein disclose methods for performing LTM. The method includes: receiving a LTM configuration in a RRC message indicating whether the UE needs to perform one of: a RLC reestablishment and a PDCP recovery during the LTM to a candidate cell; receiving one of a DL MAC CE or a DL L1 message used for triggering the LTM; performing a MAC operation comprising one of a complete MAC reset and a partial MAC reset; transmitting at least one uplink RRC message, wherein at least one uplink RRC message was transmitted within a specificized time interval before receiving the DL MAC CE or the DL L1 message; and performing at least one of the RLC reestablishment and the PDCP recovery based on the received indication.