UE-Triggered L1/L2 Handover with MAC CE Signaling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current 5G New Radio networks face challenges in reducing latency and signaling overhead during handovers, particularly in UE-triggered lower layer-based handovers, due to unclear conditions, metrics, and procedures for Layer 1/Layer 2 signaling.
Innovation Solution
The implementation of UE-triggered Layer 1/Layer 2 handover procedures, where the user equipment (UE) triggers handovers based on conditions such as reference signal quality and interference metrics, using L1/L2 filters and configured by RRC signaling, with options for direct synchronization to the target cell and controlled handover requests through MAC CE or PUCCH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If UE-triggered lower layer-based handover procedures are implemented, then latency is reduced and network efficiency is improved, but signaling overhead and procedure complexity increase due to unclear conditions and metrics for Layer 1/Layer 2 signaling
Solution Approach 1:
The patent applies parameter changes by introducing specific measurable metrics (RSRP, RSRQ, SINR) and configurable thresholds to determine handover triggering conditions. The network configures parameters such as measurement filters, reporting thresholds, and handover margins, transforming the handover decision from an ambiguous process to one based on quantifiable parameter comparisons. This resolves the contradiction by providing clear numerical criteria that reduce latency while maintaining manageable complexity through standardized parameter sets.
Solution Approach 2:
The patent implements feedback mechanisms where the UE continuously measures reference signals and provides measurement reports to the network based on configured criteria. The network uses this feedback to adjust handover parameters and make informed decisions. This feedback loop reduces handover latency by enabling proactive handover preparation while managing complexity through structured information exchange between UE and network entities.
2Productivity
If UE proactively triggers handovers based on real-time measurements, then network efficiency and user experience are improved, but signaling overhead increases due to frequent measurement reports and handover requests
Solution Approach 1:
The patent applies partial action by implementing selective measurement reporting where the UE only triggers handover procedures when specific conditions are met (e.g., threshold crossings, hysteresis margins). Instead of reporting all measurements continuously, the system uses event-triggered reporting based on configured criteria such as A3 events (neighbor becomes offset better than serving). This reduces signaling overhead while maintaining network efficiency by acting only when necessary.
Solution Approach 2:
The patent implements preliminary action through advance handover preparation where the network pre-configures measurement parameters, thresholds, and target cell information before actual handover is needed. The UE performs measurements and evaluates conditions in advance, allowing the network to prepare handover resources beforehand. This reduces the need for frequent signaling during the actual handover execution, lowering overall signaling overhead while improving network efficiency.
3Speed
If Layer 1/Layer 2 signaling is used for handover triggering, then handover speed is increased, but measurement precision and decision accuracy may be compromised due to limited measurement filtering capabilities at lower layers
Solution Approach 1:
The patent applies segmentation by dividing the handover measurement process into distinct layers: Layer 1 performs rapid signal strength measurements for quick handover detection, while Layer 3 (RRC) performs more sophisticated measurement filtering and evaluation. The measurement filter operates on Layer 1 measurements to produce filtered results that are more stable and accurate. This segmented approach enables fast handover triggering at Layer 1 while maintaining decision accuracy through Layer 3 filtering and validation.
Solution Approach 2:
The patent introduces an intermediary measurement filter that processes raw Layer 1 measurements before they are used for handover decisions. The filter smooths out rapid fluctuations in signal measurements while preserving the essential handover triggering information. This intermediary filtering layer reconciles the conflict by enabling fast Layer 1 measurements to be translated into more reliable handover decisions, maintaining both speed and precision.
Data Source
AI summary
Performing a UE-triggered lower layer-based handover may include, based on measurements associated with both a source gNB and a target gNB, determining that a UE-triggered handover utilizing layer 1 or layer 2 is to be performed. First uplink resources configured by the source gNB for a dedicated scheduling request may be determined. The dedicated scheduling request may be generated at the UE to request second uplink resources from the gNB for a physical uplink shared channel (PUSCH) a handover request in a media access control (MAC) control element (CE). The handover request carried by the MAC CE for the source gNB may be generated. In response to the handover request, a handover command from the source gNB associated with performing a handover procedure from the source gNB to the target gNB may be processed.