Layer 2 Uplink Power Control for Seamless Cell Handover
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Solution Overview
Problem
Current 5G mobile communication systems experience significant latency and overhead during cell handovers due to L3 measurements and RRC signaling, leading to increased interruption time, which is not suitable for meeting the stringent requirements of future mobile communication systems.
Innovation Solution
Implementing a method that supports layer 2 mobility by receiving specific RRC messages and MAC CEs, monitoring PDCCH identifiers, adjusting uplink transmission power based on TPC commands, and performing uplink transmissions according to scheduling information, allowing for seamless switching between cells without complete L2 resets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 measurements and RRC signaling are used for cell handover, then reliable cell switching is achieved, but interruption time and overhead increase
Solution Approach 1:
The patent segments the handover process into two distinct types: L3-based handover (using RRC signaling and full L2/L1 resets) and L2-based handover (using MAC CE commands and maintaining L2 continuity). This segmentation allows the system to choose the appropriate handover type based on service requirements, enabling fast handover for time-sensitive services while maintaining reliability for other scenarios.
Solution Approach 2:
The patent changes the control parameter from L3 RRC signaling to L2 MAC CE signaling for certain handover scenarios. By using MAC CE commands instead of RRC reconfiguration messages, the signaling overhead is reduced and processing time is minimized, directly addressing the interruption time issue while maintaining handover reliability through proper power control adjustments.
2Reliability
If L3 measurements and RRC signaling are used for cell handover, then complete L2 reset is performed, but overhead and latency increase
Solution Approach 1:
The patent extracts the essential handover function from the complex L3 RRC signaling layer and implements it at the L2 MAC layer using MAC CE commands. This extraction removes the heavy RRC signaling overhead and L2/L1 reset requirements, keeping only the necessary power control adjustments at L2, thereby reducing device complexity and signaling overhead while maintaining handover completeness.
Solution Approach 2:
The patent performs preliminary configuration of multiple cell groups and their associated TPC commands before handover is needed. The UE is pre-configured with multiple serving cell groups, each with its own TPC command reception and application rules. This preliminary setup enables rapid handover execution without requiring complex real-time configuration changes, reducing both overhead and processing complexity.
3Measurement precision
If TPC command is adjusted during L2 mobility, then uplink power control accuracy is improved, but power control complexity increases
Solution Approach 1:
The patent merges the power control functionality across multiple serving cell groups by implementing a unified TPC command reception and application mechanism at the MAC layer. The UE monitors PDCCH for TPC commands from multiple cell groups and applies them in a standardized manner, combining the power control functions into a single coherent process that maintains accuracy without proportionally increasing complexity.
Solution Approach 2:
The patent applies partial power control adjustments by only modifying the TPC command application for the specific serving cell group undergoing handover, while maintaining existing power control for other cell groups. This partial action approach improves power control accuracy for the transitioning cell without requiring complete reconfiguration of all power control parameters, thereby limiting the increase in complexity.
Data Source
AI summary
A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes receiving from a base station a first RRC message and a second RRC message, receiving from the base station a first MAC CE, monitoring PDCCH for the first identifier and the second identifier, adjusting uplink transmission power based on TPC command in PDCCH addressed by the second identifier, performing uplink transmission based on uplink scheduling information in PDCCH addressed by the first identifier, receiving from the base station a second MAC CE, and adjusting uplink transmission power based on TPC command in PDCCH addressed by the fourth identifier, performing uplink transmission based on uplink scheduling information in PDCCH addressed by the second identifier.