Layer 2 Mobility Handover Timing Advance Mechanism
Find Innovative SolutionsGenerate Solutions
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 service requirements of future mobile communication systems.
Innovation Solution
The method involves transmitting UECapabilityInformation to the base station, receiving RRCReconfiguration, and performing L2 mobility by determining Timing Advance between downlink and uplink, allowing for seamless handovers with reduced interruption time by managing PDCCH orders and preamble transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 measurements and RRC signaling are used for cell handover, then handover reliability is improved, but interruption time and latency increase
Solution Approach 1:
The patent segments the handover process into two distinct types: L3 mobility (traditional RRC-based handover) and L2 mobility (new MAC CE-based handover). This segmentation allows the system to choose different handover mechanisms based on service requirements, enabling low-latency handovers for URLLC services while maintaining reliable handovers for other services through the traditional L3 mechanism.
Solution Approach 2:
The patent introduces MAC Control Elements (MAC CEs) as an intermediary mechanism between the physical layer and RRC layer for handover execution. This intermediary allows handover commands to be transmitted and executed at the MAC layer without requiring full RRC reconfiguration, thereby reducing interruption time while maintaining handover reliability through the structured MAC CE format and confirmation mechanism.
2Reliability
If L3 measurements and RRC signaling are used for cell handover, then handover completeness is improved, but overhead increases
Solution Approach 1:
The patent extracts the essential handover execution function from the RRC signaling layer and places it at the MAC layer through MAC CEs. This extraction removes the heavy RRC reconfiguration overhead while retaining the core handover functionality, reducing signaling overhead by eliminating the need for complete RRC message exchanges during handover execution.
Solution Approach 2:
The patent segments handover signaling into two parts: L3 mobility signaling (RRC-based) for complete handover management and L2 mobility signaling (MAC CE-based) for rapid handover execution. This segmentation allows the system to use lightweight MAC CE signaling for the critical handover execution phase, reducing overall signaling overhead while maintaining handover completeness through the coordinated use of both signaling types.
3Area of stationary object
If traditional handover mechanism is used, then service coverage is improved, but latency increases
Solution Approach 1:
The patent introduces dynamic handover mechanism selection, allowing the system to adaptively choose between L3 mobility and L2 mobility based on service requirements and radio conditions. This dynamics enables the system to use fast L2 handover for time-critical services within coverage areas while falling back to reliable L3 handover when needed, optimizing both latency and service coverage adaptively.
Solution Approach 2:
The patent changes the handover execution parameters by introducing a new handover type indicator in MAC CEs that specifies whether to execute L3 or L2 mobility. This parameter change allows the same MAC CE structure to support both traditional and accelerated handover modes, enabling low-latency handovers for specific services while maintaining backward compatibility and broad service coverage through parameter-based differentiation.
Data Source
AI summary
A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes transmitting the UECapabilityInformation to the base station, receiving a RRCReconfigruation from the base station, receiving a PDCCH order from the base station, transmitting a preamble to the base station based on the PDCCH order, receiving a response from the base station and determining Timing advance between downlink and uplink (TTA). If the type1 PDCCH order was received, the terminal determining TTA of a first cell based on the first field (TAC) and the subcarrier spacing for a first PUSCH transmission. The first cell is the cell where the first PDCCH order was received. If the type2 PDCCH order was received, the terminal determining TTA of a second cell based on the first field and the subcarrier spacing for the preamble transmission and the second field (CMG identifier).