Temporary Reference Signal-Based SCell Activation via RRC
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Solution Overview
Problem
Current methods for Secondary Cell (SCell) activation in wireless communications, particularly in carrier aggregation scenarios, face delays due to the need for synchronization with the first Synchronization Signal Block (SSB), which can take several seconds, hindering fast activation especially during high-volume data arrival.
Innovation Solution
The introduction of temporary reference signals (TRSs) allows for immediate activation of SCells by providing additional reference signals for the User Equipment (UE) to measure and synchronize, reducing the activation time by using aperiodic tracking reference signals (A-TRSs) triggered through Radio Resource Control (RRC) messages or Medium Access Control (MAC) Control Elements (CEs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE waits for the first Synchronization Signal Block (SSB) to achieve synchronization during SCell activation, then synchronization accuracy is improved, but activation delay increases to several seconds
Solution Approach 1:
The network transmits temporary reference signals (TRSs) before the first SSB arrives during the SCell activation process. These preliminary reference signals allow the UE to perform measurements and achieve synchronization ahead of time, eliminating the need to wait for the SSB. The TRSs are transmitted at a known time point after the activation command, enabling the UE to complete synchronization measurements before the SSB arrival and reduce activation delay while maintaining synchronization accuracy
Solution Approach 2:
Temporary reference signals (TRSs) are introduced as an intermediary element between the activation command and the first SSB. The TRSs serve as a bridge that enables the UE to perform synchronization measurements without directly relying on the SSB arrival time. This intermediary mechanism allows the UE to achieve synchronization based on TRS measurements while the SSB is being prepared, effectively decoupling the activation timing from the SSB arrival and reducing overall activation delay
2Speed
If the network configures dormant BWP for SCell to enable fast activation, then activation speed is improved, but the UE stops monitoring PDCCH and transmitting SRS/PUSCH/PUCCH during dormant state
Solution Approach 1:
The system dynamically transitions the SCell between dormant BWP and active BWP states based on traffic conditions. When fast activation is needed, the UE is configured with a dormant BWP that allows quick state transitions. The network can trigger the UE to switch from dormant to active state using DCI or MAC CE commands when data transmission is required, enabling the SCell to provide immediate data transmission capability without the several-second delay of traditional activation while maintaining the ability to quickly deactivate when not in use
Data Source
AI summary
A method performed by a user equipment, UE, for temporary reference signal-based secondary cell, SCell, activation via radio resource control, RRC, is provided. The method includes receiving a RRC message indicating that the SCell is to be activated. The RRC message includes configuration information associated with a temporary reference signal, TRS. Based on the configuration information in the RRC message, the UE receives the TRS. The UE transmits a channel state information, CSI, report for the SCell based on the TRS.