SCELL Activation Time Reduction via Preliminary UE Measurements
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Solution Overview
Problem
In LTE systems, the activation time of secondary cells (SCELLs) for carrier aggregation is often lengthy, especially in scenarios where the UE lacks prior knowledge of the SCELL, leading to energy inefficiencies and scheduling delays, particularly due to the need for reacquiring synchronization and AGC information.
Innovation Solution
The proposed solution involves early measurement attempts by the UE to acquire prior knowledge of AGC control, RF characteristics, and timing/frequency synchronization information, either before or after SCELL configuration, and adaptive measurement intervals based on a state machine to ensure quick SCELL activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the UE performs measurements and acquires prior knowledge before SCELL configuration, then the SCELL activation time is reduced, but the UE complexity and processing overhead increase
Solution Approach 1:
The UE performs measurements and acquires synchronization and AGC information of candidate SCELLs before receiving the SCELL configuration. This preliminary action ensures that when the SCELL activation command is received, the UE already has valid prior knowledge, significantly reducing activation time. The measurement phase occurs in advance during which the UE scans candidate frequencies and stores synchronization signals and AGC values for rapid activation.
2Speed
If the SCELL activation command is received immediately after configuration, then the network responsiveness is improved, but the activation time increases due to lack of prior knowledge
Solution Approach 1:
The network configures the UE with a list of candidate SCELL frequencies and measurement parameters before sending the activation command. The UE performs measurements on these candidates in advance, acquiring synchronization and AGC information. When the activation command is received, the UE can quickly identify and activate the appropriate SCELL using pre-acquired knowledge, maintaining fast network responsiveness while minimizing activation time.
Solution Approach 2:
The system dynamically adapts the measurement and activation process based on network conditions and UE capabilities. The network can configure different measurement cycles and candidate SCELL lists according to traffic patterns and mobility conditions. The UE adjusts its measurement strategy dynamically, performing measurements only when beneficial, thus balancing network responsiveness with activation speed.
3Reliability
If the UE performs regular measurements on deactivated SCELL, then the prior knowledge is maintained, but the energy consumption increases
Solution Approach 1:
The UE performs measurements on deactivated SCELLs periodically rather than continuously, based on configured measurement cycles. The measurement frequency is adjusted dynamically - more frequent measurements when the SCELL is likely to be activated soon, and less frequent measurements when activation is less probable. This periodic approach maintains the validity of prior knowledge while significantly reducing energy consumption compared to continuous monitoring.
Data Source
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AI summary
An effective SCELL activation procedure is proposed to reduce the SCELL activation time. For carrier aggregation, a secondary cell (SCELL) needs to be configured and then activated before a UE can perform normal operation. In a first embodiment, the UE performs measurements on a list of candidate SCELLs before SCELL configuration. In a second embodiment, the UE performs measurements on a configured SCELL with high priority after the SCELL is configured. In a third embodiment, the UE performs deactivated-state SCELL measurements with adaptive SCELL measurement interval based on a configured measurement cycle and a state machine. Small SCELL activation time allows energy saving and network scheduling gain.