Secondary Cell Activation Delay Reduction in NR Carrier Aggregation
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Solution Overview
Problem
Current carrier aggregation techniques in wireless communications face challenges in reducing the SCell activation delay, which can lead to latency during bursty downlink traffic, especially when activating secondary cells in Frequency Range 2 (FR2) without an active serving cell.
Innovation Solution
The method involves receiving a first MAC control element on a primary cell to activate a secondary cell, initiating time-frequency tracking based on a synchronization signal block without waiting for a third MAC control element, and performing a channel state information reporting process using a semi-persistent CSI-RS resource set, allowing for early transmission of a measurement report indicating reference signal received power measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device waits for the third MAC CE to activate the SP CSI-RS resource set before performing time-frequency tracking, then the activation process ensures proper channel state information readiness, but the SCell activation delay increases
Solution Approach 1:
The device performs time-frequency tracking based on SSB indicated in the first TCI state before receiving the third MAC CE for SP CSI-RS activation. This preliminary action allows the device to prepare the SCell in advance, reducing activation delay while maintaining reliability through subsequent CSI reporting based on the SP CSI-RS resource set once activated
Solution Approach 2:
The SCell activation process is segmented into independent stages: (1) receiving first MAC CE and performing time-frequency tracking based on SSB, (2) receiving second MAC CE for TCI state indication, and (3) receiving third MAC CE for SP CSI-RS activation. This segmentation allows parallel processing of tracking and CSI preparation, reducing overall activation delay
2Device complexity
If the device performs time-frequency tracking only after receiving all MAC CEs including the third MAC CE for SP CSI-RS activation, then the activation process maintains strict procedural order, but the data throughput during bursty traffic decreases due to increased latency
Solution Approach 1:
Time-frequency tracking is performed in advance based on SSB before SP CSI-RS activation, allowing the device to be ready for data transmission sooner. The CSI reporting is then performed based on the SP CSI-RS resource set once activated, ensuring proper procedural order while reducing latency for bursty traffic
Solution Approach 2:
The activation procedure allows dynamic timing where time-frequency tracking can start as soon as the first MAC CE and TCI state are received, while CSI reporting waits for SP CSI-RS activation. This dynamic approach optimizes throughput by allowing earlier synchronization without sacrificing CSI accuracy
Data Source
AI summary
A method of activating a secondary cell (SCell) can include receiving on a primary cell (PCell) at a user equipment (UE) a first medium access control (MAC) control element (CE) for activating the SCell, receiving on the PCell a second MAC CE for indicating a first transmission configuration indication (TCI) state for receiving one of a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH) of the SCell, starting to perform a time-frequency tracking process in the SCell based on a synchronization signal block (SSB) indicated in the first TCI state without waiting for an arrival of a third MAC CE on the PCell for activating a semi-persistent (SP) channel state information reference signal (CSI-RS) resource set of the SCell, and performing a CSI reporting process based on the SP CSI-RS resource set activated by the third MAC CE on the SCell.