SCell Activation MAC-CE for Low-Latency Aperiodic CSI Reporting
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Solution Overview
Problem
In wireless communication systems, the activation of secondary cells (SCells) is delayed due to the latency in receiving channel state information (CSI) reports, which hinders the network's ability to schedule downlink communications until the CSI report is received, thereby prolonging the SCell activation process.
Innovation Solution
A network entity transmits a single Medium Access Control (MAC)-Control Element (CE) that jointly activates an SCell and triggers aperiodic CSI reporting, along with aperiodic tracking reference signals (AP-TRSs), indicating aperiodic channel and interference measurement resources (AP-CMR/IMR) pairs, allowing the user equipment (UE) to generate and transmit CSI reports with reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a separate MAC-CE is used to trigger aperiodic CSI reporting after SCell activation, then the CSI report can be generated with reduced latency, but the SCell activation process is prolonged due to additional signaling steps
Solution Approach 1:
The patent combines the SCell activation command and aperiodic CSI reporting trigger into a single MAC-CE message. This merging eliminates the sequential signaling steps where a separate trigger would be sent after activation, allowing the UE to initiate CSI reporting immediately upon receiving the activation command, thus reducing both activation duration and CSI generation latency simultaneously.
Solution Approach 2:
The MAC-CE is configured in advance to contain both the activation command and the CSI reporting trigger. By preparing this combined message beforehand with pre-configured resource indicators (AP-CMR/IMR pairs), the network eliminates the need for additional signaling steps, allowing the UE to immediately activate the SCell and start CSI reporting without waiting for separate triggers.
2Ease of operation
If multiple MAC-CE messages are exchanged for SCell activation and CSI triggering, then precise control over CSI reporting is achieved, but signaling overhead and activation latency increase
Solution Approach 1:
The patent merges multiple control functions (SCell activation and aperiodic CSI triggering) into a single MAC-CE message. This combined approach maintains precise control over CSI reporting by including specific trigger indicators and resource configuration references within the same message that activates the SCell, thereby eliminating the need for multiple separate signaling exchanges.
Solution Approach 2:
The MAC-CE message is designed with multi-functionality, serving both as an SCell activation command and as a trigger for aperiodic CSI reporting. The message structure includes fields that can indicate both activation parameters and CSI reporting triggers, allowing a single message to perform multiple control functions that previously required separate messages.
3Measurement precision
If aperiodic reference signals are transmitted immediately upon SCell activation, then measurement accuracy is improved, but the activation process is delayed due to waiting for reference signal availability
Solution Approach 1:
The network pre-configures aperiodic channel measurement resources (AP-CMR) and interference measurement resources (AP-IMR) pairs in advance within the MAC-CE message. These reference signal resources are prepared and indicated before the actual SCell activation occurs, allowing the UE to immediately transmit and measure reference signals as soon as the SCell is activated, without waiting for resource configuration or signal availability.
Solution Approach 2:
The patent combines the reference signal resource configuration and the activation command into a single signaling message. By merging the indication of AP-CMR/IMR pairs with the activation command, the UE receives both the authorization to activate the SCell and the specific measurement resources to use, enabling immediate measurement transmission upon activation and eliminating delays associated with separate resource allocation procedures.
Data Source
AI summary
This disclosure provides systems, methods and apparatuses that support channel state information (CSI) reporting techniques for secondary cell (SCell) activation. A user equipment (UE) may receive one or more medium access control-control elements (MAC-CEs) that indicate a secondary cell (SCell) activation command, an aperiodic tracking reference signal (AP-TRS) trigger, and an aperiodic channel state information (AP-CSI) report trigger. The network entity may signal the SCell activation command, the AP-TRS trigger, and the AP-CSI report trigger in the same MAC-CE or in separate MAC-CEs. The UE may receive and measure AP-TRS in accordance with the AP-TRS trigger indicated by the one or more MAC-CEs, and may perform measurements via an aperiodic channel measurement resource (AP-CMR) and an aperiodic interference measurement resource (AP-IMR) in accordance with the AP-CSI report trigger indicated by the one or more MAC-CEs. Accordingly, the UE may transmit an AP-CSI report associated with the measurements.