Aperiodic SRS Transmission via Downlink Grant in Carrier Aggregation
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Solution Overview
Problem
In carrier aggregation systems, there is a lack of defined methods for aperiodic sounding reference signal (SRS) transmission, specifically determining which uplink component carrier (UL CC) to use for aperiodic SRS transmission among multiple UL CCs, which affects channel estimation and scheduling reliability.
Innovation Solution
An aperiodic SRS transmission method where the specific UL CC is determined based on a downlink (DL) grant, with the DL grant containing a message to trigger the transmission, and the UL CC is linked to the DL CC that transmits the DL grant, using system information to establish this link, and allocating the SRS within the available bandwidth of the specific UL CC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If aperiodic SRS transmission is implemented in carrier aggregation systems, then channel estimation capability is improved, but there is no defined method for determining which UL CC to use, causing scheduling reliability to deteriorate
Solution Approach 1:
The patent introduces a downlink grant as an intermediary mechanism that carries a trigger message to indicate which uplink component carrier should be used for aperiodic SRS transmission. This intermediary resolves the ambiguity by providing explicit signaling from the network to the user equipment, allowing the UE to determine the correct UL CC based on the received trigger message without requiring complex autonomous decision-making logic.
2Productivity
If multiple UL CCs are configured for carrier aggregation, then system capacity is improved, but the complexity of determining the specific UL CC for aperiodic SRS transmission increases
Solution Approach 1:
The system implements self-service through automated trigger message signaling, where the network automatically provides the necessary information (via downlink grant trigger messages) to guide the UE's SRS transmission decisions. This eliminates the need for complex autonomous determination algorithms at the UE side, as the system itself provides the answer through standardized signaling mechanisms.
Solution Approach 2:
The downlink grant mechanism serves multiple functions: it provides scheduling information, carries trigger messages for aperiodic SRS, and indicates the target UL CC for SRS transmission. This multi-functional approach consolidates what could be separate complex signaling mechanisms into a single universal control structure, reducing overall system complexity while maintaining support for multiple UL CCs.
Data Source
AI summary
A method for transmitting, by a user equipment (UE), an aperiodic sounding reference signal (SRS) in a wireless communication system, the method including receiving, via a physical downlink control channel (PDCCH), downlink control information (DCI) for downlink scheduling. The DCI includes an SRS request for triggering transmission of the aperiodic SRS. The method further includes detecting the SRS request; and transmitting the aperiodic SRS on an uplink (UL) component carrier (CC), which is linked to a downlink (DL) CC in which a physical downlink shared channel (PDSCH) is scheduled by the DCI, among a plurality of UL CCs. If a carrier indicator field (CIF) is configured, the UL CC is indicated by the CIF.