DMRS-Based CQI Reporting for URLLC Latency
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Solution Overview
Problem
Conventional channel state information (CSI) reporting methods are inadequate for ultra-reliable low latency communication (URLLC) systems due to high latency and reliability requirements, as they rely on aperiodic CSI reporting based on CSI-RSs, which is too slow and may provide outdated information during retransmissions.
Innovation Solution
Implementing demodulation reference signal (DMRS) based CQI reporting, where user equipment (UE) calculates and reports channel quality indicators (CQI) based on DMRS received from the base station, allowing for faster and more accurate reporting, including hybrid automatic repeat request (HARQ) feedback, to reduce latency and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aperiodic CSI reporting based on CSI-RS is used, then channel state information can be reported, but the reporting latency is high and the information may be outdated during retransmissions
Solution Approach 1:
The patent changes the fundamental parameter of reference signal type from CSI-RS to DMRS. By using DMRS which is transmitted with every PDSCH including retransmissions, the CQI reporting latency is reduced and the information remains up-to-date, directly resolving the contradiction between reliability and time loss
Solution Approach 2:
The patent configures the UE to calculate CQI based on DMRS in advance for potential retransmissions. The UE prepares CQI reports using DMRS that will be available when needed, so when a retransmission occurs, the CQI information is already ready and current, eliminating the delay of waiting for new CSI-RS measurements
2Reliability
If CQI reporting is performed frequently to maintain up-to-date information, then reliability improves, but signaling overhead increases
Solution Approach 1:
The patent makes the DMRS serve multiple functions: it is used for both demodulation of the PDSCH and for CQI calculation. This multi-functionality allows CQI reporting to be derived from existing reference signals without requiring additional dedicated resources, thus improving reliability while minimizing overhead
Solution Approach 2:
The system uses the DMRS that is already being transmitted for channel demodulation purposes to also serve CQI reporting. The existing DMRS structure and transmission resources are leveraged to provide CQI information, eliminating the need for separate CQI measurement resources and reducing overall signaling overhead
Data Source
AI summary
Methods, systems, and devices channel quality indicator (CQI) reporting based on demodulation reference signal (DMRS) from a base station are described. In some cases, a base station may configure a user equipment (UE) with such DMRS based CQI reporting (e.g., by transmitting a CQI reporting configuration to the UE). The CQI reporting configuration may specify the UE is to report CQI based on DMRS and, in some cases, may configure the UE to report the CQI with hybrid automatic repeat request (HARQ) feedback. A UE may receive a control message that indicates a resource for reception of a downlink transmission and an uplink control resource for transmission of CQI information. The UE may identify a DMRS of the downlink transmission, calculate a CQI based on the DMRS, and transmit the calculated CQI to the base station via the uplink control resource indicated by the received control message.