CSI-RS Configuration in DRS Resources for NR-U
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Solution Overview
Problem
In New Radio-Unlicensed (NR-U) systems, the transmission of channel state information resource signals (CSI-RS) faces challenges due to listen-before-talk (LBT) procedures, which can delay or prevent the transmission of downlink control information (DCI), especially in unlicensed spectrum where CSI-RS have lower priority compared to discovery reference signals (DRS).
Innovation Solution
Configuring CSI-RS as part of DRS resources to leverage the higher priority channel access mechanism, allowing CSI-RS transmission using category-2 LBT, and signaling CSI-RS configurations through DCI to user equipment (UE) devices, enabling essential measurements like RLM or time-frequency offset tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSI-RS transmission uses standard downlink priority mechanism, then transmission follows normal scheduling procedures, but transmission is delayed or blocked by LBT procedures in unlicensed spectrum
Solution Approach 1:
The patent combines CSI-RS transmission with DRS transmission by configuring CSI-RS resources within DRS resource sets. This merging allows CSI-RS to inherit the higher priority channel access mechanism of DRS, enabling transmission without being blocked by standard LBT procedures that would otherwise delay or prevent CSI-RS transmission in unlicensed spectrum.
Solution Approach 2:
The patent changes the channel access parameter by assigning category-2 LBT (higher priority) to CSI-RS transmissions instead of the standard downlink priority. This is achieved by configuring CSI-RS as part of DRS resources, which automatically grants the higher priority channel access category, thereby reducing transmission delays and improving reliability in unlicensed spectrum.
2Ease of operation
If CSI-RS is transmitted with lower priority in unlicensed spectrum, then normal scheduling is maintained, but channel access is blocked by higher priority DRS transmissions
Solution Approach 1:
The patent merges CSI-RS configuration with DRS resource configuration, allowing CSI-RS to be transmitted using the same high-priority channel access mechanism as DRS. This resolves the contradiction by maintaining scheduling simplicity while dramatically improving channel access reliability, as CSI-RS transmissions are no longer blocked by the lower priority status that would cause them to yield to DRS transmissions.
3Adaptability or versatility
If separate configuration mechanisms are used for CSI-RS and DRS, then independent control is maintained, but system complexity increases
Solution Approach 1:
The patent makes the DRS resource configuration mechanism universal by enabling it to configure both DRS and CSI-RS resources through a single configuration framework. This multi-functionality allows the system to maintain configuration flexibility while reducing complexity, as one unified configuration mechanism replaces what would otherwise require separate independent configuration procedures for CSI-RS and DRS.
Data Source
AI summary
Systems, methods, and circuitries are provided for configuring and indicating channel state information resource signals (CSI-RS) using discovery reference signal (DRS) resources. An example method includes determining discovery reference signal (DRS) resources for use in carrying channel state information reference signals (CSI-RS); generating CSI-RS configuration information that defines at least one CSI-RS using the DRS resources; and signaling the CSI-RS configuration information to a user equipment (UE) device.