Precoded CSI-RS Measurement for MU-MIMO CQI Feedback
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Solution Overview
Problem
In LTE systems, the channel quality index (CQI) feedback based on single user MIMO assumptions does not match the actual downlink channel quality in multi-user MIMO scenarios, leading to inefficient resource allocation and potential decoding errors in terminals.
Innovation Solution
A method where the base station dynamically indicates resource numbers to terminals, allowing them to measure and feedback CQI based on precoded CSI-RS, reducing the need for terminals to measure and feedback CQI for all time-frequency resources, thereby optimizing resource consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the terminal measures CQI for all CSI-RS ports to ensure accurate channel quality feedback, then the measurement precision is improved, but the resource consumption of the terminal increases
Solution Approach 1:
The patent extracts only the necessary CQI measurement from a subset of CSI-RS ports (specifically the port corresponding to the terminal's allocation) rather than requiring measurements from all ports. This extraction approach maintains the accuracy needed for MU-MIMO while significantly reducing terminal processing resources and energy consumption.
Solution Approach 2:
The patent applies local quality by having the terminal measure CQI only on specific time-frequency resources allocated to its designated CSI-RS port, rather than uniformly across all ports. This localized measurement approach optimizes resource usage by concentrating measurement efforts only where needed for the terminal's specific communication channel.
2Loss of information
If the terminal feeds back CQI for all time-frequency resources to ensure complete channel information, then the information completeness is improved, but the uplink resource usage increases
Solution Approach 1:
The patent extracts only the essential CQI information corresponding to the terminal's allocated resources and designated CSI-RS port, eliminating redundant feedback for other ports. This extraction ensures that the base station receives sufficient information for accurate channel quality assessment while minimizing uplink resource consumption.
Solution Approach 2:
The patent inverts the traditional approach by having the base station indicate to the terminal which specific resources to measure and report, rather than requiring the terminal to report all measurements. This inversion of the feedback mechanism reduces uplink overhead while maintaining information completeness for MU-MIMO operations.
3Object-generated harmful factors
If the base station uses preset algorithms to reconstruct precoding matrices for MU-MIMO, then the interference reduction is improved, but the CQI accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by having the base station pre-indicate to the terminal which CSI-RS port and time-frequency resources correspond to the terminal's allocation before the terminal performs measurement. This preliminary indication ensures that the terminal measures on the correct resources that reflect the actual MU-MIMO channel conditions after precoding, thereby maintaining CQI accuracy while still using preset algorithms for interference reduction.
Solution Approach 2:
The patent enhances feedback by having the terminal report CQI based on measurements of the precoded CSI-RS on indicated resources, which provides accurate feedback about the actual channel quality after MU-MIMO precoding is applied. This feedback mechanism ensures that the CQI reflects both the interference reduction achieved by precoding and the actual channel conditions.
Data Source
AI summary
Embodiments of the present invention disclose a channel quality index measurement method and apparatus. The method includes: determining, by a base station, a target CSI-RS on each of time-frequency resources corresponding to resource numbers of a terminal, where the target CSI-RS is a precoded CSI-RS, and the time-frequency resource is a resource element used to transmit the CSI-RS or the target CSI-RS; sending, by the base station, the target CSI-RS on each of the time-frequency resources corresponding to the resource numbers to the terminal on the time-frequency resource; sending, by the base station to the terminal, indication information used to indicate the resource numbers of the terminal; and receiving, by the base station, a CQI that is sent by the terminal and that is used to indicate channel quality.