CSI Reporting Common Transmission Rank for CoMP
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Solution Overview
Problem
Existing solutions for MIMO with spatial multiplexing in LTE do not effectively address efficient rank determination for CoMP CSI feedback, leading to degraded system performance and increased complexity in determining channel quality and suitable precoder weights.
Innovation Solution
Implementing a method where a common transmission rank is determined based on a subset of CSI-RS resources for CSI reporting, reducing signaling overhead and enabling more efficient CSI feedback and rank adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate CSI feedback is determined for each CSI-RS resource, then measurement precision for each resource is improved, but device complexity and signaling overhead increase
Solution Approach 1:
The invention segments the CSI feedback into two parts: a common transmission rank determined from a subset of CSI-RS resources, and resource-specific precoder matrix indices and channel quality indicators. This segmentation allows the complex rank determination to be performed once commonly, while maintaining precise per-resource measurements for precoding and quality assessment.
Solution Approach 2:
The common transmission rank determined from a subset of CSI-RS resources is made universal and applied to all CSI-RS resources in the set. This multi-functional approach allows a single rank determination to serve multiple resources, reducing terminal complexity while maintaining measurement precision through resource-specific precoder and CQI reporting.
2Adaptability or versatility
If separate CSI feedback is determined for each CSI-RS resource, then adaptability to each resource is improved, but loss of time for CSI reporting increases
Solution Approach 1:
The invention performs preliminary action by determining the common transmission rank in advance based on a subset of CSI-RS resources before generating the full CSI feedback for each resource. This preliminary rank determination reduces the computational time required for complete CSI reporting while maintaining adaptability through subsequent resource-specific precoder and CQI calculations.
3Device complexity
If common transmission rank is determined for a set of CSI-RS resources, then device complexity is reduced, but measurement precision for individual resources may deteriorate
Solution Approach 1:
The invention applies local quality by making the precoder matrix index and channel quality indicator resource-specific while keeping the transmission rank common across resources. This allows the CSI feedback to have uniform rank structure (reducing complexity) while maintaining local optimization for each resource through resource-specific precoding and quality metrics.
Data Source
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AI summary
A method implemented by a wireless terminal of reporting channel state information to a wireless communication network is disclosed. The wireless terminal receives reference symbols on a set of channel state information reference symbol (CSI-RS) resources, and determines a common transmission rank for the set of CSI-RS resources, based on the reference symbols received on a subset of those CSI-RS resources. The terminal then generates CSI feedback as a function of the common transmission rank, and transmits the CSI feedback to the communication network. The CSI feedback may include the common transmission rank itself, or may include different transmission ranks for different CSI-RS resources each determined as a function of the common transmission rank. A complementary method in which a network node uses such a CSI feedback to perform rank adaptation for the set of CSI-RS resources is also disclosed.