UCI Code Rate Control for CSI Reporting Reliability
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Solution Overview
Problem
In CoMP and CA communication systems, the high code-rate issues during aperiodic CSI reporting for UEs configured with multiple CSI processes lead to unreliable decoding of UCI at the eNB, especially when extended-CP is used, resulting in high code rates that hinder reliable transmission of CQI, A/N, RI, and SRS in the same subframe.
Innovation Solution
The proposed solution involves adjusting the threshold number of PRBs for UCI-only PUSCH triggering based on the number of CSI processes and configured DL serving cells, using table selection for the CSI request field to ensure a code rate less than 0.5, and extending the CSI process definition to encompass Rel-8/9/10 feedback configurations for flexible TM configuration across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If aperiodic CSI reporting is performed for UEs configured with multiple CSI processes, then detailed channel state information can be provided to the NodeB, but the code rate increases leading to unreliable decoding of UCI at the eNB
Solution Approach 1:
The patent changes the parameter of code rate by adjusting the threshold number of PRBs for UCI-only PUSCH triggering. When the number of PRBs is below the threshold, aperiodic CSI reporting is triggered; when above, periodic reporting is used. This parameter adjustment ensures the code rate remains below 0.5, maintaining decoding reliability while still transmitting comprehensive CSI information.
Solution Approach 2:
The patent implements dynamic selection between aperiodic and periodic CSI reporting modes based on real-time channel conditions and buffer status. The eNB dynamically adjusts the PRB threshold and triggers appropriate reporting modes, allowing the system to adapt to varying traffic conditions while maintaining optimal code rates for reliable decoding.
2Reliability
If extended-CP is used for transmission, then robustness against multipath delay spread is improved, but the code rate increases hindering reliable transmission of CQI, A/N, RI, and SRS in the same subframe
Solution Approach 1:
The patent adjusts the PRB threshold parameter specifically for extended-CP configurations to account for the reduced spectral efficiency. By setting an appropriate threshold, the system ensures that when extended-CP is used, the code rate remains manageable and below 0.5, preventing overload conditions while maintaining the robustness benefits of extended cyclic prefix.
3Loss of information
If multiple CSI processes are configured for a UE, then comprehensive channel state information can be obtained, but the code rate increases making reliable decoding difficult
Solution Approach 1:
The patent segments the CSI reporting into multiple processes, each with its own PRB allocation and triggering conditions. By dividing the overall CSI reporting task into separate processes (e.g., different CSI process IDs), the system can manage code rates individually for each process while collectively providing comprehensive channel state information. This segmentation prevents any single report from exceeding the code rate threshold.
Data Source
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AI summary
A method for CSI report transmission includes detecting a collision in a subframe, between a first PUCCH CSI report of one serving cell with which a UE is configured in one of transmission modes 1 to 9, and a second PUCCH CSI report of another serving cell with which the UE is configured in transmission mode 10. Upon the reporting types of the collided PUCCH CSI reports having a same priority, the method transmits the first PUCCH CSI report if the CSI process index of the second PUCCH CSI report has a positive value other than 1. A method for CSI report transmission includes configuring, via a higher layer, a UE configured in transmission mode 10 whether to create a respective CSI report(s) for each aperiodic CSI process or not, using an information element including at least three one-bit variables.