Terminal Device Rank Indicator Selection via Dynamic Power Offsets
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Solution Overview
Problem
In wireless communication systems, especially in unlicensed bands, the Effective Isotropic Radiated Power (EIRP) limit restricts transmission power, leading to suboptimal Channel State Information (CSI) feedback due to fixed CSI-RS power, resulting in incorrect SNR calculations and improper Rank Indicator (RI) selection for MIMO transmission schemes.
Innovation Solution
A method in terminal devices to determine power offsets between CSI-RS and downlink data transmission for each candidate rank, calculating SNR based on these offsets, and selecting the optimal rank for CSI feedback to improve RI selection and feedback accuracy under EIRP limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fixed CSI-RS transmission power is used in unlicensed bands, then EIRP limit compliance is achieved, but RI selection accuracy deteriorates due to incorrect SNR calculations
Solution Approach 1:
The patent applies dynamics by making the CSI-RS transmission power variable rather than fixed. The base station determines different transmission powers for CSI-RS based on the rank indicator, allowing the power to adapt dynamically to different MIMO transmission schemes. This resolves the contradiction by enabling both EIRP limit compliance and accurate SNR calculation through dynamic power adjustment.
Solution Approach 2:
The patent changes the power parameter of CSI-RS transmission based on the rank indicator. Different transmission powers are assigned to CSI-RS depending on the selected rank, which allows accurate SNR calculation for each rank while maintaining EIRP limit compliance. This parameter change approach directly addresses the technical contradiction.
2Productivity
If maximum transmission power is used for all ranks, then system throughput is improved, but EIRP limit is violated due to beamforming gain variations
Solution Approach 1:
The patent adjusts the transmission power parameter of CSI-RS based on the rank indicator and beamforming gain. By changing the power level according to the specific rank being evaluated, the system can simulate different transmission scenarios accurately while ensuring EIRP limit compliance, thus maintaining high throughput without violations.
Solution Approach 2:
The system dynamically adjusts CSI-RS transmission power according to the rank indicator selected by the terminal device. This dynamic adaptation allows the system to optimize throughput for each rank while automatically ensuring EIRP limit compliance, resolving the contradiction between throughput maximization and regulatory compliance.
3Measurement precision
If rank-based power adaptation is implemented, then RI feedback accuracy is improved, but device complexity increases due to multiple SNR calculations
Solution Approach 1:
The terminal device performs self-service by autonomously determining the rank indicator based on SNR calculations for different candidate ranks. The base station provides the necessary power offset information, and the terminal independently evaluates multiple ranks and selects the optimal one, improving accuracy while distributing the computational burden appropriately.
Solution Approach 2:
The base station performs preliminary action by pre-determining and signaling the power offset for different ranks to the terminal device. This preliminary provision of power information simplifies the terminal's task, as it only needs to calculate SNR based on the provided offsets rather than determining absolute powers, thus improving accuracy without excessive complexity.
Data Source
AI summary
The present disclosure provides a method in a terminal device for Channel State Information, CSI, feedback. The method includes: determining, for each of a plurality of candidate ranks, a power offset between a CSI Reference Signal, CSI-RS, and a downlink data transmission; calculating, for each of the plurality of candidate ranks, a Signal-to-Noise Ratio, SNR, of the downlink data transmission based on the power offset determined for the corresponding candidate rank; selecting a rank from the plurality of candidate ranks based on the respective SNRs calculated for the plurality of candidate ranks; and transmitting a Rank Indicator, RI, indicating the selected rank to a network device.