Uplink SRS Precoding for FDD MIMO CSI Acquisition
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Solution Overview
Problem
Current sounding reference symbol (SRS) techniques in uplink Multiple-Input and Multiple-Output (MIMO) communication systems face challenges in efficiently acquiring Channel State Information (CSI) as the number of uplink transmission ports increases, leading to complex processes and resource inefficiencies, particularly in Frequency-Domain Duplex (FDD) systems, which are incompatible with channel reciprocity used in Time-Domain Duplex (TDD).
Innovation Solution
A method involving precoding uplink sounding reference symbols based on initial and final rank indicators and vectors/matrices received from a network entity, transforming these to reduce the number of SRS resources needed, allowing for a more efficient and flexible uplink transmission design by only sounding a partial set of transmission ports, thereby conserving network resources and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional SRS sounding techniques sound all potential transmission ports to obtain complete CSI, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the complete CSI acquisition process into two stages: first acquiring wideband channel information using a reduced set of SRS resources, then acquiring subband-specific information. This segmentation allows the system to obtain sufficient CSI for codebook generation without sounding all potential transmission ports, thereby reducing SRS resource requirements while maintaining measurement precision.
Solution Approach 2:
The patent applies partial action by acquiring only the necessary portion of channel information needed for effective codebook-based transmission. Instead of obtaining complete CSI for all potential transmission ports, the system acquires sufficient wideband channel statistics and subband-specific information to generate accurate codebooks, reducing the total SRS resources required while maintaining transmission performance.
2Adaptability or versatility
If the number of uplink transmission ports increases to support features like IAB, MTC, and V2X, then adaptability is improved, but loss of energy increases
Solution Approach 1:
The patent segments the channel sounding process into wideband and subband components, allowing the system to support multiple transmission ports and diverse features (IAB, MTC, V2X) efficiently. By acquiring wideband channel statistics once and reusing them across different scenarios, the system reduces repeated SRS transmissions and associated power consumption while maintaining adaptability to various feature requirements.
Solution Approach 2:
The patent performs preliminary acquisition of wideband channel information that can be reused across multiple transmission scenarios and features. This preliminary action reduces the need for repeated full-channel sounding when supporting multiple features like IAB, MTC, and V2X, thereby reducing overall power consumption while maintaining system adaptability.
3Adaptability or versatility
If traditional SRS techniques are used in FDD systems, then channel reciprocity compatibility is improved, but measurement precision deteriorates
Solution Approach 1:
The patent performs preliminary acquisition of wideband channel statistics using SRS resources, creating a foundation for codebook generation that is particularly valuable in FDD systems where channel reciprocity cannot be exploited. This preliminary wideband information, combined with subband-specific measurements, enables accurate CSI acquisition in FDD systems without relying on channel reciprocity, thereby maintaining measurement precision while ensuring FDD compatibility.
Data Source
AI summary
Various communication systems may benefit from improved sounding reference symbol sounding techniques. An apparatus may comprise at least one memory comprising computer program code and at least one processor. The at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to precode at least one uplink sounding reference symbol based upon at least one initial rank indicator and at least one first vector/matrix received from a network entity. The apparatus further transforms the first vector/matrix and a second vector matrix received from the network entity into a third vector/matrix based upon a final rank indicator received from the network entity. The apparatus further transmits data based upon the third vector/matrix.