Non-Codebook Uplink MIMO Beam Selection via UE Autonomous Precoder Determination
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Solution Overview
Problem
Current 5G NR standards lack a predefined codebook for non-codebook based uplink (UL) MIMO transmission, making it challenging for transmission and reception points (TRP) to determine the optimal precoders and transmission rank for user equipment (UE) beams, which affects the efficiency of UL MIMO communication.
Innovation Solution
The method involves UE selecting precoders and determining the transmission rank for uplink transmission beams, with the TRP allocating sounding reference signal (SRS) resources and identifying the selected precoders and rank for a subset of beams based on the UE's measurements, allowing for dynamic beam selection and improved spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If non-codebook based UL MIMO transmission is used, then spatial resolution and beam selection flexibility are improved, but the complexity of determining optimal precoders and transmission rank increases
Solution Approach 1:
The UE autonomously determines precoders and transmission rank based on its own channel measurements and beam management information, without requiring the TRP to explicitly signal these parameters. The UE selects precoders from a codebook and determines the transmission rank independently, then communicates only the selected precoder indices and rank to the TRP, thereby improving spatial resolution while reducing control signaling complexity.
Solution Approach 2:
The system performs beam management and channel measurement in advance to establish a set of candidate beams and their corresponding quality metrics before the actual UL MIMO transmission. This preliminary beam selection and channel characterization enables the UE to quickly determine optimal precoders and rank without complex real-time calculations during data transmission.
2Productivity
If UE autonomously determines precoders and transmission rank, then transmission efficiency is improved, but the accuracy of TRP beam selection may deteriorate
Solution Approach 1:
The UE provides feedback to the TRP by reporting the selected precoder indices and transmission rank based on its autonomous determination. The TRP uses this feedback along with its own channel measurements from SRS signals to verify and refine the beam selection. This feedback mechanism ensures that both the UE's autonomous decisions and the TRP's beam selection accuracy are maintained.
Solution Approach 2:
The system combines the UE's autonomous precoder and rank determination with the TRP's channel measurements and beam management capabilities. The UE determines precoders based on downlink channel measurements and uplink channel reciprocity, while the TRP validates these selections using SRS measurements, merging both perspectives to achieve optimal transmission.
3Ease of manufacture
If codebook based UL MIMO is used, then precoder selection is standardized and simple, but spatial resolution and beam flexibility are limited
Solution Approach 1:
The system transitions from static codebook-based precoder selection to dynamic non-codebook based selection where the UE autonomously determines precoders based on current channel conditions and beam management information. This dynamic approach allows the precoder selection to adapt to changing channel characteristics and beam configurations, improving spatial resolution while maintaining standardization through defined procedures for precoder determination and reporting.
Data Source
AI summary
A method and an apparatus for selecting beams for non-codebook based uplink multiple-input and multiple-output are disclosed. In an embodiment, a method implemented by a user equipment (UE) includes receiving an allocation of at least one sounding reference signal (SRS) resource in an uplink subframe from a transmission and reception point (TRP) for a first set of uplink transmission beams, transmitting precoded SRSs in the at least one SRS resource to the TRP, wherein the precoded SRSs are precoded with UE-selected precoders and at least one rank and receiving an identification of two or more precoders for a second set of uplink transmission beams, wherein the second set of uplink transmission beams is selected from the first set of uplink transmission beams, and wherein the two or more precoders are based on the precoded SRSs.