Uplink Precoder Indication Using Two-Stage Time-Domain Signaling
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently indicating uplink precoders due to increased signaling overhead, especially with multiple antennas and multi-user MIMO scenarios, where indicating separate TPMI for each PRG results in significant signaling overhead.
Innovation Solution
A two-stage time-domain uplink precoder indication method where the network entity first indicates TD precoder indices in a control message and subsequently provides TD precoder coefficients in an uplink grant, allowing the UE to generate an FD precoder using FFT, reducing signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate TPMI is indicated for each PRG, then precoder accuracy is improved, but signaling overhead increases significantly
Solution Approach 1:
The precoder indication is divided into two stages: first indicating a subset of TD precoder indices (coarse granularity), then providing specific TD precoder coefficients for those selected indices (fine granularity). This segmentation allows the system to achieve accurate precoding while reducing the overall signaling overhead compared to indicating separate TPMI for each PRG.
Solution Approach 2:
The network entity first indicates a subset of TD precoder indices in advance before providing the specific precoder coefficients. This preliminary indication allows the UE to prepare for the subsequent coefficient reception and reduces the immediate signaling burden, effectively managing the trade-off between accuracy and overhead.
2Reliability
If full FD precoder is used, then precoder performance is maintained, but signaling overhead increases
Solution Approach 1:
Instead of transmitting the complete FD precoder information, the system extracts and transmits only the essential TD precoder coefficients after selecting a subset of indices. The UE then reconstructs the full FD precoder locally using FFT transformation, thereby maintaining precoder performance while significantly reducing the signaling overhead.
Solution Approach 2:
The UE reconstructs the full FD precoder by applying FFT to the received TD precoder coefficients, creating a local copy of the complete precoder information without requiring the network to transmit all the original FD precoder data. This copying approach maintains performance while reducing overhead.
3Loss of information
If two-stage indication is implemented, then signaling overhead is reduced, but system complexity increases
Solution Approach 1:
The UE performs the FFT transformation itself to reconstruct the FD precoder from the received TD coefficients, eliminating the need for the network to perform and transmit the complete transformation. This self-service approach reduces network complexity while maintaining the two-stage indication benefits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces signaling overhead while maintaining accurate precoder performance by approximating the full FD precoder, facilitating efficient uplink communication with reduced bit usage.
Implementation Method 1
generating a frequency domain (FD) precoder for the uplink shared channel communication based on each respective TD precoder coefficient
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may perform uplink codebook-based precoding in which a network entity may transmit downlink control information (DCI) to the UE to indicate an uplink precoder for the UE to use for a subsequent uplink transmission. A network entity may indicate in an uplink grant less than all of the time domain (TD) precoder coefficients of a TD precoder, and the network entity may indicate the indices of the TD precoder that correspond to the included TD precoder coefficients. The indicated TD precoder coefficients may correspond to the strongest (e.g., the highest value) TD precoder coefficients. When the UE transforms the TD uplink precoder to a frequency domain (FD) precoder using the indicated TD precoder coefficients, the resulting FD precoder may be approximate to the FD precoder that would be generated using all of the TD precoder coefficients.