Uplink Non-Codebook Precoder Signaling via SRS
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Solution Overview
Problem
Current uplink codebook-based transmission schemes in wireless communication systems, such as LTE, incur high computational complexity and signaling overhead due to the need for base stations to measure and signal precoders for uplink multiple-input multiple-output (MIMO) transmissions.
Innovation Solution
Implementing an uplink non-codebook based transmission scheme where base stations receive precoded sounding reference signals (SRS) from user equipment (UE), determine the transmission rank and precoder, and feedback the configuration to the UE, allowing the UE to determine the precoder for PUSCH transmissions without explicit precoding matrix indication in the uplink grant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If codebook-based transmission scheme is used, then precoder configuration is explicit and reliable, but computational complexity and signaling overhead increase
Solution Approach 1:
The patent extracts the precoder indication from the traditional codebook-based signaling mechanism. Instead of explicitly signaling precoder indices through codebooks, the system uses SRI (SRS Resource Indication) to implicitly indicate precoder configuration. The base station measures SRS resources and determines precoders independently, removing the need for complex codebook management and explicit precoder signaling while maintaining reliable precoder configuration through SRI-based indication.
Solution Approach 2:
The SRI field in the uplink grant is given multi-functionality: it simultaneously indicates both the SRS resource to be used and the precoder configuration for PUSCH transmission. This universal indication mechanism eliminates the need for separate precoder signaling and codebook management, reducing computational complexity while maintaining reliable precoder configuration through the unified SRI parameter.
2Loss of information
If codebook-based transmission scheme is used, then precoder signaling is explicit, but signaling overhead increases
Solution Approach 1:
The SRI field serves multiple purposes simultaneously: it indicates the SRS resource selection and the precoder configuration for PUSCH transmission. By giving this single parameter universal functionality, the patent eliminates the need for separate precoder indication signaling, thereby reducing signaling overhead while ensuring complete precoder information transmission through the SRI parameter.
Solution Approach 2:
The patent removes explicit precoder signaling from the communication protocol by extracting the precoder indication function and integrating it into the SRI mechanism. The base station determines precoders based on SRS measurements and conveys the selection through SRI, eliminating redundant precoder information signaling while maintaining complete precoder information transmission.
3Device complexity
If non-codebook based transmission is implemented, then computational complexity and signaling overhead are reduced, but explicit precoder indication is removed
Solution Approach 1:
The SRI acts as an intermediary parameter that bridges the gap between non-codebook-based transmission and precoder indication. Instead of explicitly signaling precoders, the SRI indirectly conveys precoder information by indicating which SRS resource (with its associated precoder) should be used for PUSCH transmission. This intermediary mechanism maintains precoder information transmission while avoiding explicit precoder signaling.
Solution Approach 2:
Instead of the base station signaling the precoder directly to the UE (traditional approach), the system inverts the logic: the base station measures SRS resources, determines the optimal precoder, and indicates the SRS resource that contains the precoder information through SRI. The UE then derives the precoder from the indicated SRS resource, reversing the traditional signaling direction and eliminating explicit precoder indication while maintaining complete information transmission.
Data Source
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AI summary
Techniques and apparatus for configuring transmission rank and/or precoder(s) to support uplink non-codebook based transmission are provided. One technique includes receiving sounding reference signal (SRS) resource(s) from a user equipment (UE), where each SRS resource is associated with one or more precoded ports. At least one of a transmission rank or a set of precoders is determined based on the SRS resource(s). An indication of at least one of the SRS resource(s) is signaled to the UE. The UE uses the indication of the at least one of the SRS resource(s) to send an uplink transmission.