Uplink SRS Precoding with Downlink Interference Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless communication systems face challenges in efficiently utilizing uplink resources for transmitting sounding reference signals (SRS) and downlink channel quality information, particularly due to the high computational complexity involved in pre-whitening SRS with interference covariance matrices (Rnn) across the entire bandwidth.
Innovation Solution
Implementing a multi-stage Rnn feedback mechanism where the user equipment (UE) computes the Rnn matrix over only a portion of the frequency band used for SRS transmission, reducing computational complexity and enabling precoding of SRS with downlink channel quality estimates without requiring additional uplink resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE computes the Rnn matrix over the entire bandwidth for SRS precoding, then the channel quality estimation accuracy is improved, but the computational complexity and time required increase significantly
Solution Approach 1:
The patent divides the entire bandwidth into multiple frequency subbands and computes the Rnn interference covariance matrix separately for each subband instead of the entire bandwidth. This segmentation reduces the computational complexity from O(N²) for full bandwidth to O(k×M²) where k is the number of subbands and M is the subband size (M < N), while still providing accurate channel quality estimation for each subband where SRS is transmitted.
2Measurement precision
If the UE computes the Rnn matrix over the entire bandwidth for SRS precoding, then the channel quality estimation accuracy is improved, but the time required for processing increases
Solution Approach 1:
The patent segments the bandwidth computation task into smaller parallel subband computations. The UE computes Rnn matrices for multiple subbands simultaneously or in a pipelined manner, reducing the total processing time from T_full to T_subband × k where T_subband < T_full due to smaller matrix operations and potential parallelization across k subbands.
3Measurement precision
If additional uplink resources are allocated for transmitting channel quality information, then the feedback accuracy is improved, but the uplink resource consumption increases
Solution Approach 1:
The patent merges the channel quality feedback information into the SRS transmission by precoding the SRS with the computed Rnn matrix. Instead of transmitting separate CSI feedback resources, the precoded SRS itself carries the channel quality information implicitly through its transmission characteristics, eliminating the need for additional dedicated uplink feedback resources while maintaining feedback accuracy.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Certain aspects of the present disclosure relate to methods and apparatus relating to precoding reference signals for uplink transmissions with downlink interference information. In certain aspects, a method, performed by a user equipment (UE) comprises receiving, from a base station, one or more signals for use in estimating channel quality for a downlink between the base station and the UE. The method also includes determining a first frequency resource and a second frequency resource from a frequency band allocated for transmitting a reference signal (RS). The method further includes computing a first downlink channel quality estimate for the first frequency resource using the one or more signals, transmitting a first RS precoded using the first downlink channel quality estimate, computing a second downlink channel quality estimate for the second frequency resource using the one or more signals and transmitting a second RS precoded using the second downlink channel quality estimate.