Differential Phase Feedback for Wireless CSI Overhead Reduction
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Solution Overview
Problem
In wireless communications, the overhead of channel state information (CSI) feedback increases linearly with the number of sub-bands, leading to reduced efficiency and excess latency due to the large amount of feedback required for beamforming in wireless multiple-access systems.
Innovation Solution
Implementing differential phase feedback in the frequency domain, where user equipment (UE) reports absolute phase values for one sub-band and differential phase values for the remaining sub-bands within a sub-band group, reducing the feedback overhead by using fewer bits to convey phase information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If absolute phase values are reported for all sub-bands, then frequency domain feedback granularity is improved, but feedback overhead increases linearly with the number of sub-bands
Solution Approach 1:
The patent segments the frequency domain into sub-band groups, where the first sub-band of each group reports absolute phase values while subsequent sub-bands report differential phase values relative to the first sub-band. This segmentation reduces the number of absolute phase values that need to be transmitted, thereby reducing feedback overhead while maintaining frequency domain feedback granularity.
Solution Approach 2:
The patent changes the parameter representation from absolute phase values for all sub-bands to a hybrid approach where only the first sub-band of each group uses absolute phase values and subsequent sub-bands use differential phase values. This parameter change reduces the total number of bits required for feedback while preserving the necessary frequency domain information.
2Quantity of substance
If differential phase feedback is implemented, then feedback overhead is reduced, but frequency domain feedback granularity may be compromised
Solution Approach 1:
By segmenting the frequency domain into sub-band groups and applying differential phase feedback only to subsequent sub-bands within each group (rather than across the entire frequency range), the patent maintains frequency domain feedback granularity for the most critical sub-bands while reducing overall feedback overhead through differential encoding in other sub-bands.
3Measurement precision
If the number of sub-bands is increased, then frequency resolution is improved, but CSI feedback payload size increases
Solution Approach 1:
The patent changes the parameter encoding strategy based on the number of sub-bands. When the number of sub-bands increases, the patent applies differential phase feedback to subsequent sub-bands within sub-band groups, which reduces the payload size growth rate while maintaining the frequency resolution benefits of increased sub-band counting.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. In some systems, a user equipment (UE) may transmit feedback to a base station indicating phase values for sub-bands in a bandwidth part (BWP). The base station may use the phase feedback to perform precoding on a set of beams. To support a reduced payload overhead for the feedback, the UE may implement differential phase feedback. For example, the UE may divide the BWP into a number of sub-band groups and may generate, for each sub-band group of each beam, a first set of bits indicating an absolute phase value for a first sub-band of the sub-band group. The UE may additionally generate a second set of bits indicating differential phase values for the other sub-bands of each sub-band group. The UE may report the first and second sets of bits for the beams to the base station for precoding.