Codebook Subset Restriction Signaling for Lower Precoder Overhead
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Solution Overview
Problem
The existing methods for signaling codebook subset restrictions in wireless communication systems face high overhead due to the need for bitmaps that individually restrict each precoder, especially in large antenna arrays and multi-dimensional scenarios, where the number of possible configurations becomes excessively large, leading to inefficient use of resources.
Innovation Solution
A method that generates codebook subset restriction signaling by jointly restricting precoders within groups based on common components, such as beam precoders, using a Kronecker product structure and bit patterns that depend on reference configurations, reducing the number of bits required for signaling by assuming correlations in precoder restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual bitmap restriction for each precoder is used, then precise control of precoder selection is achieved, but signaling overhead becomes excessively large
Solution Approach 1:
The codebook is divided into multiple groups, with each group containing multiple precoders. Instead of individually restricting each precoder, the system applies restriction at the group level, significantly reducing the number of bits required for signaling while maintaining effective control over precoder selection
Solution Approach 2:
Multiple precoders within each group are merged under a single restriction indicator. The bitmap now represents groups rather than individual precoders, combining the control function for multiple precoders into a single signaling unit, thereby reducing overhead
2Reliability
If large codebook size is used, then better channel condition matching is achieved, but the number of possible restriction configurations becomes excessively large
Solution Approach 1:
The large codebook is segmented into multiple smaller groups. This allows the system to maintain a large overall codebook for better channel matching while applying restriction management at the smaller group level, making the configuration and signaling tractable
Solution Approach 2:
The restriction approach transitions from individual precoder dimension to group dimension. By adding the grouping dimension, the system can manage large codebooks efficiently, where the number of restriction configurations is determined by the number of groups rather than the total number of precoders
Data Source
AI summary
A network node signals to a wireless communication device which precoders in a codebook are restricted from being used. The network node in this regard generates codebook subset restriction signaling that, for each of one or more groups of precoders, jointly restricts the precoders in the group by restricting a certain component (e.g., a certain beam precoder) that the precoders in the group have in common. This signaling may be for instance rank-agnostic signaling that jointly restricts the precoders in a group without regard to the precoders' transmission rank. Regardless, the network node sends the generated signaling to the wireless communication device.