Precoder Codebook Segmentation for Wireless Feedback Overhead
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Solution Overview
Problem
As the number of antenna ports increases in wireless communication networks, existing approaches to precoding control and precoder evaluation do not scale well, leading to significant computational burdens on wireless devices and increased signaling overhead, particularly on the PUCCH, which affects battery life and efficiency.
Innovation Solution
Implementing a method that dynamically identifies a reduced set of precoders based on channel characteristics and uses a defined mapping function to map these precoders to a smaller set of index values, reducing signaling overhead while allowing for precoder selection matched to current channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of antenna ports is increased to support more transmission layers, then the precoder codebook size increases, but the number of feedback bits required in the CSI report increases significantly
Solution Approach 1:
The codebook is segmented into multiple codebook subsets, each associated with a different number of transmission layers (ranks). The UE is configured with a specific codebook subset index that corresponds to the current transmission scenario. This segmentation allows the system to support multiple transmission layers while maintaining a manageable feedback overhead by only reporting the subset index rather than individual precoder indices for all possible layers.
Solution Approach 2:
The codebook configuration is made dynamic through RRC signaling, where the network can configure different codebook subset indices based on current channel conditions and transmission requirements. This dynamic adaptation allows the system to adjust the effective codebook size and feedback requirements in real-time, supporting variable numbers of transmission layers without permanently increasing feedback overhead.
2Adaptability or versatility
If the precoder codebook is expanded to support more antenna ports, then precoding versatility improves, but computational burden on wireless devices increases
Solution Approach 1:
The large codebook for many antenna ports is segmented into multiple smaller codebook subsets, each optimized for specific transmission scenarios (different ranks). The UE only needs to evaluate and report precoders within its configured subset, dramatically reducing the computational burden of codebook evaluation while still having access to the full range of precoding options through network-controlled subset selection.
Solution Approach 2:
Different codebook subsets are designed with local optimizations for specific transmission scenarios. Each subset contains precoders tailored to particular rank configurations and channel conditions, allowing the UE to perform simpler, more targeted computations rather than evaluating a single large codebook across all possible scenarios.
3Measurement precision
If CSI reporting is performed on PUCCH with increased precoder options, then precoder selection accuracy improves, but PUCCH overhead increases significantly
Solution Approach 1:
The precoder indication is segmented into two parts: a codebook subset index (reported on PUCCH with low overhead) and implicit precoder information (determined by the network based on the subset index). This segmentation allows accurate precoder selection while keeping PUCCH overhead minimal, as the subset index requires far fewer bits than a full precoder index would require.
Solution Approach 2:
The codebook subset index acts as an intermediary that conveys essential precoder selection information on the PUCCH with minimal overhead. The network uses this subset index to determine the actual precoder configuration, effectively decoupling the limited-capacity PUCCH from the need to transmit detailed precoder information.
Data Source
AI summary
Techniques disclosed herein involve network-side and device-side operations that provide for the advantageous use of a reduced set of precoders within a larger full set of precoders. The reduced set is identified dynamically, based on characteristics of the channel between a radio network node and a wireless device, and the use of a defined mapping function that maps the reduced set of precoders within the larger full set to a reduced set of index values. Reporting precoders from the reduced set offers significant reductions in signaling overhead because of the smaller size of the index values used to index the reduced set, while simultaneously offering the ability to choose from precoders matched to current channel conditions.