Subband Precoder Indication for Low-Overhead Uplink Beamforming
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Solution Overview
Problem
Conventional wireless communication systems face challenges in efficiently indicating precoders for multiple subbands due to high signaling overhead, which affects beamforming gains and transmission efficiency, particularly in next-generation wireless technologies like 5G NR.
Innovation Solution
Implementing frequency selective precoder indication techniques by transmitting an uplink scheduling grant with subband precoding information and resource allocation, allowing user equipment to determine and apply multiple subband precoders for each subband, reducing signaling overhead through the use of indices and codewords.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional wideband precoding is used with a single precoder for all subbands, then device complexity and signaling overhead are reduced, but transmission efficiency and beamforming gains deteriorate due to inability to adapt to frequency-selective channel conditions
Solution Approach 1:
The patent divides the frequency band into multiple subbands and applies different precoders to each subband. The uplink scheduling grant includes subband precoding information that enables the UE to determine multiple subband precoders (e.g., first precoder for first subband, second precoder for second subband) instead of using a single wideband precoder for all subbands. This segmentation allows adaptation to frequency-selective channel conditions while managing signaling overhead through compact representation methods.
2Productivity
If frequency selective precoding with multiple subband precoders is implemented, then transmission efficiency and beamforming gains are improved, but signaling overhead increases
Solution Approach 1:
The patent combines multiple precoding information elements into a unified subband precoding information structure within the uplink scheduling grant. This includes merging the indication of multiple subband precoders with resource allocation information, allowing the network to signal frequency-selective precoding requirements efficiently. The combined structure reduces redundant signaling and enables compact representation of multiple precoders.
Solution Approach 2:
The patent uses codebook-based precoding where pre-defined precoder matrices are stored in both the network and UE. Instead of signaling complete precoder matrices, the network signals compact codebook indices that reference pre-agreed precoders. This copying approach allows the UE to determine the actual precoders from local codebooks using minimal signaling overhead, effectively reducing information loss while maintaining beamforming performance.
3Reliability
If subband precoding information is included in uplink scheduling grant, then beamforming gains are maintained, but the complexity of processing and determining multiple precoders increases
Solution Approach 1:
The patent performs preliminary configuration of codebooks and precoder relationships before actual data transmission. The network and UE pre-agree on codebook structures and precoder mappings during system initialization or RRC configuration. When subband precoding information is received in the uplink scheduling grant, the UE can quickly determine the appropriate precoders by referencing pre-configured codebooks rather than performing complex real-time precoder design, thus maintaining beamforming gains while reducing processing complexity.
Data Source
AI summary
Wireless communications systems and methods related to wireless communications in a system are provided. A user equipment (UE) may receive from a base station (BS), an uplink (UL) scheduling grant indicating subband precoding information and a resource allocation spanning a plurality of subbands. The UE may determine a plurality of subband precoders based on the subband precoding information. Each precoder of the plurality of subband precoders may be associated with a subband of the plurality of subbands. The UE may transmit to the BS, an UL communication signal in the resource allocation using the plurality of subband precoders.