Uplink Explicit Channel Feedback for Beamforming
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Solution Overview
Problem
In link-budget limited communications systems, such as those operating above 6 GHz, the transmission of large numbers of sounding reference signals (SRS) for channel estimation consumes significant uplink resources, leading to performance degradation due to high path-loss and limited available beams.
Innovation Solution
A system and method for explicit feedback in the uplink, where a user device generates and transmits explicit channel feedback on a modified resource using a single transmit-receive beam combination with the highest channel quality, allowing for efficient conveyance of channel information without the need for extensive beamforming and resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of SRS symbols are transmitted to facilitate channel estimation between each transmit antenna and each receive antenna, then channel estimation performance is improved, but uplink resource consumption increases significantly
Solution Approach 1:
The patent extracts only the essential channel feedback information needed for downlink beamforming from the complete channel state, rather than transmitting full channel measurements. The UE selects a single best TRBC and transmits feedback only for that combination, eliminating redundant feedback for other beam combinations while maintaining sufficient channel estimation accuracy for downlink transmission.
Solution Approach 2:
The patent applies partial action by transmitting feedback for only one selected TRBC instead of all possible TRBCs. This partial feedback approach provides sufficient information for downlink beamforming without the excessive resource consumption of complete channel state feedback, achieving a practical balance between performance and overhead.
2Loss of information
If the UE transmits feedback for multiple TRBCs using different beams, then comprehensive channel information is obtained, but beam switching and RF circuit switching increase latency
Solution Approach 1:
The patent applies preliminary action by having the UE identify and select the single best TRBC in advance before feedback transmission. This pre-selection eliminates the need for dynamic beam switching during feedback transmission, as all feedback is prepared and sent using the predetermined best beam combination, thereby reducing latency while maintaining information quality.
Solution Approach 2:
Instead of transmitting feedback for multiple TRBCs by switching beams (the conventional approach), the patent inverts the approach by selecting one best TRBC and transmitting all necessary feedback information through that single beam combination. This inversion eliminates beam switching overhead while still providing sufficient channel information for downlink beamforming.
3Reliability
If beamforming is applied to meet performance requirements in high path-loss environments, then link budget is improved, but the number of required SRS transmissions increases
Solution Approach 1:
The patent implements an efficient feedback mechanism where the UE provides compressed channel feedback for a single best TRBC. This feedback enables the gNB to perform downlink beamforming with accurate channel information while avoiding the need for extensive SRS transmissions, thus maintaining link budget performance without sacrificing system efficiency.
Solution Approach 2:
The patent changes the feedback parameter structure by transmitting feedback for only one selected TRBC instead of multiple TRBCs. This parameter reduction maintains the essential channel information needed for beamforming in high path-loss environments while significantly reducing the number of SRS transmissions required, thereby improving overall system efficiency.
Data Source
AI summary
A method for transmitting feedback includes generating explicit channel feedback for a plurality of transmit beam-receive beam combinations (TRBCs) between the user device and a transmit-receive point (TRP), generating a modified resource in accordance with explicit feedback configuration information, the modified resource configured to convey the explicit channel feedback, wherein an explicit channel feedback associated with each TRBC is conveyed on a different data symbol of the modified resource, and transmitting the modified resource to the TRP using a single TRBC.