Beamforming Weights Using Shared Feedback for Cellular Channels
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Solution Overview
Problem
Current cellular systems face challenges in beamforming for different downlink physical channels, such as PDCCH and PDSCH, as they require distinct performance criteria, leading to increased computational complexity and feedback overhead when using separate feedback mechanisms.
Innovation Solution
The method involves projecting the estimated channel matrix onto spatial orthonormal functions to generate coefficients, which are then filtered based on channel-specific parameters to compute beamforming weights for multiple downlink channels using the same feedback, allowing for tailored beamforming for each channel type without substantial increases in complexity or overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate feedback mechanisms are used for different downlink physical channels (PDCCH, PDSCH), then each channel can be beamformed to satisfy its specific performance criteria, but feedback overhead and computational complexity substantially increase
Solution Approach 1:
The patent merges the feedback mechanisms for PDCCH and PDSCH into a single unified feedback process. The UE provides one set of channel state information feedback that is used to derive beamforming weights for both control and data channels, eliminating the need for separate feedback transmissions and reducing overall feedback overhead while maintaining channel-specific performance requirements through different filtering parameters.
Solution Approach 2:
The patent makes the single feedback mechanism universal by enabling it to serve multiple downlink physical channels simultaneously. The same feedback information is processed through channel-specific filtering parameters to generate appropriate beamforming weights for both PDCCH and PDSCH, allowing one feedback mechanism to fulfill multiple channel-specific beamforming requirements.
2Reliability
If separate feedback mechanisms are used for different downlink physical channels, then channel-specific beamforming performance is improved, but feedback delay increases causing beamforming to lag
Solution Approach 1:
By combining the feedback requirements into a single unified feedback transmission, the patent eliminates the need for multiple separate feedback rounds. This single feedback mechanism provides timely channel state information that is immediately processed through channel-specific filtering to generate beamforming weights for both PDCCH and PDSCH, reducing feedback delay and preventing beamforming lag.
3Reliability
If the precoding waveform is modified to satisfy different performance criteria for each physical downlink channel, then channel-specific reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by using channel-specific filtering parameters that are tailored to the requirements of each downlink physical channel. The same feedback information is processed differently for PDCCH and PDSCH through channel-specific filtering, allowing each channel to receive beamforming optimized for its specific performance criteria without requiring separate feedback mechanisms or substantially increasing computational complexity.
Data Source
AI summary
Embodiments of a method in a base station for precoding a downlink transmission are disclosed. In some embodiments, the method comprises obtaining, for a time instant k, an estimate of a channel matrix for a wireless channel for a downlink from the base station to a wireless device and projecting the estimate of the channel matrix onto one or more sets of spatial orthonormal functions, thereby obtaining respective sets of coefficients. The method further comprises, for each set of spatial orthonormal functions, filtering the set of coefficients for the time instant k based on a filtering parameter that is specific to a downlink channel to be transmitted. The method further comprises generating beamforming weights using the filtered set of coefficients for at least one of the sets of spatial orthonormal functions, and precoding the downlink channel using the beamforming weights.