Frequency Band Extrapolation for Beamforming Weight Computation
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Solution Overview
Problem
In wideband wireless communication systems, the lack of channel signature information across all frequency subbands reduces the reliability of beamforming techniques, and feedback of estimated channel coefficients from mobile stations to base stations requires excessive overhead in TDD systems.
Innovation Solution
The frequency extrapolation beamforming weight computation process derives knowledge of channel behavior in unmeasured frequency subbands by computing channel covariance matrices from received baseband signals, estimating uplink beamforming weights, and projecting them to determine downlink beamforming weights for reliable transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beamforming techniques are used in wideband wireless communication systems with bandwidth larger than coherent frequency bandwidth, then transmission capacity is improved, but reliability of beamforming decreases due to uncorrelated channel signatures in different frequency subbands
Solution Approach 1:
The wideband frequency spectrum is segmented into multiple frequency subbands, each processed independently to capture local channel characteristics. This allows beamforming weights to be optimized for each subband while maintaining overall system reliability across the wide bandwidth.
Solution Approach 2:
The patent changes the parameter of beamforming weight computation by introducing frequency-dependent weights that adapt to channel conditions in each subband. This allows the system to maintain reliable beamforming performance across different frequency ranges despite channel signature uncorrelation.
2Loss of information
If all estimated channel coefficients in all frequency subbands are fed back from mobile station to base station, then complete channel information is obtained for accurate beamforming, but transmission overhead increases excessively
Solution Approach 1:
The patent extracts only the essential channel information needed for beamforming weight computation rather than transmitting all channel coefficients. By extracting and feeding back only critical parameters, the system maintains beamforming accuracy while dramatically reducing feedback overhead.
Solution Approach 2:
Instead of transmitting complete channel coefficient data, the system uses a simplified representation or model that captures the essential channel characteristics needed for beamforming. This copying approach reduces the amount of data that needs to be fed back while preserving the information necessary for reliable beamforming.
3Reliability
If channel covariance matrices are computed from received baseband signals to derive channel knowledge in unmeasured frequency subbands, then beamforming reliability in wideband systems is improved, but computational complexity increases
Solution Approach 1:
The patent performs preliminary computation of channel covariance matrices from available baseband signals before actual beamforming operations. This preliminary action captures channel statistics that can be reused across multiple transmissions and frequency subbands, reducing the need for repeated complex computations.
Solution Approach 2:
The computed channel covariance matrices serve multiple functions: they characterize channel conditions in measured subbands, enable extrapolation to unmeasured subbands, and provide a foundation for beamforming weight computation across the entire bandwidth. This multi-functionality reduces overall computational requirements.
Data Source
AI summary
Techniques are provided to facilitate the computation of beamforming weights used by a first communication device when sending a transmission via a plurality of antennas to a second communication device where knowledge of the behavior of the channel between the first communication device and the second communication device is limited to a portion of a wide frequency band. A frequency extrapolation beamforming weight computation process is provided to derive knowledge in other frequency subbands based on information contained in the received transmission from the second communication device.