MIMO Beamforming Weight Computation via Sliding Window Channel Estimation
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Solution Overview
Problem
In MIMO wireless communication systems, determining accurate beamforming weights for downlink transmissions is challenging when the second wireless device transmits fewer spatial streams than the first device, as it lacks sufficient channel information.
Innovation Solution
The first wireless device extracts full channel information from received uplink streams using a sliding window approach across adjacent subcarriers, computing downlink beamforming weights by jointly examining spatial information carried on multiple frequency bins, even when fewer than the desired number of spatial streams are transmitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the second wireless device transmits fewer spatial streams than the first device, then the uplink transmission resource is reduced, but the downlink beamforming weight computation accuracy deteriorates due to insufficient channel information
Solution Approach 1:
The patent transforms the channel estimation problem from a spatial dimension limitation to a frequency dimension solution. By using a sliding window approach across adjacent subcarriers in the frequency domain, the system accumulates sufficient channel information even when the number of spatial streams is reduced. This dimensional transition allows accurate beamforming weight computation without requiring proportional uplink spatial stream transmission.
2Reliability
If channel information from all antennas is required for accurate beamforming weight computation, then the system reliability is improved, but the complexity of obtaining sufficient channel information increases when spatial streams are reduced
Solution Approach 1:
The patent performs preliminary channel information accumulation across multiple adjacent subcarriers before computing beamforming weights. By proactively gathering channel state information from the frequency domain using a sliding window approach, the system prepares sufficient data in advance, eliminating the need for complex spatial stream configurations and simplifying the overall channel acquisition process.
3Loss of information
If the same number of spatial streams are transmitted in both uplink and downlink, then the channel information availability is improved, but the adaptability of the system to unequal spatial multiplexing scenarios deteriorates
Solution Approach 1:
The patent creates a universal channel estimation method that functions effectively regardless of whether uplink and downlink spatial stream counts are equal or unequal. The sliding window approach across frequency subcarriers provides a multi-functional solution that adapts to various spatial multiplexing configurations, making the system versatile while maintaining channel information availability through frequency-domain accumulation.
Data Source
AI summary
Techniques are provided to allow for implicit determination of the full spatial signature of a wireless channel between first and second wireless devices for multiple-input multiple-output (MIMO) wireless communication between the first and second wireless devices. The first wireless device receives uplink signals at a plurality of antennas of the first wireless device that are transmitted via a plurality of antennas of a second wireless device. Values at a plurality of subcarriers of the received signals across the plurality of antennas of the first wireless device are derived. Using a sliding window for groups of adjacent subcarriers, downlink beamforming weights are computed for each group of subcarriers using channel information of one or more proximate groups of subcarriers. The downlink beamforming weights for the respective groups of subcarriers are applied to a number of spatial streams in a downlink transmission to be transmitted to the second wireless device.