Adaptive Transmit Beamforming for FDD Systems
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Solution Overview
Problem
Conventional FDD systems for transmit beamforming in wireless communication are slow to adapt to changing channel conditions due to their closed-loop mode operation, which increases overhead and reduces efficiency in estimating state information for improved SINR.
Innovation Solution
An open-loop method for estimating state information of a wireless channel in FDD systems, where the mobile station estimates channel impulse responses using known training sequences and transforms them into the frequency domain to determine frequency responses for beamforming, allowing for quicker adaptation to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop mode is used for channel state information estimation in FDD systems, then the transmitter can obtain channel state information for beamforming, but the system becomes slow to adapt to changing channel conditions and increases overhead
Solution Approach 1:
The receiver estimates channel state information in advance based on received signals and feeds back compressed indications to the transmitter. This preliminary estimation allows the transmitter to have channel state information available before actual beamforming transmission, enabling faster adaptation compared to waiting for continuous feedback loops.
Solution Approach 2:
A compressed indication of channel state information acts as an intermediary between the full channel state estimation and the transmitter's beamforming control. This intermediary representation reduces overhead while still enabling the transmitter to adapt to channel changes, bridging the gap between estimation accuracy and feedback efficiency.
2Measurement precision
If closed-loop mode is used for channel state information estimation in FDD systems, then the transmitter can obtain channel state information for beamforming, but the overhead is increased
Solution Approach 1:
The essential channel state information is extracted and fed back to the transmitter in a compressed form. Instead of transmitting complete channel state data, only the most critical compressed indications are sent, reducing feedback overhead while maintaining sufficient accuracy for beamforming operations.
Solution Approach 2:
The channel state information is transformed from its original detailed form into a compressed representation with changed parameters. This parameter transformation reduces the amount of data that needs to be fed back to the transmitter, lowering overhead while preserving the essential information needed for beamforming.
3Productivity
If TDD system uses same frequency band for both directions, then the transmitter can form estimate of channel state information based on received signal, but this approach cannot be directly applied to FDD systems
Solution Approach 1:
The patent develops a channel estimation method that works universally for both TDD and FDD systems. By using reference signals that can be transmitted in both directions and applying cross-correlation techniques, the same fundamental approach can estimate channel state information regardless of whether the system uses time-division or frequency-division duplexing.
Solution Approach 2:
The patent transitions from frequency-domain correlation (suitable for TDD) to time-domain correlation (suitable for FDD). By changing the domain in which correlation is performed, the method adapts to the different characteristics of FDD systems where uplink and downlink use different frequency bands, making the approach versatile across duplexing modes.
Data Source
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AI summary
Embodiments of a method and apparatus for performing an adaptive transmission scheme in a frequency division duplexing communication system based on channel state information estimated using an open-loop mode are described herein. In one example, the method includes estimating an impulse response of a channel using a signal received over a first frequency band of the channel from a device, transforming the impulse response into a frequency response of the channel, and subsequently performing the adaptive transmission scheme using the frequency response to transmit a signal to the device over a second frequency band of the channel that is different from the first frequency band.