Subband Uplink Precoding Under DCI Capacity Limits
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Solution Overview
Problem
Existing wireless communication systems face limitations in indicating frequency-selective uplink precoding due to the limited capacity of downlink control information (DCI) for precoding matrix indicators, which restricts the ability to support enhanced precoding techniques for UEs with complex antenna configurations.
Innovation Solution
A base station transmits subband uplink precoding information through multiple control messages, including medium access control-control elements (MAC-CE) and physical downlink shared channels, to enable frequency-selective precoding, allowing UEs to use subband-specific precoding matrices for improved communication reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wideband precoding matrix indicators are used in DCI, then the control message capacity is maintained, but frequency-selective precoding capability is lost
Solution Approach 1:
The precoding information is segmented into wideband PMI and subband PMI components. The wideband PMI provides overall precoding direction while subband PMI provides frequency-specific adjustments. This segmentation allows frequency-selective precoding capability to be added without requiring the entire DCI to carry all precoding details, thus preserving DCI capacity while enabling adaptability.
Solution Approach 2:
A subband PMI field is introduced as an intermediary element between the wideband PMI and the actual frequency-selective precoding application. This intermediary carries the frequency-selective information needed for enhanced precoding while keeping the main DCI structure intact, resolving the conflict between capacity constraints and adaptability requirements.
2Measurement precision
If subband-specific precoding information is transmitted, then precoding precision is improved, but control signaling overhead increases
Solution Approach 1:
Instead of applying uniform precoding across the entire bandwidth, the system applies local quality variations by transmitting subband-specific PMI information. This allows precise precoding adjustments in specific frequency regions where needed, improving precoding precision while limiting the increase in control signaling overhead to only the necessary subband information rather than complete re-specification of all precoding parameters.
Data Source
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AI summary
Methods, systems, and devices for wireless communication are described. In some systems, a base station may transmit subband uplink precoding information to a user equipment (UE). The base station may transmit a first control message to the UE to indicate a set of downlink resources for a downlink message associated with the subband uplink precoding information for the UE. The base station may transmit a second control message to the UE to indicate a set of uplink resources for an uplink message. The base station may transmit the downlink message to the UE via the set of downlink resources indicated by the first control message. The downlink message, the second control message, or both may include the subband uplink precoding information for the UE. The UE may transmit an uplink message to the base station via the set of uplink resources using the subband uplink precoding information.