Joint Transmission Rank Feedback for MIMO Distributed Antenna Arrays
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Solution Overview
Problem
Current mobile terminal feedback operates on a single-transmission point basis, limiting the maximum supported rank in MIMO systems, even when multiple transmission points are available, as it reports the rank based on the maximum individual transmission point capability rather than considering combined ranks across multiple points.
Innovation Solution
A method and apparatus that determine a joint transmission rank and precoding matrix across multiple transmission points, allowing for higher rank transmissions by diagonalizing or semi-diagonalizing per-cell feedback, enabling the mobile terminal to exploit low rank feedback for enhanced MIMO operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If mobile terminal feedback operates on a single-transmission point basis, then the feedback processing complexity is reduced, but the maximum supported transmission rank is limited
Solution Approach 1:
The feedback mechanism is segmented into two distinct components: per-transmission-point feedback ( reporting rank and precoding matrix for each individual transmission point) and joint feedback (reporting a separate joint transmission rank). This segmentation allows the system to maintain simple per-point feedback processing while adding a specific joint feedback element to enable higher rank transmissions across multiple points without overwhelming complexity
Solution Approach 2:
The invention transitions from a single-dimension feedback approach (single transmission point rank) to a multi-dimensional approach by introducing joint transmission rank as an additional dimension. This allows the system to report ranks both individually for each transmission point and collectively across multiple points, effectively increasing the maximum supported transmission rank while maintaining the simplicity of individual point feedback
2Productivity
If the system supports higher rank transmissions across multiple transmission points, then spectral efficiency is improved, but the feedback mechanism complexity increases
Solution Approach 1:
The feedback mechanism is segmented into two distinct components: per-transmission-point feedback ( reporting rank and precoding matrix for each individual transmission point) and joint feedback (reporting a separate joint transmission rank). This segmentation allows the system to maintain simple per-point feedback processing while adding a specific joint feedback element to enable higher rank transmissions across multiple points without overwhelming complexity
Solution Approach 2:
The system implements partial joint feedback by reporting only the essential joint transmission rank parameter in addition to per-point feedback, rather than requiring complete joint precoding matrix feedback. This partial approach provides sufficient information for higher rank transmissions while avoiding excessive feedback complexity
Data Source
AI summary
A method, apparatus and computer program product are provided for reporting low rank feedback information for each transmission point up to a maximum rank per transmission point. In this regard, a method includes determining a transmission rank and a precoding matrix for each of at least two transmission points of a plurality of transmission points. A method also includes determining a joint transmission rank based on at least two of the plurality of transmission points. A method also includes selecting a joint transmission precoding matrix based on the determined precoding matrix for each of the at least two transmission points and the determined joint transmission rank. The method further includes causing channel state information “CSI” to be transmitted to an access point, wherein the CSI describes the selected joint transmission precoding matrix.