Joint-Coded RI and PMI Feedback for 8-Antenna MIMO Systems
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Solution Overview
Problem
The legacy MIMO wireless communication system struggles to support extended antenna configurations, as the existing feedback information is insufficient for correct operation with multiple antennas, particularly when transitioning from 4 transmission antennas to 8, leading to inefficiencies in system capacity and performance.
Innovation Solution
A method and apparatus are introduced to efficiently transmit and receive channel status information (CSI) using a joint-coded rank indicator (RI) and wideband precoding matrix indicators (PMI) across multiple subframes, allowing for the correct configuration and support of MIMO operations with extended antenna configurations by indicating a user equipment (UE) preferred precoding matrix, specifically using a combination of PMIs to select appropriate precoding codebook subsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If legacy MIMO feedback information is used for extended antenna configurations, then system compatibility is maintained, but feedback accuracy and MIMO operation correctness deteriorate
Solution Approach 1:
The PMI feedback is segmented into two parts: first PMI indicating a subset of codebooks, and second PMI indicating a specific precoding matrix within that subset. This segmentation allows the system to support extended antenna configurations (8Tx) by dividing the large codebook into manageable subsets, thereby maintaining feedback accuracy while adapting to new antenna configurations.
Solution Approach 2:
The feedback mechanism transitions from a single-dimension PMI indicator to a two-dimension indicator system (first PMI + second PMI). This dimensional expansion enables the system to accurately represent precoding matrices for extended antenna configurations by adding an additional layer of codebook subset selection.
2Loss of information
If joint-coded RI and first PMI are transmitted in one subframe while second PMI and CQI are transmitted in another subframe, then feedback information completeness is improved, but transmission time and system complexity increase
Solution Approach 1:
The feedback information is segmented across two subframes: first subframe carries RI and first PMI (codebook subset selection), while second subframe carries second PMI (specific matrix selection) and CQI. This segmentation distributes the feedback burden over time, ensuring complete information transmission while managing uplink resource constraints.
Solution Approach 2:
The first PMI (codebook subset selection) is transmitted in advance in the first subframe along with RI, preparing the base station for the subsequent second PMI transmission. This preliminary action allows the receiver to have partial feedback information earlier, enabling intermediate processing while the complete feedback arrives in the second subframe.
Data Source
AI summary
A method and apparatus for performing effective feedback in a wireless communication system supporting multiple antennas. A method for transmitting CSI of downlink transmission via uplink in a wireless communication system includes transmitting a joint-coded rank indicator (RI) and a first wideband (WB) precoding matrix indicator (PMI) at a first subframe, and transmitting a wideband channel quality indicator (WB CQI) and a second WB PMI at a second subframe. A user equipment (UE) preferred precoding matrix is indicated by a combination of the first PMI and the second PMI. If the RI is Rank-1 or Rank-2, the first PMI indicates one of subsets each having 8 indexes from among 16 indexes of the first PMI of a precoding codebook.