CSI Codebook Feedback for High-Speed FD-MIMO Precoding

The patent transitions from static closed-loop pre-coding to dynamic open-loop MIMO transmission, where pre-coding matrixes are selected alternately from a predefined set without requiring real-time CSI feedback. This dynamic approach adapts to high-speed scenarios where channel conditions change rapidly, preventing CSI from becoming outdated while maintaining transmission performance.

The patent eliminates the dependency on CSI feedback by implementing open-loop transmission. Instead of relying on terminal feedback that becomes outdated in high-speed scenarios, the system uses a predefined set of pre-coding matrixes that are applied alternately, removing the feedback loop that causes timing mismatches in fast-changing channels.

Instead of traversing all possible pre-coding matrixes in the codebook, the patent applies a partial action approach by selecting and applying pre-coding matrixes alternately from a predefined set. This reduces the traversal burden from examining all N matrixes to using a manageable subset, significantly lowering implementation complexity while maintaining adequate beamforming flexibility for FD-MIMO systems.

The patent segments the large codebook of pre-coding matrixes into a smaller predefined set that can be managed and traversed efficiently. By dividing the comprehensive codebook into a selective subset used in open-loop transmission, the system reduces the traversal complexity from O(N) to a manageable level, enabling practical implementation in FD-MIMO systems.