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# Table 2 Different representations of CSI in different stages

From: A limited feedback scheme for massive MIMO systems based on principal component analysis

Representations | Implications |
---|---|

h
| Original high-dimensional CSI estimated by MS |

Low-dimensional CSI after normalization | |

\({\bar {\mathbf {h}}}\) | and compression, that is \({\bar {\mathbf {h}} = \frac {{{\mathbf {h}\bar {\mathbf {U}}}}}{{\left \| {{\mathbf {h}\bar {\mathbf {U}}}} \right \|}}}\) |

\({\hat {\mathbf {h}}}\) | Quantized low-dimensional CSI |

h⌢ | High-dimensional CSI recovered from \({\hat {\mathbf {h}}}\) |

High-dimensional CSI recovered from \({\bar {\mathbf {h}}}\) | |

\({\tilde {\mathbf {h}}}\) | (with no quantization error of low-dimensional CSI) |