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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)