Figure 1

The partitioning of the frequency-domain channel matrix $H_d^{(m\mathrm{,}n)}$. Its rows correspond to the positions of the received samples; its columns to the positions of the pilots and data. Note that $H_{\mathsf{\text{d}}}^{\left(m,n\right)}$ is in principle a full matrix, but with most of its energy concentrated around the diagonal. This effect is represented in the figure by the different shades.