# Multiuser Equalizer for Hybrid Massive MIMO mmWave CE-OFDM Systems
## Appendix A  
In this section, it is presented the solution for full-digital case, since the design of hybrid equalizer has the aim to minimize the norm of difference between \(\mathbf{W}_{d,k}^{(i)}\!\left(\mathbf{W}_{a}\right)^{H}\) and the feedforward filter for the full-digital case, \(\mathbf{W}_{fd,k}^{(i)}\in\mathbb{C}^{\mathrm{t}\times\mathrm{N}_{\mathrm{r}}}\). The design for fully digital equalizer was proposed in [27], to minimize the \(\mathrm{MSE}_{k}^{(i)}=\mathbb{E}[\|\mathbf{\widetilde{c}}_{k}^{(i)}- \mathbf{c}_{k}\|^{2}]\), given by (13) for \(\mathbf{W}_{a}=\mathbf{I}_{\mathrm{N}_{\mathrm{r}}}\), such that:  
\[\begin{split}&\left(\mathbf{W}_{fd,k}^{(i)}\mathbf{B}_{d,k}^{(i)} \right)=\mathrm{argminMSE}_{k}^{(i)}\\ &\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad  
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