## 3 System-Level Configuration
### Link-Level Simulations  
The performance of the adopted scheme, namely, the joint design of the precoder and phase-shifts of the RIS elements, is assessed considering a MIMO-OFDM link, and compared against other MIMO-OFDM systems. Monte Carlo simulations were run according to the system model presented previously.  
Figure 6 shows the BER performance versus the distance between the transmitter and the receiver. The distance between the Tx--Transmitter and the Rx--receiver is presented in the x axis in Figure 6. For this comparison, we use a transmitted power of \(P_{user}\) = 10  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Smart City @ 3.6** & **Smart City @ 28** \\ \hline Area (m\({}^{2}\)) & 660 \(\times\) 550 m\({}^{2}\) & 660 \(\times\) 550 m\({}^{2}\) \\ Carrier frequency & 3.6 GHz & 28 GHz \\ Cell range w/o RIS & 134 m & 134 m \\ \multirow{2}{*}{IoT device mobility IoT device distribution (horizontal)} & \multirow{2}{*}{0 km/h} & \multirow{2}{*}{0 km/h} \\  & & \\ \end{tabular}
\end{table}
Table 1: Parameters of the smart city scenario.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Stadium Stands** & **Stadium Turf** \\ \hline Area (m\({}^{2}\)) & 168 \(\times\) 126 m\({}^{2}\) & 144 \(\times\) 108 m\({}^{2}\) \\ Carrier frequency & 28 GHz & 28 GHz \\ Cell range w/o RIS & 57 m & 57 m \\ \multirow{2}{*}{User mobility User distribution (horizontal)} & \multirow{2}{*}{0 km/h} & \multirow{2}{*}{3 km/h} \\ User distribution (horizontal) & & Uniform \\ Maximum UEs attached & Up to 20,923 & Up to 18,277 \\ Transmission power & 35 dBm \& 24 dBm & 35 dBm \& 24 dBm \\ BS antenna gains & 0 dBi & 0 dBi \\ Area of RIS elements & 29.16 mm\({}^{2}\) & 29.16 mm\({}^{2}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of the stadium with pitch scenario.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Factory w/Low BS** & **Factory w/High BS** \\ \hline Area (m\({}^{2}\)) & 300 \(\times\) 150 m\({}^{2}\) & 300 \(\times\) 150 m\({}^{2}\) \\ Carrier frequency & 100 GHz & 100 GHz \\ Cell range w/o RIS & 70 m & 70 m \\ \multirow{2}{*}{User mobility User distribution (horizontal)} & \multirow{2}{*}{50 km/h} & \multirow{2}{*}{50 km/h} \\  & & \\ \end{tabular}
\end{table}
Table 3: Parameters of the indoor factory scenario.  
dBm. We observe curves for five different configurations. The parameters used are \(N_{tx}=64\), \(N_{s}=3\), \(N_{rx}=16\), \(N_{ris}=144\) or \(576\) elements, and \(N_{c}=1\). Curves with the proposed AM-SVD-APG algorithm are presented and assume the existence of direct and indirect links between the transmitter and receiver. BER values should decrease along with the reduction in the distance between transmitter and receiver. When this distance is increased, the opposite occurs and there is a distance beyond which the received signal strength becomes low to the point it results in error rates above 0.001. We can check that in Figure 6, BER values are already greater than 0.001 for a distance of 20 m in the case of the curve without RIS, where we are assuming an NLOS link with high attenuation loss between Tx-Rx. When RISs are adopted, it can be seen that the curves improve and the distances where the BER becomes higher than 0.001 increase, reaching 70 m for the case of an RIS with 576 elements combined with the AM-SVD algorithm. To compare with our algorithm, we include results obtained with the APG algorithm from [23]. It can be observed that our scheme clearly outperforms APG.