## 3 System-Level Configuration
### System-Level Simulations
When users are transmitting a higher number of PRBs, the size of packets transmitted is higher and more likely to suffer deep fading. In this case, the link diversity of RIS + BS provided by the C-RAN is able to cope with the expected decrease in throughput. Figure 12: Coverage vs. transmit power for the stadium with pitch scenario for two different number of resource blocks: HPBS transmit power (35 dBm), \(N_{tx}\) = 64, \(N_{rx}\) = 16, \(N_{ris}\) = 576. The third evaluated scenario is the indoor factory, which is the only one with a higher frequency band at sub-THz. The system operates at 100 GHz, which, due to its shorter wavelength, allows us to work with more elements at the RIS, i.e., \(N_{RIS}=576\) up to 2304. The maximum transmit power of BS is 30 mW (14.8 dBm). Users are placed uniformly around two sites with TRPs equipped with UPA antennas per sector, localized 75 m close to the walls of the indoor factory (see Figure 5 and Table 3). We considered there to be a high clutter density inside the Factory, with both low BS antenna height and high BS antenna height. For this scenario, we keep the 5G NR numerology at 3, with \(\Delta\)f = 120 KHz, a bandwidth of 400 MHz, and 112 symbols transmitted in every millisecond, just as in the stadium scenario. Thus, it is possible to directly compare the two scenarios in spite of there being different frequency bands and areas. In all simulations in the factory environment, each transmitting TRP has a UPA with \(N_{tx}\) = 256 antennas, and the user receiver side has \(N_{rx}\) = 16. Different numbers of transmitted symbols per subcarrier were considered in the simulations, and \(N_{s}\) = 3. When there are no active RIS panels in the factory, there are only two BSs, each with three sectors, making a total of six sectors. In this case, users are uniformly distributed within a radius of 70 m (see Table 3). When simulating performance curves with BSs and RISs operating simultaneously, users that are connected to BSs will be uniformly distributed within a radius of 50 m. Some 16 RIS panels are uniformly distributed inside the scenario, and users served by them are distributed within a radius of 25 m.  
In Figure 14, the throughput performance versus \(N_{tx}\) in the factory scenario is shown, with low BS antenna height and RIS panels, for two different resource blocks. The scenario parameters are \(N_{tx}\) = 256, \(N_{rx}\) = 16, \(N_{s}\) = 3. An assignment of 11 PRBs per user gives \(N_{c}\) = 132, and 25 PRBs per user gives \(N_{c}\) = 300. With 11 PRBs per user, \(3300/120\) = 25 is the number of users per sector. With 25 PRBs per user, \(3300/3000\) = 11 is the number of users per sector. As there are six sectors in the Factory, and the total number of users is 150 or 66 for 11 PRBs and 25 PRBs, respectively. When users are exclusively served by the TRPs of BSs with direct links, i.e., 100%BS + 0%RIS, we have a total throughput of approximately  
Table 1.0 Throughput vs. number of resource blocks for the stadium scenario in the maximum load sector: \(N_{s}\) = 3, \(N_{tx}\) = 64, \(N_{rx}\) = 16, \(N_{ris}\) = 576. LPBS transmit power (24 dBm). 41 Gbps for 150 users (pink line), and a total throughput of 37 Gbps for 66 users (red line). In the factory, there are 16 \(\times\) 3 = 48 RIS panels and 2 \(\times\) 3 = 6 TRPs (one per sector). When users at cell borders start to be served by RIS panels, 48 users must be subtracted, resulting in 150 - 48 = 102 users served by six TRPs. The 48 users are served by RIS 48/150 = 0.32 (blue lines), and the remaining 68% users are served by TRPs 68%BS + 32%RIS,11 RB. In the case of 25 PRB (black lines), the total number of users is 66; we have 48 users served by RIS (i.e., 48/66 = 0.73) and the remaining \(66-48=18\) users served by TRPs (i.e.,18/66 = 0.27), 27%BS + 73%RIS,25 RB. We observed that increasing the number of RIS panels from 576 up to 2304 only increases the throughput slightly. This increment is more noticeable for 25 RB.