## 5 Results
### Coverage Analysis  
The first part of the simulation studies compares the coverage of the state-of-the-art network-centric architecture and that of the novel UCCF M-MIMO architecture. For this purpose, we generated radio channel coefficients for 3542 users uniformly distributed throughout the considered network area, with an inter-user space of 5 m. For each user and a varying number of serving RUs, we computed the Received Signal Strength (RSS) using the term _Desired signal_ from (3), assuming that \(p_{i,l,r}=\frac{P_{l}}{N_{\mathrm{R}}}\), and the MRT precoder. The results, presented as a map of the RSS averaged over the RBs, for both the network-centric architecture (each user can only be served by one RU providing the highest RSRP calculated using (10)) and the UCCF architecture with six serving RUs, are depicted in Figure 3. The benefits of utilizing the UCCF M-MIMO network architecture are especially visible in the alley on the right, where multiple micro-RUs were deployed. For the UCCF M-MIMO network architecture with six RUs serving the UEs, the radio signal within the alley maintains an average RSS oscillating around \(-35\) dBm. On the other hand, for the network-centric architecture, clear boundaries between cells are visible, with the average RSS dropping below \(-45\) dBm.  
To gain better insights into the relationship between the observed RSS and the number of RUs serving a single UE, we examined the ratio between the RSS averaged over the RBs for the UCCF M-MIMO and network-centric architectures under varying numbers of RUs serving a single UE. The Cumulative Distribution Function (CDF) of this ratio is  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Center frequency \(f\) & 3.6 GHz \\ Number of RBs \(N_{\mathrm{rb}}\) & 69 \\ Time slot duration \(T_{\mathrm{slot}}\) & 0.5 ms \\ Subcarrier spacing & 30 kHz \\ Number of CU–DUs & 1 centralized and virtual \\ Number of RUs \(N_{\mathrm{ru}}\) & 6 (1 macro-RU, 5 micro-RUs) \\ RU installation height & macro-RU: 45 m; micro-RUs: 6 m \\ Rapp PA model smoothing factor \(p\) & 12 \\ Transmit power \(P_{l}\) & macro-RU: 46 dBm; micro-RUs: 30 dBm \\ Number of antennas \(M_{l}\) & macro-RU: 128; micro-RUs: 32 \\ Threshold of correlation coefficient \(\Delta\) & 0.7 \\ Maximum number of spatial layers \(N_{\mathrm{L}}\) & macro-RU: 32; micro-RUs: 8 \\ Wireless InSite configuration & 15 reflections, 1 diffraction \\ \hline \hline \end{tabular}
\end{table}
Table 2: Simulation parameters.  
depicted in Figure 4. We can see that the maximal gain related to the utilization of the UCCF M-MIMO network architecture over the network-centric approach is about 11 dB when using six RUs. This observation aligns with the findings from the coverage map. However, it can be seen that while a significant gain in the average RSS ratio can be observed between two and three RUs serving a single UE, for four, five, and six RUs, the gain is marginal. This somehow motivates the idea of forming serving clusters. It is worth mentioning that significant improvements in the average RSS can be observed for about 25% of UEs. This is because in many locations, the RSS from one RU is much higher than from others, e.g., the middle part of the considered area is mostly covered by the macro-RU, and the UEs placed therein benefit marginally from UCCF M-MIMO.