# 5G/B5G mmWave Cellular Networks with MEC Prefetching Based on User Context Information +
## 4 Computer Simulation
### Numerical Analysis  
Figure 8 plots the system rates for the 28 and 60 GHz mmWave bands against the backhaul capacity with several prefetching algorithms: WPF, Round-Robin (RR), and without prefetching. In the case of backhaul capacity with 0 bps, the system rate approaches that of the macro cell--it is about 100 Mbps. On the other hand, unlimited backhaul capacity, such as 10 Gbps, diminishes the effectiveness of the prefetching. The prefetching can enhance the system rate under the constraint of the backhaul capacity. Several existing works (e.g., [42; 43]) have shown the high capacity provided by mmWave. In this study, we impose a backhaul constraint on it, resulting in the \"w/o prefetching\" characteristics shown in the figure. By applying prefetching, the demand traffic can be appropriately allocated to the limited backhaul resources and immediately delivered to the end user; it can fully leverage the capability of the millimeter wave. The prefetching is effective up to a 3 Gbps backhaul capacity for the 28 GHz band and 10 Gbps capacity for the 60 GHz band. The 60 GHz band requires larger backhaul links due to its higher access rate, which allows more benefit from prefetching. The proposed prefetching algorithm can further improve system rate compared to an RR-based one. With the 60 GHz band, the proposed WPF with 1 Gbps-backhaul can achieve about 95% of the maximal system rate, which is conventionally realized by 10 Gbps-backhaul. Although there are various algorithms and stochastic constraints for prefetching and mobility prediction as introduced in [11; 12; 26], they are treated as ideal in this study. This point needs to be evaluated in a more detailed manner, and we would like to discuss it in our future work. Figure 9 shows the average download time with the backhaul capacity. This is measured by the total time required to completely transfer a UE's demanded traffic. The maximum download time in the case of only macro cell is about 40 s. For the backhaul capacity of 1 Gbps, the proposed prefetching algorithm can reduce the delay by factors of approximately 67% and 26% in the 28 and 60 GHz bands, respectively, as compared to the conventional case without MEC and prefetching. Figure 10 shows the system rate against the number of users with backhaul capacity of 1 Gbps and a time window of 500 s. The system rate increases linearly and drastically from 0 to 300 users because this network system has surplus communication resources, and the congestion of demand traffic rarely happens in the region. From 300 to 500 users, congestion of the traffic demand starts due to the shortage of resources, and the system rate increases slowly and tends to saturate. From 500 or more UE, the system reaches the upper limits. Comparing two prefetching algorithms and conventional one, the gap of system rate among them tends to be enlarged as the number of users increases; the proposed approach \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline US antenna elements & 2 \\ BS antenna height (Macro/Small) & 25 m/10 m/4 m \\ UE antenna height & 1.5 m \\ BS antenna beam pattern (Macro/Small) & 3 GPP-LTE [38]/5G-NR/IEEE802.11 ad \\ UE antenna beam pattern & Half-wave dipole \\ Channel model & QuaDRiGa [39] \\ Tx power (Macro/Small) & 46 dBm/10 dBm \\ LOS probability (Macro/Small) & [38]/[40] \\ Path loss model (Macro/Small) & [38]/[40] \\ Shadowing std. (Macro/Small) & [38]/[40] \\ Backhaul capacity & 0 bps, 1 Mbps-30 Gbps \\ Prefetching window & 0-100, 500 s \\ PF coefficient & 3 \\ Storage limitation & 0–10 GB, Infinity \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._becomes more advantageous. In short, in an environment where many users exist, the usefulness of the prefetching including our proposed algorithm could be more important. Figure 11 shows the normalized loss of the system rate against different storage limits and time windows on the conditions of 1 Gbps backhaul capacity with 60 GHz band, WPF algorithm, and 200 UE.