## 5 Results and Analysis
### Impact of Using Existing 4G Infrastructure  
5G is being rolled out massively worldwide, and most of the countries have invested in deploying 4G infrastructure. Nepal rolled out 4G on 1 January 2017 and invested about 142 million dollars to deploy 4G nationwide. Deploying 5G will incur a huge amount of investment again, and there will be a longer time to repay the investment. Using existing 4G infrastructure such as towers, backbone infrastructure (microwave/optical fiber), and civil infrastructure reduces the initial investment substantially. This paper analyzed the impact of existing 4G infrastructure for deployment of 5G networks. We have carried out simulations for two scenarios, i.e., urban and suburban areas, taking two use cases separately for each scenario. We calculated the requirement of RRUs with or without using existing 4G infrastructure as listed in Table 6. We conducted a financial analysis calculating the cost of components such as backhaul optical fiber, civil work for ducting and trending to lay optical fiber backhaul, and microwaves for backhaul connections and Table 7 shows the cost calculation of the resources. Both backhaul and optical fiber installation can be used as redundancy for backhaul, and reliability can be ensured even if a disaster happens. ever, using the existing 4G infrastructure, there are already 19 4G sites, and the required number of new macro-RRUs sites is 16. Using existing sites, up to 54.2% of resources and their cost can be saved in suburban areas as illustrated in Tables 6 and 7. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \multicolumn{2}{c}{**Urban**} & \multicolumn{2}{c}{**Suburban**} \\ \hline Components & \begin{tabular}{c} 5G \\ Greenfield \\ \end{tabular} & \begin{tabular}{c} 5G with 4G \\ sites \\ \end{tabular} & \
\begin{tabular}{c} 5G \\ Greenfield \\ \end{tabular} &
\begin{tabular}{c} 5G with 4G \\ sites \\ \end{tabular} \\ \hline Initial requirement (coverage and Capacity Dimensioning) & & & & \\ \hline Number of New RRU required (28 GHz) & 70 & 40 & \(\times\) & \(\times\) \\ \hline Number of New RRU required (3.5 GHz) & \(\times\) & \(\times\) & 35 & 16 \\ \hline Number of Existing 4G sites & \(\times\) & 30 & \(\times\) & 19 \\ \hline Final requirement (After Optimization) & & & & \\ \hline Number of New RRU required (28 GHz) & 66 & 41 & \(\times\) & \(\times\) \\ \hline Number of New RRU required (3.5 GHz) & 8 & 8 & 35 & 16 \\ \hline Number of Existing 4G sites & \(\times\) & 30 & \(\times\) & 19 \\ \hline Total number of new sites required & 74 & 49 & 35 & 16 \\ \hline Total length of Civil work for ducting and trenching (m) & 14,800 & 9800 & 17,500 & 8000 \\ \hline Number of new Backbone sites required (Microwave/Optical Fiber) sites & 74 & 49 & 35 & 16 \\ \hline Total Backhauling Fiber length (m) & 16,280 & 10,780 & 18,550 & 8480 \\ \hline Final requirement (After Carrier Aggregation) & & & & \\ \hline Number of New RRU required (28 GHz) & 66 & 41 & \(\times\) & \(\times\) \\ \hline Number of Carrier aggregated sites (28 GHz + 3.5 GHz) & 10 & 10 & \(\times\) & \(\times\) \\ \hline Total number of new sites required & 66 & 41 & 35 & 16 \\ \hline Total length of Civil work for ducting and trenching (m) & 13,200 & 8200 & 17,500 & 8000 \\ \hline Number of new Backbone sites required (Microwave/Optical Fiber) sites & 66 & 41 & 35 & 16 \\ \hline Total Backhauling Fiber length (m) & 14,520 & 9020 & 18,550 & 8480 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: RRU requirements for 5G optimization.