# Fronthaul Design for Wireless Networks
## 4 Fronthaul Design Study Results
### Individual Links Assessment
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & \multirow{2}{*}{\(\begin{array}{c}\text{{U}}_{max}\\ \text{(\text{\text{\textminus}})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{T}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{R}}_{i}^{\text{(0,01\%)}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{H}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{h}}_{\text{\textminus}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{h}}_{\text{\textminus}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{h}}_{\text{\textminus}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{h}}_{\text{\textminus}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{h}}_{\text{\textminus}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{\(\begin{array}{c}\text{{D}}\\ \text{(\text{\textminus})}\end{array}\)} & \multirow{2}{*}{**Rain Intensity**} & \multirow{2}{*}{**Fog Intensity**} \\ \hline S(r\_1/f\_1) & & & 15 & & & 10 & & Low & Low \\ S(r\_h/f\_1) & & & 135 & & & 10 & & High & Low \\ S(r\_1/f\_h) & & & 15 & & & 360 & & Low & High \\ S(r\_h/f\_h) & & & 135 & & & 360 & & High & High \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Characteristics of the test scenarios. Figure 4: Cost-effective solutions for S(r_1/f_1). Figure 5: Cost-effective solutions for S(r_h/f_l). Figure 6: Cost-effective solutions for S(r_l)/f_h). Due to the low rain and low fog intensities considered in S(r_l/f_l), this scenario has very good wireless propagation conditions for both MRT and FSO technologies. Accordingly and as can be observed in Figure 4, an FSO system should be adopted for these weather conditions when the required bit rate is low to medium (lower than 1 Gbps) and the link distance is small (below 4 km) or when the required bit rate is higher (1 to 1.5 Gbps, at least) and the link distance is within a narrow range of small distances (2.5 to 3 km); for the medium bit rate requirement range (570 Mbps to 1.1 Gbps) and for medium link distances (4.5 to 11 km), MRT systems are the best choice; the MRT technology also yields the best results for a wider range of link distances (namely from 4 to 11.5 km and from 4 to 16.5 km), but for lower bit rate requirements (below 570 Mbps and below 400 Mbps, respectively); for all the remaining cases, FO systems are the best choice. Some conclusions can be drawn from these results: first, there is a trade-off between bit rate and distance ranges regarding the cost-effectiveness of MRT and FSO solutions; secondly, the feasibility of a wireless link does not necessarily mean that it is a cost-effective solution; for instance, although FSO links are practicable regarding small distances and high bit rate requirements (notably greater than 1 Gbps), FO systems are a better cost-effective choice in these cases if the link distance is closer to zero (an equivalent example could be given regarding MRT versus FO systems and with respect to small to medium link distances and medium bit rate requirements); nevertheless, FSO solutions can be used as a fallback in these cases, namely if the FO technology cannot be used, e.g., due to the orography of the terrain or the necessity of a quick installation following a natural disaster. Considering now S(r_h/f_l), which is a scenario characterized by high rain and low fog intensities, Figure 5 shows that both wireless technologies decreased their cost-effective performance in terms of maximum link distance when compared to S(r_l/f_l); this performance decrease was more pronounced regarding MRT systems, especially in the case of medium bit rate requirements (they had a reduction of 6 km regarding the maximum feasible link length).