## 2 Materials and Methods
### Wi-Fi Network Design
#### 2.2.1 Wi-Fi Network Coverage Design  
The first step in system dimensioning involves determining the number of BS transmitters required to cover the whole campus. For this, we needed to estimate the maximum path loss following the approach described in [19]. Then, the link budget was calculated to determine whether the power level received will be sufficient for the link to function correctly and also assess the quality of the signal. This parameter is difficult to assess, as it depends on the user's needs. Wi-Fi transmitters required for optimal Wi-Fi coverage were installed on solar-powered street lighting poles to minimize cost and GHG impacts.  
Figure 2: Geographical location of the proposed case study. Standalone solar-powered Wi-Fi built at ENST (Algiers, Algeria) [18].  
In order to determine the path loss (PL), different propagation models were considered. The most suitable model for the Wi-Fi network is the Egli model [19]. The Egli model for median path loss over irregular terrain is  
\[\mathrm{PL}_{50}\ =\mathrm{G}_{\mathrm{b}}\mathrm{G}_{\mathrm{m}}\left[\frac{ \mathrm{h}_{\mathrm{b}}\mathrm{h}_{\mathrm{m}}}{\mathrm{d}^{2}}\right]^{2}\left( \frac{40}{\mathrm{f}}\right)^{2}\mathrm{P}_{\mathrm{t}} \tag{1}\]  
where  
\(\mathrm{PL}_{50}\): path loss (W);  
\(\mathrm{G}_{\mathrm{b}}\): gain of base transmitter (dB);  
\(\mathrm{G}_{\mathrm{m}}\): gain of mobile transmitter (dB);  
\(\mathrm{h}_{\mathrm{b}}\): height of base station antenna (m);  
\(\mathrm{h}_{\mathrm{m}}\): height of mobile station antenna (m);  
d: link distance (m);  
f: frequency (MHz);  
\(\mathrm{P}_{\mathrm{t}}\): Transmit power (W).  
The power components of the link budget related to the transmitter side are critical. This is often represented by the effective isotropic radiated power (EIRP), given by:  
\[\mathrm{EIRP}\ =\ \mathrm{P}_{\mathrm{t}}-\ \mathrm{L}_{\mathrm{c}}+\mathrm{G}_{ \mathrm{a}} \tag{2}\]  
where  
\(\mathrm{P}_{\mathrm{t}}\): transmit power (dBm);  
\(\mathrm{L}_{\mathrm{c}}\): cable loss (dB);  
\(\mathrm{G}_{\mathrm{a}}\): transmitter antenna gain (dBi).  
The power component of the link budget related to the receiver side is represented by the received power (\(\mathrm{P}_{\mathrm{r}}\)):  
\[\mathrm{P}_{\mathrm{r}}(\mathrm{dBm})=\mathrm{EIRP}-\mathrm{PL}+\mathrm{G}_{ \mathrm{R}}-\mathrm{L}_{\mathrm{c}} \tag{3}\]  
where  
PL: path loss (dB);  
\(\mathrm{G}_{\mathrm{R}}\): receiver antenna gain (dBi).  
In order to properly detect the transmitted signal, the following conditions must be satisfied.  
\[\mathrm{Received\ power\ >\ Receiver\ sensitivity} \tag{4}\]  
The proposed coverage design of the Wi-Fi-based BS allows us to determine the number of cells to optimize signal coverage. The total number of cells is given by:  
\[\mathrm{Number\ of\ cells}=\frac{\mathrm{Total\ area}}{\pi\cdot\mathrm{R}} \tag{5}\]  
where R is the range of each BS.  
The number of access points (NPC) for each cell is determined by the following ratio:  
\[\mathrm{NPC}\ =\ \frac{\mathrm{BPT}}{\mathrm{BPP}} \tag{6}\]  
where  
BPT: total bandwidth;  
BPP: bandwidth offered by an access point.  
The total number of access points (NPT) in the network will then be:  
\[\mathrm{NPT}\ =\ \mathrm{NPC}\cdot\mathrm{NC} \tag{7}\]where  
NPC: number of access points per cell;  
NC: number of cells.