# Beyond the Horizon, Backhaul Connectivity for Offshore IoT Devices
## 2 Methodology
### Average Measured Pathloss Campaign  
Average measurement of path loss campaign is carried out in the Malaysian region over the South China Sea as shown on a Google map in Figure 2.  
The received signal level is measured using a spectrum analyzer. System constants, listed in Table 1, are used to calculate propagation pathloss. System constants such as power transmitted \(P_{T}\), antenna gains \(G_{T}\) and \(G_{R}\), power amplifier gain \(G_{PA}\), low noise amplifier gain \(G_{INA}\) are obtained from the manufacturer datasheet. Insertion Losses \(IL\) includes Coaxial cable losses which are computed for both transmitter and receiver at 5.8 GHz. Pathloss in dB is computed using following equation:  
\[PL(dB)=P_{T}+G_{T}+G_{R}+G_{PA}+G_{LNA}-IL-P_{R} \tag{1}\]  
At the transmitter site in Figure 3a, Vector Signal Generator (VSG) is used to generate signal carrier frequency at 5.8 GHz with maximum transmit power of +23 dBm. Wideband power amplifier is used in series with VSG, having output power of 3 Watts, to make the total output power transmitted to be +33 dBm at 5.8 GHz. Broadband Horn Antenna with 12 dBi Gain is used to transmit the signal in the air. At the receiver site in Figure 3b,Spectrum Analyzer is used to receive the carrier signal with center frequency of 5.8 GHz. A Low Noise Amplifier (LNA) is used in series with Spectrum Analyzer, which provides an additional gain of 26 dB. Broadband Horn Antenna with 12 dBi Gain, similar to the transmitter, is used to receive the signal in the air. A MATLAB script featuring SCPI commands is used to control the instrument and to acquire discrete time data from Spectrum Analyzer. The center frequency and span of Spectrum analyzer is set to 5.8 GHz and 10 KHz respectively.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Definition** & **Constant Value** \\ \hline \(P_{T}\) & Transmitted Power (dBm) & 23 \\ \(G_{T}\) & Tx Horn Antenna Gain (dBi) & 12 \\ \(G_{R}\) & Rx Horn Antenna Gain (dBi) & 12 \\ \(G_{BA}\) & Power Amplifier Gain (dB) & 33 \\ \(G_{\text{LNA}}\) & Low Noise Amplifier Gain (dB) & 26 \\ \(IL\) & Insertion Loss (dB) & 22 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Constant parameter values for measurement campaign.  
Figure 3: Block Diagram of: **(a)**. Transmitter site equipment **(b)**. Receiver site equipment.  
Figure 2: Google Map of six link paths for measurement campaign over the Malaysian Region of the South China Sea from 10 km to 100 km.  
Once Received Signal Strength (\(RSL\)) is acquired from the spectrum analyzer, post-processing is performed to de-embed the system constants and to obtain propagation Pathloss. System constants include total power transmitted (\(P_{T}\)), antenna gains (\(G_{T}\) and \(G_{R}\)), low noise amplifier gain (\(G_{LNA}\)) are obtained from the manufacturer datasheet. \(L_{T}\) and \(L_{R}\) are the Coaxial cable losses at the transmitter and receiver respectively and are experimentally computed at 5.8 GHz. Pathloss was calculated by de-embedding constant values shown in Table 1.  
The average path loss values were recorded for a short period of time during measurement and therefore, may vary with climatic conditions. Additional fading needs to be calculated over and above average measured path loss to accurately ascertain the fade margin required for a reliable backhaul link.