# A 100 Gbps OFDM-Based 28 GHz Millimeter-Wave Radio over Fiber Fronthaul System for 5G
## 6 Results
#### Quality Factor and Bit Error Rate Analysis  
In this paper, throughput performance in terms of QF and BER are analyzed and compared between employing coherent and direct detection in the receiver system. We first analyze a case for the three modulation formats for a varying fiber length from 5 km to 35 km without using DSP compensation. The second case is analyzed for employing DSP compensation for the same varying fiber length. In Tables 3 and 4, a summary of the QF and BER for 16-PSK employing coherent and direct detection without using DSP compensation are shown. The two detection \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fiber Length (km)** & **Quality Factor** & **Bit Error Rate** &
\begin{tabular}{c} **Log** \\ **(Min BER)** \\ \end{tabular} \\ \hline
5 & 3.14 & 0.000136991 & \(-\)3.86 \\ \hline
10 & 2.61 & 0.001197244 & \(-\)2.92 \\ \hline
20 & 1.39 & 0.028868851 & \(-\)1.54 \\ \hline
35 & 0.43 & 0.186653212 & \(-\)0.73 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Quality factor and bit error rate for 16-QAM employing direct detection without DSP compensation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fiber Length (km)** & **Quality Factor** & **Bit Error Rate** &
\begin{tabular}{c} **Log** \\ **(Min BER)** \\ \end{tabular} \\ \hline
5 & 3.51 & \(8.69\times 10^{-5}\) & \(-\)4.06 \\ \hline
10 & 2.83 & \(37.22\times 10^{-5}\) & \(-\)3.43 \\ \hline
20 & 1.73 & 0.006154481 & \(-\)2.21 \\ \hline
35 & 0.66 & 0.045819372 & \(-\)1.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Quality factor and bit error rate for 64-QAM employing direct detection without DSP compensation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fiber Length (km)** & **Quality Factor** & **Bit Error Rate** &
\begin{tabular}{c} **Log** \\ **(Min BER)** \\ \end{tabular} \\ \hline
5 & 3.51 & \(8.69\times 10^{-5}\) & \(-\)4.06 \\ \hline
10 & 2.83 & \(37.22\times 10^{-5}\) & \(-\)3.43 \\ \hline
20 & 1.73 & 0.006154481 & \(-\)2.21 \\ \hline
35 & 0.66 & 0.045819372 & \(-\)1.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Quality factor and bit error rate for 16-QAM employing direct detection without DSP compensation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fiber Length (km)** & **Quality Factor** & **Bit Error Rate** &
\begin{tabular}{c} **Log** \\ **(Min BER)** \\ \end{tabular} \\ \hline
5 & 3.51 & \(8.69\times 10^{-5}\) & \(-\)4.06 \\ \hline
10 & 2.83 & \(37.22\times 10^{-5}\) & \(-\)3.43 \\ \hline
20 & 1.73 & 0.006154481 & \(-\)2.21 \\ \hline
35 & 0.66 & 0.045819372 & \(-\)1.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Quality factor and bit error rate for 16-QAM employing coherent detection without DSP compensation. Table 9 shows the QF and BER performance for 64-QAM with coherent detection when DSP compensation is used. The system shows very good QF and BER performance values for all the fiber lengths. The down-converted OFDM signal and the carrier phase estimation is shown in Figure 13.  
However, Table 10 shows acceptable QF and BER values for a transmission distance up to 10 km when 64-QAM format with direct detection are employed and DSP compensation is used. Figure 14 shows the constellations of the down-converted OFDM signal and the carrier phase estimation of the symbols at 5 km. Figure 12: (**a**) Shows the relationship between the system quality factors and the transmission distance (**b**) Shows the relationship between the bit error rate and the transmission distance. Figure 13: (**a**) Shows the down-converted RF-OFDM signal after down-conversion (**b**) Carrier phase estimation for 64-QAM with coherent detection using DSP compensation at a fiber length of 5 km.