## 4 Custom A-IFOF Transceiver Preliminary Evaluation and Integration to Deployed MNO's Infrastructure  
Figure 3 shows that the experimental setup used an initial evaluation of a FiWi link, involving the Tx side of the presented transceiver, the RFSoC board serving as signal generator and the EML unit for optical modulation. These measurements and their off-line post-processing have also been the baseline for the definition of the real-time receiver side DSP development. To explore the reconfigurability potential of the platform, in this set of measurements the FPGA clock was real-time adjusted at 256 MHz or 500 MHz, corresponding to the transmission of 204 MHz or 394 MHz of useful bandwidth after zero-padding (52 out of 256 sub-carriers). The above band sizes were selected having in mind the latest 3 GPP new radio (NR) specifications [37]. Furthermore, the modulation format of the sub-carriers was real-time adjusted to QPSK or 16-quadrature amplitude modulation (QAM16). Employing the digital up-conversion stage of the DAC board, a complex OFDM-based radio waveform at an intermediate frequency (IF) of 750 MHz was generated. The complex radio was then fed to a frequency translation stage in order to further upconvert the IF to 3.5 GHz through an analog active mixer. The additional mixing stage enabled the modification of the IF value by adding one more degree of flexibility to the setup. The output of the active mixer was then connected to the RF port of a bias tee that was responsible for driving the electro-absorption modulator (EAM) segment of the EML. The driving voltage for the EAM section of the chip was set at 560 mVpp, whereas the reverse bias voltage of \"\(-\)\" 0.63 V was used to ensure linear operation. The laser segment of the EML was injected with a 110 mA current while it operated at 23.6 \({}^{\circ}\)C, providing + 2 dBm of optical power at the emission wavelength of 1560.42 nm. The optical output \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Unit** & **Power Consumption (Watt)** \\ \hline \multirow{4}{*}{RFSoC} & FPGA fabric & 2.3 \\  & CPUs (used for signal & 2.7 \\  & performance monitoring) & \\  & RFSoC clocks & 1.2 \\  & DAC/ADC units & 3.3 \\ Electro–optic modules & Optical modulation & 2.07 (Driver) + 0.2 (EML) \\ Photoreciever & 1.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Power Consumption per Unit. Figure 3: FiWi transmission experimental setup that was used in the initial performance evaluation of the implemented A-IFoF transceiver. was then transmitted over a fiber spool of SSMF. The IFoF signal of\(-3.5\) dBm was detected by an off-the-shelf 14 GHz linear photoreceiver after its propagation over a 25 km SSMF spool. The photoreceiver output was connected to the IF-to-mmWave upconverter radio board that was operating at 60-GHz and a V-band directional transmitter-side antenna module (Tx-antenna). An identical receiver side antenna module (Rx antenna) that was located at a 3 m horizontal distance was used to receive the mmWave radio waveforms. Both of the commercial V-band radio [38; 39] components operated at 60 GHz and allowed for OTA transmission, while the standard pyramidal gain horn antennas featured 23 dBi gain and 10\({}^{\circ}\) beamwidth. At the receiver side, an off-line DSP was applied to the signal, including the demodulation of the received OFDM symbols, as well as a ZF equalization algorithm. For the channel estimation, 21 pilot sub-carriers that were multiplexed with the data subcarriers were also transmitted. Figure 4 depicts the EVM performance of the transmitted OFDM-based IFoF signals after the 7 km and 25 km fiber link as well a set of constellation diagrams that were obtained after the post-processing chain.