# QPSK MMW Wireless Communication System Based On p-i-n InGaAs Photomixer
## 5 Conclusions  
We have demonstrated QPSK MMW wireless communication based on an off-the-shelf InGaAs p-i-n photomixer. The experiment showed the capabilities of the photomixer for wireless communication use. Throughout the experiment, we used only customer available components, which represents a promising solution for 5 th generation wireless communications, IoT, fast point-to-point communication for autonomous driving, and usage on available optical telecom infrastructures. Here, we showed the transmission of a 100 Mbps data rate QPSK modulated signal, even though the photomixer has a 2 THz bandwidth, which can used for higher data rates and advanced modulation formats. As shown in the above results, wireless communication based on customer available photomixer and optical telecom infrastructures is more feasible in the near future. In the current experiments, we have shown results of low data rate and modulation scheme based on the available lab equipment.  
In future work, further research will be done based on the photomixer for higher data rates and advanced formats, such as M-QAM and Orthogonal Frequency-Division Multiplexing (OFDM) formats.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & \begin{tabular}{c} **Carrier Frequency** \\ **(GHz)** \\ \end{tabular} & \begin{tabular}{c} **Data Rate** \\ **(Gb/s)** \\ \end{tabular} & \begin{tabular}{c} **BER/EVM** \\ **(Gb/s)** \\ \end{tabular} & \
\begin{tabular}{c} **Demodulation** \\ **Method** \\ \end{tabular} &
\begin{tabular}{c} **Transmission** \\ **Distance (m)** \\ \end{tabular} \\ \hline
[4] & 100 & 100 & \(<\)3.8 \(\times\) 10\({}^{-3}\) & Off-line DSP & 0.7 \\
[10] & 87.5 & 100 & 10\({}^{-3}\) & Off-line DSP & 1.2 \\
[17] & 196 & 0.1 & EVM \(<\) 10\% & Same Tx/Rx & 0.5 \\
[18] & 120 & 10 & \(<\)10\({}^{-10}\) & Real time & 200 \\
[19] & 146 & 1 & -* & Off-line DSP & 0.025 \\
[20] & 200 & 1 & \(<\)10\({}^{-9}\) & Real time & 2.6 \\ This work & 90 & 0.1 & \(1.23\times 10^{-4}\) & Real time & 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summarization and comparison of reported MMW wireless communication link researches with carrier wave frequency under 200 GHz.  
The work will include a detailed characterization of the wireless channel link for different formats, a long-distance wireless transmission as shown in this paper, and applying different FEC techniques to improve the performance of the wireless link. Assuming an Additive White Gaussian Noise (AWGN) channel and FEC based on Reed-Solomon code, i.e., RS(255,239) as used in undersea lightwave systems [21] and Optical Transport Network (OTN) standards [22], which is the first-generation FEC [23], input BER of \(10^{-4}\) can be improved to post-FEC BER of \(10^{-12}\) with 7% overhead. This algorithm can provide approximately 6 dB Net Coding Gain (NCG), very significant performance improvement in high-speed wireless networks. In addition to this type of FEC, more powerful FEC codes such as turbo codes, Turbo Product Codes (TPC), and Low-Density Parity-Check Codes (LDPC) are already developed [24]. For example, the LPDC in [25] can correct a BER of \(10^{-3}\) to \(10^{-12}\) with an overhead of 7%, and the Bose-Chaudhuri-Hocquenghem (BCH)-based turbo code can correct a BER of \(10^{-2}\) to \(10^{-12}\) with an overhead of 21.5% [23]. The different FEC algorithm encoders and decoders will be realized using Field-Programmable Gate Array (FPGA) implementations.  
Conceptualization, A.A.; formal analysis, A.W.; investigation, A.W.; writing--original draft preparation, A.W.; validation, A.W., A.A., and D.R.; data curation, A.W.; resources, A.A., D.R., and A.W.; writing--review and editing, A.W., A.A., and D.R.; supervision, A.A.; funding acquisition, A.A.; All authors have read and agreed to the published version of the manuscript.  
This work was partially supported by the Ministry of Science and Technology, Israel.  
The authors declare no conflicts of interest.