# An Evaluation of Orbital Angular Momentum Multiplexing Technology
## 4 Experimental Demonstration Wireless OAM Multiplexing Technology using 28 GHz
### Experimental OAM-MIMO Multiplexing Results Using Multiple UCAs  
We conducted experiments on the OAM-MIMO multiplexing using our implemented antennas. Figure 10 and Table 4 show the experimental setup and parameters. Tx signals were generated by offline digital signal processing and fed into our implemented Tx antenna. Outputs of the Rx signals were fed into a digital oscilloscope that worked as an analog-to-digital convertor as in the OAM multiplexing experiments. In these experiments, the digital oscilloscope was equipped with four ports and reception was done sequentially using the ports. This also did not significantly affect the results since the channel environments were static in the shield room as in the OAM multiplexing experiments. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **Mode \(-\)2** & **Mode \(-\)1** & **Mode 0** & **Mode +1** & **Mode +2** \\ \hline \multirow{4}{*}{\begin{tabular}{c} Antenna \\ selection \\ \end{tabular} } & Tx antenna & UCA No. 4 & UCA No. 2 & UCA No. 0 & UCA No. 3 & UCA No. 1 \\  & Rx antenna & UCA No. 3 & UCA No. 4 & UCA No. 0 & UCA No. 3 & UCA No. 1 \\  & BER (raw) & 0.0114 & 0.0228 & 0.0201 & 0.0192 & 0.0428 \\  & BER (coded) & 0.0000 & 0.0000 & 0.0000 & 0.0000 & 0.0024 \\ \hline \multirow{4}{*}{\begin{tabular}{c} Receiver \\ diversity \\ \end{tabular} } & Tx antenna & UCA No. 4 & UCA No. 2 & UCA No. 0 & UCA No. 3 & UCA No. 1 \\  & Rx antenna & UCA No. 3 & \
\begin{tabular}{c} UCA No. 2, \\ No. 4 \\ \end{tabular} & UCA No. 0 & UCA No. 3 &
\begin{tabular}{c} UCA No. 1, \\ No. 2 \\ \end{tabular} \\  & BER (raw) & 0.0105 & 0.0015 & 0.0022 & 0.0278 & 0.0385 \\  & BER (coded) & 0.0000 & 0.0000 & 0.0000 & 0.0000 & 0.0000 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental results (OAM multiplexing). Figure 9: Experimental environment (OAM multiplexing). We used eleven streams for the OAM-MIMO multiplexing experiment. Two Tx UCAs (UCA No. 1 and No. 4), respectively, transmitted five OAM modes (0, \(\pm\)1, \(\pm\)2) and UCA No. 0 transmitted OAM mode 0. We used the received signals of all Rx UCAs for the equalization. Table 5 summarizes the modulations, channel coding rates and corresponding transmission rates used in the experiment. The propagation loss was calculated with Equation (2) with UCA sizes and distance between Tx and Rx. We confirmed that successful error-free transmissions were obtained in all streams with the usage of the forward error correction. Total transmission rate was 100 Gbps at a 10 m transmission distance. The results indicated a new milestone was reached in terms of point-to-point wireless transmission. In addition, we recently extended our work by extending the baseband signal processing to successfully achieve 120 Gbit/s using a total of 11 OAM modes [19]. This is the state-of-the-art results that have been published in the literature. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Center frequency & 28.5 GHz & OAM modes & \(-\)2, \(-\)1, 0, 1, 2 \\ Signal bandwidth & 2 GHz & Number of streams & 11 \\ Number of UCAs & 4 & Signal carrier & Single carrier \\ Number of antenna elements & 16 & Modulation & 16 QAM/64 QAM \\ Number of antenna elements & 65 & Channel coding & LDPC (DVB-S2) \\ Diameter of UCA & 24, 26, 48, 60 cm & Equalization & Freq. domain equalization \\ Tx/Rx distance & 10 m & Block size & 256 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Experimental parameters (OAM-MIMO multiplexing). Figure 10: Experimental environment (OAM-MIMO multiplexing).