# Experimental Evaluation of Display Field Communication Based on Machine Learning and Modern Design
## 5 Experimental Evaluation
### Performance According to Distance, Camera Angle, and Image Rotation  
In this section, we examine the BER performance of the proposed scheme according to the display-camera distance, camera angle, and display rotation. Table 6 shows the laboratory setup of our experiments for this section. For all the experiments, we used the color Lena image with a PSNR fixed at 30 dB. First, in experiment 1, we vary the distance between the transmitter, i.e., the display, and the camera, i.e., the receiver. Figure 14 shows a laboratory experimental setup for two different distances \((D)\). Figure 15 illustrates the BER performance of the proposed scheme according to distance. We can observe that for all the color channels, the error rate was zero until the distance of 78 cm. In the case of the red and green channels, the error rate was zero until 98 cm. For the blue channel, however, the error rate gradually increases after 78 cm. As a result, we can say that error-free performance was achieved up to a distance of 78 m. In other words, it is possible to transmit data without any error up to a distance of 78 cm. That \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Experiment 1 (\(D\))** & **Experiment 2 (\(A\))** & **Experiment 3 (\(R\))** \\ \hline Input Image & Lena color & Lena color & Lena color \\ Input image size & \(256\times 256\) p & \(256\times 256\) p & \(256\times 256\) p \\ No. of binary data bits & 500 & 500 & 500 \\ No. of encoded data bits & 2518 & 2518 & 2518 \\ Lower sub-band position & rows 5 to 15 & rows 5 to 15 & rows 5 to 15 \\ Distance \((D)\) & 28 cm to 98 cm & 28 cm & 28 cm \\ Camera angle \((A)\) & \(0^{\circ}\) & \(-60^{\circ}\) to \(-60^{\circ}\) & \(0^{\circ}\) \\ Image rotation \((R)\) & \(0^{\circ}\) & \(0^{\circ}\) & \(-60^{\circ}\) to \(-60^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Experimental parameters for distance, angle, and rotation evaluation. Figure 14: Experimental setup according to display-camera distance. (**a**) \(D\) = 98 cm. (**b**) \(D\) = 28 cm. Figure 13: Comparison of EVM according to PSNR. (**a**) \(128\times 128\) pixel size. (**b**) \(256\times 256\) pixel size. is quite motivating for the real application scenario, where normal users can easily decode data from the screen if they are within a distance of 78 cm from the transmitting screen. Figure 16 shows an experimental setup according to the angle \((A)\) between the display and the camera. In the experiment, the angle between the display and the camera is changed from \(-60^{\circ}\) to \(60^{\circ}\). At the same time, the distance is fixed at 28 cm. Figure 17 depicts the BER performance of the proposed scheme depending on the angle. We can observe that for the red and green channels, the error rate was close to zero until the angle of \(\pm 40^{\circ}\). When the angle becomes larger than \(\pm 40^{\circ}\), the error rate of the blue channel increases significantly. In the case of the green channel, we obtained error-free performance. Figure 18 depicts the experimental setup of the proposed scheme according to the angle of rotation of the transmitted image or the display \((R)\). The image is rotated from \(-60^{\circ}\) to \(60^{\circ}\). At the same time, the distance is fixed at 28 cm and the angle is \(0^{\circ}\). Figure 19 shows the BER performance of the proposed scheme depending on the angle of the rotation of the display. We can see that the error performance of red and green channels is close to zero until a rotation of \(\pm 40^{\circ}\). After that, the error increases. This is because as the image is  
Figure 16: Experimental setup according to display-camera angle. (**a**) \(A=0^{\circ}\). (**b**) \(A=-60^{\circ}\). Figure 17: BER performance according to display-camera angle. Figure 15: BER performance according to display-camera distance. rotated from 0\({}^{\circ}\) to \(\pm\)60\({}^{\circ}\), we get difficulty in mapping the four corner points of the image during the distortion correction stage at the receiver.