# Advanced Technology in ATSC3.0: Boosting Data Signal Rates Using Polarization Properties and FSS +
## 4 Computer Simulation Result  
We conducted computer simulations to evaluate the proposed method described in the previous section. The simulation parameters are shown in Table 1. In these simulations, we assumed a 5-path Rayleigh fading channel, which results in random phase variations and fluctuations in received signal strength for each multipath component. The Doppler shift was set to 10 Hz to reflect a typical mobile environment. The only broadcasting baseline refers to the conventional ATSC 3.0 system, where the interference from TxID signals is assumed to be negligible, essentially at the noise level. Therefore, in this paper, we model this baseline by considering data transmission exclusively through the vertically polarized antenna, with interference from the horizontally polarized antenna assumed to be zero. This approach reflects the ideal condition where the impact of cross-polarization interference is negligible. For the proposed system, we evaluated the performance under different cross-polarization discrimination (XPD) values, which varied between 5 and 15 dB depending on the environmental conditions. Simulations were performed with XPD values of 5, 10,  
Figure 6: Model of the polarization antenna pairs between the transmitter and receiver  
and 15 dB, using a spreading code length of 4. Subsequently, we fixed the XPD at 15 dB and compared the FSS (frequency symbol spreading) spreading code lengths of 4 and 16 to evaluate the impact of spreading on system performance. For forward error correction (FEC), convolutional coding with a rate of \(1/2\) and constraint length of 7 was employed, along with Viterbi decoding. This combination is well-suited for mitigating bit errors in frequency-selective fading channels. Channel estimation was assumed to be ideal, and perfect synchronization was considered in both the time and frequency domains, ensuring accurate demodulation and decoding throughout the simulation process. Figure 7 illustrates the bit error rate (BER) performance of the proposed method compared to only broadcasting. Assuming XPD of 5 dB, the BER performance significantly decreased compared to only broadcasting. However, as XPD increased to 10 dB and 15 dB, the BER performance approached that of broadcasting only. At XPD of 10 dB, we can achieve the BER of \(10^{-2}\) with Eb/No of 30 dB, and it is expected that further BER improvement by implementing FEC. Figure 8 shows the throughput of the proposed method compared to only broadcasting. When XPD is 5 dB, more information is transmitted with SNR between 10-25 dB compared to the conventional method. In addition, when XPD is 10-15 dB, an additional throughput improvement of about 15% can be achieved. Next, we will demonstrate the frequency diversity of FSS. Figure 9 shows the simulation results when FSS spread length of the additional data is varied from 4 to 16. In this simulation, we assume XPD is 15 dB. Observing Figure 9, with increasing the spread length, the frequency diversity can be achieved significantly. In particular for BER of \(10^{-3}\), we can achieve about 7 dB gain. This is because the impact of frequency selective fading could be distributed over more subcarriers by increasing the spreading code length. Finally, to demonstrate the effectiveness of adaptive modulation (AM), we evaluated the system performance across different modulation schemes with the XPD value fixed at 15 dB. The results, shown in Figure 10, present the total throughput for data transmitted from both the vertical and horizontal antennas as the modulation scheme transitions from QPSK to 16 QAM. The modulation switching based on SNR can be summarized as follows: