# LDM-Ex-FDM: A Novel Multi-Service Transmission Scheme for the ATSC 3.0 System
## 4 Simulation Results and Analysis
### LDM-Ex-FDM Performance with Equal Interval Symbol Puncturing (EISP)  
This subsection simulates the multi-service transmission performance of the LDM-Ex-FDM scheme with EISP. The BER performance of the traditional scheme and the proposed scheme for receiving mobile services and fixed services in the AWGN channel is shown in Figures 12 and 13, respectively. In Figure 12, the SNR thresholds of mobile service of these two schemes are almost the same under the AWGN channel. It can be observed in Figure 13 that when the puncturing rate of BICM symbols for fixed service data is \(1/12\), the BER performance of the newly proposed LDM-Ex-FDM transmission scheme outperforms that of the traditional _LDM_ scheme by about 0.45 dB @BER = \(10^{-5}\) under the AWGN channel. This is due to the fact that the SNR of _EL2_ that occupies part of the subcarriers for FDM transmission is higher than that of _EL1_ in _LDM_. Moreover, when the puncturing rate is set at \(1/6\), the improvement of the BER performance of the proposed scheme is up to 0.9 dB. The BER performance for mobile services and fixed services in the multipath channel is shown in Figures 14 and 15, respectively. In Figure 14, the SNR thresholds of mobile service of these two schemes are almost the same in the multipath channel. In Figure 15, it is observed that the LDM-Ex-FDM scheme can achieve the BER performance improvement of up to 1.8 dB @BER = \(10^{-6}\) under the multipath channel when the puncturing rate is \(1/12\), and improvement of about 2.5 dB when the puncturing rate is set at \(1/6\). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Echo** & **Power (dB)** & **Time Delay (\%)** \\ \hline
1 & \(-3\) & 0 \\
2 & 0 & 0.2 \\
3 & \(-2\) & 0.5 \\
4 & \(-6\) & 1.6 \\
5 & \(-8\) & 2.3 \\
6 & \(-10\) & 5.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Profile of the multipath channel model. Figure 11: Scattered pilot (SP) orthogonal frequency division multiplexing (OFDM) subcarriers. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Fast Fourier transform (FFT) size & 16k \\ Scattered pilot (SP) pattern & SP8\_2 \\ Cyclic prefix (CP) & 1/16 \\ Core layer (_CL_) low-density parity-check & 16,200 \\ (LDPC) code length & 16,200 \\ _CL_ LDPC code rate & 5/15 \\ _CL_ number of iterations & 50 \\ _CL_ constellation & quadrature phase-shift keying (QPSK) \\ Enhanced layer (_EL_) LDPC code length & 16,200 \\ _EL_ LDPC code rate & 11/15 \\ _EL_ number of iterations & 50 \\ _EL_ constellation & non-uniform (NU)\(-16\) quadrature amplitude modulation (QAM), NU\(-64\)QAM \\ Puncturing rate (\(\gamma\)) & 1/6, 1/12 \\ Injection level (\(\Delta\)) & 10 dB, 12 dB, 15 dB \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Basic transmission parameters. Another observation extracted from Figures 13 and 15 is that when the number of occupied subcarriers of \(EL2\) doubles, the SNR performance improvement is nearly doubled, i.e., from 0.45 to 0.9 dB, under AWGN channel. In the multipath fading channel, however, when the number of occupied subcarriers of \(EL2\) doubles, the BER performance gain is only increased by about 38%, i.e., from 1.8 to 2.5 dB. It can be inferred that the demodulation performance of fixed service can be significantly improved by selecting an appropriate number of occupied subcarriers. Figure 12: Bit error rate (BER) performance of mobile service in ATSC 3.0 system with and without LDM-Ex-FDM scheme with perfect channel impulse response (CIR) over the AWGN channel, where the parameters of the ATSC 3.0 system were set to \(\Delta=10\) and 12 dB, the \(CL\) constellation was set to QPSK, the \(EL\) constellation was set to \(\text{NU}-64\text{QAM}\), and the puncturing rate of the LDM-Ex-FDM scheme was set to \(1/12\).