# Enhanced LDM for Next-Generation Digital Broadcasting Transmission
## 4 Compute and Simulation Results
### Simulation Results
Figure 8: BER performance of mobile service with En-LDM and traditional LDM systems under the multipath channel, where the injection levels were set to \(\Delta=10\) dB and \(15\) dB, the CL constellation was set to QPSK, the EL constellation was set to NU\(-64\)QAM, the puncturing rate of the En-LDM scheme was set to \(1/13\), and the LDPC code rates of CL and EL were set to \(5/15\) and \(11/15\), respectively. Figure 7: BER performance of mobile service with En-LDM and traditional LDM systems under the additive white Gaussian noise (AWGN) channel, where the injection levels were set to \(\Delta=10\) and \(15\) dB, the core layer (CL) constellation was set to QPSK, the enhanced layer (EL) constellation was set to NU\(-64\)QAM, the puncturing rate of the En-LDM scheme was set to \(1/13\), and the LDPC code rates of CL and EL were set to \(5/15\) and \(11/15\), respectively. As shown in Figures 7 and 8, the BER performance of mobile service in the proposed En-LDM system and the traditional LDM system are almost the same under the AWGN channel or multipath channel. For delivering robust mobile service, we considered the injection levels of 10 and 15 dB, where the CL has a power level 10 and 15 dB higher than EL. It can be easily seen from Figures 7 and 8 that when the injection level is increased from 10 to 15 dB, the SNR threshold of mobile service will be reduced by about 0.41 and 0.57 dB under the AWGN and multipath channels, respectively. Figure 10: BER performance of fixed service with En-LDM and traditional LDM systems under the multipath channel, where the injection levels were set to \(\Delta=10\) and 15 dB, the CL constellation was set to QPSK, the EL constellation was set to NU\(-\)64 QAM, the puncturing rate of the En-LDM scheme was set to 1/13, and the LDPC code rates of CL and EL were set to 5/15 and 11/15, respectively. Figure 9: BER performance of fixed service with En-LDM and traditional LDM systems under the AWGN channel, where the injection levels were set to \(\Delta=10\) and 15 dB, the CL constellation was set to QPSK, the EL constellation was set to NU\(-\)64 QAM, the puncturing rate of the En-LDM scheme was set to 1/13, and the LDPC code rates of CL and EL were set to 5/15 and 11/15, respectively. As shown in Figures 9 and 10, the BER performance of the fixed service in the En-LDM system is better than that of the traditional LDM. When the LDPC coded bit puncturing rate of fixed service data is set to 1/13, the SNR threshold for fixed service in the En-LDM system is 0.21 and 2.15 dB lower than the traditional LDM system under the AWGN and multipath channels, respectively. In addition, it can be observed that when the injection level is increased from 10 to 15 dB, the SNR threshold of fixed service will increase by about 4.65 and 4.70 dB under the AWGN and multipath channels, respectively. This means that in the case of a higher injection level, the impact of the adjustment of the injection level on the SNR threshold of EL is significantly higher than that of CL. The most important finding here is that the BER performance of the fixed service in the En-LDM system converges faster than the traditional LDM system under the multipath channel. This advantage of En-LDM is mainly due to the higher robustness of data extracted based on LDPC coded bit puncturing through core layer transmission, which facilitates correct decoding at the receiving end. To evaluate the performance of fixed service in the En-LDM system, simulation performances are shown in Figure 11 for fixed service in multipath channels under different code rates. It can be observed that when the LDPC code rate of the EL configuration increases from 9/15 to 11/15, the En-LDM system improves the BER performance of the fixed service from 1.7 to 2.2 dB compared to the traditional LDM system. This implies that En-LDM may perform better than traditional LDM system at high code rates for EL configurations.