Protograph LDPC-Coded Superposition Bandwidth-Efficient Modulation for MIMO Channels with Mixed-ADC Architectures for Future Wireless Networks

Low-resolution ADCs provide a power- and cost-efficient solution for large-scale MIMO systems in next-generation wireless networks (B5G/6G, IoT). However, coarse quantization under high-order modulation increases noise and interference, degrading signal detection performance. This paper proposes a mixed-ADC architecture combined with superposition modulation to improve both performance and spectral efficiency. A modified protograph-based EXIT (PEXIT) algorithm is developed to characterize system behavior, incorporating MIMO fading, heterogeneous ADC resolutions, and LDPC decoding effects. The method accurately predicts decoding thresholds across diverse antenna configurations and power allocation strategies. Simulation results confirm that the mixed-ADC approach yields significant performance gains, especially in setups with a limited number of receive antennas.