Multi-User Physical Network Coding Scheme with Low-Resolution ADCs at the Base Station

In this paper, we investigate the application of Physical Layer Network Coding (PNC) in Multi-user Massive MIMO systems that use low-resolution analog-to-digital (ADC) converters on the receiving side to reduce hardware costs and power consumption. We explore the performance gains from combining massive multiple-input multiple-output (MIMO) and PNC techniques. PNC helps reduce the number of timeslots needed for end-to-end communication, thereby boosting the capacity of the wireless system. We utilize a method that transforms the chan-nel between a massive-antenna relay and multiple multi-antenna user terminals using a Sum-Difference (SD) matrix before applying a linear signal detection algorithm. By using an approximation model to establish the relationship between the input and output of a low-resolution ADC, we derive an expression that accounts for the finite number of quantization levels to compute the Log-Likelihood Ratio (LLR) of the network-coded bit. We evaluate the error performance of the proposed scheme through extensive simulations across different resolution levels and multi-user configurations. The results demonstrate that the PNC technique significantly outperforms conventional network coding, as the PNC processing algorithm leverages the benefits of signal superposition in wireless MIMO channels.