A Combined MMSE/MMSE-IRC Receiver with Alternating Projections Successive Interference Cancellation for ICI Mitigation in 5G-NR Uplink

The evolution from 4G Long-Term Evolution (LTE) to 5G New Radio (NR) has increased cell density in cellular deployments, thereby increasing inter-cell interference (ICI), which is most significant in cell-edge scenarios. The Minimum Mean Square Error–Interference Rejection Combining (MMSE-IRC) receiver was widely adopted in LTE systems around Release 11 as a practical implementation for advanced interference rejection. Although not standardized in 3GPP specifications, it was commonly used in 3GPP studies and has been effectively used in 5G-NR environments. In this paper, we propose new versions of the Alternating Projections Hard Successive Interference Cancellation (AP-HSIC) equalizer algorithm that combine the Minimum Mean Square Error (MMSE) and MMSE-IRC equalizers (denoted MMSE-AP-HSIC and MMSE-IRC-AP-HSIC, respectively). The effectiveness of the new approach is demonstrated by Block Error Rate (BLER) analysis for Quadrature Phase Shift Keying (QPSK), 16-QAM, and 64-QAM modulations. Physical Uplink Shared Channel (PUSCH) 5G-NR receiver simulations demonstrate the differences between the proposed algorithms and the classical AP-HSIC, MMSE, and MMSE-IRC equalizer algorithms. Simulation results show that the proposed scheme, MMSE-IRC-AP-HSIC, outperforms the conventional MMSE-IRC scheme in cell-edge scenarios.