Research on MIMO Detection Method for 5G Redcap UE with High Order Modulation

This paper proposes a simplified MIMO detection method for 5G reduced capability (Redcap) user equipment (UE) with high order modulation, which achieves a compromise between computational complexity and detection performance. With the freezing of the 5G Redcap standard for internet of thing (IoT) scenario applications, significant cost reduction is achieved by reducing UE capabilities. Redcap UE specifies that the maximum number of receiving antennas is 2, and the maximum modulation order is 256. Regarding this regulation, the MIMO detection method of two receiving antennas with 256-order quadrature amplitude modulation (256-QAM) is studied, which can improve detection performance and ensure low computational complexity. In existing works, QR decomposition (QRD)-M is a high-performance MIMO detection method, but its complexity is still high with 256-QAM. This paper proposes a further simplified MIMO detection scheme with 256-QAM based on QRD-M. The simulation results show that this method has better performance than linear detection, and has only a slight decrease in performance compared to QRD-M. This method also has reference value for MIMO detection of larger than two receiving antennas with high order modulation.