Robust massive MIMO equilization for mmWave systems with low resolution ADCs

Leveraging the available millimeter wave spectrum will be important for 5G. In this work, we investigate the performance of digital beamforming with low resolution Analog-to-Digital-Converters based on link level simulations including channel estimation, Multiple Input Multiple Output (MIMO) equalization and channel decoding. We consider the recently agreed 3GPP NR type 1 Orthogonal Frequency Division Multiplexing (OFDM) reference signals. The comparison shows sequential Dichotomous Coordinate Descent (DCD) outperforms Minimum Mean Square Error (MMSE)-based MIMO equalization both in terms of detection performance and complexity. We also show that the DCD based algorithm is more robust to channel estimation errors. In contrast to the common believe we also show that the complexity of MMSE equalization for a massive MIMO system is not dominated by the matrix inversion but by the computation of the Gram matrix.