BER Analysis for a MIMO-NOMA System Using QPSK Modulation and Linear MMSE Detection

In this paper, the bit error rate (BER) performance is investigated for a two-user downlink multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA) system that employs quadrature phase shift keying (QPSK) modulation and linear minimum mean-squared error (MMSE) detection for each user's signal. In addition to error propagation from successive interference cancellation considered by existing related works for single-input single-output NOMA systems, multiple access interference is taken into account for MIMO-NOMA transmission. Exact BER expressions are derived for both users under the availability of perfect channel state information. Computer simulation results are given to verify the accuracy of the derived BER expressions.