Inter-Numerology Interference in Mixed Numerology MIMO-OFDM Systems in Spatially Correlated, Time-Varying Fading Channels

5G New Radio (NR) employs a mixed-numerology orthogonal frequency-division multiplexing (OFDM)-based physical layer and makes extensive use of multiple-input-multiple-output (MIMO) techniques. Unlike conventional single-numerology OFDM systems, subcarriers of different numerologies interfere with each other causing inter-numerology interference (INI). In such MIMO-OFDM systems, we derive novel expressions for the INI covariance matrix at each user. The novelty and strength of our results come from the comprehensive model our analysis is based on. Our model accounts for the wideband and spatial correlation aspects of the channel and time-variations within an OFDM symbol caused by Doppler spread as well as phase noise. The INI covariance turns out to be proportional to the receive spatial correlation matrix, with the proportionality constants depending on the transmit spatial correlation matrix, the temporal auto-correlation of the channel, phase noise auto-correlation, and transmit signal covariances of the users.