On the capacity of MIMO Wiener phase-noise channels

The capacity of multiple-antenna systems affected by Wiener phase noise is investigated. We present a non-asymptotic capacity upper bound that is shown to be tight in the large-SNR regime. The capacity upper bound is compared with a lower bound obtained by evaluating numerically the information rates achievable with QAM constellations. For a Wiener phase-noise process with standard deviation of the phase increments equal to 6°, our results suggest that QAM constellations incur a penalty of more than 3 dB for medium/high SNR values.