  We study the impact of channel aging on the uplink of a cell-free massive
multiple-input multiple-output system with hardware impairments. We consider a
dynamic analog-to-digital converter architecture at the access points (APs),
and low-resolution digital-to-analog converters at the user equipments (UEs).
We derive a closed-form spectral efficiency expression by considering i)
practical spatially-correlated Rician channels; ii) hardware impairments at the
APs and the UEs; iii) channel aging; and iv) large-scale fading decoding
(LSFD). We show that LSFD can effectively mitigate the detrimental effects of
i) channel aging for both low and high UE velocities; and ii) inter-user
interference for low-velocity UEs but not for high-velocity UEs.
