  In this work, we investigate the impact of channel aging and electromagnetic
interference (EMI) on spatially correlated reconfigurable intelligent surface
(RIS) assisted cell-free massive multiple-input multiple-output (MIMO) systems.
To effectively handle channel aging and EMI, we employ a novel two-phase
channel estimation scheme with fractional power control-aided pilot assignment
during the uplink channel estimation phase. This scheme provides improved
channel estimates compared to existing approaches. The closed-form uplink and
downlink spectral efficiency (SE) expressions incorporating fractional power
control are derived to enable system performance evaluation. Additionally, we
introduce the system's power consumption model to analyze energy efficiency
(EE). Our numerical results illustrate the theoretical results and demonstrate
the system performance with channel aging and EMI. Specifically, the proposed
two-phase channel estimation scheme enhances estimation accuracy, compensating
for performance degradation caused by channel aging and EMI. We find that
increasing the number of access points (APs), RISs, antennas per AP, and
elements per RIS can help to mitigate the SE performance degradation. We also
find that an optimal number of APs can be selected to achieve energy efficiency
(EE) maximization. However, in severe EMI environments, the benefits of
deploying more RISs cannot be fully realized.
