  Reconfigurable intelligent surfaces (RIS) have been presented as a solution
to realize the concept of smart radio environments, wherein uninterrupted
coverage and extremely high quality of service can be ensured. In this paper,
assuming that multiple RIS are deployed in the propagation environment, the
performance of a cascaded RIS network affected by imperfect phase estimation is
evaluated. Specifically, we derive closed-form expressions for the outage
probability, the ergodic capacity and the average symbol error probability that
can be utilized to evaluate the coverage of the proposed network, as well as
the average capacity and the data transmission accuracy. Finally, we validate
the derived expressions through simulations and show that by choosing the
number of the participating RIS correctly, a cascaded RIS network can
outperform a single RIS aided system and extend the network's coverage
efficiently.
