  Reconfigurable intelligent surfaces (RISs) are considered a promising
technology for boosting the coverage and for enhancing the spectral efficiency
of wireless systems, as well as for taming the wireless environment. The
potential benefits of RISs are currently being analyzed and various approaches
are being proposed to address some challenges for their integration in wireless
networks. Currently available studies to quantify the potential gains of
deploying RISs in wireless networks are limited to simple network topologies,
while no system-level assessments have been reported to date. Network-level,
e.g., on the scale of hundreds of square meters, simulations are, however, the
first step to quantify the actual value of emerging technologies and the
steppingstone before considering large scale system-level experimental
evaluations and network deployments. Towards this direction, this article
reports the first system-level simulation results and analysis of an RIS
deployment in a typical urban city that is served by a fifth-generation
cellular network. The obtained system-level simulation results unveil that the
benefits of RISs vary depending on the operating frequency and the size of the
surfaces. Specifically, we investigate the performance improvement that RISs
can provide, in terms of outdoor and indoor coverage and ergodic rate, when
deployed in mid (C-band) and high (millimeter-wave) frequency bands. For
example, the obtained results unveil that the deployment of RISs enhances the
coverage of cell-edge users from 77% to 95% in the C-band and from 46% to 95%
in the millimeter-wave band.
