  Very recent studies showed that in a fully loaded dense small cell network
(SCN), the coverage probability performance will continuously decrease with the
network densification. Such new results were captured in IEEE ComSoc Technology
News with an alarming title of "Will Densification Be the Death of 5G?". In
this paper, we revisit this issue from more practical views of realistic
network deployment, such as a finite number of active base stations (BSs) and
user equipments (UEs), a decreasing BS transmission power with the network
densification, etc. Particularly, in dense SCNs, due to an oversupply of BSs
with respect to UEs, a large number of BSs can be put into idle modes without
signal transmission, if there is no active UE within their coverage areas.
Setting those BSs into idle modes mitigates unnecessary inter-cell interference
and reduces energy consumption. In this paper, we investigate the performance
impact of such BS idle mode capability (IMC) on dense SCNs. Different from
existing work, we consider a realistic path loss model incorporating both
line-of-sight (LoS) and non-line-of-sight (NLoS) transmissions. Moreover, we
obtain analytical results for the coverage probability, the area spectral
efficiency (ASE) and the energy efficiency (EE) performance for SCNs with the
BS IMC and show that the performance impact of the IMC on dense SCNs is
significant. As the BS density surpasses the UE density in dense SCNs, the
coverage probability will continuously increase toward one, addressing previous
concerns on "the death of 5G". Finally, the performance improvement in terms of
the EE performance is also investigated for dense SCNs using practical energy
models developed in the Green-Touch project.
