  Besides advanced telecommunications techniques, the most prominent evolution
of wireless networks is the densification of network deployment. In particular,
the increasing access points/users density and reduced cell size significantly
enhance spatial reuse, thereby improving network capacity. Nevertheless, does
network ultra-densification and over-deployment always boost the performance of
wireless networks? Since the distance from transmitters to receivers is greatly
reduced in dense networks, signal is more likely to be propagated from long- to
short-range region. Without considering short-range propagation features,
conventional understanding of the impact of network densification becomes
doubtful. With this regard, it is imperative to reconsider the pros and cons
brought by network densification. In this article, we first discuss the
short-range propagation features in densely deployed network and verify through
experimental results the validity of the proposed short-range propagation
model. Considering short-range propagation, we further explore the fundamental
impact of network densification on network capacity, aided by which a concrete
interpretation of ultra-densification is presented from the network capacity
perspective. Meanwhile, as short-range propagation makes interference more
complicated and difficult to handle, we discuss possible approaches to further
enhance network capacity in ultra-dense wireless networks. Moreover, key
challenges are presented to suggest future directions.
