How Dense is Ultra-Dense for Wireless Networks: From Far- to Near-Field Communications

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 farto near-field region. Without considering near-field propagation features, conventional understandings of the impact of network densification become doubtful. With this regard, it is imperative to reconsider the pros and cons brought by network densification. In this article, we first discuss the near-field propagation features in densely deployed network and verify through experimental results the validity of the proposed near-field propagation model. Considering near-field propagation, we further explore how dense is ultra-dense for wireless networks and provide a concrete interpretation of ultra-densification from the spatial throughput perspective. Meanwhile, as near-field propagation makes interference more complicated and difficult to handle, we shed light on the key challenges of applying interference management in ultra-dense wireless networks. Moreover, possible solutions are presented to suggest future directions.