It has long been the trend that modern wireless networks have been getting denser as time goes on; where, by the term dense, we refer to the gap between network nodes (the ‘points of presence’ of the network) and the average area intended to be covered by the single node. Till now, this has primarily been driven by the increasing demands for bandwidth for users, exponentially increasing numbers of users and the deployment of networks in higher and higher frequencies. The last point is important because scattering increases (and hence, the effective radius decreases) as the network node uses a higher frequency.
This trend was predicted well in advance by (Gupta, et al., 2000), (Gastpar, et al., 2002)and others; that the capacity of the different types of wireless networks (cellular, relay, local area, mesh, etc.) network increases O(N^(1/2)); where N is the number of network nodes or points of presence in a given area. In recent times, one of the driving factors is also the miniaturization of digital and RF hardware (which allows lower footprint deployments) and the development of new types of architectures, such as the centralized ‘cloud RAN’ for cellular networks.