As we move to 5G, costs and energy
consumption will, ideally, decrease, but at least they should
not increase on a per-link basis. Since the per-link data rates
being offered will be increasing by about 100×, this means
that the Joules per bit and cost per bit will need to fall by at
least 100×. In this article, we do not address energy and cost
in a quantitative fashion, but we are intentionally advocating
technological solutions that promise reasonable cost and power
scaling. For example, mmWave spectrum should be 10–100×
cheaper per Hz than the 3G and 4G spectrum below 3 GHz.
Similarly, small cells should be 10–100× cheaper and more
power efficient than macrocells. A major cost consideration
for 5G, even more so than in 4G due to the new BS densities
and increased bandwidth, is the backhaul from the network
edges into the core. We address backhaul and other economic
considerations in Section IV-C. As for energy efficiency, we
address this more substantially in Section III-C.