Verizon and AT&T face significant engineering challenges to build on their initial, limited roll-outs of 5G in millimeter wave spectrum, and deliver broad coverage and high data rates given their lack of midband airwaves, which are ideal for first-phase 5G. The two companies have always invested large sums in their own technologies and architectures, so if anyone can make a powerful service platform at viable cost, with mmWave spectrum, these two are likely to do so. Some initial tactics have included advanced deployment of MIMO antennas and beamforming, as well as migration roadmaps to highly virtualized networks and to automation. But making a high performance network that reaches users indoors as well as out, given the limited range and indoor…