As wireless communication evolves toward 5G, both fixed broadband and mobile broadband will play a crucial part in providing the gigabit-per-second infrastructure for a connected society. This article proposes an MGB system as the solution to two critical problems in this evolution: last-mile access for fixed broadband and small cell backhaul for mobile broadband. The key idea is to use spectrum that is already available in the millimeter-wave bands for fixed wireless access with optimized dynamic beamforming and massive MIMO infrastructure to achieve high capacity with wide area coverage. This article explains the MGB concept and describes potential array architectures for realizing the system. Simulations demonstrate that with 500 MHz of bandwidth (at 39 GHz band) and 28 dBm transmission power (55 dBm EIRP), it is possible to provide more than 11 Gb/s backhaul capacity for 96 small cells within a 1 km radius.