  This white paper explores the road to implementing broadband connectivity in
future 6G wireless systems. Different categories of use cases are considered,
from extreme capacity with peak data rates up to 1 Tbps, to raising the typical
data rates by orders-of-magnitude, to support broadband connectivity at railway
speeds up to 1000 km/h. To achieve these goals, not only the terrestrial
networks will be evolved but they will also be integrated with satellite
networks, all facilitating autonomous systems and various interconnected
structures. We believe that several categories of enablers at the
infrastructure, spectrum, and protocol/ algorithmic levels are required to
realize the intended broadband connectivity goals in 6G. At the infrastructure
level, we consider ultra-massive MIMO technology (possibly implemented using
holographic radio), intelligent reflecting surfaces, user-centric and scalable
cell-free networking, integrated access and backhaul, and integrated space and
terrestrial networks. At the spectrum level, the network must seamlessly
utilize sub-6 GHz bands for coverage and spatial multiplexing of many devices,
while higher bands will be used for pushing the peak rates of point-to-point
links. The latter path will lead to THz communications complemented by visible
light communications in specific scenarios. At the protocol/algorithmic level,
the enablers include improved coding, modulation, and waveforms to achieve
lower latencies, higher reliability, and reduced complexity. Different options
will be needed to optimally support different use cases. The resource
efficiency can be further improved by using various combinations of full-duplex
radios, interference management based on rate-splitting, machine-learning-based
optimization, coded caching, and broadcasting.
