The FCC gathers Form 477 mobile data every 6 months, and publishes the results regularly. Overall, the data documents, at a Census block level, the providers, (e.g. “ATT”), the technology (e.g. “3G” or “4GLTE”), and the percentage of the block served. I3 uses the data based on the “Actual Area Methodology” datasets.
For block groups and tracts, we sum the areas served at the block level to compute the area served at the larger level. Only blocks with at least 0.04% of the block covered are included.
Like the Wireline data, the data is self-reported, and does not account for the vagaries of wireless transmission. So your Census area might be included, but if the cell towers are not in good range, you might not have a signal.
As of now, 5G data is not being reported.