Checking and challenging coverage

A carrier's filed map is a promise about its own network, made in software. The FCC tests those promises, and it lets anyone with a phone test them too. This page covers what the FCC found and how to add a test of your own.

What the FCC found when it drove the maps

In 2018 and 2019 FCC staff drove more than 10,000 miles across twelve states to check the maps three carriers had filed for a rural subsidy program, running speed tests where the maps said 5 Mbps 4G LTE service existed. The staff report, published in December 2019, found that only 62.3 percent of the tests met the speed the maps predicted, and that in a sixth of the tested areas the phone found no 4G signal from the carrier at all. The report concluded the maps had overstated coverage, cancelled the program's challenge round, and led directly to the stricter Broadband Data Collection rules the current filings follow.

The new rules fix the modelling assumptions, publish the models behind each map, and build in a standing challenge process. They do not change what a map is: a prediction, made by the party with the strongest interest in a generous one.

Testing a filing yourself

The FCC publishes a free app, FCC Speed Test, for iPhone and Android. Besides an ordinary speed test it has a challenge mode: it records the carrier, the download and upload speeds, latency, the phone's location and whether you were outdoors or in a vehicle, in the form the FCC accepts as evidence. A few points about running one:

  • Test outdoors or in a vehicle, matching the environment the filing claims. An indoor test does not count against an outdoor map.
  • Test on the carrier's own network, not on wifi and not while roaming. The app checks this.
  • Take several tests spread around the area over more than one day. One failed test can be a busy cell; a pattern is a challenge.
  • Note the speed tier you are testing against. A 5G filing at 7/1 Mbps is not disproved by a 20 Mbps result.

What happens to a challenge

The FCC pools challenge tests each month. When enough tests in one area fall short of the filed speed, under thresholds that scale with how many tests there are, the area becomes a cognizable challenge and the carrier is notified. The carrier then has to either accept it, which removes the area from its map, or rebut it with its own on-the-ground tests or engineering data, which the FCC reviews. State, local and tribal governments and other organizations can file the same kind of challenge in bulk from their own drive tests. Resolved challenges are published with each map release, and a carrier that loses one has a smaller map on the next filing.

Before switching carriers over a map

A filing is a reasonable first filter and a poor last word. Three cheaper checks come before a contract:

  • Ask neighbours which carrier they use, and look at their phones indoors. Nothing on a map beats a phone on the same couch.
  • Most carriers offer a free trial of a week or more on an eSIM, with no change to your existing line. Run it at home, at work and on the drive between.
  • Look at the county page for the whole area you move through, not just the home address. The in-vehicle column is the one that describes a commute.

Sources

  • FCC, Mobility Fund Phase II Coverage Maps Investigation Staff Report, December 2019.
  • FCC Broadband Data Collection help centre, mobile challenge process and FCC Speed Test app guides.