This one is gonna get a little geeky, so if that is not your cup of tea, but can just skip this post knowing that the feds did not shut down cell service to keep the crowd from communicating; the crowd did it to itself.
Many people reported that they had no cell service as the rioters stormed the Capitol. These reports are accurate, but here is what likely happened.
One 4G cell can reasonably handle a hundred users. After that, everyone else gets the equivalent of a busy signal.
A cell site can have multiple cell sectors. A Verizon one off the west lawn of the Capitol has 12. 12×100 = 1200 calls. 2 blocks south is another one with 8 sectors. A few blocks north is one with 5. Assuming all of those are pointed directly at the Capitol – and they are not, we have (12+8+5) x 100.
AT&T appears to have 6 sites with about 23 cells.
T-Mobile appears to have 6 sites with 38 cells.
And Sprint has 7 sites with 30 cells.
Add those all together (25+23+38+30) x 100 and you might be able to support as many as 11,500 users.
But if all of the AT&T slots are in use, it makes no difference to your phone is Verizon has capacity. Add to that the fact that probably less than half of those cells are pointed at the Capitol and maybe, if you are lucky, 5,000 can get service.
Then you have the problem of network bandwidth. If everyone is streaming video in real time that takes a lot more bandwidth than calls to grandma.
On a normal day, that is fine.
But when there are tens of thousands people are there and a lot of them are trying to use the phone, it is guaranteed that some people are going to be out of luck.
In places like football stadiums, the carriers have data about how many of the say, 80,000, people want to use their phone at once, where they are in the stadium and statistically, they know exactly how much capacity to build.
In this case, no one called the cell carriers a year in advance to say that we plan to invade the Capitol at 1PM on this day and would you please make sure that you have enough capacity.
Even if they had, there would be no way for the carriers to where in or out of the building the people were and which carrier they used. One off events are almost guaranteed to fail.
Which brings us to the point that in case of a disaster, counting on your cell phone to work is like tossing a coin. Your land line, assuming the infrastructure has not been damaged, will more likely work because the carrier knows where each phone is and they can build enough capacity.
Credit: PC Magazine