Why did Chengdu receive an epidemic prevention message from Mianyang?

At present, mobile phone positioning mainly depends on the base station of the mobile phone. When traveling, the mobile phone will constantly search for base station signals and choose the base station with the strongest signal to keep connected, so that you can communicate.

So in the process of your personal activities, the advantage is that although you haven't been to a certain place, your mobile phone may be connected to the local base station, and then you may receive a short message from the foreign CDC.