When the 3/4G network is a mobile phone network, the objects that need to be connected are people, so you need to know how many people there are and the population density.
China: 1.4 billion people
The most densely populated cities: Shenzhen (5400), Shanghai (3800), Dongguan (3300), Foshan (2100), Guangzhou (1800)..., Beijing (1300);
The Guinness record in the world is Macau: 100,000 people per square kilometer!
So the maximum capacity of 4G network is: 100,000/km2
The number of "things" far exceeds people, and the capacity of 5G reaches: 1 million per square kilometer