Relationship between cellular networks and PSTN - especially in relation to the internet I want to theoretically understand the general relationship between the PSTN (public switched telephone network), cellular networks, and the Internet. I understand that the PSTN provides the infrastructure that ISPs buy in order to offer provide internet subscribers with shared lines. What about cellular networks and how Internet is accessed over a mobile phone? Are cellular networks, with all their stations and satellites, also ultimately connected underground with the PSTN? Is the PSTN therefore the lowest level of communication for all networks? Or is it that cellular networks are independent of the underground telephone lines and exists fine even without it?

PSTN == ancient circuit switched analog voice communication network. It has been increasingly converted to digital carrier over the decades. But, the "last mile" is still analog, and entirely digital everywhere else -- even transported by IP in many cases. It's only relation to "the internet" was by use of dialup modems. Today DSL rides on the same physical infrastructure, but is _not_ part of the PSTN.

Cellular == in it's early days, basically a wireless version of the PSTN. Today it's a totally digital packet switched system. In this sense, data is data. Internet and voice are just streams of 1's and 0's.

The Internet is a global packet switched communication network crisscrossing a multitude of technologies, some wired (dialup modems, DSL, cable, fiber, etc) and some not (terrestrial microwave, laser, satellite, shortwave radio, IR, ultrasonic, etc)